< draft-ietf-nfsv4-rfc3010bis-04.txt		draft-ietf-nfsv4-rfc3010bis-05.txt >
			A new Request for Comments is now available in online RFC libraries.
	NFS version 4 Working Group S. Shepler		RFC 3530
	INTERNET-DRAFT Sun Microsystems, Inc.
	Obsoletes: 3010 C. Beame
	Document: draft-ietf-nfsv4-rfc3010bis-04.txt Hummingbird Ltd.
	B. Callaghan
	Sun Microsystems, Inc.
	M. Eisler
	Network Appliance, Inc.
	D. Noveck
	Network Appliance, Inc.
	D. Robinson
	Sun Microsystems, Inc.
	R. Thurlow
	Sun Microsystems, Inc.
	October 2002
	NFS version 4 Protocol
	Status of this Memo
	This document is an Internet-Draft and is in full conformance with
	all provisions of Section 10 of RFC2026.
	Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF), its areas, and its working groups. Note that
	other groups may also distribute working documents as Internet-
	Drafts.
	Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet- Drafts as reference
	material or to cite them other than as "work in progress."
	The list of current Internet-Drafts can be accessed at
	http://www.ietf.org/ietf/1id-abstracts.txt
	The list of Internet-Draft Shadow Directories can be accessed at
	http://www.ietf.org/shadow.html.
	Abstract
	This document replaces [RFC3010] as the definition of the NFS version
	4 protocol.
	Draft Specification NFS version 4 Protocol October 2002
	NFS version 4 is a distributed filesystem protocol which owes
	heritage to NFS protocol versions 2 [RFC1094] and 3 [RFC1813].
	Unlike earlier versions, the NFS version 4 protocol supports
	traditional file access while integrating support for file locking
	and the mount protocol. In addition, support for strong security
	(and its negotiation), compound operations, client caching, and
	internationalization have been added. Of course, attention has been
	applied to making NFS version 4 operate well in an Internet
	environment.
	Copyright
	Copyright (C) The Internet Society (2000-2002). All Rights Reserved.
	Key Words
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [RFC2119].
	Draft Specification NFS version 4 Protocol October 2002
	Table of Contents
	1. Changes since RFC3010 . . . . . . . . . . . . . . . . . . . . 7
	1.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 8
	1.2. Inconsistencies of this Document with Section 18 . . . . . 8
	1.3. Overview of NFS version 4 Features . . . . . . . . . . . . 9
	1.3.1. RPC and Security . . . . . . . . . . . . . . . . . . . . 9
	1.3.2. Procedure and Operation Structure . . . . . . . . . . . . 9
	1.3.3. Filesystem Model . . . . . . . . . . . . . . . . . . . 10
	1.3.3.1. Filehandle Types . . . . . . . . . . . . . . . . . . 10
	1.3.3.2. Attribute Types . . . . . . . . . . . . . . . . . . . 11
	1.3.3.3. Filesystem Replication and Migration . . . . . . . . 11
	1.3.4. OPEN and CLOSE . . . . . . . . . . . . . . . . . . . . 12
	1.3.5. File locking . . . . . . . . . . . . . . . . . . . . . 12
	1.3.6. Client Caching and Delegation . . . . . . . . . . . . . 12
	1.4. General Definitions . . . . . . . . . . . . . . . . . . . 13
	2. Protocol Data Types . . . . . . . . . . . . . . . . . . . . 15
	2.1. Basic Data Types . . . . . . . . . . . . . . . . . . . . 15
	2.2. Structured Data Types . . . . . . . . . . . . . . . . . . 16
	3. RPC and Security Flavor . . . . . . . . . . . . . . . . . . 22
	3.1. Ports and Transports . . . . . . . . . . . . . . . . . . 22
	3.1.1. Client Retransmission Behavior . . . . . . . . . . . . 22
	3.2. Security Flavors . . . . . . . . . . . . . . . . . . . . 23
	3.2.1. Security mechanisms for NFS version 4 . . . . . . . . . 23
	3.2.1.1. Kerberos V5 as a security triple . . . . . . . . . . 23
	3.2.1.2. LIPKEY as a security triple . . . . . . . . . . . . . 24
	3.2.1.3. SPKM-3 as a security triple . . . . . . . . . . . . . 25
	3.3. Security Negotiation . . . . . . . . . . . . . . . . . . 25
	3.3.1. SECINFO . . . . . . . . . . . . . . . . . . . . . . . . 25
	3.3.2. Security Error . . . . . . . . . . . . . . . . . . . . 26
	3.4. Callback RPC Authentication . . . . . . . . . . . . . . . 26
	4. Filehandles . . . . . . . . . . . . . . . . . . . . . . . . 28
	4.1. Obtaining the First Filehandle . . . . . . . . . . . . . 28
	4.1.1. Root Filehandle . . . . . . . . . . . . . . . . . . . . 28
	4.1.2. Public Filehandle . . . . . . . . . . . . . . . . . . . 28
	4.2. Filehandle Types . . . . . . . . . . . . . . . . . . . . 29
	4.2.1. General Properties of a Filehandle . . . . . . . . . . 29
	4.2.2. Persistent Filehandle . . . . . . . . . . . . . . . . . 30
	4.2.3. Volatile Filehandle . . . . . . . . . . . . . . . . . . 30
	4.2.4. One Method of Constructing a Volatile Filehandle . . . 31
	4.3. Client Recovery from Filehandle Expiration . . . . . . . 32
	5. File Attributes . . . . . . . . . . . . . . . . . . . . . . 34
	5.1. Mandatory Attributes . . . . . . . . . . . . . . . . . . 35
	5.2. Recommended Attributes . . . . . . . . . . . . . . . . . 35
	5.3. Named Attributes . . . . . . . . . . . . . . . . . . . . 35
	5.4. Classification of Attributes . . . . . . . . . . . . . . 36
	5.5. Mandatory Attributes - Definitions . . . . . . . . . . . 38
	5.6. Recommended Attributes - Definitions . . . . . . . . . . 40
	5.7. Time Access . . . . . . . . . . . . . . . . . . . . . . . 45
	5.8. Interpreting owner and owner_group . . . . . . . . . . . 45
	5.9. Character Case Attributes . . . . . . . . . . . . . . . . 47
	5.10. Quota Attributes . . . . . . . . . . . . . . . . . . . . 47
	Draft Specification NFS version 4 Protocol October 2002
	5.11. Access Control Lists . . . . . . . . . . . . . . . . . . 48
	5.11.1. ACE type . . . . . . . . . . . . . . . . . . . . . . . 49
	5.11.2. ACE Access Mask . . . . . . . . . . . . . . . . . . . 50
	5.11.3. ACE flag . . . . . . . . . . . . . . . . . . . . . . . 52
	5.11.4. ACE who . . . . . . . . . . . . . . . . . . . . . . . 53
	5.11.5. Mode Attribute . . . . . . . . . . . . . . . . . . . . 54
	5.11.6. Mode and ACL Attribute . . . . . . . . . . . . . . . . 55
	5.11.7. mounted_on_fileid . . . . . . . . . . . . . . . . . . 55
	6. Filesystem Migration and Replication . . . . . . . . . . . 57
	6.1. Replication . . . . . . . . . . . . . . . . . . . . . . . 57
	6.2. Migration . . . . . . . . . . . . . . . . . . . . . . . . 57
	6.3. Interpretation of the fs_locations Attribute . . . . . . 58
	6.4. Filehandle Recovery for Migration or Replication . . . . 59
	7. NFS Server Name Space . . . . . . . . . . . . . . . . . . . 60
	7.1. Server Exports . . . . . . . . . . . . . . . . . . . . . 60
	7.2. Browsing Exports . . . . . . . . . . . . . . . . . . . . 60
	7.3. Server Pseudo Filesystem . . . . . . . . . . . . . . . . 60
	7.4. Multiple Roots . . . . . . . . . . . . . . . . . . . . . 61
	7.5. Filehandle Volatility . . . . . . . . . . . . . . . . . . 61
	7.6. Exported Root . . . . . . . . . . . . . . . . . . . . . . 61
	7.7. Mount Point Crossing . . . . . . . . . . . . . . . . . . 62
	7.8. Security Policy and Name Space Presentation . . . . . . . 62
	8. File Locking and Share Reservations . . . . . . . . . . . . 64
	8.1. Locking . . . . . . . . . . . . . . . . . . . . . . . . . 64
	8.1.1. Client ID . . . . . . . . . . . . . . . . . . . . . . . 64
	8.1.2. Server Release of Clientid . . . . . . . . . . . . . . 67
	8.1.3. lock_owner and stateid Definition . . . . . . . . . . . 68
	8.1.4. Use of the stateid and Locking . . . . . . . . . . . . 69
	8.1.5. Sequencing of Lock Requests . . . . . . . . . . . . . . 71
	8.1.6. Recovery from Replayed Requests . . . . . . . . . . . . 72
	8.1.7. Releasing lock_owner State . . . . . . . . . . . . . . 73
	8.1.8. Use of Open Confirmation . . . . . . . . . . . . . . . 73
	8.2. Lock Ranges . . . . . . . . . . . . . . . . . . . . . . . 74
	8.3. Upgrading and Downgrading Locks . . . . . . . . . . . . . 74
	8.4. Blocking Locks . . . . . . . . . . . . . . . . . . . . . 75
	8.5. Lease Renewal . . . . . . . . . . . . . . . . . . . . . . 75
	8.6. Crash Recovery . . . . . . . . . . . . . . . . . . . . . 76
	8.6.1. Client Failure and Recovery . . . . . . . . . . . . . . 77
	8.6.2. Server Failure and Recovery . . . . . . . . . . . . . . 77
	8.6.3. Network Partitions and Recovery . . . . . . . . . . . . 79
	8.7. Recovery from a Lock Request Timeout or Abort . . . . . . 82
	8.8. Server Revocation of Locks . . . . . . . . . . . . . . . 83
	8.9. Share Reservations . . . . . . . . . . . . . . . . . . . 84
	8.10. OPEN/CLOSE Operations . . . . . . . . . . . . . . . . . 84
	8.10.1. Close and Retention of State Information . . . . . . . 85
	8.11. Open Upgrade and Downgrade . . . . . . . . . . . . . . . 86
	8.12. Short and Long Leases . . . . . . . . . . . . . . . . . 86
	8.13. Clocks, Propagation Delay, and Calculating Lease
	Expiration . . . . . . . . . . . . . . . . . . . . . . . 87
	8.14. Migration, Replication and State . . . . . . . . . . . . 87
	8.14.1. Migration and State . . . . . . . . . . . . . . . . . 88
	8.14.2. Replication and State . . . . . . . . . . . . . . . . 88
	Draft Specification NFS version 4 Protocol October 2002
	8.14.3. Notification of Migrated Lease . . . . . . . . . . . . 89
	8.14.4. Migration and the Lease_time Attribute . . . . . . . . 89
	9. Client-Side Caching . . . . . . . . . . . . . . . . . . . . 91
	9.1. Performance Challenges for Client-Side Caching . . . . . 91
	9.2. Delegation and Callbacks . . . . . . . . . . . . . . . . 92
	9.2.1. Delegation Recovery . . . . . . . . . . . . . . . . . . 93
	9.3. Data Caching . . . . . . . . . . . . . . . . . . . . . . 95
	9.3.1. Data Caching and OPENs . . . . . . . . . . . . . . . . 95
	9.3.2. Data Caching and File Locking . . . . . . . . . . . . . 96
	9.3.3. Data Caching and Mandatory File Locking . . . . . . . . 98
	9.3.4. Data Caching and File Identity . . . . . . . . . . . . 98
	9.4. Open Delegation . . . . . . . . . . . . . . . . . . . . . 99
	9.4.1. Open Delegation and Data Caching . . . . . . . . . . . 102
	9.4.2. Open Delegation and File Locks . . . . . . . . . . . . 103
	9.4.3. Handling of CB_GETATTR . . . . . . . . . . . . . . . . 103
	9.4.4. Recall of Open Delegation . . . . . . . . . . . . . . . 106
	9.4.5. Clients that Fail to Honor Delegation Recalls . . . . . 108
	9.4.6. Delegation Revocation . . . . . . . . . . . . . . . . . 108
	9.5. Data Caching and Revocation . . . . . . . . . . . . . . . 109
	9.5.1. Revocation Recovery for Write Open Delegation . . . . . 109
	9.6. Attribute Caching . . . . . . . . . . . . . . . . . . . . 110
	9.7. Data and Metadata Caching and Memory Mapped Files . . . . 112
	9.8. Name Caching . . . . . . . . . . . . . . . . . . . . . . 114
	9.9. Directory Caching . . . . . . . . . . . . . . . . . . . . 115
	10. Minor Versioning . . . . . . . . . . . . . . . . . . . . . 117
	11. Internationalization . . . . . . . . . . . . . . . . . . . 120
	11.1. Universal Versus Local Character Sets . . . . . . . . . 120
	11.2. Overview of Universal Character Set Standards . . . . . 121
	11.3. Difficulties with UCS-4, UCS-2, Unicode . . . . . . . . 122
	11.4. UTF-8 and its solutions . . . . . . . . . . . . . . . . 122
	11.5. Normalization . . . . . . . . . . . . . . . . . . . . . 123
	11.6. UTF-8 Related Errors . . . . . . . . . . . . . . . . . . 123
	12. Error Definitions . . . . . . . . . . . . . . . . . . . . 125
	13. NFS version 4 Requests . . . . . . . . . . . . . . . . . . 131
	13.1. Compound Procedure . . . . . . . . . . . . . . . . . . . 131
	13.2. Evaluation of a Compound Request . . . . . . . . . . . . 132
	13.3. Synchronous Modifying Operations . . . . . . . . . . . . 132
	13.4. Operation Values . . . . . . . . . . . . . . . . . . . . 133
	14. NFS version 4 Procedures . . . . . . . . . . . . . . . . . 134
	14.1. Procedure 0: NULL - No Operation . . . . . . . . . . . . 134
	14.2. Procedure 1: COMPOUND - Compound Operations . . . . . . 135
	14.2.1. Operation 3: ACCESS - Check Access Rights . . . . . . 138
	14.2.2. Operation 4: CLOSE - Close File . . . . . . . . . . . 141
	14.2.3. Operation 5: COMMIT - Commit Cached Data . . . . . . . 143
	14.2.4. Operation 6: CREATE - Create a Non-Regular File Object 146
	14.2.5. Operation 7: DELEGPURGE - Purge Delegations Awaiting
	Recovery . . . . . . . . . . . . . . . . . . . . . . . 149
	14.2.6. Operation 8: DELEGRETURN - Return Delegation . . . . . 151
	14.2.7. Operation 9: GETATTR - Get Attributes . . . . . . . . 152
	14.2.8. Operation 10: GETFH - Get Current Filehandle . . . . . 154
	14.2.9. Operation 11: LINK - Create Link to a File . . . . . . 156
	14.2.10. Operation 12: LOCK - Create Lock . . . . . . . . . . 158
	Draft Specification NFS version 4 Protocol October 2002
	14.2.11. Operation 13: LOCKT - Test For Lock . . . . . . . . . 162
	14.2.12. Operation 14: LOCKU - Unlock File . . . . . . . . . . 164
	14.2.13. Operation 15: LOOKUP - Lookup Filename . . . . . . . 166
	14.2.14. Operation 16: LOOKUPP - Lookup Parent Directory . . . 169
	14.2.15. Operation 17: NVERIFY - Verify Difference in
	Attributes . . . . . . . . . . . . . . . . . . . . . 170
	14.2.16. Operation 18: OPEN - Open a Regular File . . . . . . 172
	14.2.17. Operation 19: OPENATTR - Open Named Attribute
	Directory . . . . . . . . . . . . . . . . . . . . . . 182
	14.2.18. Operation 20: OPEN_CONFIRM - Confirm Open . . . . . . 184
	14.2.19. Operation 21: OPEN_DOWNGRADE - Reduce Open File Access 187
	14.2.20. Operation 22: PUTFH - Set Current Filehandle . . . . 189
	14.2.21. Operation 23: PUTPUBFH - Set Public Filehandle . . . 190
	14.2.22. Operation 24: PUTROOTFH - Set Root Filehandle . . . . 192
	14.2.23. Operation 25: READ - Read from File . . . . . . . . . 193
	14.2.24. Operation 26: READDIR - Read Directory . . . . . . . 196
	14.2.25. Operation 27: READLINK - Read Symbolic Link . . . . . 200
	14.2.26. Operation 28: REMOVE - Remove Filesystem Object . . . 202
	14.2.27. Operation 29: RENAME - Rename Directory Entry . . . . 205
	14.2.28. Operation 30: RENEW - Renew a Lease . . . . . . . . . 208
	14.2.29. Operation 31: RESTOREFH - Restore Saved Filehandle . 210
	14.2.30. Operation 32: SAVEFH - Save Current Filehandle . . . 212
	14.2.31. Operation 33: SECINFO - Obtain Available Security . . 213
	14.2.32. Operation 34: SETATTR - Set Attributes . . . . . . . 217
	14.2.33. Operation 35: SETCLIENTID - Negotiate Clientid . . . 220
	14.2.34. Operation 36: SETCLIENTID_CONFIRM - Confirm Clientid 224
	14.2.35. Operation 37: VERIFY - Verify Same Attributes . . . . 228
	14.2.36. Operation 38: WRITE - Write to File . . . . . . . . . 230
	14.2.37. Operation 39: RELEASE_LOCKOWNER - Release Lockowner
	State . . . . . . . . . . . . . . . . . . . . . . . . 235
	14.2.38. Operation 10044: ILLEGAL - Illegal operation . . . . 237
	15. NFS version 4 Callback Procedures . . . . . . . . . . . . 238
	15.1. Procedure 0: CB_NULL - No Operation . . . . . . . . . . 238
	15.2. Procedure 1: CB_COMPOUND - Compound Operations . . . . . 239
	15.2.1. Operation 3: CB_GETATTR - Get Attributes . . . . . . . 241
	15.2.2. Operation 4: CB_RECALL - Recall an Open Delegation . . 243
	15.2.3. Operation 10044: CB_ILLEGAL - Illegal Callback
	Operation . . . . . . . . . . . . . . . . . . . . . . 245
	16. Security Considerations . . . . . . . . . . . . . . . . . 246
	17. IANA Considerations . . . . . . . . . . . . . . . . . . . 247
	17.1. Named Attribute Definition . . . . . . . . . . . . . . . 247
	17.2. ONC RPC Network Identifiers (netids) . . . . . . . . . . 247
	18. RPC definition file . . . . . . . . . . . . . . . . . . . 248
	19. Normative References . . . . . . . . . . . . . . . . . . . 280
	20. Informative References . . . . . . . . . . . . . . . . . . 281
	21. Authors . . . . . . . . . . . . . . . . . . . . . . . . . 285
	21.1. Editor's Address . . . . . . . . . . . . . . . . . . . . 285
	21.2. Authors' Addresses . . . . . . . . . . . . . . . . . . . 285
	21.3. Acknowledgements . . . . . . . . . . . . . . . . . . . . 286
	22. Full Copyright Statement . . . . . . . . . . . . . . . . . 287
	Draft Specification NFS version 4 Protocol October 2002
	1. Changes since RFC3010
	This definition of the NFS version 4 protocol replaces or obsoletes
	the definition present in [RFC3010]. While portions of the two
	documents have remained the same, there have been substantive changes
	in others. The changes made between [RFC3010] and this document
	represent implementation experience and further review of the
	protocol. While some modifications were made for ease of
	implementation or clarification, most updates represent errors or
	situations where the [RFC3010] definition were untenable.
	The following list is not all inclusive of all changes but presents
	some of the most notable changes or additions made:
	o The state model has added an open_owner4 identifier. This was
	done to accommodate Posix based clients and the model they use
	for file locking. For Posix clients, an open_owner4 would
	correspond to a file descriptor potentially shared amongst a set
	of processes and the lock_owner4 identifier would correspond to
	a process that is locking a file.
	o Clarifications and error conditions were added for the handling
	of the owner and group attributes. Since these attributes are
	string based (as opposed to the numeric uid/gid of previous
	versions of NFS), translations may not be available and hence
	the changes made.
	o Clarifications for the ACL and mode attributes to address
	evaluation and partial support.
	o For identifiers that are defined as XDR opaque, limits were set
	on their size.
	o Added the mounted_on_filed attribute to allow Posix clients to
	correctly construct local mounts.
	o Modified the SETCLIENTID/SETCLIENTID_CONFIRM operations to deal
	correctly with confirmation details along with adding the
	ability to specify new client callback information. Also added
	clarification of the callback information itself.
	o Added a new operation LOCKOWNER_RELEASE to enable notifying the
	server that a lock_owner4 will no longer be used by the client.
	o RENEW operation changes to identify the client correctly and
	allow for additional error returns.
	o Verify error return possibilities for all operations.
	o Remove use of the pathname4 data type from LOOKUP and OPEN in
	favor of having the client construct a sequence of LOOKUP
	Draft Specification NFS version 4 Protocol October 2002
	operations to acheive the same effect.
	1.1. Introduction
	The NFS version 4 protocol is a further revision of the NFS protocol
	defined already by versions 2 [RFC1094] and 3 [RFC1813]. It retains
	the essential characteristics of previous versions: design for easy
	recovery, independent of transport protocols, operating systems and
	filesystems, simplicity, and good performance. The NFS version 4
	revision has the following goals:
	o Improved access and good performance on the Internet.
	The protocol is designed to transit firewalls easily, perform
	well where latency is high and bandwidth is low, and scale to
	very large numbers of clients per server.
	o Strong security with negotiation built into the protocol.
	The protocol builds on the work of the ONCRPC working group in
	supporting the RPCSEC_GSS protocol. Additionally, the NFS
	version 4 protocol provides a mechanism to allow clients and
	servers the ability to negotiate security and require clients
	and servers to support a minimal set of security schemes.
	o Good cross-platform interoperability.
	The protocol features a filesystem model that provides a useful,
	common set of features that does not unduly favor one filesystem
	or operating system over another.
	o Designed for protocol extensions.
	The protocol is designed to accept standard extensions that do
	not compromise backward compatibility.
	1.2. Inconsistencies of this Document with Section 18
	Section 18, RPC Definition File, contains the definitions in XDR
	description language of the constructs used by the protocol. Prior
	to Section 18, several of the constructs are reproduced for purposes
	of explanation. The reader is warned of the possibility of errors in
	the reproduced constructs outside of Section 18. For any part of the
	document that is inconsistent with Section 18, Section 18 is to be
	considered authoritative.
	Draft Specification NFS version 4 Protocol October 2002
	1.3. Overview of NFS version 4 Features
	To provide a reasonable context for the reader, the major features of
	NFS version 4 protocol will be reviewed in brief. This will be done
	to provide an appropriate context for both the reader who is familiar
	with the previous versions of the NFS protocol and the reader that is
	new to the NFS protocols. For the reader new to the NFS protocols,
	there is still a fundamental knowledge that is expected. The reader
	should be familiar with the XDR and RPC protocols as described in
	[RFC1831] and [RFC1832]. A basic knowledge of filesystems and
	distributed filesystems is expected as well.
	1.3.1. RPC and Security
	As with previous versions of NFS, the External Data Representation
	(XDR) and Remote Procedure Call (RPC) mechanisms used for the NFS
	version 4 protocol are those defined in [RFC1831] and [RFC1832]. To
	meet end to end security requirements, the RPCSEC_GSS framework
	[RFC2203] will be used to extend the basic RPC security. With the
	use of RPCSEC_GSS, various mechanisms can be provided to offer
	authentication, integrity, and privacy to the NFS version 4 protocol.
	Kerberos V5 will be used as described in [RFC1964] to provide one
	security framework. The LIPKEY GSS-API mechanism described in
	[RFC2847] will be used to provide for the use of user password and
	server public key by the NFS version 4 protocol. With the use of
	RPCSEC_GSS, other mechanisms may also be specified and used for NFS
	version 4 security.
	To enable in-band security negotiation, the NFS version 4 protocol
	has added a new operation which provides the client a method of
	querying the server about its policies regarding which security
	mechanisms must be used for access to the server's filesystem
	resources. With this, the client can securely match the security
	mechanism that meets the policies specified at both the client and
	server.
	1.3.2. Procedure and Operation Structure
	A significant departure from the previous versions of the NFS
	protocol is the introduction of the COMPOUND procedure. For the NFS
	version 4 protocol, there are two RPC procedures, NULL and COMPOUND.
	The COMPOUND procedure is defined in terms of operations and these
	operations correspond more closely to the traditional NFS procedures.
	With the use of the COMPOUND procedure, the client is able to build
	simple or complex requests. These COMPOUND requests allow for a
	reduction in the number of RPCs needed for logical filesystem
	operations. For example, without previous contact with a server a
	client will be able to read data from a file in one request by
	combining LOOKUP, OPEN, and READ operations in a single COMPOUND RPC.
	With previous versions of the NFS protocol, this type of single
	Draft Specification NFS version 4 Protocol October 2002
	request was not possible.
	The model used for COMPOUND is very simple. There is no logical OR
	or ANDing of operations. The operations combined within a COMPOUND
	request are evaluated in order by the server. Once an operation
	returns a failing result, the evaluation ends and the results of all
	evaluated operations are returned to the client.
	The NFS version 4 protocol continues to have the client refer to a
	file or directory at the server by a "filehandle". The COMPOUND
	procedure has a method of passing a filehandle from one operation to
	another within the sequence of operations. There is a concept of a
	"current filehandle" and "saved filehandle". Most operations use the
	"current filehandle" as the filesystem object to operate upon. The
	"saved filehandle" is used as temporary filehandle storage within a
	COMPOUND procedure as well as an additional operand for certain
	operations.
	1.3.3. Filesystem Model
	The general filesystem model used for the NFS version 4 protocol is
	the same as previous versions. The server filesystem is hierarchical
	with the regular files contained within being treated as opaque byte
	streams. In a slight departure, file and directory names are encoded
	with UTF-8 to deal with the basics of internationalization.
	The NFS version 4 protocol does not require a separate protocol to
	provide for the initial mapping between path name and filehandle.
	Instead of using the older MOUNT protocol for this mapping, the
	server provides a ROOT filehandle that represents the logical root or
	top of the filesystem tree provided by the server. The server
	provides multiple filesystems by gluing them together with pseudo
	filesystems. These pseudo filesystems provide for potential gaps in
	the path names between real filesystems.
	1.3.3.1. Filehandle Types
	In previous versions of the NFS protocol, the filehandle provided by
	the server was guaranteed to be valid or persistent for the lifetime
	of the filesystem object to which it referred. For some server
	implementations, this persistence requirement has been difficult to
	meet. For the NFS version 4 protocol, this requirement has been
	relaxed by introducing another type of filehandle, volatile. With
	persistent and volatile filehandle types, the server implementation
	can match the abilities of the filesystem at the server along with
	the operating environment. The client will have knowledge of the
	type of filehandle being provided by the server and can be prepared
	to deal with the semantics of each.
	Draft Specification NFS version 4 Protocol October 2002
	1.3.3.2. Attribute Types
	The NFS version 4 protocol introduces three classes of filesystem or
	file attributes. Like the additional filehandle type, the
	classification of file attributes has been done to ease server
	implementations along with extending the overall functionality of the
	NFS protocol. This attribute model is structured to be extensible
	such that new attributes can be introduced in minor revisions of the
	protocol without requiring significant rework.
	The three classifications are: mandatory, recommended and named
	attributes. This is a significant departure from the previous
	attribute model used in the NFS protocol. Previously, the attributes
	for the filesystem and file objects were a fixed set of mainly UNIX
	attributes. If the server or client did not support a particular
	attribute, it would have to simulate the attribute the best it could.
	Mandatory attributes are the minimal set of file or filesystem
	attributes that must be provided by the server and must be properly
	represented by the server. Recommended attributes represent
	different filesystem types and operating environments. The
	recommended attributes will allow for better interoperability and the
	inclusion of more operating environments. The mandatory and
	recommended attribute sets are traditional file or filesystem
	attributes. The third type of attribute is the named attribute. A
	named attribute is an opaque byte stream that is associated with a
	directory or file and referred to by a string name. Named attributes
	are meant to be used by client applications as a method to associate
	application specific data with a regular file or directory.
	One significant addition to the recommended set of file attributes is
	the Access Control List (ACL) attribute. This attribute provides for
	directory and file access control beyond the model used in previous
	versions of the NFS protocol. The ACL definition allows for
	specification of user and group level access control.
	1.3.3.3. Filesystem Replication and Migration
	With the use of a special file attribute, the ability to migrate or
	replicate server filesystems is enabled within the protocol. The
	filesystem locations attribute provides a method for the client to
	probe the server about the location of a filesystem. In the event of
	a migration of a filesystem, the client will receive an error when
	operating on the filesystem and it can then query as to the new file
	system location. Similar steps are used for replication, the client
	is able to query the server for the multiple available locations of a
	particular filesystem. From this information, the client can use its
	own policies to access the appropriate filesystem location.
	Draft Specification NFS version 4 Protocol October 2002
	1.3.4. OPEN and CLOSE
	The NFS version 4 protocol introduces OPEN and CLOSE operations. The
	OPEN operation provides a single point where file lookup, creation,
	and share semantics can be combined. The CLOSE operation also
	provides for the release of state accumulated by OPEN.
	1.3.5. File locking
	With the NFS version 4 protocol, the support for byte range file
	locking is part of the NFS protocol. The file locking support is
	structured so that an RPC callback mechanism is not required. This
	is a departure from the previous versions of the NFS file locking
	protocol, Network Lock Manager (NLM). The state associated with file
	locks is maintained at the server under a lease-based model. The
	server defines a single lease period for all state held by a NFS
	client. If the client does not renew its lease within the defined
	period, all state associated with the client's lease may be released
	by the server. The client may renew its lease with use of the RENEW
	operation or implicitly by use of other operations (primarily READ).
	1.3.6. Client Caching and Delegation
	The file, attribute, and directory caching for the NFS version 4
	protocol is similar to previous versions. Attributes and directory
	information are cached for a duration determined by the client. At
	the end of a predefined timeout, the client will query the server to
	see if the related filesystem object has been updated.
	For file data, the client checks its cache validity when the file is
	opened. A query is sent to the server to determine if the file has
	been changed. Based on this information, the client determines if
	the data cache for the file should kept or released. Also, when the
	file is closed, any modified data is written to the server.
	If an application wants to serialize access to file data, file
	locking of the file data ranges in question should be used.
	The major addition to NFS version 4 in the area of caching is the
	ability of the server to delegate certain responsibilities to the
	client. When the server grants a delegation for a file to a client,
	the client is guaranteed certain semantics with respect to the
	sharing of that file with other clients. At OPEN, the server may
	provide the client either a read or write delegation for the file.
	If the client is granted a read delegation, it is assured that no
	other client has the ability to write to the file for the duration of
	the delegation. If the client is granted a write delegation, the
	client is assured that no other client has read or write access to
	the file.
	Draft Specification NFS version 4 Protocol October 2002
	Delegations can be recalled by the server. If another client
	requests access to the file in such a way that the access conflicts
	with the granted delegation, the server is able to notify the initial
	client and recall the delegation. This requires that a callback path
	exist between the server and client. If this callback path does not
	exist, then delegations can not be granted. The essence of a
	delegation is that it allows the client to locally service operations
	such as OPEN, CLOSE, LOCK, LOCKU, READ, WRITE without immediate
	interaction with the server.
	1.4. General Definitions
	The following definitions are provided for the purpose of providing
	an appropriate context for the reader.
	Client The "client" is the entity that accesses the NFS server's
	resources. The client may be an application which contains
	the logic to access the NFS server directly. The client
	may also be the traditional operating system client remote
	filesystem services for a set of applications.
	In the case of file locking the client is the entity that
	maintains a set of locks on behalf of one or more
	applications. This client is responsible for crash or
	failure recovery for those locks it manages.
	Note that multiple clients may share the same transport and
	multiple clients may exist on the same network node.
	Clientid A 64-bit quantity used as a unique, short-hand reference to
	a client supplied Verifier and ID. The server is
	responsible for supplying the Clientid.
	Lease An interval of time defined by the server for which the
	client is irrevocably granted a lock. At the end of a
	lease period the lock may be revoked if the lease has not
	been extended. The lock must be revoked if a conflicting
	lock has been granted after the lease interval.
	All leases granted by a server have the same fixed
	interval. Note that the fixed interval was chosen to
	alleviate the expense a server would have in maintaining
	state about variable length leases across server failures.
	Lock The term "lock" is used to refer to both record (byte-
	range) locks as well as share reservations unless
	specifically stated otherwise.
	Server The "Server" is the entity responsible for coordinating
	client access to a set of filesystems.
	Draft Specification NFS version 4 Protocol October 2002
	Stable Storage
	NFS version 4 servers must be able to recover without data
	loss from multiple power failures (including cascading
	power failures, that is, several power failures in quick
	succession), operating system failures, and hardware
	failure of components other than the storage medium itself
	(for example, disk, nonvolatile RAM).
	Some examples of stable storage that are allowable for an
	NFS server include:
	1. Media commit of data, that is, the modified data has
	been successfully written to the disk media,
	for example, the disk platter.
	2. An immediate reply disk drive with battery-backed
	on-drive intermediate storage or uninterruptible power
	system (UPS).
	3. Server commit of data with battery-backed intermediate
	storage and recovery software.
	4. Cache commit with uninterruptible power system (UPS)
	and recovery software.
	Stateid A 128-bit quantity returned by a server that uniquely
	defines the open and locking state provided by the server
	for a specific open or lock owner for a specific file.
	Stateids composed of all bits 0 or all bits 1 have special
	meaning and are reserved values.
	Verifier A 64-bit quantity generated by the client that the server
	can use to determine if the client has restarted and lost
	all previous lock state.
	Draft Specification NFS version 4 Protocol October 2002
	2. Protocol Data Types
	The syntax and semantics to describe the data types of the NFS
	version 4 protocol are defined in the XDR [RFC1832] and RPC [RFC1831]
	documents. The next sections build upon the XDR data types to define
	types and structures specific to this protocol.
	2.1. Basic Data Types
	Data Type Definition
	_____________________________________________________________________
	int32_t typedef int int32_t;
	uint32_t typedef unsigned int uint32_t;
	int64_t typedef hyper int64_t;
	uint64_t typedef unsigned hyper uint64_t;
	attrlist4 typedef opaque attrlist4<>;
	Used for file/directory attributes
	bitmap4 typedef uint32_t bitmap4<>;
	Used in attribute array encoding.
	changeid4 typedef uint64_t changeid4;
	Used in definition of change_info
	clientid4 typedef uint64_t clientid4;
	Shorthand reference to client identification
	component4 typedef utf8string component4;
	Represents path name components
	count4 typedef uint32_t count4;
	Various count parameters (READ, WRITE, COMMIT)
	length4 typedef uint64_t length4;
	Describes LOCK lengths
	linktext4 typedef utf8string linktext4;
	Symbolic link contents
	mode4 typedef uint32_t mode4;
	Mode attribute data type
	nfs_cookie4 typedef uint64_t nfs_cookie4;
	Opaque cookie value for READDIR
	nfs_fh4 typedef opaque nfs_fh4<NFS4_FHSIZE>;
	Filehandle definition; NFS4_FHSIZE is defined as 128
	Draft Specification NFS version 4 Protocol October 2002
	nfs_ftype4 enum nfs_ftype4;
	Various defined file types
	nfsstat4 enum nfsstat4;
	Return value for operations
	offset4 typedef uint64_t offset4;
	Various offset designations (READ, WRITE, LOCK, COMMIT)
	pathname4 typedef component4 pathname4<>;
	Represents path name for LOOKUP, OPEN and others
	qop4 typedef uint32_t qop4;
	Quality of protection designation in SECINFO
	sec_oid4 typedef opaque sec_oid4<>;
	Security Object Identifier
	The sec_oid4 data type is not really opaque.
	Instead contains an ASN.1 OBJECT IDENTIFIER as used
	by GSS-API in the mech_type argument to
	GSS_Init_sec_context. See [RFC2743] for details.
	seqid4 typedef uint32_t seqid4;
	Sequence identifier used for file locking
	utf8string typedef opaque utf8string<>;
	UTF-8 encoding for strings
	verifier4 typedef opaque verifier4[NFS4_VERIFIER_SIZE];
	Verifier used for various operations (COMMIT, CREATE,
	OPEN, READDIR, SETCLIENTID, SETCLIENTID_CONFIRM, WRITE)
	NFS4_VERIFIER_SIZE is defined as 8.
	2.2. Structured Data Types
	nfstime4
	struct nfstime4 {
	int64_t seconds;
	uint32_t nseconds;
	}
	The nfstime4 structure gives the number of seconds and
	nanoseconds since midnight or 0 hour January 1, 1970 Coordinated
	Universal Time (UTC). Values greater than zero for the seconds
	field denote dates after the 0 hour January 1, 1970. Values
	less than zero for the seconds field denote dates before the 0
	hour January 1, 1970. In both cases, the nseconds field is to
	be added to the seconds field for the final time representation.
	For example, if the time to be represented is one-half second
	Draft Specification NFS version 4 Protocol October 2002
	before 0 hour January 1, 1970, the seconds field would have a
	value of negative one (-1) and the nseconds fields would have a
	value of one-half second (500000000). Values greater than
	999,999,999 for nseconds are considered invalid.
	This data type is used to pass time and date information. A
	server converts to and from its local representation of time
	when processing time values, preserving as much accuracy as
	possible. If the precision of timestamps stored for a filesystem
	object is less than defined, loss of precision can occur. An
	adjunct time maintenance protocol is recommended to reduce
	client and server time skew.
	time_how4
	enum time_how4 {
	SET_TO_SERVER_TIME4 = 0,
	SET_TO_CLIENT_TIME4 = 1
	};
	settime4
	union settime4 switch (time_how4 set_it) {
	case SET_TO_CLIENT_TIME4:
	nfstime4 time;
	default:
	void;
	};
	The above definitions are used as the attribute definitions to
	set time values. If set_it is SET_TO_SERVER_TIME4, then the
	server uses its local representation of time for the time value.
	specdata4
	struct specdata4 {
	uint32_t specdata1; /* major device number */
	uint32_t specdata2; /* minor device number */
	};
	This data type represents additional information for the device
	file types NF4CHR and NF4BLK.
	fsid4
	struct fsid4 {
	uint64_t major;
	uint64_t minor;
	Draft Specification NFS version 4 Protocol October 2002
	};
	This type is the filesystem identifier that is used as a
	mandatory attribute.
	fs_location4
	struct fs_location4 {
	utf8string server<>;
	pathname4 rootpath;
	};
	fs_locations4
	struct fs_locations4 {
	pathname4 fs_root;
	fs_location4 locations<>;
	};
	The fs_location4 and fs_locations4 data types are used for the
	fs_locations recommended attribute which is used for migration
	and replication support.
	fattr4
	struct fattr4 {
	bitmap4 attrmask;
	attrlist4 attr_vals;
	};
	The fattr4 structure is used to represent file and directory
	attributes.
	The bitmap is a counted array of 32 bit integers used to contain
	bit values. The position of the integer in the array that
	contains bit n can be computed from the expression (n / 32) and
	its bit within that integer is (n mod 32).
	0 1
	+-----------+-----------+-----------+--
	| count | 31 .. 0 | 63 .. 32 |
	+-----------+-----------+-----------+--
	change_info4
	struct change_info4 {
	bool atomic;
	changeid4 before;
	Draft Specification NFS version 4 Protocol October 2002
	changeid4 after;
	};
	This structure is used with the CREATE, LINK, REMOVE, RENAME
	operations to let the client know the value of the change
	attribute for the directory in which the target filesystem
	object resides.
	clientaddr4
	struct clientaddr4 {
	/* see struct rpcb in RFC1833 */
	string r_netid<>; /* network id */
	string r_addr<>; /* universal address */
	};
	The clientaddr4 structure is used as part of the SETCLIENTID
	operation to either specify the address of the client that is
	using a clientid or as part of the callback registration. The
	r_netid and r_addr fields are specified in [RFC1833], but they
	are underspecified in [RFC1833] as far as what they should look
	like for specific protocols.
	For TCP over IPv4 and for UDP over IPv4, the format of r_addr is
	the US-ASCII string:
	h1.h2.h3.h4.p1.p2
	The prefix, "h1.h2.h3.h4", is the standard textual form for
	representing an IPv4 address, which is always four octets long.
	Assuming big-endian ordering, h1, h2, h3, and h4, are
	respectively, the first through fourth octets each converted to
	ASCII-decimal. Assuming big-endian ordering, p1 and p2 are,
	respectively, the first and second octets each converted to
	ASCII-decimal. For example, if a host, in big-endian order, has
	an address of 0x0A010307 and there is a service listening on, in
	big endian order, port 0x020F (decimal 527), then complete
	universal address is "10.1.3.7.2.15".
	For TCP over IPv4 the value of r_netid is the string "tcp". For
	UDP over IPv4 the value of r_netid is the string "udp".
	For TCP over IPv4 and for UDP over IPv6, the format of r_addr is
	the US-ASCII string:
	x1:x2:x3:x4:x5:x6:x7:x8.p1.p2
	The suffix "p1.p2" is the service port, and is computed the same
	way as with universal addresses for TCP and UDP over IPv4. The
	prefix, "x1:x2:x3:x4:x5:x6:x7:x8", is the standard textual form
	for representing an IPv6 address as defined in Section 2.2 of
	Draft Specification NFS version 4 Protocol October 2002
	[RFC1884]. Additionally, the two alternative forms specified in
	Section 2.2 of [RFC1884] are also acceptable.
	For TCP over IPv6 the value of r_netid is the string "tcp6".
	For UDP over IPv6 the value of r_netid is the string "udp6".
	cb_client4
	struct cb_client4 {
	unsigned int cb_program;
	clientaddr4 cb_location;
	};
	This structure is used by the client to inform the server of its
	call back address; includes the program number and client
	address.
	nfs_client_id4
	struct nfs_client_id4 {
	verifier4 verifier;
	opaque id<NFS4_OPAQUE_LIMIT>;
	};
	This structure is part of the arguments to the SETCLIENTID
	operation. NFS4_OPAQUE_LIMIT is defined as 1024.
	open_owner4
	struct open_owner4 {
	clientid4 clientid;
	opaque owner<NFS4_OPAQUE_LIMIT>;
	};
	This structure is used to identify the owner of open state.
	NFS4_OPAQUE_LIMIT is defined as 1024.
	lock_owner4
	struct lock_owner4 {
	clientid4 clientid;
	opaque owner<NFS4_OPAQUE_LIMIT>;
	};
	This structure is used to identify the owner of file locking
	state. NFS4_OPAQUE_LIMIT is defined as 1024.
	Draft Specification NFS version 4 Protocol October 2002
	open_to_lock_owner4
	struct open_to_lock_owner4 {
	seqid4 open_seqid;
	stateid4 open_stateid;
	seqid4 lock_seqid;
	lock_owner4 lock_owner;
	};
	This structure is used for the first LOCK operation done for an
	open_owner4. It provides both the open_stateid and lock_owner
	such that the transition is made from a valid open_stateid
	sequence to that of the new lock_stateid sequence. Using this
	mechanism avoids the confirmation of the lock_owner/lock_seqid
	pair since it is tied to established state in the form of the
	open_stateid/open_seqid.
	stateid4
	struct stateid4 {
	uint32_t seqid;
	opaque other[12];
	};
	This structure is used for the various state sharing mechanisms
	between the client and server. For the client, this data
	structure is read-only. The starting value of the seqid field
	is undefined. The server is required to increment the seqid
	field monotonically at each transition of the stateid. This is
	important since the client will inspect the seqid in OPEN
	stateids to determine the order of OPEN processing done by the
	server.
	Draft Specification NFS version 4 Protocol October 2002
	3. RPC and Security Flavor
	The NFS version 4 protocol is a Remote Procedure Call (RPC)
	application that uses RPC version 2 and the corresponding eXternal
	Data Representation (XDR) as defined in [RFC1831] and [RFC1832]. The
	RPCSEC_GSS security flavor as defined in [RFC2203] MUST be used as
	the mechanism to deliver stronger security for the NFS version 4
	protocol.
	3.1. Ports and Transports
	Historically, NFS version 2 and version 3 servers have resided on
	port 2049. The registered port 2049 [RFC1700] for the NFS protocol
	should be the default configuration. Using the registered port for
	NFS services means the NFS client will not need to use the RPC
	binding protocols as described in [RFC1833]; this will allow NFS to
	transit firewalls.
	Where an NFS version 4 implementation supports operation over the IP
	network protocol, the supported transports between NFS and IP must be
	among the IETF-approved congestion control transport protocols, which
	include TCP and SCTP. To enhance the possibilities for
	interoperability, an NFS version 4 implementation SHOULD support
	operation over the TCP transport protocol.
	If TCP is used as the transport, the client and server SHOULD use
	persistent connections. This will prevent the weakening of TCP's
	congestion control via short lived connections and will improve
	performance for the WAN environment by eliminating the need for SYN
	handshakes.
	Note that for various timers, the client and server should avoid
	inadvertent synchronization of those timers. For further discussion
	of the general issue refer to [Floyd].
	3.1.1. Client Retransmission Behavior
	When processing a request received over a reliable transport such as
	TCP, the NFS version 4 server MUST NOT silently drop the request,
	except if the transport connection has been broken. Given such a
	contract between NFS version 4 clients and servers, clients MUST NOT
	retry a request unless one or both of the following are true:
	o The transport connection has been broken
	o The procedure being retried is the NULL procedure
	Since reliable transports, such as TCP, do not always synchronously
	inform a peer when the other peer has broken the connection (for
	example, when an NFS server reboots), so the NFS version 4 client may
	Draft Specification NFS version 4 Protocol October 2002
	want to actively "probe" the connection to see if has been broken.
	Use of the NULL procedure is one recommended way to do so. So, when
	a client experiences a remote procedure call timeout (of some
	arbitrary implementation specific amount), rather than retrying the
	remote procedure call, it could instead issue a NULL procedure call
	to the server. If the server has died, the transport connection break
	will eventually be indicated to the NFS version 4 client. The client
	can then reconnect, and then retry the original request. If the NULL
	procedure call gets a response, the connection has not broken. The
	client can decide to wait longer for the original request's response,
	or it can break the transport connection and reconnect before re-
	sending the original request.
	For callbacks from the server to the client, the same rules apply,
	but the server doing the callback becomes the client, and the client
	receiving the callback becomes the server.
	3.2. Security Flavors
	Traditional RPC implementations have included AUTH_NONE, AUTH_SYS,
	AUTH_DH, and AUTH_KRB4 as security flavors. With [RFC2203] an
	additional security flavor of RPCSEC_GSS has been introduced which
	uses the functionality of GSS-API [RFC2743]. This allows for the use
	of various security mechanisms by the RPC layer without the
	additional implementation overhead of adding RPC security flavors.
	For NFS version 4, the RPCSEC_GSS security flavor MUST be used to
	enable the mandatory security mechanism. Other flavors, such as,
	AUTH_NONE, AUTH_SYS, and AUTH_DH MAY be implemented as well.
	3.2.1. Security mechanisms for NFS version 4
	The use of RPCSEC_GSS requires selection of: mechanism, quality of
	protection, and service (authentication, integrity, privacy). The
	remainder of this document will refer to these three parameters of
	the RPCSEC_GSS security as the security triple.
	3.2.1.1. Kerberos V5 as a security triple
	The Kerberos V5 GSS-API mechanism as described in [RFC1964] MUST be
	implemented and provide the following security triples.
	column descriptions:
	1 == number of pseudo flavor
	2 == name of pseudo flavor
	3 == mechanism's OID
	4 == mechanism's algorithm(s)
	5 == RPCSEC_GSS service
	1 2 3 4 5
	-----------------------------------------------------------------------
	Draft Specification NFS version 4 Protocol October 2002
	390003 krb5 1.2.840.113554.1.2.2 DES MAC MD5 rpc_gss_svc_none
	390004 krb5i 1.2.840.113554.1.2.2 DES MAC MD5 rpc_gss_svc_integrity
	390005 krb5p 1.2.840.113554.1.2.2 DES MAC MD5 rpc_gss_svc_privacy
	for integrity,
	and 56 bit DES
	for privacy.
	Note that the pseudo flavor is presented here as a mapping aid to the
	implementor. Because this NFS protocol includes a method to
	negotiate security and it understands the GSS-API mechanism, the
	pseudo flavor is not needed. The pseudo flavor is needed for NFS
	version 3 since the security negotiation is done via the MOUNT
	protocol.
	For a discussion of NFS' use of RPCSEC_GSS and Kerberos V5, please
	see [RFC2623].
	3.2.1.2. LIPKEY as a security triple
	The LIPKEY GSS-API mechanism as described in [RFC2847] MUST be
	implemented and provide the following security triples. The
	definition of the columns matches the previous subsection "Kerberos
	V5 as security triple"
	1 2 3 4 5
	-----------------------------------------------------------------------
	390006 lipkey 1.3.6.1.5.5.9 negotiated rpc_gss_svc_none
	390007 lipkey-i 1.3.6.1.5.5.9 negotiated rpc_gss_svc_integrity
	390008 lipkey-p 1.3.6.1.5.5.9 negotiated rpc_gss_svc_privacy
	The mechanism algorithm is listed as "negotiated". This is because
	LIPKEY is layered on SPKM-3 and in SPKM-3 [RFC2847] the
	confidentiality and integrity algorithms are negotiated. Since
	SPKM-3 specifies HMAC-MD5 for integrity as MANDATORY, 128 bit
	cast5CBC for confidentiality for privacy as MANDATORY, and further
	specifies that HMAC-MD5 and cast5CBC MUST be listed first before
	weaker algorithms, specifying "negotiated" in column 4 does not
	impair interoperability. In the event an SPKM-3 peer does not
	support the mandatory algorithms, the other peer is free to accept or
	reject the GSS-API context creation.
	Because SPKM-3 negotiates the algorithms, subsequent calls to
	LIPKEY's GSS_Wrap() and GSS_GetMIC() by RPCSEC_GSS will use a quality
	of protection value of 0 (zero). See section 5.2 of [RFC2025] for an
	explanation.
	LIPKEY uses SPKM-3 to create a secure channel in which to pass a user
	name and password from the client to the server. Once the user name
	and password have been accepted by the server, calls to the LIPKEY
	context are redirected to the SPKM-3 context. See [RFC2847] for more
	details.
	Draft Specification NFS version 4 Protocol October 2002
	3.2.1.3. SPKM-3 as a security triple
	The SPKM-3 GSS-API mechanism as described in [RFC2847] MUST be
	implemented and provide the following security triples. The
	definition of the columns matches the previous subsection "Kerberos
	V5 as security triple".
	1 2 3 4 5
	-----------------------------------------------------------------------
	390009 spkm3 1.3.6.1.5.5.1.3 negotiated rpc_gss_svc_none
	390010 spkm3i 1.3.6.1.5.5.1.3 negotiated rpc_gss_svc_integrity
	390011 spkm3p 1.3.6.1.5.5.1.3 negotiated rpc_gss_svc_privacy
	For a discussion as to why the mechanism algorithm is listed as
	"negotiated", see the previous section "LIPKEY as a security triple."
	Because SPKM-3 negotiates the algorithms, subsequent calls to SPKM-
	3's GSS_Wrap() and GSS_GetMIC() by RPCSEC_GSS will use a quality of
	protection value of 0 (zero). See section 5.2 of [RFC2025] for an
	explanation.
	Even though LIPKEY is layered over SPKM-3, SPKM-3 is specified as a
	mandatory set of triples to handle the situations where the initiator
	(the client) is anonymous or where the initiator has its own
	certificate. If the initiator is anonymous, there will not be a user
	name and password to send to the target (the server). If the
	initiator has its own certificate, then using passwords is
	superfluous.
	3.3. Security Negotiation
	With the NFS version 4 server potentially offering multiple security
	mechanisms, the client needs a method to determine or negotiate which
	mechanism is to be used for its communication with the server. The
	NFS server may have multiple points within its filesystem name space
	that are available for use by NFS clients. In turn the NFS server
	may be configured such that each of these entry points may have
	different or multiple security mechanisms in use.
	The security negotiation between client and server must be done with
	a secure channel to eliminate the possibility of a third party
	intercepting the negotiation sequence and forcing the client and
	server to choose a lower level of security than required or desired.
	See the section "Security Considerations" for further discussion.
	3.3.1. SECINFO
	The new SECINFO operation will allow the client to determine, on a
	per filehandle basis, what security triple is to be used for server
	access. In general, the client will not have to use the SECINFO
	Draft Specification NFS version 4 Protocol October 2002
	operation except during initial communication with the server or when
	the client crosses policy boundaries at the server. It is possible
	that the server's policies change during the client's interaction
	therefore forcing the client to negotiate a new security triple.
	3.3.2. Security Error
	Based on the assumption that each NFS version 4 client and server
	must support a minimum set of security (i.e. LIPKEY, SPKM-3, and
	Kerberos-V5 all under RPCSEC_GSS), the NFS client will start its
	communication with the server with one of the minimal security
	triples. During communication with the server, the client may
	receive an NFS error of NFS4ERR_WRONGSEC. This error allows the
	server to notify the client that the security triple currently being
	used is not appropriate for access to the server's filesystem
	resources. The client is then responsible for determining what
	security triples are available at the server and choose one which is
	appropriate for the client. See the section for the "SECINFO"
	operation for further discussion of how the client will respond to
	the NFS4ERR_WRONGSEC error and use SECINFO.
	3.4. Callback RPC Authentication
	Except as noted elsewhere in this section, the callback RPC
	(described later) MUST mutually authenticate the NFS server to the
	principal that acquired the clientid (also described later), using
	the security flavor the original SETCLIENTID operation used.
	For AUTH_NONE, there are no principals, so this is a non-issue.
	AUTH_SYS has no notions of mutual authentication or a server
	principal, so the callback from the server simply uses the AUTH_SYS
	credential that the user used when he set up the delegation.
	For AUTH_DH, one commonly used convention is that the server uses the
	credential corresponding to this AUTH_DH principal:
	unix.host@domain
	where host and domain are variables corresponding to the name of
	server host and directory services domain in which it lives such as a
	Network Information System domain or a DNS domain.
	Because LIPKEY is layered over SPKM-3, it is permissible for the
	server to use SPKM-3 and not LIPKEY for the callback even if the
	client used LIPKEY for SETCLIENTID.
	Regardless of what security mechanism under RPCSEC_GSS is being used,
	the NFS server, MUST identify itself in GSS-API via a
	GSS_C_NT_HOSTBASED_SERVICE name type. GSS_C_NT_HOSTBASED_SERVICE
	Draft Specification NFS version 4 Protocol October 2002
	names are of the form:
	service@hostname
	For NFS, the "service" element is
	nfs
	Implementations of security mechanisms will convert nfs@hostname to
	various different forms. For Kerberos V5 and LIPKEY, the following
	form is RECOMMENDED:
	nfs/hostname
	For Kerberos V5, nfs/hostname would be a server principal in the
	Kerberos Key Distribution Center database. For LIPKEY, this would be
	the username passed to the target (the NFS version 4 client that
	receives the callback).
	It should be noted that LIPKEY may not work for callbacks, since the
	LIPKEY client uses a user id/password. If the NFS client receiving
	the callback can authenticate the NFS server's user name/password
	pair, and if the user that the NFS server is authenticating to has a
	public key certificate, then it works.
	In situations where the NFS client uses LIPKEY and uses a per-host
	principal for the SETCLIENTID operation, instead of using LIPKEY for
	SETCLIENTID, it is RECOMMENDED that SPKM-3 with mutual authentication
	be used. This effectively means that the client will use a
	certificate to authenticate and identify the initiator to the target
	on the NFS server. Using SPKM-3 and not LIPKEY has the following
	advantages:
	o When the server does a callback, it must authenticate to the
	principal used in the SETCLIENTID. Even if LIPKEY is used,
	because LIPKEY is layered over SPKM-3, the NFS client will need
	to have a certificate that corresponds to the principal used in
	the SETCLIENTID operation. From an administrative perspective,
	having a user name, password, and certificate for both the
	client and server is redundant.
	o LIPKEY was intended to minimize additional infrastructure
	requirements beyond a certificate for the target, and the
	expectation is that existing password infrastructure can be
	leveraged for the initiator. In some environments, a per-host
	password does not exist yet. If certificates are used for any
	per-host principals, then additional password infrastructure is
	not needed.
	o In cases when a host is both an NFS client and server, it can
	share the same per-host certificate.
	Draft Specification NFS version 4 Protocol October 2002
	4. Filehandles
	The filehandle in the NFS protocol is a per server unique identifier
	for a filesystem object. The contents of the filehandle are opaque
	to the client. Therefore, the server is responsible for translating
	the filehandle to an internal representation of the filesystem
	object.
	4.1. Obtaining the First Filehandle
	The operations of the NFS protocol are defined in terms of one or
	more filehandles. Therefore, the client needs a filehandle to
	initiate communication with the server. With the NFS version 2
	protocol [RFC1094] and the NFS version 3 protocol [RFC1813], there
	exists an ancillary protocol to obtain this first filehandle. The
	MOUNT protocol, RPC program number 100005, provides the mechanism of
	translating a string based filesystem path name to a filehandle which
	can then be used by the NFS protocols.
	The MOUNT protocol has deficiencies in the area of security and use
	via firewalls. This is one reason that the use of the public
	filehandle was introduced in [RFC2054] and [RFC2055]. With the use
	of the public filehandle in combination with the LOOKUP operation in
	the NFS version 2 and 3 protocols, it has been demonstrated that the
	MOUNT protocol is unnecessary for viable interaction between NFS
	client and server.
	Therefore, the NFS version 4 protocol will not use an ancillary
	protocol for translation from string based path names to a
	filehandle. Two special filehandles will be used as starting points
	for the NFS client.
	4.1.1. Root Filehandle
	The first of the special filehandles is the ROOT filehandle. The
	ROOT filehandle is the "conceptual" root of the filesystem name space
	at the NFS server. The client uses or starts with the ROOT
	filehandle by employing the PUTROOTFH operation. The PUTROOTFH
	operation instructs the server to set the "current" filehandle to the
	ROOT of the server's file tree. Once this PUTROOTFH operation is
	used, the client can then traverse the entirety of the server's file
	tree with the LOOKUP operation. A complete discussion of the server
	name space is in the section "NFS Server Name Space".
	4.1.2. Public Filehandle
	The second special filehandle is the PUBLIC filehandle. Unlike the
	ROOT filehandle, the PUBLIC filehandle may be bound or represent an
	arbitrary filesystem object at the server. The server is responsible
	Draft Specification NFS version 4 Protocol October 2002
	for this binding. It may be that the PUBLIC filehandle and the ROOT
	filehandle refer to the same filesystem object. However, it is up to
	the administrative software at the server and the policies of the
	server administrator to define the binding of the PUBLIC filehandle
	and server filesystem object. The client may not make any
	assumptions about this binding. The client uses the PUBLIC filehandle
	via the PUTPUBFH operation.
	4.2. Filehandle Types
	In the NFS version 2 and 3 protocols, there was one type of
	filehandle with a single set of semantics. This type of filehandle
	is termed "persistent" in NFS Version 4. The semantics of a
	persistent filehandle remain the same as before. A new type of
	filehandle introduced in NFS Version 4 is the "volatile" filehandle,
	which attempts to accommodate certain server environments.
	The volatile filehandle type was introduced to address server
	functionality or implementation issues which make correct
	implementation of a persistent filehandle infeasible. Some server
	environments do not provide a filesystem level invariant that can be
	used to construct a persistent filehandle. The underlying server
	filesystem may not provide the invariant or the server's filesystem
	programming interfaces may not provide access to the needed
	invariant. Volatile filehandles may ease the implementation of
	server functionality such as hierarchical storage management or
	filesystem reorganization or migration. However, the volatile
	filehandle increases the implementation burden for the client.
	Since the client will need to handle persistent and volatile
	filehandles differently, a file attribute is defined which may be
	used by the client to determine the filehandle types being returned
	by the server.
	4.2.1. General Properties of a Filehandle
	The filehandle contains all the information the server needs to
	distinguish an individual file. To the client, the filehandle is
	opaque. The client stores filehandles for use in a later request and
	can compare two filehandles from the same server for equality by
	doing a byte-by-byte comparison. However, the client MUST NOT
	otherwise interpret the contents of filehandles. If two filehandles
	from the same server are equal, they MUST refer to the same file.
	Servers SHOULD try to maintain a one-to-one correspondence between
	filehandles and files but this is not required. Clients MUST use
	filehandle comparisons only to improve performance, not for correct
	behavior. All clients need to be prepared for situations in which it
	cannot be determined whether two filehandles denote the same object
	and in such cases, avoid making invalid assumptions which might cause
	incorrect behavior. Further discussion of filehandle and attribute
	Draft Specification NFS version 4 Protocol October 2002
	comparison in the context of data caching is presented in the section
	"Data Caching and File Identity".
	As an example, in the case that two different path names when
	traversed at the server terminate at the same filesystem object, the
	server SHOULD return the same filehandle for each path. This can
	occur if a hard link is used to create two file names which refer to
	the same underlying file object and associated data. For example, if
	paths /a/b/c and /a/d/c refer to the same file, the server SHOULD
	return the same filehandle for both path names traversals.
	4.2.2. Persistent Filehandle
	A persistent filehandle is defined as having a fixed value for the
	lifetime of the filesystem object to which it refers. Once the
	server creates the filehandle for a filesystem object, the server
	MUST accept the same filehandle for the object for the lifetime of
	the object. If the server restarts or reboots the NFS server must
	honor the same filehandle value as it did in the server's previous
	instantiation. Similarly, if the filesystem is migrated, the new NFS
	server must honor the same filehandle as the old NFS server.
	The persistent filehandle will be become stale or invalid when the
	filesystem object is removed. When the server is presented with a
	persistent filehandle that refers to a deleted object, it MUST return
	an error of NFS4ERR_STALE. A filehandle may become stale when the
	filesystem containing the object is no longer available. The file
	system may become unavailable if it exists on removable media and the
	media is no longer available at the server or the filesystem in whole
	has been destroyed or the filesystem has simply been removed from the
	server's name space (i.e. unmounted in a UNIX environment).
	4.2.3. Volatile Filehandle
	A volatile filehandle does not share the same longevity
	characteristics of a persistent filehandle. The server may determine
	that a volatile filehandle is no longer valid at many different
	points in time. If the server can definitively determine that a
	volatile filehandle refers to an object that has been removed, the
	server should return NFS4ERR_STALE to the client (as is the case for
	persistent filehandles). In all other cases where the server
	determines that a volatile filehandle can no longer be used, it
	should return an error of NFS4ERR_FHEXPIRED.
	The mandatory attribute "fh_expire_type" is used by the client to
	determine what type of filehandle the server is providing for a
	particular filesystem. This attribute is a bitmask with the
	following values:
	Draft Specification NFS version 4 Protocol October 2002
	FH4_PERSISTENT
	The value of FH4_PERSISTENT is used to indicate a persistent
	filehandle, which is valid until the object is removed from the
	filesystem. The server will not return NFS4ERR_FHEXPIRED for
	this filehandle. FH4_PERSISTENT is defined as a value in which
	none of the bits specified below are set.
	FH4_VOLATILE_ANY
	The filehandle may expire at any time, except as specifically
	excluded (i.e. FH4_NO_EXPIRE_WITH_OPEN).
	FH4_NOEXPIRE_WITH_OPEN
	May only be set when FH4_VOLATILE_ANY is set. If this bit is
	set, then the meaning of FH4_VOLATILE_ANY is qualified to
	exclude any expiration of the filehandle when it is open.
	FH4_VOL_MIGRATION
	The filehandle will expire as a result of migration. If
	FH4_VOL_ANY is set, FH4_VOL_MIGRATION is redundant.
	FH4_VOL_RENAME
	The filehandle will expire during rename. This includes a
	rename by the requesting client or a rename by any other client.
	If FH4_VOL_ANY is set, FH4_VOL_RENAME is redundant.
	Servers which provide volatile filehandles that may expire while
	open (i.e. if FH4_VOL_MIGRATION or FH4_VOL_RENAME is set or if
	FH4_VOLATILE_ANY is set and FH4_NOEXPIRE_WITH_OPEN not set),
	should deny a RENAME or REMOVE that would affect an OPEN file of
	any of the components leading to the OPEN file. In addition,
	the server should deny all RENAME or REMOVE requests during the
	grace period upon server restart.
	Note that the bits FH4_VOL_MIGRATION and FH4_VOL_RENAME allow
	the client to determine that expiration has occurred whenever a
	specific event occurs, without an explicit filehandle expiration
	error from the server. FH4_VOL_ANY does not provide this form
	of information. In situations where the server will expire many,
	but not all filehandles upon migration (e.g. all but those that
	are open), FH4_VOLATILE_ANY (in this case with
	FH4_NOEXPIRE_WITH_OPEN) is a better choice since the client may
	not assume that all filehandles will expire when migration
	occurs, and it is likely that additional expirations will occur
	(as a result of file CLOSE) that are separated in time from the
	migration event itself.
	4.2.4. One Method of Constructing a Volatile Filehandle
	A volatile filehandle, while opaque to the client could contain:
	[volatile bit = 1 | server boot time | slot | generation number]
	Draft Specification NFS version 4 Protocol October 2002
	o slot is an index in the server volatile filehandle table
	o generation number is the generation number for the table
	entry/slot
	When the client presents a volatile filehandle, the server makes the
	following checks, which assume that the check for the volatile bit
	has passed. If the server boot time is less than the current server
	boot time, return NFS4ERR_FHEXPIRED. If slot is out of range, return
	NFS4ERR_BADHANDLE. If the generation number does not match, return
	NFS4ERR_FHEXPIRED.
	When the server reboots, the table is gone (it is volatile).
	If volatile bit is 0, then it is a persistent filehandle with a
	different structure following it.
	4.3. Client Recovery from Filehandle Expiration
	If possible, the client SHOULD recover from the receipt of an
	NFS4ERR_FHEXPIRED error. The client must take on additional
	responsibility so that it may prepare itself to recover from the
	expiration of a volatile filehandle. If the server returns
	persistent filehandles, the client does not need these additional
	steps.
	For volatile filehandles, most commonly the client will need to store
	the component names leading up to and including the filesystem object
	in question. With these names, the client should be able to recover
	by finding a filehandle in the name space that is still available or
	by starting at the root of the server's filesystem name space.
	If the expired filehandle refers to an object that has been removed
	from the filesystem, obviously the client will not be able to recover
	from the expired filehandle.
	It is also possible that the expired filehandle refers to a file that
	has been renamed. If the file was renamed by another client, again
	it is possible that the original client will not be able to recover.
	However, in the case that the client itself is renaming the file and
	the file is open, it is possible that the client may be able to
	recover. The client can determine the new path name based on the
	processing of the rename request. The client can then regenerate the
	new filehandle based on the new path name. The client could also use
	the compound operation mechanism to construct a set of operations
	like:
	RENAME A B
	LOOKUP B
	GETFH
	Note that the COMPOUND procedure does not provide atomicity. This
	example only reduces the overhead of recovering from an expired
	Draft Specification NFS version 4 Protocol October 2002
	filehandle.
	Draft Specification NFS version 4 Protocol October 2002
	5. File Attributes
	To meet the requirements of extensibility and increased
	interoperability with non-UNIX platforms, attributes must be handled
	in a flexible manner. The NFS version 3 fattr3 structure contains a
	fixed list of attributes that not all clients and servers are able to
	support or care about. The fattr3 structure can not be extended as
	new needs arise and it provides no way to indicate non-support. With
	the NFS version 4 protocol, the client is able query what attributes
	the server supports and construct requests with only those supported
	attributes (or a subset thereof).
	To this end, attributes are divided into three groups: mandatory,
	recommended, and named. Both mandatory and recommended attributes
	are supported in the NFS version 4 protocol by a specific and well-
	defined encoding and are identified by number. They are requested by
	setting a bit in the bit vector sent in the GETATTR request; the
	server response includes a bit vector to list what attributes were
	returned in the response. New mandatory or recommended attributes
	may be added to the NFS protocol between major revisions by
	publishing a standards-track RFC which allocates a new attribute
	number value and defines the encoding for the attribute. See the
	section "Minor Versioning" for further discussion.
	Named attributes are accessed by the new OPENATTR operation, which
	accesses a hidden directory of attributes associated with a file
	system object. OPENATTR takes a filehandle for the object and
	returns the filehandle for the attribute hierarchy. The filehandle
	for the named attributes is a directory object accessible by LOOKUP
	or READDIR and contains files whose names represent the named
	attributes and whose data bytes are the value of the attribute. For
	example:
	LOOKUP "foo" ; look up file
	GETATTR attrbits
	OPENATTR ; access foo's named attributes
	LOOKUP "x11icon" ; look up specific attribute
	READ 0,4096 ; read stream of bytes
	Named attributes are intended for data needed by applications rather
	than by an NFS client implementation. NFS implementors are strongly
	encouraged to define their new attributes as recommended attributes
	by bringing them to the IETF standards-track process.
	The set of attributes which are classified as mandatory is
	deliberately small since servers must do whatever it takes to support
	them. A server should support as many of the recommended attributes
	as possible but by their definition, the server is not required to
	support all of them. Attributes are deemed mandatory if the data is
	both needed by a large number of clients and is not otherwise
	Draft Specification NFS version 4 Protocol October 2002
	reasonably computable by the client when support is not provided on
	the server.
	Note that the hidden directory returned by OPENATTR is a convenience
	for protocol processing. The client should not make any assumptions
	about the server's implementation of named attributes and whether the
	underlying filesystem at the server has a named attribute directory
	or not. Therefore, operations such as SETATTR and GETATTR on the
	named attribute directory are undefined.
	5.1. Mandatory Attributes
	These MUST be supported by every NFS version 4 client and server in
	order to ensure a minimum level of interoperability. The server must
	store and return these attributes and the client must be able to
	function with an attribute set limited to these attributes. With
	just the mandatory attributes some client functionality may be
	impaired or limited in some ways. A client may ask for any of these
	attributes to be returned by setting a bit in the GETATTR request and
	the server must return their value.
	5.2. Recommended Attributes
	These attributes are understood well enough to warrant support in the
	NFS version 4 protocol. However, they may not be supported on all
	clients and servers. A client may ask for any of these attributes to
	be returned by setting a bit in the GETATTR request but must handle
	the case where the server does not return them. A client may ask for
	the set of attributes the server supports and should not request
	attributes the server does not support. A server should be tolerant
	of requests for unsupported attributes and simply not return them
	rather than considering the request an error. It is expected that
	servers will support all attributes they comfortably can and only
	fail to support attributes which are difficult to support in their
	operating environments. A server should provide attributes whenever
	they don't have to "tell lies" to the client. For example, a file
	modification time should be either an accurate time or should not be
	supported by the server. This will not always be comfortable to
	clients but the client is better positioned decide whether and how to
	fabricate or construct an attribute or whether to do without the
	attribute.
	5.3. Named Attributes
	These attributes are not supported by direct encoding in the NFS
	Version 4 protocol but are accessed by string names rather than
	numbers and correspond to an uninterpreted stream of bytes which are
	stored with the filesystem object. The name space for these
	Draft Specification NFS version 4 Protocol October 2002
	attributes may be accessed by using the OPENATTR operation. The
	OPENATTR operation returns a filehandle for a virtual "attribute
	directory" and further perusal of the name space may be done using
	READDIR and LOOKUP operations on this filehandle. Named attributes
	may then be examined or changed by normal READ and WRITE and CREATE
	operations on the filehandles returned from READDIR and LOOKUP.
	Named attributes may have attributes.
	It is recommended that servers support arbitrary named attributes. A
	client should not depend on the ability to store any named attributes
	in the server's filesystem. If a server does support named
	attributes, a client which is also able to handle them should be able
	to copy a file's data and meta-data with complete transparency from
	one location to another; this would imply that names allowed for
	regular directory entries are valid for named attribute names as
	well.
	Names of attributes will not be controlled by this document or other
	IETF standards track documents. See the section "IANA
	Considerations" for further discussion.
	5.4. Classification of Attributes
	Each of the Mandatory and Recommended attributes can be classified in
	one of three categories: per server, per filesystem, or per
	filesystem object. Note that it is possible that some per filesystem
	attributes may vary within the filesystem. See the "homogeneous"
	attribute for its definition. Note that the attributes
	time_access_set and time_modify_set are not listed in this section
	because they are write-only attributes corresponding to time_access
	and time_modify, and are used in a special instance of SETATTR.
	o The per server attribute is:
	lease_time
	o The per filesystem attributes are:
	supp_attr, fh_expire_type, link_support, symlink_support,
	unique_handles, aclsupport, cansettime, case_insensitive,
	case_preserving, chown_restricted, files_avail, files_free,
	files_total, fs_locations, homogeneous, maxfilesize, maxname,
	maxread, maxwrite, no_trunc, space_avail, space_free,
	space_total, time_delta
	o The per filesystem object attributes are:
	type, change, size, named_attr, fsid, rdattr_error, filehandle,
	ACL, archive, fileid, hidden, maxlink, mimetype, mode, numlinks,
	owner, owner_group, rawdev, space_used, system, time_access,
	time_backup, time_create, time_metadata, time_modify,
	Draft Specification NFS version 4 Protocol October 2002
	mounted_on_fileid
	For quota_avail_hard, quota_avail_soft, and quota_used see their
	definitions below for the appropriate classification.
	Draft Specification NFS version 4 Protocol October 2002
	5.5. Mandatory Attributes - Definitions
	Name # DataType Access Description
	___________________________________________________________________
	supp_attr 0 bitmap READ The bit vector which
	would retrieve all
	mandatory and
	recommended attributes
	that are supported for
	this object. The
	scope of this
	attribute applies to
	all objects with a
	matching fsid.
	type 1 nfs4_ftype READ The type of the object
	(file, directory,
	symlink, etc.)
	fh_expire_type 2 uint32 READ Server uses this to
	specify filehandle
	expiration behavior to
	the client. See the
	section "Filehandles"
	for additional
	description.
	change 3 uint64 READ A value created by the
	server that the client
	can use to determine
	if file data,
	directory contents or
	attributes of the
	object have been
	modified. The server
	may return the
	object's time_metadata
	attribute for this
	attribute's value but
	only if the filesystem
	object can not be
	updated more
	frequently than the
	resolution of
	time_metadata.
	size 4 uint64 R/W The size of the object
	in bytes.
	Draft Specification NFS version 4 Protocol October 2002
	link_support 5 bool READ True, if the object's
	filesystem supports
	hard links.
	symlink_support 6 bool READ True, if the object's
	filesystem supports
	symbolic links.
	named_attr 7 bool READ True, if this object
	has named attributes.
	In other words, object
	has a non-empty named
	attribute directory.
	fsid 8 fsid4 READ Unique filesystem
	identifier for the
	filesystem holding
	this object. fsid
	contains major and
	minor components each
	of which are uint64.
	unique_handles 9 bool READ True, if two distinct
	filehandles guaranteed
	to refer to two
	different filesystem
	objects.
	lease_time 10 nfs_lease4 READ Duration of leases at
	server in seconds.
	rdattr_error 11 enum READ Error returned from
	getattr during
	readdir.
	filehandle 19 nfs_fh4 READ The filehandle of this
	object (primarily for
	readdir requests).
	Draft Specification NFS version 4 Protocol October 2002
	5.6. Recommended Attributes - Definitions
	Name # Data Type Access Description
	______________________________________________________________________
	ACL 12 nfsace4<> R/W The access control
	list for the object.
	aclsupport 13 uint32 READ Indicates what types
	of ACLs are supported
	on the current
	filesystem.
	archive 14 bool R/W True, if this file
	has been archived
	since the time of
	last modification
	(deprecated in favor
	of time_backup).
	cansettime 15 bool READ True, if the server
	able to change the
	times for a
	filesystem object as
	specified in a
	SETATTR operation.
	case_insensitive 16 bool READ True, if filename
	comparisons on this
	filesystem are case
	insensitive.
	case_preserving 17 bool READ True, if filename
	case on this
	filesystem are
	preserved.
	chown_restricted 18 bool READ If TRUE, the server
	will reject any
	request to change
	either the owner or
	the group associated
	with a file if the
	caller is not a
	privileged user (for
	example, "root" in
	UNIX operating
	environments or in
	Windows 2000 the
	"Take Ownership"
	privilege).
	Draft Specification NFS version 4 Protocol October 2002
	fileid 20 uint64 READ A number uniquely
	identifying the file
	within the
	filesystem.
	files_avail 21 uint64 READ File slots available
	to this user on the
	filesystem containing
	this object - this
	should be the
	smallest relevant
	limit.
	files_free 22 uint64 READ Free file slots on
	the filesystem
	containing this
	object - this should
	be the smallest
	relevant limit.
	files_total 23 uint64 READ Total file slots on
	the filesystem
	containing this
	object.
	fs_locations 24 fs_locations READ Locations where this
	filesystem may be
	found. If the server
	returns NFS4ERR_MOVED
	as an error, this
	attribute MUST be
	supported.
	hidden 25 bool R/W True, if the file is
	considered hidden
	with respect to the
	Windows API?
	homogeneous 26 bool READ True, if this
	object's filesystem
	is homogeneous, i.e.
	are per filesystem
	attributes the same
	for all filesystem's
	objects.
	maxfilesize 27 uint64 READ Maximum supported
	file size for the
	filesystem of this
	object.
	Draft Specification NFS version 4 Protocol October 2002
	maxlink 28 uint32 READ Maximum number of
	links for this
	object.
	maxname 29 uint32 READ Maximum filename size
	supported for this
	object.
	maxread 30 uint64 READ Maximum read size
	supported for this
	object.
	maxwrite 31 uint64 READ Maximum write size
	supported for this
	object. This
	attribute SHOULD be
	supported if the file
	is writable. Lack of
	this attribute can
	lead to the client
	either wasting
	bandwidth or not
	receiving the best
	performance.
	mimetype 32 utf8<> R/W MIME body
	type/subtype of this
	object.
	mode 33 mode4 R/W UNIX-style mode and
	permission bits for
	this object.
	no_trunc 34 bool READ True, if a name
	longer than name_max
	is used, an error be
	returned and name is
	not truncated.
	numlinks 35 uint32 READ Number of hard links
	to this object.
	owner 36 utf8<> R/W The string name of
	the owner of this
	object.
	owner_group 37 utf8<> R/W The string name of
	the group ownership
	of this object.
	Draft Specification NFS version 4 Protocol October 2002
	quota_avail_hard 38 uint64 READ For definition see
	"Quota Attributes"
	section below.
	quota_avail_soft 39 uint64 READ For definition see
	"Quota Attributes"
	section below.
	quota_used 40 uint64 READ For definition see
	"Quota Attributes"
	section below.
	rawdev 41 specdata4 READ Raw device
	identifier. UNIX
	device major/minor
	node information. If
	the value of type is
	not NF4BLK or NF4CHR,
	the value return
	SHOULD NOT be
	considered useful.
	space_avail 42 uint64 READ Disk space in bytes
	available to this
	user on the
	filesystem containing
	this object - this
	should be the
	smallest relevant
	limit.
	space_free 43 uint64 READ Free disk space in
	bytes on the
	filesystem containing
	this object - this
	should be the
	smallest relevant
	limit.
	space_total 44 uint64 READ Total disk space in
	bytes on the
	filesystem containing
	this object.
	space_used 45 uint64 READ Number of filesystem
	bytes allocated to
	this object.
	Draft Specification NFS version 4 Protocol October 2002
	system 46 bool R/W True, if this file is
	a "system" file with
	respect to the
	Windows API?
	time_access 47 nfstime4 READ The time of last
	access to the object
	by a read that was
	satisfied by the
	server.
	time_access_set 48 settime4 WRITE Set the time of last
	access to the object.
	SETATTR use only.
	time_backup 49 nfstime4 R/W The time of last
	backup of the object.
	time_create 50 nfstime4 R/W The time of creation
	of the object. This
	attribute does not
	have any relation to
	the traditional UNIX
	file attribute
	"ctime" or "change
	time".
	time_delta 51 nfstime4 READ Smallest useful
	server time
	granularity.
	time_metadata 52 nfstime4 READ The time of last
	meta-data
	modification of the
	object.
	time_modify 53 nfstime4 READ The time of last
	modification to the
	object.
	time_modify_set 54 settime4 WRITE Set the time of last
	modification to the
	object. SETATTR use
	only.
	mounted_on_fileid 55 uint64 READ Like fileid, but if
	the target filehandle
	is the root of a
	filesystem return the
	fileid of the
	underlying directory.
	Draft Specification NFS version 4 Protocol October 2002
	5.7. Time Access
	As defined above, the time_access attribute represents the time of
	last access to the object by a read that was satisfied by the server.
	The notion of what is an "access" depends on server's operating
	environment and/or the server's filesystem semantics. For example,
	for servers obeying POSIX semantics, time_access would be updated
	only by the READLINK, READ, and READDIR operations and not any of the
	operations that modify the content of the object. Of course, setting
	the corresponding time_access_set attribute is another way to modify
	the time_access attribute.
	Whenever the file object resides on a writable filesystem, the server
	should make best efforts to record time_access into stable storage.
	However, to mitigate the performance effects of doing so, and most
	especially whenever the server is satisfying the read of the object's
	content from its cache, the server MAY cache access time updates and
	lazily write them to stable storage. It is also acceptable to give
	administrators of the server the option to disable time_access
	updates.
	5.8. Interpreting owner and owner_group
	The recommended attributes "owner" and "owner_group" (and also users
	and groups within the "acl" attribute) are represented in terms of a
	UTF-8 string. To avoid a representation that is tied to a particular
	underlying implementation at the client or server, the use of the
	UTF-8 string has been chosen. Note that section 6.1 of [RFC2624]
	provides additional rationale. It is expected that the client and
	server will have their own local representation of owner and
	owner_group that is used for local storage or presentation to the end
	user. Therefore, it is expected that when these attributes are
	transferred between the client and server that the local
	representation is translated to a syntax of the form
	"user@dns_domain". This will allow for a client and server that do
	not use the same local representation the ability to translate to a
	common syntax that can be interpreted by both.
	Similarly, security principals may be represented in different ways
	by different security mechanisms. Servers normally translate these
	representations into a common format, generally that used by local
	storage, to serve as a means of identifying the users corresponding
	to these security principals. When these local identifiers are
	translated to the form of the owner attribute, associated with files
	created by such principals they identify, in a common format, the
	users associated with each corresponding set of security principals.
	The translation used to interpret owner and group strings is not
	specified as part of the protocol. This allows various solutions to
	be employed. For example, a local translation table may be consulted
	that maps between a numeric id to the user@dns_domain syntax. A name
	Draft Specification NFS version 4 Protocol October 2002
	service may also be used to accomplish the translation. A server may
	provide a more general service, not limited by any particular
	translation (which would only translate a limited set of possible
	strings) by storing the owner and owner_group attributes in local
	storage without any translation or it may augment a translation
	method by storing the entire string for attributes for which no
	translation is available while using the local representation for
	those cases in which a translation is available.
	Servers that do not provide support for all possible values of the
	owner and owner_group attributes, should return an error
	(NFS4ERR_BADOWNER) when a string is presented that has no
	translation, as the value to be set for a SETATTR of the owner,
	owner_group, or acl attributes. When a server does accept an owner
	or owner_group value as valid on a SETATTR (and similarly for the
	owner and group strings in an acl), it is promising to return that
	same string when a corresponding GETATTR is done. Configuration
	changes and ill-constructed name translations (those that contain
	aliasing) may make that promise impossible to honor. Servers should
	make appropriate efforts to avoid a situation in which these
	attributes have their values changed when no real change to ownership
	has occurred.
	The "dns_domain" portion of the owner string is meant to be a DNS
	domain name. For example, user@ietf.org. Servers should accept as
	valid a set of users for at least one domain. A server may treat
	other domains as having no valid translations. A more general
	service is provided when a server is capable of accepting users for
	multiple domains, or for all domains, subject to security
	constraints.
	In the case where there is no translation available to the client or
	server, the attribute value must be constructed without the "@".
	Therefore, the absence of the @ from the owner or owner_group
	attribute signifies that no translation was available at the sender
	and that the receiver of the attribute should not use that string as
	a basis for translation into its own internal format. Even though
	the attribute value can not be translated, it may still be useful.
	In the case of a client, the attribute string may be used for local
	display of ownership.
	To provide a greater degree of compatibility with previous versions
	of NFS (i.e. v2 and v3), which identified users and groups by 32-bit
	unsigned uid's and gid's, owner and group strings that consist of
	decimal numeric values with no leading zeros can be given a special
	interpretation by clients and servers which choose to provide such
	support. The receiver may treat such a user or group string as
	representing the same user as would be represented by a v2/v3 uid or
	gid having the corresponding numeric value. A server is not
	obligated to accept such a string, but may return an NFS4ERR_BADOWNER
	instead. To avoid this mechanism being used to subvert user and
	group translation, so that a client might pass all of the owners and
	Draft Specification NFS version 4 Protocol October 2002
	groups in numeric form, a server SHOULD return an NFS4ERR_BADOWNER
	error when there is a valid translation for the user or owner
	designated in this way. In that case, the client must use the
	appropriate name@domain string and not the special form for
	compatibility.
	The owner string "nobody" may be used to designate an anonymous user,
	which will be associated with a file created by a security principal
	that cannot be mapped through normal means to the owner attribute.
	5.9. Character Case Attributes
	With respect to the case_insensitive and case_preserving attributes,
	each UCS-4 character (which UTF-8 encodes) has a "long descriptive
	name" [RFC1345] which may or may not included the word "CAPITAL" or
	"SMALL". The presence of SMALL or CAPITAL allows an NFS server to
	implement unambiguous and efficient table driven mappings for case
	insensitive comparisons, and non-case-preserving storage. For
	general character handling and internationalization issues, see the
	section "Internationalization".
	5.10. Quota Attributes
	For the attributes related to filesystem quotas, the following
	definitions apply:
	quota_avail_soft
	The value in bytes which represents the amount of additional
	disk space that can be allocated to this file or directory
	before the user may reasonably be warned. It is understood that
	this space may be consumed by allocations to other files or
	directories though there is a rule as to which other files or
	directories.
	quota_avail_hard
	The value in bytes which represent the amount of additional disk
	space beyond the current allocation that can be allocated to
	this file or directory before further allocations will be
	refused. It is understood that this space may be consumed by
	allocations to other files or directories.
	quota_used
	The value in bytes which represent the amount of disc space used
	by this file or directory and possibly a number of other similar
	files or directories, where the set of "similar" meets at least
	the criterion that allocating space to any file or directory in
	the set will reduce the "quota_avail_hard" of every other file
	or directory in the set.
	Draft Specification NFS version 4 Protocol October 2002
	Note that there may be a number of distinct but overlapping sets
	of files or directories for which a quota_used value is
	maintained. E.g. "all files with a given owner", "all files with
	a given group owner". etc.
	The server is at liberty to choose any of those sets but should
	do so in a repeatable way. The rule may be configured per-
	filesystem or may be "choose the set with the smallest quota".
	5.11. Access Control Lists
	The NFS version 4 ACL attribute is an array of access control entries
	(ACE). There are various access control entry types, as defined in
	the Section "ACE type". The server is able to communicate which ACE
	types are supported by returning the appropriate value within the
	aclsupport attribute. Each ACE covers one or more operations on a
	file or directory as described in the Section "ACE Access Mask". It
	may also contain one or more flags that modify the semantics of the
	ACE as defined in the Section "ACE flag".
	The NFS ACE attribute is defined as follows:
	typedef uint32_t acetype4;
	typedef uint32_t aceflag4;
	typedef uint32_t acemask4;
	struct nfsace4 {
	acetype4 type;
	aceflag4 flag;
	acemask4 access_mask;
	utf8string who;
	};
	To determine if a request succeeds, each nfsace4 entry is processed
	in order by the server. Only ACEs which have a "who" that matches
	the requester are considered. Each ACE is processed until all of the
	bits of the requester's access have been ALLOWED. Once a bit (see
	below) has been ALLOWED by an ACCESS_ALLOWED_ACE, it is no longer
	considered in the processing of later ACEs. If an ACCESS_DENIED_ACE
	is encountered where the requester's access still has unALLOWED bits
	in common with the "access_mask" of the ACE, the request is denied.
	However, unlike the ALLOWED and DENIED ACE types, the ALARM and AUDIT
	ACE types do not affect a requester's access, and instead are for
	triggering events as a result of a requester's access attempt.
	Therefore, all AUDIT and ALARM ACEs are processed until end of the
	ACL. When the ACL is fully processed, if there are bits in
	requester's mask that have not been considered whether the server
	allows or denies the access is undefined. If there is a mode
	attribute on the file, then this cannot happen, since the mode's
	Draft Specification NFS version 4 Protocol October 2002
	MODE4_*OTH bits will map to EVERYONE@ ACEs that unambiguously specify
	the requester's access.
	The NFS version 4 ACL model is quite rich. Some server platforms may
	provide access control functionality that goes beyond the UNIX-style
	mode attribute, but which is not as rich as the NFS ACL model. So
	that users can take advantage of this more limited functionality, the
	server may indicate that it supports ACLs as long as it follows the
	guidelines for mapping between its ACL model and the NFS version 4
	ACL model.
	The situation is complicated by the fact that a server may have
	multiple modules that enforce ACLs. For example, the enforcement for
	NFS version 4 access may be different from the enforcement for local
	access, and both may be different from the enforcement for access
	through other protocols such as SMB. So it may be useful for a
	server to accept an ACL even if not all of its modules are able to
	support it.
	The guiding principle in all cases is that the server must not accept
	ACLs that appear to make the file more secure than it really is.
	5.11.1. ACE type
	Type Description
	_____________________________________________________
	ALLOW Explicitly grants the access defined in
	acemask4 to the file or directory.
	DENY Explicitly denies the access defined in
	acemask4 to the file or directory.
	AUDIT LOG (system dependent) any access
	attempt to a file or directory which
	uses any of the access methods specified
	in acemask4.
	ALARM Generate a system ALARM (system
	dependent) when any access attempt is
	made to a file or directory for the
	access methods specified in acemask4.
	A server need not support all of the above ACE types. The bitmask
	constants used to represent the above definitions within the
	aclsupport attribute are as follows:
	const ACL4_SUPPORT_ALLOW_ACL = 0x00000001;
	const ACL4_SUPPORT_DENY_ACL = 0x00000002;
	Draft Specification NFS version 4 Protocol October 2002
	const ACL4_SUPPORT_AUDIT_ACL = 0x00000004;
	const ACL4_SUPPORT_ALARM_ACL = 0x00000008;
	The semantics of the "type" field follow the descriptions provided
	above.
	The constants used for the type field (acetype4) are as follows:
	const ACE4_ACCESS_ALLOWED_ACE_TYPE = 0x00000000;
	const ACE4_ACCESS_DENIED_ACE_TYPE = 0x00000001;
	const ACE4_SYSTEM_AUDIT_ACE_TYPE = 0x00000002;
	const ACE4_SYSTEM_ALARM_ACE_TYPE = 0x00000003;
	Clients should not attempt to set an ACE unless the server claims
	support for that ACE type. If the server receives a request to set
	an ACE that it cannot store, it MUST reject the request with
	NFS4ERR_ATTRNOTSUPP. If the server receives a request to set an ACE
	that it can store but cannot enforce, the server SHOULD reject the
	request with NFS4ERR_ATTRNOTSUPP.
	Example: suppose a server can enforce NFS ACLs for NFS access but
	cannot enforce ACLs for local access. If arbitrary processes can run
	on the server, then the server SHOULD NOT indicate ACL support. On
	the other hand, if only trusted administrative programs run locally,
	then the server may indicate ACL support.
	5.11.2. ACE Access Mask
	The access_mask field contains values based on the following:
	Access Description
	_______________________________________________________________
	READ_DATA Permission to read the data of the file
	LIST_DIRECTORY Permission to list the contents of a
	directory
	WRITE_DATA Permission to modify the file's data
	ADD_FILE Permission to add a new file to a
	directory
	APPEND_DATA Permission to append data to a file
	ADD_SUBDIRECTORY Permission to create a subdirectory to a
	directory
	READ_NAMED_ATTRS Permission to read the named attributes
	of a file
	WRITE_NAMED_ATTRS Permission to write the named attributes
	of a file
	EXECUTE Permission to execute a file
	Draft Specification NFS version 4 Protocol October 2002
	DELETE_CHILD Permission to delete a file or directory
	within a directory
	READ_ATTRIBUTES The ability to read basic attributes
	(non-acls) of a file
	WRITE_ATTRIBUTES Permission to change basic attributes
	(non-acls) of a file
	DELETE Permission to Delete the file
	READ_ACL Permission to Read the ACL
	WRITE_ACL Permission to Write the ACL
	WRITE_OWNER Permission to change the owner
	SYNCHRONIZE Permission to access file locally at the
	server with synchronous reads and writes
	The bitmask constants used for the access mask field are as follows:
	const ACE4_READ_DATA = 0x00000001;
	const ACE4_LIST_DIRECTORY = 0x00000001;
	const ACE4_WRITE_DATA = 0x00000002;
	const ACE4_ADD_FILE = 0x00000002;
	const ACE4_APPEND_DATA = 0x00000004;
	const ACE4_ADD_SUBDIRECTORY = 0x00000004;
	const ACE4_READ_NAMED_ATTRS = 0x00000008;
	const ACE4_WRITE_NAMED_ATTRS = 0x00000010;
	const ACE4_EXECUTE = 0x00000020;
	const ACE4_DELETE_CHILD = 0x00000040;
	const ACE4_READ_ATTRIBUTES = 0x00000080;
	const ACE4_WRITE_ATTRIBUTES = 0x00000100;
	const ACE4_DELETE = 0x00010000;
	const ACE4_READ_ACL = 0x00020000;
	const ACE4_WRITE_ACL = 0x00040000;
	const ACE4_WRITE_OWNER = 0x00080000;
	const ACE4_SYNCHRONIZE = 0x00100000;
	Server implementations need not provide the granularity of control
	that is implied by this list of masks. For example, POSIX-based
	systems might not distinguish APPEND_DATA (the ability to append to a
	file) from WRITE_DATA (the ability to modify existing contents); both
	masks would be tied to a single ``write'' permission. When such a
	server returns attributes to the client, it would show both
	APPEND_DATA and WRITE_DATA if and only if the write permission is
	enabled.
	If a server receives a SETATTR request that it cannot accurately
	implement, it should error in the direction of more restricted
	access. For example, suppose a server cannot distinguish overwriting
	data from appending new data, as described in the previous paragraph.
	If a client submits an ACE where APPEND_DATA is set but WRITE_DATA is
	not (or vice versa), the server should reject the request with
	NFS4ERR_ATTRNOTSUPP. Nonetheless, if the ACE has type DENY, the
	server may silently turn on the other bit, so that both APPEND_DATA
	Draft Specification NFS version 4 Protocol October 2002
	and WRITE_DATA are denied.
	5.11.3. ACE flag
	The "flag" field contains values based on the following descriptions.
	ACE4_FILE_INHERIT_ACE
	Can be placed on a directory and indicates that this ACE should be
	added to each new non-directory file created.
	ACE4_DIRECTORY_INHERIT_ACE
	Can be placed on a directory and indicates that this ACE should be
	added to each new directory created.
	ACE4_INHERIT_ONLY_ACE
	Can be placed on a directory but does not apply to the directory,
	only to newly created files/directories as specified by the above two
	flags.
	ACE4_NO_PROPAGATE_INHERIT_ACE
	Can be placed on a directory. Normally when a new directory is
	created and an ACE exists on the parent directory which is marked
	ACL4_DIRECTORY_INHERIT_ACE, two ACEs are placed on the new directory.
	One for the directory itself and one which is an inheritable ACE for
	newly created directories. This flag tells the server to not place
	an ACE on the newly created directory which is inheritable by
	subdirectories of the created directory.
	ACE4_SUCCESSFUL_ACCESS_ACE_FLAG
	ACL4_FAILED_ACCESS_ACE_FLAG
	The ACE4_SUCCESSFUL_ACCESS_ACE_FLAG (SUCCESS) and
	ACE4_FAILED_ACCESS_ACE_FLAG (FAILED) flag bits relate only to
	ACE4_SYSTEM_AUDIT_ACE_TYPE (AUDIT) and ACE4_SYSTEM_ALARM_ACE_TYPE
	(ALARM) ACE types. If during the processing of the file's ACL, the
	server encounters an AUDIT or ALARM ACE that matches the principal
	attempting the OPEN, the server notes that fact, and the presence, if
	any, of the SUCCESS and FAILED flags encountered in the AUDIT or
	ALARM ACE. Once the server completes the ACL processing, and the
	share reservation processing, and the OPEN call, it then notes if the
	OPEN succeeded or failed. If the OPEN succeeded, and if the SUCCESS
	Draft Specification NFS version 4 Protocol October 2002
	flag was set for a matching AUDIT or ALARM, then the appropriate
	AUDIT or ALARM event occurs. If the OPEN failed, and if the FAILED
	flag was set for the matching AUDIT or ALARM, then the appropriate
	AUDIT or ALARM event occurs. Clearly either or both of the SUCCESS
	or FAILED can be set, but if neither is set, the AUDIT or ALARM ACE
	is not useful.
	The previously described processing applies to that of the ACCESS
	operation as well. The difference being that "success" or "failure"
	does not mean whether ACCESS returns NFS4_OK or not. Success means
	whether ACCESS returns all requested and supported bits. Failure
	means whether ACCESS failed to return a bit that was requested and
	supported.
	ACE4_IDENTIFIER_GROUP
	Indicates that the "who" refers to a GROUP as defined under UNIX.
	The bitmask constants used for the flag field are as follows:
	const ACE4_FILE_INHERIT_ACE = 0x00000001;
	const ACE4_DIRECTORY_INHERIT_ACE = 0x00000002;
	const ACE4_NO_PROPAGATE_INHERIT_ACE = 0x00000004;
	const ACE4_INHERIT_ONLY_ACE = 0x00000008;
	const ACE4_SUCCESSFUL_ACCESS_ACE_FLAG = 0x00000010;
	const ACE4_FAILED_ACCESS_ACE_FLAG = 0x00000020;
	const ACE4_IDENTIFIER_GROUP = 0x00000040;
	A server need not support any of these flags. If the server supports
	flags that are similar to, but not exactly the same as, these flags,
	the implementation may define a mapping between the protocol-defined
	flags and the implementation-defined flags. Again, the guiding
	principle is that the file not appear to be more secure than it
	really is.
	For example, suppose a client tries to set an ACE with
	ACE4_FILE_INHERIT_ACE set but not ACE4_DIRECTORY_INHERIT_ACE. If the
	server does not support any form of ACL inheritance, the server
	should reject the request with NFS4ERR_ATTRNOTSUPP. If the server
	supports a single "inherit ACE" flag that applies to both files and
	directories, the server may reject the request (i.e., requiring the
	client to set both the file and directory inheritance flags). The
	server may also accept the request and silently turn on the
	ACE4_DIRECTORY_INHERIT_ACE flag.
	5.11.4. ACE who
	There are several special identifiers ("who") which need to be
	Draft Specification NFS version 4 Protocol October 2002
	understood universally, rather than in the context of a particular
	DNS domain. Some of these identifiers cannot be understood when an
	NFS client accesses the server, but have meaning when a local process
	accesses the file. The ability to display and modify these
	permissions is permitted over NFS, even if none of the access methods
	on the server understands the identifiers.
	Who Description
	_______________________________________________________________
	"OWNER" The owner of the file.
	"GROUP" The group associated with the file.
	"EVERYONE" The world.
	"INTERACTIVE" Accessed from an interactive terminal.
	"NETWORK" Accessed via the network.
	"DIALUP" Accessed as a dialup user to the server.
	"BATCH" Accessed from a batch job.
	"ANONYMOUS" Accessed without any authentication.
	"AUTHENTICATED" Any authenticated user (opposite of
	ANONYMOUS)
	"SERVICE" Access from a system service.
	To avoid conflict, these special identifiers are distinguish by an
	appended "@" and should appear in the form "xxxx@" (note: no domain
	name after the "@"). For example: ANONYMOUS@.
	5.11.5. Mode Attribute
	The NFS version 4 mode attribute is based on the UNIX mode bits. The
	following bits are defined:
	const MODE4_SUID = 0x800; /* set user id on execution */
	const MODE4_SGID = 0x400; /* set group id on execution */
	const MODE4_SVTX = 0x200; /* save text even after use */
	const MODE4_RUSR = 0x100; /* read permission: owner */
	const MODE4_WUSR = 0x080; /* write permission: owner */
	const MODE4_XUSR = 0x040; /* execute permission: owner */
	const MODE4_RGRP = 0x020; /* read permission: group */
	const MODE4_WGRP = 0x010; /* write permission: group */
	const MODE4_XGRP = 0x008; /* execute permission: group */
	const MODE4_ROTH = 0x004; /* read permission: other */
	const MODE4_WOTH = 0x002; /* write permission: other */
	const MODE4_XOTH = 0x001; /* execute permission: other */
	Bits MODE4_RUSR, MODE4_WUSR, and MODE4_XUSR apply to the principal
	identified in the owner attribute. Bits MODE4_RGRP, MODE4_WGRP, and
	MODE4_XGRP apply to the principals identified in the owner_group
	attribute. Bits MODE4_ROTH, MODE4_WOTH, MODE4_XOTH apply to any
	principal that does not match that in the owner group, and does not
	Draft Specification NFS version 4 Protocol October 2002
	have a group matching that of the owner_group attribute.
	The remaining bits are not defined by this protocol and MUST NOT be
	used. The minor version mechanism must be used to define further bit
	usage.
	Note that in UNIX, if a file has the MODE4_SGID bit set and no
	MODE4_XGRP bit set, then READ and WRITE must use mandatory file
	locking.
	5.11.6. Mode and ACL Attribute
	The server that supports both mode and ACL must take care to
	synchronize the MODE4_*USR, MODE4_*GRP, and MODE4_*OTH bits with the
	ACEs which have respective who fields of "OWNER@", "GROUP@", and
	"EVERYONE@" so that the client can see semantically equivalent access
	permissions exist whether the client asks for owner, owner_group and
	mode attributes, or for just the ACL.
	Because the mode attribute includes bits (e.g. MODE4_SVTX) that have
	nothing to do with ACL semantics, it is permitted for clients to
	specify both the ACL attribute and mode in the same SETATTR
	operation. However, because there is no prescribed order for
	processing the attributes in a SETATTR, the client must ensure that
	ACL attribute, if specified without mode, would produce the desired
	mode bits, and conversely, the mode attribute if specified without
	ACL, would produce the desired "OWNER@", "GROUP@", and "EVERYONE@"
	ACEs.
	5.11.7. mounted_on_fileid
	UNIX-based operating environments connect a filesystem into the
	namespace by connecting (mounting) the filesystem onto the existing
	file object (the mount point, usually a directory) of an existing
	filesystem. When the mount point's parent directory is read via an
	API like readdir(), the return results are directory entries, each
	with a component name and a fileid. The fileid of the mount point's
	directory entry will be different from the fileid that the stat()
	system call returns. The stat() system call is returning the fileid
	of the root of the mounted filesystem, whereas readdir() is returning
	the fileid stat() would have returned before any filesystems were
	mounted on the mount point.
	Unlike NFS version 3, NFS version 4 allows a client's LOOKUP request
	to cross other filesystems. The client detects the filesystem
	crossing whenever the filehandle argument of LOOKUP has an fsid
	attribute different from that of the filehandle returned by LOOKUP. A
	UNIX-based client will consider this a "mount point crossing". UNIX
	has a legacy scheme for allowing a process to determine its current
	working directory. This relies on readdir() of a mount point's parent
	and stat() of the mount point returning fileids as previously
	Draft Specification NFS version 4 Protocol October 2002
	described. The mounted_on_fileid attribute corresponds to the fileid
	that readdir() would have returned as described previously.
	While the NFS version 4 client could simply fabricate a fileid
	corresponding to what mounted_on_fileid provides (and if the server
	does not support mounted_on_fileid, the client has no choice), there
	is a risk that the client will generate a fileid that conflicts with
	one that is already assigned to another object in the filesystem.
	Instead, if the server can provide the mounted_on_fileid, the
	potential for client operational problems in this area is eliminated.
	If the server detects that there is no mounted point at the target
	file object, then the value for mounted_on_fileid that it returns is
	the same as that of the fileid attribute.
	The mounted_on_fileid attribute is RECOMMENDED, so the server SHOULD
	provide it if possible, and for a UNIX-based server, this is
	straightforward. Usually, mounted_on_fileid will be requested during
	a READDIR operation, in which case it is trivial (at least for UNIX-
	based servers) to return mounted_on_fileid since it is equal to the
	fileid of a directory entry returned by readdir(). If
	mounted_on_fileid is requested in a GETATTR operation, the server
	should obey an invariant that has it returning a value that is equal
	to the file object's entry in the object's parent directory, i.e.
	what readdir() would have returned. Some operating environments
	allow a series of two or more filesystems to be mounted onto a single
	mount point. In this case, for the server to obey the aforementioned
	invariant, it will need to find the base mount point, and not the
	intermediate mount points.
	Draft Specification NFS version 4 Protocol October 2002
	6. Filesystem Migration and Replication
	With the use of the recommended attribute "fs_locations", the NFS
	version 4 server has a method of providing filesystem migration or
	replication services. For the purposes of migration and replication,
	a filesystem will be defined as all files that share a given fsid
	(both major and minor values are the same).
	The fs_locations attribute provides a list of filesystem locations.
	These locations are specified by providing the server name (either
	DNS domain or IP address) and the path name representing the root of
	the filesystem. Depending on the type of service being provided, the
	list will provide a new location or a set of alternate locations for
	the filesystem. The client will use this information to redirect its
	requests to the new server.
	6.1. Replication
	It is expected that filesystem replication will be used in the case
	of read-only data. Typically, the filesystem will be replicated on
	two or more servers. The fs_locations attribute will provide the
	list of these locations to the client. On first access of the
	filesystem, the client should obtain the value of the fs_locations
	attribute. If, in the future, the client finds the server
	unresponsive, the client may attempt to use another server specified
	by fs_locations.
	If applicable, the client must take the appropriate steps to recover
	valid filehandles from the new server. This is described in more
	detail in the following sections.
	6.2. Migration
	Filesystem migration is used to move a filesystem from one server to
	another. Migration is typically used for a filesystem that is
	writable and has a single copy. The expected use of migration is for
	load balancing or general resource reallocation. The protocol does
	not specify how the filesystem will be moved between servers. This
	server-to-server transfer mechanism is left to the server
	implementor. However, the method used to communicate the migration
	event between client and server is specified here.
	Once the servers participating in the migration have completed the
	move of the filesystem, the error NFS4ERR_MOVED will be returned for
	subsequent requests received by the original server. The
	NFS4ERR_MOVED error is returned for all operations except PUTFH and
	GETATTR. Upon receiving the NFS4ERR_MOVED error, the client will
	obtain the value of the fs_locations attribute. The client will then
	use the contents of the attribute to redirect its requests to the
	specified server. To facilitate the use of GETATTR, operations such
	Draft Specification NFS version 4 Protocol October 2002
	as PUTFH must also be accepted by the server for the migrated file
	system's filehandles. Note that if the server returns NFS4ERR_MOVED,
	the server MUST support the fs_locations attribute.
	If the client requests more attributes than just fs_locations, the
	server may return fs_locations only. This is to be expected since
	the server has migrated the filesystem and may not have a method of
	obtaining additional attribute data.
	The server implementor needs to be careful in developing a migration
	solution. The server must consider all of the state information
	clients may have outstanding at the server. This includes but is not
	limited to locking/share state, delegation state, and asynchronous
	file writes which are represented by WRITE and COMMIT verifiers. The
	server should strive to minimize the impact on its clients during and
	after the migration process.
	6.3. Interpretation of the fs_locations Attribute
	The fs_location attribute is structured in the following way:
	struct fs_location {
	utf8string server<>;
	pathname4 rootpath;
	};
	struct fs_locations {
	pathname4 fs_root;
	fs_location locations<>;
	};
	The fs_location struct is used to represent the location of a
	filesystem by providing a server name and the path to the root of the
	filesystem. For a multi-homed server or a set of servers that use
	the same rootpath, an array of server names may be provided. An
	entry in the server array is an UTF8 string and represents one of a
	traditional DNS host name, IPv4 address, or IPv6 address. It is not
	a requirement that all servers that share the same rootpath be listed
	in one fs_location struct. The array of server names is provided for
	convenience. Servers that share the same rootpath may also be listed
	in separate fs_location entries in the fs_locations attribute.
	The fs_locations struct and attribute then contains an array of
	locations. Since the name space of each server may be constructed
	differently, the "fs_root" field is provided. The path represented
	by fs_root represents the location of the filesystem in the server's
	name space. Therefore, the fs_root path is only associated with the
	server from which the fs_locations attribute was obtained. The
	fs_root path is meant to aid the client in locating the filesystem at
	the various servers listed.
	Draft Specification NFS version 4 Protocol October 2002
	As an example, there is a replicated filesystem located at two
	servers (servA and servB). At servA the filesystem is located at
	path "/a/b/c". At servB the filesystem is located at path "/x/y/z".
	In this example the client accesses the filesystem first at servA
	with a multi-component lookup path of "/a/b/c/d". Since the client
	used a multi-component lookup to obtain the filehandle at "/a/b/c/d",
	it is unaware that the filesystem's root is located in servA's name
	space at "/a/b/c". When the client switches to servB, it will need
	to determine that the directory it first referenced at servA is now
	represented by the path "/x/y/z/d" on servB. To facilitate this, the
	fs_locations attribute provided by servA would have a fs_root value
	of "/a/b/c" and two entries in fs_location. One entry in fs_location
	will be for itself (servA) and the other will be for servB with a
	path of "/x/y/z". With this information, the client is able to
	substitute "/x/y/z" for the "/a/b/c" at the beginning of its access
	path and construct "/x/y/z/d" to use for the new server.
	See the section "Security Considerations" for a discussion on the
	recommendations for the security flavor to be used by any GETATTR
	operation that requests the "fs_locations" attribute.
	6.4. Filehandle Recovery for Migration or Replication
	Filehandles for filesystems that are replicated or migrated generally
	have the same semantics as for filesystems that are not replicated or
	migrated. For example, if a filesystem has persistent filehandles
	and it is migrated to another server, the filehandle values for the
	filesystem will be valid at the new server.
	For volatile filehandles, the servers involved likely do not have a
	mechanism to transfer filehandle format and content between
	themselves. Therefore, a server may have difficulty in determining
	if a volatile filehandle from an old server should return an error of
	NFS4ERR_FHEXPIRED. Therefore, the client is informed, with the use
	of the fh_expire_type attribute, whether volatile filehandles will
	expire at the migration or replication event. If the bit
	FH4_VOL_MIGRATION is set in the fh_expire_type attribute, the client
	must treat the volatile filehandle as if the server had returned the
	NFS4ERR_FHEXPIRED error. At the migration or replication event in
	the presence of the FH4_VOL_MIGRATION bit, the client will not
	present the original or old volatile filehandle to the new server.
	The client will start its communication with the new server by
	recovering its filehandles using the saved file names.
	Draft Specification NFS version 4 Protocol October 2002
	7. NFS Server Name Space
	7.1. Server Exports
	On a UNIX server the name space describes all the files reachable by
	pathnames under the root directory or "/". On a Windows NT server
	the name space constitutes all the files on disks named by mapped
	disk letters. NFS server administrators rarely make the entire
	server's filesystem name space available to NFS clients. More often
	portions of the name space are made available via an "export"
	feature. In previous versions of the NFS protocol, the root
	filehandle for each export is obtained through the MOUNT protocol;
	the client sends a string that identifies the export of name space
	and the server returns the root filehandle for it. The MOUNT
	protocol supports an EXPORTS procedure that will enumerate the
	server's exports.
	7.2. Browsing Exports
	The NFS version 4 protocol provides a root filehandle that clients
	can use to obtain filehandles for these exports via a multi-component
	LOOKUP. A common user experience is to use a graphical user
	interface (perhaps a file "Open" dialog window) to find a file via
	progressive browsing through a directory tree. The client must be
	able to move from one export to another export via single-component,
	progressive LOOKUP operations.
	This style of browsing is not well supported by the NFS version 2 and
	3 protocols. The client expects all LOOKUP operations to remain
	within a single server filesystem. For example, the device attribute
	will not change. This prevents a client from taking name space paths
	that span exports.
	An automounter on the client can obtain a snapshot of the server's
	name space using the EXPORTS procedure of the MOUNT protocol. If it
	understands the server's pathname syntax, it can create an image of
	the server's name space on the client. The parts of the name space
	that are not exported by the server are filled in with a "pseudo
	filesystem" that allows the user to browse from one mounted
	filesystem to another. There is a drawback to this representation of
	the server's name space on the client: it is static. If the server
	administrator adds a new export the client will be unaware of it.
	7.3. Server Pseudo Filesystem
	NFS version 4 servers avoid this name space inconsistency by
	presenting all the exports within the framework of a single server
	name space. An NFS version 4 client uses LOOKUP and READDIR
	operations to browse seamlessly from one export to another. Portions
	Draft Specification NFS version 4 Protocol October 2002
	of the server name space that are not exported are bridged via a
	"pseudo filesystem" that provides a view of exported directories
	only. A pseudo filesystem has a unique fsid and behaves like a
	normal, read only filesystem.
	Based on the construction of the server's name space, it is possible
	that multiple pseudo filesystems may exist. For example,
	/a pseudo filesystem
	/a/b real filesystem
	/a/b/c pseudo filesystem
	/a/b/c/d real filesystem
	Each of the pseudo filesystems are considered separate entities and
	therefore will have a unique fsid.
	7.4. Multiple Roots
	The DOS and Windows operating environments are sometimes described as
	having "multiple roots". Filesystems are commonly represented as
	disk letters. MacOS represents filesystems as top level names. NFS
	version 4 servers for these platforms can construct a pseudo file
	system above these root names so that disk letters or volume names
	are simply directory names in the pseudo root.
	7.5. Filehandle Volatility
	The nature of the server's pseudo filesystem is that it is a logical
	representation of filesystem(s) available from the server.
	Therefore, the pseudo filesystem is most likely constructed
	dynamically when the server is first instantiated. It is expected
	that the pseudo filesystem may not have an on disk counterpart from
	which persistent filehandles could be constructed. Even though it is
	preferable that the server provide persistent filehandles for the
	pseudo filesystem, the NFS client should expect that pseudo file
	system filehandles are volatile. This can be confirmed by checking
	the associated "fh_expire_type" attribute for those filehandles in
	question. If the filehandles are volatile, the NFS client must be
	prepared to recover a filehandle value (e.g. with a multi-component
	LOOKUP) when receiving an error of NFS4ERR_FHEXPIRED.
	7.6. Exported Root
	If the server's root filesystem is exported, one might conclude that
	a pseudo-filesystem is not needed. This would be wrong. Assume the
	following filesystems on a server:
	/ disk1 (exported)
	/a disk2 (not exported)
	Draft Specification NFS version 4 Protocol October 2002
	/a/b disk3 (exported)
	Because disk2 is not exported, disk3 cannot be reached with simple
	LOOKUPs. The server must bridge the gap with a pseudo-filesystem.
	7.7. Mount Point Crossing
	The server filesystem environment may be constructed in such a way
	that one filesystem contains a directory which is 'covered' or
	mounted upon by a second filesystem. For example:
	/a/b (filesystem 1)
	/a/b/c/d (filesystem 2)
	The pseudo filesystem for this server may be constructed to look
	like:
	/ (place holder/not exported)
	/a/b (filesystem 1)
	/a/b/c/d (filesystem 2)
	It is the server's responsibility to present the pseudo filesystem
	that is complete to the client. If the client sends a lookup request
	for the path "/a/b/c/d", the server's response is the filehandle of
	the filesystem "/a/b/c/d". In previous versions of the NFS protocol,
	the server would respond with the filehandle of directory "/a/b/c/d"
	within the filesystem "/a/b".
	The NFS client will be able to determine if it crosses a server mount
	point by a change in the value of the "fsid" attribute.
	7.8. Security Policy and Name Space Presentation
	The application of the server's security policy needs to be carefully
	considered by the implementor. One may choose to limit the
	viewability of portions of the pseudo filesystem based on the
	server's perception of the client's ability to authenticate itself
	properly. However, with the support of multiple security mechanisms
	and the ability to negotiate the appropriate use of these mechanisms,
	the server is unable to properly determine if a client will be able
	to authenticate itself. If, based on its policies, the server
	chooses to limit the contents of the pseudo filesystem, the server
	may effectively hide filesystems from a client that may otherwise
	have legitimate access.
	As suggested practice, the server should apply the security policy of
	a shared resource in the server's namespace to the components of the
	resource's ancestors. For example:
	/
	Draft Specification NFS version 4 Protocol October 2002
	/a/b
	/a/b/c
	The /a/b/c directory is a real filesystem and is the shared resource.
	The security policy for /a/b/c is Kerberos with integrity. The
	server should apply the same security policy to /, /a, and /a/b.
	This allows for the extension of the protection of the server's
	namespace to the ancestors of the real shared resource.
	For the case of the use of multiple, disjoint security mechanisms in
	the server's resources, the security for a particular object in the
	server's namespace should be the union of all security mechanisms of
	all direct descendants.
	Draft Specification NFS version 4 Protocol October 2002
	8. File Locking and Share Reservations
	Integrating locking into the NFS protocol necessarily causes it to be
	stateful. With the inclusion of share reservations the protocol
	becomes substantially more dependent on state than the traditional
	combination of NFS and NLM [XNFS]. There are three components to
	making this state manageable:
	o Clear division between client and server
	o Ability to reliably detect inconsistency in state between client
	and server
	o Simple and robust recovery mechanisms
	In this model, the server owns the state information. The client
	communicates its view of this state to the server as needed. The
	client is also able to detect inconsistent state before modifying a
	file.
	To support Win32 share reservations it is necessary to atomically
	OPEN or CREATE files. Having a separate share/unshare operation
	would not allow correct implementation of the Win32 OpenFile API. In
	order to correctly implement share semantics, the previous NFS
	protocol mechanisms used when a file is opened or created (LOOKUP,
	CREATE, ACCESS) need to be replaced. The NFS version 4 protocol has
	an OPEN operation that subsumes the NFS version 3 methodology of
	LOOKUP, CREATE, and ACCESS. However, because many operations require
	a filehandle, the traditional LOOKUP is preserved to map a file name
	to filehandle without establishing state on the server. The policy
	of granting access or modifying files is managed by the server based
	on the client's state. These mechanisms can implement policy ranging
	from advisory only locking to full mandatory locking.
	8.1. Locking
	It is assumed that manipulating a lock is rare when compared to READ
	and WRITE operations. It is also assumed that crashes and network
	partitions are relatively rare. Therefore it is important that the
	READ and WRITE operations have a lightweight mechanism to indicate if
	they possess a held lock. A lock request contains the heavyweight
	information required to establish a lock and uniquely define the lock
	owner.
	The following sections describe the transition from the heavy weight
	information to the eventual stateid used for most client and server
	locking and lease interactions.
	8.1.1. Client ID
	For each LOCK request, the client must identify itself to the server.
	Draft Specification NFS version 4 Protocol October 2002
	This is done in such a way as to allow for correct lock
	identification and crash recovery. A sequence of a SETCLIENTID
	operation followed by a SETCLIENTID_CONFIRM operation is required to
	establish the identification onto the server. Establishment of
	identification by a new incarnation of the client also has the effect
	of immediately breaking any leased state that a previous incarnation
	of the client might have had on the server, as opposed to forcing the
	new client incarnation to wait for the leases to expire. Breaking
	the lease state amounts to the server removing all lock, share
	reservation, and, where the server is not supporting the
	CLAIM_DELEGATE_PREV claim type, all delegation state associated with
	same client with the same identity. For discussion of delegation
	state recovery, see the section "Delegation Recovery".
	Client identification is encapsulated in the following structure:
	struct nfs_client_id4 {
	verifier4 verifier;
	opaque id<NFS4_OPAQUE_LIMIT>;
	};
	The first field, verifier is a client incarnation verifier that is
	used to detect client reboots. Only if the verifier is different from
	that the server has previously recorded the client (as identified by
	the second field f the structure, id) does the server start the
	process of canceling the client's leased state.
	The second field, id is a variable length string that uniquely
	defines the client.
	There are several considerations for how the client generates the id
	string:
	o The string should be unique so that multiple clients do not
	present the same string. The consequences of two clients
	presenting the same string range from one client getting an
	error to one client having its leased state abruptly and
	unexpectedly canceled.
	o The string should be selected so the subsequent incarnations
	(e.g. reboots) of the same client cause the client to present
	the same string. The implementor is cautioned from an approach
	that requires the string to be recorded in a local file because
	this precludes the use of the implementation in an environment
	where there is no local disk and all file access is from an NFS
	version 4 server.
	o The string should be different for each server network address
	that the client accesses, rather than common to all server
	network addresses. The reason is that it may not be possible for
	the client to tell if same server is listening on multiple
	network addresses. If the client issues SETCLIENTID with the
	Draft Specification NFS version 4 Protocol October 2002
	same id string to each network address of such a server, the
	server will think it is the same client, and each successive
	SETCLIENTID will cause the server to begin the process of
	removing the client's previous leased state.
	o The algorithm for generating the string should not assume that
	the client's network address won't change. This includes
	changes between client incarnations and even changes while the
	client is stilling running in its current incarnation. This
	means that if the client includes just the client's and server's
	network address in the id string, there is a real risk, after
	the client gives up the network address, that another client,
	using a similar algorithm for generating the id string, will
	generate a conflicting id string.
	Given the above considerations, an example of a well generated id
	string is one that includes:
	o The server's network address.
	o The client's network address.
	o For a user level NFS version 4 client, it should contain
	additional information to distinguish the client from other user
	level clients running on the same host, such as a process id or
	other unique sequence.
	o Additional information that tends to be unique, such as one or
	more of:
	- The client machine's serial number (for privacy reasons, it is
	best to perform some one way function on the serial number).
	- A MAC address.
	- The timestamp of when the NFS version 4 software was first
	installed on the client (though this is subject to the
	previously mentioned caution about using information that is
	stored in a file, because the file might only be accessible
	over NFS version 4).
	- A true random number. However since this number ought to be
	the same between client incarnations, this shares the same
	problem as that of the using the timestamp of the software
	installation.
	As a security measure, the server MUST NOT cancel a client's leased
	state if the principal established the state for a given id string is
	not the same as the principal issuing the SETCLIENTID.
	Note that SETCLIENTID and SETCLIENTID_CONFIRM has a secondary purpose
	Draft Specification NFS version 4 Protocol October 2002
	of establishing the information the server needs to make callbacks to
	the client for purpose of supporting delegations. It is permitted to
	change this information via SETCLIENTID and SETCLIENTID_CONFIRM
	within the same incarnation of the client without removing the
	client's leased state.
	Once a SETCLIENTID and SETCLIENTID_CONFIRM sequence has successfully
	completed, the client uses the short hand client identifier, of type
	clientid4, instead of the longer and less compact nfs_client_id4
	structure. This short hand client identifier (a clientid) is
	assigned by the server and should be chosen so that it will not
	conflict with a clientid previously assigned by the server. This
	applies across server restarts or reboots. When a clientid is
	presented to a server and that clientid is not recognized, as would
	happen after a server reboot, the server will reject the request with
	the error NFS4ERR_STALE_CLIENTID. When this happens, the client must
	obtain a new clientid by use of the SETCLIENTID operation and then
	proceed to any other necessary recovery for the server reboot case
	(See the section "Server Failure and Recovery").
	The client must also employ the SETCLIENTID operation when it
	receives a NFS4ERR_STALE_STATEID error using a stateid derived from
	its current clientid, since this also indicates a server reboot which
	has invalidated the existing clientid (see the next section
	"lock_owner and stateid Definition" for details).
	See the detailed descriptions of SETCLIENTID and SETCLIENTID_CONFIRM
	for a complete specification of the operations.
	8.1.2. Server Release of Clientid
	If the server determines that the client holds no associated state
	for its clientid, the server may choose to release the clientid. The
	server may make this choice for an inactive client so that resources
	are not consumed by those intermittently active clients. If the
	client contacts the server after this release, the server must ensure
	the client receives the appropriate error so that it will use the
	SETCLIENTID/SETCLIENTID_CONFIRM sequence to establish a new identity.
	It should be clear that the server must be very hesitant to release a
	clientid since the resulting work on the client to recover from such
	an event will be the same burden as if the server had failed and
	restarted. Typically a server would not release a clientid unless
	there had been no activity from that client for many minutes.
	Note that if the id string in a SETCLIENTID request is properly
	constructed, and if the client takes care to use the same principal
	for each successive use of SETCLIENTID, then, barring an active
	denial of service attack, NFS4ERR_CLID_INUSE should never be
	returned.
	However, client bugs, server bugs, or perhaps a deliberate change of
	Draft Specification NFS version 4 Protocol October 2002
	the principal owner of the id string (such as the case of a client
	that changes security flavors, and under the new flavor, there is no
	mapping to the previous owner) will in rare cases result in
	NFS4ERR_CLID_INUSE.
	In that event, when the server gets a SETCLIENTID for a client id
	that currently has no state, or it has state, but the lease has
	expired, rather than returning NFS4ERR_CLID_INUSE, the server MUST
	allow the SETCLIENTID, and confirm the new clientid if followed by
	the appropriate SETCLIENTID_CONFIRM.
	8.1.3. lock_owner and stateid Definition
	When requesting a lock, the client must present to the server the
	clientid and an identifier for the owner of the requested lock.
	These two fields are referred to as the lock_owner and the definition
	of those fields are:
	o A clientid returned by the server as part of the client's use of
	the SETCLIENTID operation.
	o A variable length opaque array used to uniquely define the owner
	of a lock managed by the client.
	This may be a thread id, process id, or other unique value.
	When the server grants the lock, it responds with a unique stateid.
	The stateid is used as a shorthand reference to the lock_owner, since
	the server will be maintaining the correspondence between them.
	The server is free to form the stateid in any manner that it chooses
	as long as it is able to recognize invalid and out-of-date stateids.
	This requirement includes those stateids generated by earlier
	instances of the server. From this, the client can be properly
	notified of a server restart. This notification will occur when the
	client presents a stateid to the server from a previous
	instantiation.
	The server must be able to distinguish the following situations and
	return the error as specified:
	o The stateid was generated by an earlier server instance (i.e.
	before a server reboot). The error NFS4ERR_STALE_STATEID should
	be returned.
	o The stateid was generated by the current server instance but the
	stateid no longer designates the current locking state for the
	lockowner-file pair in question (i.e. one or more locking
	operations has occurred). The error NFS4ERR_OLD_STATEID should
	be returned.
	Draft Specification NFS version 4 Protocol October 2002
	This error condition will only occur when the client issues a
	locking request which changes a stateid while an I/O request
	that uses that stateid is outstanding.
	o The stateid was generated by the current server instance but the
	stateid does not designate a locking state for any active
	lockowner-file pair. The error NFS4ERR_BAD_STATEID should be
	returned.
	This error condition will occur when there has been a logic
	error on the part of the client or server. This should not
	happen.
	One mechanism that may be used to satisfy these requirements is for
	the server to,
	o divide the "other" field of each stateid into two fields:
	- A server verifier which uniquely designates a particular
	server instantiation.
	- An index into a table of locking-state structures.
	o utilize the "seqid" field of each stateid, such that seqid is
	monotonically incremented for each stateid that is associated
	with the same index into the locking-state table.
	By matching the incoming stateid and its field values with the state
	held at the server, the server is able to easily determine if a
	stateid is valid for its current instantiation and state. If the
	stateid is not valid, the appropriate error can be supplied to the
	client.
	8.1.4. Use of the stateid and Locking
	All READ, WRITE and SETATTR operations contain a stateid. For the
	purposes of this section, SETATTR operations which change the size
	attribute of a file are treated as if they are writing the area
	between the old and new size (i.e. the range truncated or added to
	the file by means of the SETATTR), even where SETATTR is not
	explicitly mentioned in the text.
	If the lock_owner performs a READ or WRITE in a situation in which it
	has established a lock or share reservation on the server (any OPEN
	constitutes a share reservation) the stateid (previously returned by
	the server) must be used to indicate what locks, including both
	record locks and share reservations, are held by the lockowner. If
	no state is established by the client, either record lock or share
	Draft Specification NFS version 4 Protocol October 2002
	reservation, a stateid of all bits 0 is used. Regardless whether a
	stateid of all bits 0, or a stateid returned by the server is used,
	if there is a conflicting share reservation or mandatory record lock
	held on the file, the server MUST refuse to service the READ or WRITE
	operation.
	Share reservations are established by OPEN operations and by their
	nature are mandatory in that when the OPEN denies READ or WRITE
	operations, that denial results in such operations being rejected
	with error NFS4ERR_LOCKED. Record locks may be implemented by the
	server as either mandatory or advisory, or the choice of mandatory or
	advisory behavior may be determined by the server on the basis of the
	file being accessed (for example, some UNIX-based servers support a
	"mandatory lock bit" on the mode attribute such that if set, record
	locks are required on the file before I/O is possible). When record
	locks are advisory, they only prevent the granting of conflicting
	lock requests and have no effect on READs or WRITEs. Mandatory
	record locks, however, prevent conflicting I/O operations. When they
	are attempted, they are rejected with NFS4ERR_LOCKED. When the
	client gets NFS4ERR_LOCKED on a file it knows it has the proper share
	reservation for, it will need to issue a LOCK request on the region
	of the file that includes the region the I/O was to be performed on,
	with an appropriate locktype (i.e. READ*_LT for a READ operation,
	WRITE*_LT for a WRITE operation).
	With NFS version 3, there was no notion of a stateid so there was no
	way to tell if the application process of the client sending the READ
	or WRITE operation had also acquired the appropriate record lock on
	the file. Thus there was no way to implement mandatory locking. With
	the stateid construct, this barrier has been removed.
	Note that for UNIX environments that support mandatory file locking,
	the distinction between advisory and mandatory locking is subtle. In
	fact, advisory and mandatory record locks are exactly the same in so
	far as the APIs and requirements on implementation. If the mandatory
	lock attribute is set on the file, the server checks to see if the
	lockowner has an appropriate shared (read) or exclusive (write)
	record lock on the region it wishes to read or write to. If there is
	no appropriate lock, the server checks if there is a conflicting lock
	(which can be done by attempting to acquire the conflicting lock on
	the behalf of the lockowner, and if successful, release the lock
	after the READ or WRITE is done), and if there is, the server returns
	NFS4ERR_LOCKED.
	For Windows environments, there are no advisory record locks, so the
	server always checks for record locks during I/O requests.
	Thus, the NFS version 4 LOCK operation does not need to distinguish
	between advisory and mandatory record locks. It is the NFS version 4
	server's processing of the READ and WRITE operations that introduces
	the distinction.
	Draft Specification NFS version 4 Protocol October 2002
	Every stateid other than the special stateid values noted in this
	section, whether returned by an OPEN-type operation (i.e. OPEN,
	OPEN_DOWNGRADE), or by a LOCK-type operation (i.e. LOCK or LOCKU),
	defines an access mode for the file (i.e. READ, WRITE, or READ-WRITE)
	as established by the original OPEN which began the stateid sequence,
	and as modified by subsequent OPENs and OPEN_DOWNGRADEs within that
	stateid sequence. When a READ, WRITE, or SETATTR which specifies the
	size attribute, is done, the operation is subject to checking against
	the access mode to verify that the operation is appropriate given the
	OPEN with which the operation is associated.
	In the case of WRITE-type operations (i.e. WRITEs and SETATTRs which
	set size), the server must verify that the access mode allows writing
	and return an NFS4ERR_OPENMODE error if it does not. In the case, of
	READ, the server may perform the corresponding check on the access
	mode, or it may choose to allow READ on opens for WRITE only, to
	accommodate clients whose write implementation may unavoidably do
	reads (e.g. due to buffer cache constraints). However, even if READs
	are allowed in these circumstances, the server MUST still check for
	locks that conflict with the READ (e.g. another open specify denial
	of READs). Note that a server which does enforce the access mode
	check on READs need not explicitly check for conflicting share
	reservations since the existence of OPEN for read access guarantees
	that no conflicting share reservation can exist.
	A stateid of all bits 1 (one) MAY allow READ operations to bypass
	locking checks at the server. However, WRITE operations with a
	stateid with bits all 1 (one) MUST NOT bypass locking checks and are
	treated exactly the same as if a stateid of all bits 0 were used.
	A lock may not be granted while a READ or WRITE operation using one
	of the special stateids is being performed and the range of the lock
	request conflicts with the range of the READ or WRITE operation. For
	the purposes of this paragraph, a conflict occurs when a shared lock
	is requested and a WRITE operation is being performed, or an
	exclusive lock is requested and either a READ or a WRITE operation is
	being performed. A SETATTR that sets size is treated similarly to a
	WRITE as discussed above.
	8.1.5. Sequencing of Lock Requests
	Locking is different than most NFS operations as it requires "at-
	most-one" semantics that are not provided by ONCRPC. ONCRPC over a
	reliable transport is not sufficient because a sequence of locking
	requests may span multiple TCP connections. In the face of
	retransmission or reordering, lock or unlock requests must have a
	well defined and consistent behavior. To accomplish this, each lock
	request contains a sequence number that is a consecutively increasing
	integer. Different lock_owners have different sequences. The server
	maintains the last sequence number (L) received and the response that
	was returned. The first request issued for any given lock_owner is
	Draft Specification NFS version 4 Protocol October 2002
	issued with a sequence number of zero.
	Note that for requests that contain a sequence number, for each
	lock_owner, there should be no more than one outstanding request.
	If a request (r) with a previous sequence number (r < L) is received,
	it is rejected with the return of error NFS4ERR_BAD_SEQID. Given a
	properly-functioning client, the response to (r) must have been
	received before the last request (L) was sent. If a duplicate of
	last request (r == L) is received, the stored response is returned.
	If a request beyond the next sequence (r == L + 2) is received, it is
	rejected with the return of error NFS4ERR_BAD_SEQID. Sequence
	history is reinitialized whenever the SETCLIENTID/SETCLIENTID_CONFIRM
	sequence changes the client verifier.
	Since the sequence number is represented with an unsigned 32-bit
	integer, the arithmetic involved with the sequence number is mod
	2^32.
	It is critical the server maintain the last response sent to the
	client to provide a more reliable cache of duplicate non-idempotent
	requests than that of the traditional cache described in [Juszczak].
	The traditional duplicate request cache uses a least recently used
	algorithm for removing unneeded requests. However, the last lock
	request and response on a given lock_owner must be cached as long as
	the lock state exists on the server.
	The client MUST monotonically increment the sequence number for the
	CLOSE, LOCK, LOCKU, OPEN, OPEN_CONFIRM, and OPEN_DOWNGRADE
	operations. This is true even in the event that the previous
	operation that used the sequence number received an error. The only
	exception to this rule is if the previous operation received one of
	the following errors: NFS4ERR_STALE_CLIENTID, NFS4ERR_STALE_STATEID,
	NFS4ERR_BAD_STATEID, NFS4ERR_BAD_SEQID, NFS4ERR_BADXDR,
	NFS4ERR_RESOURCE, NFS4ERR_NOFILEHANDLE.
	8.1.6. Recovery from Replayed Requests
	As described above, the sequence number is per lock_owner. As long
	as the server maintains the last sequence number received and follows
	the methods described above, there are no risks of a Byzantine router
	re-sending old requests. The server need only maintain the
	(lock_owner, sequence number) state as long as there are open files
	or closed files with locks outstanding.
	LOCK, LOCKU, OPEN, OPEN_DOWNGRADE, and CLOSE each contain a sequence
	number and therefore the risk of the replay of these operations
	resulting in undesired effects is non-existent while the server
	maintains the lock_owner state.
	Draft Specification NFS version 4 Protocol October 2002
	8.1.7. Releasing lock_owner State
	When a particular lock_owner no longer holds open or file locking
	state at the server, the server may choose to release the sequence
	number state associated with the lock_owner. The server may make
	this choice based on lease expiration, for the reclamation of server
	memory, or other implementation specific details. In any event, the
	server is able to do this safely only when the lock_owner no longer
	is being utilized by the client. The server may choose to hold the
	lock_owner state in the event that retransmitted requests are
	received. However, the period to hold this state is implementation
	specific.
	In the case that a LOCK, LOCKU, OPEN_DOWNGRADE, or CLOSE is
	retransmitted after the server has previously released the lock_owner
	state, the server will find that the lock_owner has no files open and
	an error will be returned to the client. If the lock_owner does have
	a file open, the stateid will not match and again an error is
	returned to the client.
	8.1.8. Use of Open Confirmation
	In the case that an OPEN is retransmitted and the lock_owner is being
	used for the first time or the lock_owner state has been previously
	released by the server, the use of the OPEN_CONFIRM operation will
	prevent incorrect behavior. When the server observes the use of the
	lock_owner for the first time, it will direct the client to perform
	the OPEN_CONFIRM for the corresponding OPEN. This sequence
	establishes the use of an lock_owner and associated sequence number.
	Since the OPEN_CONFIRM sequence connects a new open_owner on the
	server with an existing open_owner on a client, the sequence number
	may have any value. The OPEN_CONFIRM step assures the server that
	the value received is the correct one. See the section "OPEN_CONFIRM
	- Confirm Open" for further details.
	There are a number of situations in which the requirement to confirm
	an OPEN would pose difficulties for the client and server, in that
	they would be prevented from acting in a timely fashion on
	information received, because that information would be provisional,
	subject to deletion upon non-confirmation. Fortunately, these are
	situations in which the server can avoid the need for confirmation
	when responding to open requests. The two constraints are:
	o The server must not bestow a delegation for any open which would
	require confirmation.
	o The server MUST NOT require confirmation on a reclaim-type open
	(i.e. one specifying claim type CLAIM_PREVIOUS or
	CLAIM_DELEGATE_PREV).
	Draft Specification NFS version 4 Protocol October 2002
	These constraints are related in that reclaim-type opens are the only
	ones in which the server may be required to send a delegation. For
	CLAIM_NULL, sending the delegation is optional while for
	CLAIM_DELEGATE_CUR, no delegation is sent.
	Delegations being sent with an open requiring confirmation are
	troublesome because recovering from non-confirmation adds undue
	complexity to the protocol while requiring confirmation on reclaim-
	type opens poses difficulties in that the inability to resolve the
	status of the reclaim until lease expiration may make it difficult to
	have timely determination of the set of locks being reclaimed (since
	the grace period may expire).
	Requiring open confirmation on reclaim-type opens is avoidable
	because of the nature of the environments in which such opens are
	done. For CLAIM_PREVIOUS opens, this is immediately after server
	reboot, so there should be no time for lockowners to be created,
	found to be unused, and recycled. For CLAIM_DELEGATE_PREV opens, we
	are dealing with a client reboot situation. A server which supports
	delegation can be sure that no lockowners for that client have been
	recycled since client initialization and thus can ensure that
	confirmation will not be required.
	8.2. Lock Ranges
	The protocol allows a lock owner to request a lock with a byte range
	and then either upgrade or unlock a sub-range of the initial lock.
	It is expected that this will be an uncommon type of request. In any
	case, servers or server filesystems may not be able to support sub-
	range lock semantics. In the event that a server receives a locking
	request that represents a sub-range of current locking state for the
	lock owner, the server is allowed to return the error
	NFS4ERR_LOCK_RANGE to signify that it does not support sub-range lock
	operations. Therefore, the client should be prepared to receive this
	error and, if appropriate, report the error to the requesting
	application.
	The client is discouraged from combining multiple independent locking
	ranges that happen to be adjacent into a single request since the
	server may not support sub-range requests and for reasons related to
	the recovery of file locking state in the event of server failure.
	As discussed in the section "Server Failure and Recovery" below, the
	server may employ certain optimizations during recovery that work
	effectively only when the client's behavior during lock recovery is
	similar to the client's locking behavior prior to server failure.
	8.3. Upgrading and Downgrading Locks
	If a client has a write lock on a record, it can request an atomic
	downgrade of the lock to a read lock via the LOCK request, by setting
	Draft Specification NFS version 4 Protocol October 2002
	the type to READ_LT. If the server supports atomic downgrade, the
	request will succeed. If not, it will return NFS4ERR_LOCK_NOTSUPP.
	The client should be prepared to receive this error, and if
	appropriate, report the error to the requesting application.
	If a client has a read lock on a record, it can request an atomic
	upgrade of the lock to a write lock via the LOCK request by setting
	the type to WRITE_LT or WRITEW_LT. If the server does not support
	atomic upgrade, it will return NFS4ERR_LOCK_NOTSUPP. If the upgrade
	can be achieved without an existing conflict, the request will
	succeed. Otherwise, the server will return either NFS4ERR_DENIED or
	NFS4ERR_DEADLOCK. The error NFS4ERR_DEADLOCK is returned if the
	client issued the LOCK request with the type set to WRITEW_LT and the
	server has detected a deadlock. The client should be prepared to
	receive such errors and if appropriate, report the error to the
	requesting application.
	8.4. Blocking Locks
	Some clients require the support of blocking locks. The NFS version
	4 protocol must not rely on a callback mechanism and therefore is
	unable to notify a client when a previously denied lock has been
	granted. Clients have no choice but to continually poll for the
	lock. This presents a fairness problem. Two new lock types are
	added, READW and WRITEW, and are used to indicate to the server that
	the client is requesting a blocking lock. The server should maintain
	an ordered list of pending blocking locks. When the conflicting lock
	is released, the server may wait the lease period for the first
	waiting client to re-request the lock. After the lease period
	expires the next waiting client request is allowed the lock. Clients
	are required to poll at an interval sufficiently small that it is
	likely to acquire the lock in a timely manner. The server is not
	required to maintain a list of pending blocked locks as it is used to
	increase fairness and not correct operation. Because of the
	unordered nature of crash recovery, storing of lock state to stable
	storage would be required to guarantee ordered granting of blocking
	locks.
	Servers may also note the lock types and delay returning denial of
	the request to allow extra time for a conflicting lock to be
	released, allowing a successful return. In this way, clients can
	avoid the burden of needlessly frequent polling for blocking locks.
	The server should take care in the length of delay in the event the
	client retransmits the request.
	8.5. Lease Renewal
	The purpose of a lease is to allow a server to remove stale locks
	that are held by a client that has crashed or is otherwise
	unreachable. It is not a mechanism for cache consistency and lease
	Draft Specification NFS version 4 Protocol October 2002
	renewals may not be denied if the lease interval has not expired.
	The following events cause implicit renewal of all of the leases for
	a given client (i.e. all those sharing a given clientid). Each of
	these is a positive indication that the client is still active and
	that the associated state held at the server, for the client, is
	still valid.
	o An OPEN with a valid clientid.
	o Any operation made with a valid stateid (CLOSE, DELEGPURGE,
	DELEGRETURN, LOCK, LOCKU, OPEN, OPEN_CONFIRM, OPEN_DOWNGRADE,
	READ, RENEW, SETATTR, WRITE). This does not include the special
	stateids of all bits 0 or all bits 1.
	Note that if the client had restarted or rebooted, the
	client would not be making these requests without issuing
	the SETCLIENTID/SETCLIENTID_CONFIRM sequence. The use of
	the SETCLIENTID/SETCLIENTID_CONFIRM sequence (one that
	changes the client verifier) notifies the server to drop
	the locking state associated with the client.
	SETCLIENTID/SETCLIENTID_CONFIRM never renews a lease.
	If the server has rebooted, the stateids
	(NFS4ERR_STALE_STATEID error) or the clientid
	(NFS4ERR_STALE_CLIENTID error) will not be valid hence
	preventing spurious renewals.
	This approach allows for low overhead lease renewal which scales
	well. In the typical case no extra RPC calls are required for lease
	renewal and in the worst case one RPC is required every lease period
	(i.e. a RENEW operation). The number of locks held by the client is
	not a factor since all state for the client is involved with the
	lease renewal action.
	Since all operations that create a new lease also renew existing
	leases, the server must maintain a common lease expiration time for
	all valid leases for a given client. This lease time can then be
	easily updated upon implicit lease renewal actions.
	8.6. Crash Recovery
	The important requirement in crash recovery is that both the client
	and the server know when the other has failed. Additionally, it is
	required that a client sees a consistent view of data across server
	restarts or reboots. All READ and WRITE operations that may have
	been queued within the client or network buffers must wait until the
	client has successfully recovered the locks protecting the READ and
	WRITE operations.
	Draft Specification NFS version 4 Protocol October 2002
	8.6.1. Client Failure and Recovery
	In the event that a client fails, the server may recover the client's
	locks when the associated leases have expired. Conflicting locks
	from another client may only be granted after this lease expiration.
	If the client is able to restart or reinitialize within the lease
	period the client may be forced to wait the remainder of the lease
	period before obtaining new locks.
	To minimize client delay upon restart, lock requests are associated
	with an instance of the client by a client supplied verifier. This
	verifier is part of the initial SETCLIENTID call made by the client.
	The server returns a clientid as a result of the SETCLIENTID
	operation. The client then confirms the use of the clientid with
	SETCLIENTID_CONFIRM. The clientid in combination with an opaque
	owner field is then used by the client to identify the lock owner for
	OPEN. This chain of associations is then used to identify all locks
	for a particular client.
	Since the verifier will be changed by the client upon each
	initialization, the server can compare a new verifier to the verifier
	associated with currently held locks and determine that they do not
	match. This signifies the client's new instantiation and subsequent
	loss of locking state. As a result, the server is free to release
	all locks held which are associated with the old clientid which was
	derived from the old verifier.
	Note that the verifier must have the same uniqueness properties of
	the verifier for the COMMIT operation.
	8.6.2. Server Failure and Recovery
	If the server loses locking state (usually as a result of a restart
	or reboot), it must allow clients time to discover this fact and re-
	establish the lost locking state. The client must be able to re-
	establish the locking state without having the server deny valid
	requests because the server has granted conflicting access to another
	client. Likewise, if there is the possibility that clients have not
	yet re-established their locking state for a file, the server must
	disallow READ and WRITE operations for that file. The duration of
	this recovery period is equal to the duration of the lease period.
	A client can determine that server failure (and thus loss of locking
	state) has occurred, when it receives one of two errors. The
	NFS4ERR_STALE_STATEID error indicates a stateid invalidated by a
	reboot or restart. The NFS4ERR_STALE_CLIENTID error indicates a
	clientid invalidated by reboot or restart. When either of these are
	received, the client must establish a new clientid (See the section
	"Client ID") and re-establish the locking state as discussed below.
	The period of special handling of locking and READs and WRITEs, equal
	Draft Specification NFS version 4 Protocol October 2002
	in duration to the lease period, is referred to as the "grace
	period". During the grace period, clients recover locks and the
	associated state by reclaim-type locking requests (i.e. LOCK requests
	with reclaim set to true and OPEN operations with a claim type of
	CLAIM_PREVIOUS). During the grace period, the server must reject
	READ and WRITE operations and non-reclaim locking requests (i.e.
	other LOCK and OPEN operations) with an error of NFS4ERR_GRACE.
	If the server can reliably determine that granting a non-reclaim
	request will not conflict with reclamation of locks by other clients,
	the NFS4ERR_GRACE error does not have to be returned and the non-
	reclaim client request can be serviced. For the server to be able to
	service READ and WRITE operations during the grace period, it must
	again be able to guarantee that no possible conflict could arise
	between an impending reclaim locking request and the READ or WRITE
	operation. If the server is unable to offer that guarantee, the
	NFS4ERR_GRACE error must be returned to the client.
	For a server to provide simple, valid handling during the grace
	period, the easiest method is to simply reject all non-reclaim
	locking requests and READ and WRITE operations by returning the
	NFS4ERR_GRACE error. However, a server may keep information about
	granted locks in stable storage. With this information, the server
	could determine if a regular lock or READ or WRITE operation can be
	safely processed.
	For example, if a count of locks on a given file is available in
	stable storage, the server can track reclaimed locks for the file and
	when all reclaims have been processed, non-reclaim locking requests
	may be processed. This way the server can ensure that non-reclaim
	locking requests will not conflict with potential reclaim requests.
	With respect to I/O requests, if the server is able to determine that
	there are no outstanding reclaim requests for a file by information
	from stable storage or another similar mechanism, the processing of
	I/O requests could proceed normally for the file.
	To reiterate, for a server that allows non-reclaim lock and I/O
	requests to be processed during the grace period, it MUST determine
	that no lock subsequently reclaimed will be rejected and that no lock
	subsequently reclaimed would have prevented any I/O operation
	processed during the grace period.
	Clients should be prepared for the return of NFS4ERR_GRACE errors for
	non-reclaim lock and I/O requests. In this case the client should
	employ a retry mechanism for the request. A delay (on the order of
	several seconds) between retries should be used to avoid overwhelming
	the server. Further discussion of the general issue is included in
	[Floyd]. The client must account for the server that is able to
	perform I/O and non-reclaim locking requests within the grace period
	as well as those that can not do so.
	A reclaim-type locking request outside the server's grace period can
	Draft Specification NFS version 4 Protocol October 2002
	only succeed if the server can guarantee that no conflicting lock or
	I/O request has been granted since reboot or restart.
	A server may, upon restart, establish a new value for the lease
	period. Therefore, clients should, once a new clientid is
	established, refetch the lease_time attribute and use it as the basis
	for lease renewal for the lease associated with that server. However,
	the server must establish, for this restart event, a grace period at
	least as long as the lease period for the previous server
	instantiation. This allows the client state obtained during the
	previous server instance to be reliably re-established.
	8.6.3. Network Partitions and Recovery
	If the duration of a network partition is greater than the lease
	period provided by the server, the server will have not received a
	lease renewal from the client. If this occurs, the server may free
	all locks held for the client. As a result, all stateids held by the
	client will become invalid or stale. Once the client is able to
	reach the server after such a network partition, all I/O submitted by
	the client with the now invalid stateids will fail with the server
	returning the error NFS4ERR_EXPIRED. Once this error is received,
	the client will suitably notify the application that held the lock.
	As a courtesy to the client or as an optimization, the server may
	continue to hold locks on behalf of a client for which recent
	communication has extended beyond the lease period. If the server
	receives a lock or I/O request that conflicts with one of these
	courtesy locks, the server must free the courtesy lock and grant the
	new request.
	When a network partition is combined with a server reboot, there are
	edge conditions that place requirements on the server in order to
	avoid silent data corruption following the server reboot. Two of
	these edge conditions are known, and are discussed below.
	The first edge condition has the following scenario:
	1. Client A acquires a lock.
	2. Client A and server experience mutual network partition,
	such that client A is unable to renew its lease.
	3. Client A's lease expires, so server releases lock.
	4. Client B acquires a lock that would have conflicted with
	that of Client A.
	5. Client B releases the lock
	Draft Specification NFS version 4 Protocol October 2002
	6. Server reboots
	7. Network partition between client A and server heals.
	8. Client A issues a RENEW operation, and gets back a
	NFS4ERR_STALE_CLIENTID.
	9. Client A reclaims its lock within the server's grace period.
	Thus, at the final step, the server has erroneously granted client
	A's lock reclaim. If client B modified the object the lock was
	protecting, client A will experience object corruption.
	The second known edge condition follows:
	1. Client A acquires a lock.
	2. Server reboots.
	3. Client A and server experience mutual network partition,
	such that client A is unable to reclaim its lock within the
	grace period.
	4. Server's reclaim grace period ends. Client A has no locks
	recorded on server.
	5. Client B acquires a lock that would have conflicted with
	that of Client A.
	6. Client B releases the lock
	7. Server reboots a second time
	8. Network partition between client A and server heals.
	9. Client A issues a RENEW operation, and gets back a
	NFS4ERR_STALE_CLIENTID.
	10. Client A reclaims its lock within the server's grace period.
	As with the first edge condition, the final step of the scenario of
	the second edge condition has the server erroneously granting client
	A's lock reclaim.
	Solving the first and second edge conditions requires that the server
	either assume after it reboots that edge condition occurs, and thus
	return NFS4ERR_NO_GRACE for all reclaim attempts, or that the server
	record some information stable storage. The amount of information
	the server records in stable storage is in inverse proportion to how
	harsh the server wants to be whenever the edge conditions occur. The
	server that is completely tolerant of all edge conditions will record
	in stable storage every lock that is acquired, removing the lock
	Draft Specification NFS version 4 Protocol October 2002
	record from stable storage only when the lock is unlocked by the
	client and the lock's lockowner advances the sequence number such
	that the lock release is not the last stateful event for the
	lockowner's sequence. For the two aforementioned edge conditions, the
	harshest a server can be, and still support a grace period for
	reclaims, requires that the server record in stable storage
	information some minimal information. For example, a server
	implementation could, for each client, save in stable storage a
	record containing:
	o the client's id string
	o a boolean that indicates if the client's lease expired or if
	there was administrative intervention (see the section,
	Server Revocation of Locks) to revoke a record lock, share
	reservation, or delegation
	o a timestamp that is updated the first time after a server
	boot or reboot the client acquires record locking, share
	reservation, or delegation state on the server. The
	timestamp need not be updated on subsequent lock requests
	until the server reboots.
	The server implementation would also record in the stable storage the
	timestamps from the two most recent server reboots.
	Assuming the above record keeping, for the first edge condition,
	after the server reboots, the record that client A's lease expired
	means that another client could have acquired a conflicting record
	lock, share reservation, or delegation. Hence the server must reject
	a reclaim from client A with the error NFS4ERR_NO_GRACE.
	For the second edge condition, after the server reboots for a second
	time, the record that the client had an unexpired record lock, share
	reservation, or delegation established before the server's previous
	incarnation means that the server must reject a reclaim from client A
	with the error NFS4ERR_NO_GRACE.
	Regardless of the level and approach to record keeping, the server
	MUST implement one of the following strategies (which apply to
	reclaims of share reservations, record locks, and delegations):
	1. Reject all reclaims with NFS4ERR_NO_GRACE. This is
	superharsh, but necessary if the server does not want to
	record lock state in stable storage.
	2. Record sufficient state in stable storage such that all
	known edge conditions involving server reboot, including the
	two noted in this section, are detected. False positives are
	acceptable. Note that at this time, it is not known if there
	are other edge conditions.
	Draft Specification NFS version 4 Protocol October 2002
	In the event, after a server reboot, the server determines
	that there is unrecoverable damage or corruption to the the
	stable storage, then for all clients and/or locks affected,
	the server MUST return NFS4ERR_NO_GRACE.
	A mandate for the client's handling of the NFS4ERR_NO_GRACE error is
	outside the scope of this specification, since the strategies for
	such handling are very dependent on the client's operating
	environment. However, one potential approach is described below.
	When the client receives NFS4ERR_NO_GRACE, it could examine the
	change attribute of the objects the client is trying to reclaim state
	for, and use that to determine whether to re-establish the state via
	normal OPEN or LOCK requests. This is acceptable provided the
	client's operating environment allows it. In otherwords, the client
	implementor is advised to document for his users the behavior. The
	client could also inform the application that its record lock or
	share reservations (whether they were delegated or not) have been
	lost, such as via a UNIX signal, a GUI pop-up window, etc. See the
	section, "Data Caching and Revocation" for a discussion of what the
	client should do for dealing with unreclaimed delegations on client
	state.
	For further discussion of revocation of locks see the section "Server
	Revocation of Locks".
	8.7. Recovery from a Lock Request Timeout or Abort
	In the event a lock request times out, a client may decide to not
	retry the request. The client may also abort the request when the
	process for which it was issued is terminated (e.g. in UNIX due to a
	signal). It is possible though that the server received the request
	and acted upon it. This would change the state on the server without
	the client being aware of the change. It is paramount that the
	client re-synchronize state with server before it attempts any other
	operation that takes a seqid and/or a stateid with the same
	lock_owner. This is straightforward to do without a special re-
	synchronize operation.
	Since the server maintains the last lock request and response
	received on the lock_owner, for each lock_owner, the client should
	cache the last lock request it sent such that the lock request did
	not receive a response. From this, the next time the client does a
	lock operation for the lock_owner, it can send the cached request, if
	there is one, and if the request was one that established state (e.g.
	a LOCK or OPEN operation), the server will return the cached result
	or if never saw the request, perform it. The client can follow up
	with a request to remove the state (e.g. a LOCKU or CLOSE operation).
	With this approach, the sequencing and stateid information on the
	client and server for the given lock_owner will re-synchronize and in
	turn the lock state will re-synchronize.
	Draft Specification NFS version 4 Protocol October 2002
	8.8. Server Revocation of Locks
	At any point, the server can revoke locks held by a client and the
	client must be prepared for this event. When the client detects that
	its locks have been or may have been revoked, the client is
	responsible for validating the state information between itself and
	the server. Validating locking state for the client means that it
	must verify or reclaim state for each lock currently held.
	The first instance of lock revocation is upon server reboot or re-
	initialization. In this instance the client will receive an error
	(NFS4ERR_STALE_STATEID or NFS4ERR_STALE_CLIENTID) and the client will
	proceed with normal crash recovery as described in the previous
	section.
	The second lock revocation event is the inability to renew the lease
	before expiration. While this is considered a rare or unusual event,
	the client must be prepared to recover. Both the server and client
	will be able to detect the failure to renew the lease and are capable
	of recovering without data corruption. For the server, it tracks the
	last renewal event serviced for the client and knows when the lease
	will expire. Similarly, the client must track operations which will
	renew the lease period. Using the time that each such request was
	sent and the time that the corresponding reply was received, the
	client should bound the time that the corresponding renewal could
	have occurred on the server and thus determine if it is possible that
	a lease period expiration could have occurred.
	The third lock revocation event can occur as a result of
	administrative intervention within the lease period. While this is
	considered a rare event, it is possible that the server's
	administrator has decided to release or revoke a particular lock held
	by the client. As a result of revocation, the client will receive an
	error of NFS4ERR_ADMIN_REVOKED. In this instance the client may
	assume that only the lock_owner's locks have been lost. The client
	notifies the lock holder appropriately. The client may not assume
	the lease period has been renewed as a result of failed operation.
	When the client determines the lease period may have expired, the
	client must mark all locks held for the associated lease as
	"unvalidated". This means the client has been unable to re-establish
	or confirm the appropriate lock state with the server. As described
	in the previous section on crash recovery, there are scenarios in
	which the server may grant conflicting locks after the lease period
	has expired for a client. When it is possible that the lease period
	has expired, the client must validate each lock currently held to
	ensure that a conflicting lock has not been granted. The client may
	accomplish this task by issuing an I/O request, either a pending I/O
	or a zero-length read, specifying the stateid associated with the
	lock in question. If the response to the request is success, the
	client has validated all of the locks governed by that stateid and
	re-established the appropriate state between itself and the server.
	Draft Specification NFS version 4 Protocol October 2002
	If the I/O request is not successful, then one or more of the locks
	associated with the stateid was revoked by the server and the client
	must notify the owner.
	8.9. Share Reservations
	A share reservation is a mechanism to control access to a file. It
	is a separate and independent mechanism from record locking. When a
	client opens a file, it issues an OPEN operation to the server
	specifying the type of access required (READ, WRITE, or BOTH) and the
	type of access to deny others (deny NONE, READ, WRITE, or BOTH). If
	the OPEN fails the client will fail the application's open request.
	Pseudo-code definition of the semantics:
	if (request.access == 0)
	return (NFS4ERR_INVAL)
	else
	if ((request.access & file_state.deny)) ||
	(request.deny & file_state.access))
	return (NFS4ERR_DENIED)
	This checking of share reservations on OPEN is done with no exception
	for an existing OPEN for the same open_owner.
	The constants used for the OPEN and OPEN_DOWNGRADE operations for the
	access and deny fields are as follows:
	const OPEN4_SHARE_ACCESS_READ = 0x00000001;
	const OPEN4_SHARE_ACCESS_WRITE = 0x00000002;
	const OPEN4_SHARE_ACCESS_BOTH = 0x00000003;
	const OPEN4_SHARE_DENY_NONE = 0x00000000;
	const OPEN4_SHARE_DENY_READ = 0x00000001;
	const OPEN4_SHARE_DENY_WRITE = 0x00000002;
	const OPEN4_SHARE_DENY_BOTH = 0x00000003;
	8.10. OPEN/CLOSE Operations
	To provide correct share semantics, a client MUST use the OPEN
	operation to obtain the initial filehandle and indicate the desired
	access and what if any access to deny. Even if the client intends to
	use a stateid of all 0's or all 1's, it must still obtain the
	filehandle for the regular file with the OPEN operation so the
	appropriate share semantics can be applied. For clients that do not
	have a deny mode built into their open programming interfaces, deny
	equal to NONE should be used.
	Draft Specification NFS version 4 Protocol October 2002
	The OPEN operation with the CREATE flag, also subsumes the CREATE
	operation for regular files as used in previous versions of the NFS
	protocol. This allows a create with a share to be done atomically.
	The CLOSE operation removes all share reservations held by the
	lock_owner on that file. If record locks are held, the client SHOULD
	release all locks before issuing a CLOSE. The server MAY free all
	outstanding locks on CLOSE but some servers may not support the CLOSE
	of a file that still has record locks held. The server MUST return
	failure, NFS4ERR_LOCKS_HELD, if any locks would exist after the
	CLOSE.
	The LOOKUP operation will return a filehandle without establishing
	any lock state on the server. Without a valid stateid, the server
	will assume the client has the least access. For example, a file
	opened with deny READ/WRITE cannot be accessed using a filehandle
	obtained through LOOKUP because it would not have a valid stateid
	(i.e. using a stateid of all bits 0 or all bits 1).
	8.10.1. Close and Retention of State Information
	Since a CLOSE operation requests deallocation of a stateid, dealing
	with retransmission of the CLOSE, may pose special difficulties,
	since the state information, which normally would be used to
	determine the state of the open file being designated, might be
	deallocated, resulting in an NFS4ERR_BAD_STATEID error.
	Servers may deal with this problem in a number of ways. To provide
	the greatest degree assurance that the protocol is being used
	properly, a server should, rather than deallocate the stateid, mark
	it as close-pending, and retain the stateid with this status, until
	later deallocation. In this way, a retransmitted CLOSE can be
	recognized since the stateid points to state information with this
	distinctive status, so that it can be handled without error.
	When adopting this strategy, a server should retain the state
	information until the earliest of:
	o Another validly sequenced request for the same lockowner, that
	is not a retransmission.
	o The time that a lockowner is freed by the server due to period
	with no activity.
	o All locks for the client are freed as a result of a SETCLIENTID.
	Servers may avoid this complexity, at the cost of less complete
	protocol error checking, by simply responding NFS4_OK in the event of
	a CLOSE for a deallocated stateid, on the assumption that this case
	must be caused by a retransmitted close. When adopting this
	Draft Specification NFS version 4 Protocol October 2002
	approach, it is desirable to at least log an error when returning a
	no-error indication in this situation. If the server maintains a
	reply-cache mechanism, it can verify the CLOSE is indeed a
	retransmission and avoid error logging in most cases.
	8.11. Open Upgrade and Downgrade
	When an OPEN is done for a file and the lockowner for which the open
	is being done already has the file open, the result is to upgrade the
	open file status maintained on the server to include the access and
	deny bits specified by the new OPEN as well as those for the existing
	OPEN. The result is that there is one open file, as far as the
	protocol is concerned, and it includes the union of the access and
	deny bits for all of the OPEN requests completed. Only a single
	CLOSE will be done to reset the effects of both OPENs. Note that the
	client, when issuing the OPEN, may not know that the same file is in
	fact being opened. The above only applies if both OPENs result in
	the OPENed object being designated by the same filehandle.
	When the server chooses to export multiple filehandles corresponding
	to the same file object and returns different filehandles on two
	different OPENs of the same file object, the server MUST NOT "OR"
	together the access and deny bits and coalesce the two open files.
	Instead the server must maintain separate OPENs with separate
	stateids and will require separate CLOSEs to free them.
	When multiple open files on the client are merged into a single open
	file object on the server, the close of one of the open files (on the
	client) may necessitate change of the access and deny status of the
	open file on the server. This is because the union of the access and
	deny bits for the remaining opens may be smaller (i.e. a proper
	subset) than previously. The OPEN_DOWNGRADE operation is used to
	make the necessary change and the client should use it to update the
	server so that share reservation requests by other clients are
	handled properly.
	8.12. Short and Long Leases
	When determining the time period for the server lease, the usual
	lease tradeoffs apply. Short leases are good for fast server
	recovery at a cost of increased RENEW or READ (with zero length)
	requests. Longer leases are certainly kinder and gentler to servers
	trying to handle very large numbers of clients. The number of RENEW
	requests drop in proportion to the lease time. The disadvantages of
	long leases are slower recovery after server failure (the server must
	wait for the leases to expire and the grace period to elapse before
	granting new lock requests) and increased file contention (if client
	fails to transmit an unlock request then server must wait for lease
	expiration before granting new locks).
	Draft Specification NFS version 4 Protocol October 2002
	Long leases are usable if the server is able to store lease state in
	non-volatile memory. Upon recovery, the server can reconstruct the
	lease state from its non-volatile memory and continue operation with
	its clients and therefore long leases would not be an issue.
	8.13. Clocks, Propagation Delay, and Calculating Lease Expiration
	To avoid the need for synchronized clocks, lease times are granted by
	the server as a time delta. However, there is a requirement that the
	client and server clocks do not drift excessively over the duration
	of the lock. There is also the issue of propagation delay across the
	network which could easily be several hundred milliseconds as well as
	the possibility that requests will be lost and need to be
	retransmitted.
	To take propagation delay into account, the client should subtract it
	from lease times (e.g. if the client estimates the one-way
	propagation delay as 200 msec, then it can assume that the lease is
	already 200 msec old when it gets it). In addition, it will take
	another 200 msec to get a response back to the server. So the client
	must send a lock renewal or write data back to the server 400 msec
	before the lease would expire.
	The server's lease period configuration should take into account the
	network distance of the clients that will be accessing the server's
	resources. It is expected that the lease period will take into
	account the network propagation delays and other network delay
	factors for the client population. Since the protocol does not allow
	for an automatic method to determine an appropriate lease period, the
	server's administrator may have to tune the lease period.
	8.14. Migration, Replication and State
	When responsibility for handling a given file system is transferred
	to a new server (migration) or the client chooses to use an alternate
	server (e.g. in response to server unresponsiveness) in the context
	of file system replication, the appropriate handling of state shared
	between the client and server (i.e. locks, leases, stateids, and
	clientids) is as described below. The handling differs between
	migration and replication. For related discussion of file server
	state and recover of such see the sections under "File Locking and
	Share Reservations"
	If server replica or a server immigrating a filesystem agrees to, or
	is expected to, accept opaque values from the client that originated
	from another server, then it is a wise implementation practice for
	the servers to encode the "opaque" values in network byte order. This
	way, servers acting as replicas or immigrating filesystems will be
	able to parse values like stateids, directory cookies, filehandles,
	etc. even if their native byte order is different from other servers
	Draft Specification NFS version 4 Protocol October 2002
	cooperating in the replication and migration of the filesystem.
	8.14.1. Migration and State
	In the case of migration, the servers involved in the migration of a
	filesystem SHOULD transfer all server state from the original to the
	new server. This must be done in a way that is transparent to the
	client. This state transfer will ease the client's transition when a
	filesystem migration occurs. If the servers are successful in
	transferring all state, the client will continue to use stateids
	assigned by the original server. Therefore the new server must
	recognize these stateids as valid. This holds true for the clientid
	as well. Since responsibility for an entire filesystem is
	transferred with a migration event, there is no possibility that
	conflicts will arise on the new server as a result of the transfer of
	locks.
	As part of the transfer of information between servers, leases would
	be transferred as well. The leases being transferred to the new
	server will typically have a different expiration time from those for
	the same client, previously on the old server. To maintain the
	property that all leases on a given server for a given client expire
	at the same time, the server should advance the expiration time to
	the later of the leases being transferred or the leases already
	present. This allows the client to maintain lease renewal of both
	classes without special effort.
	The servers may choose not to transfer the state information upon
	migration. However, this choice is discouraged. In this case, when
	the client presents state information from the original server, the
	client must be prepared to receive either NFS4ERR_STALE_CLIENTID or
	NFS4ERR_STALE_STATEID from the new server. The client should then
	recover its state information as it normally would in response to a
	server failure. The new server must take care to allow for the
	recovery of state information as it would in the event of server
	restart.
	8.14.2. Replication and State
	Since client switch-over in the case of replication is not under
	server control, the handling of state is different. In this case,
	leases, stateids and clientids do not have validity across a
	transition from one server to another. The client must re-establish
	its locks on the new server. This can be compared to the re-
	establishment of locks by means of reclaim-type requests after a
	server reboot. The difference is that the server has no provision to
	distinguish requests reclaiming locks from those obtaining new locks
	or to defer the latter. Thus, a client re-establishing a lock on the
	new server (by means of a LOCK or OPEN request), may have the
	requests denied due to a conflicting lock. Since replication is
	Draft Specification NFS version 4 Protocol October 2002
	intended for read-only use of filesystems, such denial of locks
	should not pose large difficulties in practice. When an attempt to
	re-establish a lock on a new server is denied, the client should
	treat the situation as if his original lock had been revoked.
	8.14.3. Notification of Migrated Lease
	In the case of lease renewal, the client may not be submitting
	requests for a filesystem that has been migrated to another server.
	This can occur because of the implicit lease renewal mechanism. The
	client renews leases for all filesystems when submitting a request to
	any one filesystem at the server.
	In order for the client to schedule renewal of leases that may have
	been relocated to the new server, the client must find out about
	lease relocation before those leases expire. To accomplish this, all
	operations which implicitly renew leases for a client (i.e. OPEN,
	CLOSE, READ, WRITE, RENEW, LOCK, LOCKT, LOCKU), will return the error
	NFS4ERR_LEASE_MOVED if responsibility for any of the leases to be
	renewed has been transferred to a new server. This condition will
	continue until the client receives an NFS4ERR_MOVED error and the
	server receives the subsequent GETATTR(fs_locations) for an access to
	each filesystem for which a lease has been moved to a new server.
	When a client receives an NFS4ERR_LEASE_MOVED error, it should
	perform an operation on each filesystem associated with the server in
	question. When the client receives an NFS4ERR_MOVED error, the
	client can follow the normal process to obtain the new server
	information (through the fs_locations attribute) and perform renewal
	of those leases on the new server. If the server has not had state
	transferred to it transparently, the client will receive either
	NFS4ERR_STALE_CLIENTID or NFS4ERR_STALE_STATEID from the new server,
	as described above, and the client can then recover state information
	as it does in the event of server failure.
	8.14.4. Migration and the Lease_time Attribute
	In order that the client may appropriately manage its leases in the
	case of migration, the destination server must establish proper
	values for the lease_time attribute.
	When state is transferred transparently, that state should include
	the correct value of the lease_time attribute. The lease_time
	attribute on the destination server must never be less than that on
	the source since this would result in premature expiration of leases
	granted by the source server. Upon migration in which state is
	transferred transparently, the client is under no obligation to re-
	fetch the lease_time attribute and may continue to use the value
	previously fetched (on the source server).
	Draft Specification NFS version 4 Protocol October 2002
	If state has not been transferred transparently (i.e. the client sees
	a real or simulated server reboot), the client should fetch the value
	of lease_time on the new (i.e. destination) server, and use it for
	subsequent locking requests. However the server must respect a grace
	period at least as long as the lease_time on the source server, in
	order to ensure that clients have ample time to reclaim their locks
	before potentially conflicting non-reclaimed locks are granted. The
	means by which the new server obtains the value of lease_time on the
	old server is left to the server implementations. It is not
	specified by the NFS version 4 protocol.
	Draft Specification NFS version 4 Protocol October 2002
	9. Client-Side Caching
	Client-side caching of data, of file attributes, and of file names is
	essential to providing good performance with the NFS protocol.
	Providing distributed cache coherence is a difficult problem and
	previous versions of the NFS protocol have not attempted it.
	Instead, several NFS client implementation techniques have been used
	to reduce the problems that a lack of coherence poses for users.
	These techniques have not been clearly defined by earlier protocol
	specifications and it is often unclear what is valid or invalid
	client behavior.
	The NFS version 4 protocol uses many techniques similar to those that
	have been used in previous protocol versions. The NFS version 4
	protocol does not provide distributed cache coherence. However, it
	defines a more limited set of caching guarantees to allow locks and
	share reservations to be used without destructive interference from
	client side caching.
	In addition, the NFS version 4 protocol introduces a delegation
	mechanism which allows many decisions normally made by the server to
	be made locally by clients. This mechanism provides efficient
	support of the common cases where sharing is infrequent or where
	sharing is read-only.
	9.1. Performance Challenges for Client-Side Caching
	Caching techniques used in previous versions of the NFS protocol have
	been successful in providing good performance. However, several
	scalability challenges can arise when those techniques are used with
	very large numbers of clients. This is particularly true when
	clients are geographically distributed which classically increases
	the latency for cache revalidation requests.
	The previous versions of the NFS protocol repeat their file data
	cache validation requests at the time the file is opened. This
	behavior can have serious performance drawbacks. A common case is
	one in which a file is only accessed by a single client. Therefore,
	sharing is infrequent.
	In this case, repeated reference to the server to find that no
	conflicts exist is expensive. A better option with regards to
	performance is to allow a client that repeatedly opens a file to do
	so without reference to the server. This is done until potentially
	conflicting operations from another client actually occur.
	A similar situation arises in connection with file locking. Sending
	file lock and unlock requests to the server as well as the read and
	write requests necessary to make data caching consistent with the
	locking semantics (see the section "Data Caching and File Locking")
	can severely limit performance. When locking is used to provide
	Draft Specification NFS version 4 Protocol October 2002
	protection against infrequent conflicts, a large penalty is incurred.
	This penalty may discourage the use of file locking by applications.
	The NFS version 4 protocol provides more aggressive caching
	strategies with the following design goals:
	o Compatibility with a large range of server semantics.
	o Provide the same caching benefits as previous versions of the
	NFS protocol when unable to provide the more aggressive model.
	o Requirements for aggressive caching are organized so that a
	large portion of the benefit can be obtained even when not all
	of the requirements can be met.
	The appropriate requirements for the server are discussed in later
	sections in which specific forms of caching are covered. (see the
	section "Open Delegation").
	9.2. Delegation and Callbacks
	Recallable delegation of server responsibilities for a file to a
	client improves performance by avoiding repeated requests to the
	server in the absence of inter-client conflict. With the use of a
	"callback" RPC from server to client, a server recalls delegated
	responsibilities when another client engages in sharing of a
	delegated file.
	A delegation is passed from the server to the client, specifying the
	object of the delegation and the type of delegation. There are
	different types of delegations but each type contains a stateid to be
	used to represent the delegation when performing operations that
	depend on the delegation. This stateid is similar to those
	associated with locks and share reservations but differs in that the
	stateid for a delegation is associated with a clientid and may be
	used on behalf of all the open_owners for the given client. A
	delegation is made to the client as a whole and not to any specific
	process or thread of control within it.
	Because callback RPCs may not work in all environments (due to
	firewalls, for example), correct protocol operation does not depend
	on them. Preliminary testing of callback functionality by means of a
	CB_NULL procedure determines whether callbacks can be supported. The
	CB_NULL procedure checks the continuity of the callback path. A
	server makes a preliminary assessment of callback availability to a
	given client and avoids delegating responsibilities until it has
	determined that callbacks are supported. Because the granting of a
	delegation is always conditional upon the absence of conflicting
	access, clients must not assume that a delegation will be granted and
	they must always be prepared for OPENs to be processed without any
	Draft Specification NFS version 4 Protocol October 2002
	delegations being granted.
	Once granted, a delegation behaves in most ways like a lock. There
	is an associated lease that is subject to renewal together with all
	of the other leases held by that client.
	Unlike locks, an operation by a second client to a delegated file
	will cause the server to recall a delegation through a callback.
	On recall, the client holding the delegation must flush modified
	state (such as modified data) to the server and return the
	delegation. The conflicting request will not receive a response
	until the recall is complete. The recall is considered complete when
	the client returns the delegation or the server times out on the
	recall and revokes the delegation as a result of the timeout.
	Following the resolution of the recall, the server has the
	information necessary to grant or deny the second client's request.
	At the time the client receives a delegation recall, it may have
	substantial state that needs to be flushed to the server. Therefore,
	the server should allow sufficient time for the delegation to be
	returned since it may involve numerous RPCs to the server. If the
	server is able to determine that the client is diligently flushing
	state to the server as a result of the recall, the server may extend
	the usual time allowed for a recall. However, the time allowed for
	recall completion should not be unbounded.
	An example of this is when responsibility to mediate opens on a given
	file is delegated to a client (see the section "Open Delegation").
	The server will not know what opens are in effect on the client.
	Without this knowledge the server will be unable to determine if the
	access and deny state for the file allows any particular open until
	the delegation for the file has been returned.
	A client failure or a network partition can result in failure to
	respond to a recall callback. In this case, the server will revoke
	the delegation which in turn will render useless any modified state
	still on the client.
	9.2.1. Delegation Recovery
	There are three situations that delegation recovery must deal with:
	o Client reboot or restart
	o Server reboot or restart
	o Network partition (full or callback-only)
	In the event the client reboots or restarts, the failure to renew
	Draft Specification NFS version 4 Protocol October 2002
	leases will result in the revocation of record locks and share
	reservations. Delegations, however, may be treated a bit
	differently.
	There will be situations in which delegations will need to be
	reestablished after a client reboots or restarts. The reason for
	this is the client may have file data stored locally and this data
	was associated with the previously held delegations. The client will
	need to reestablish the appropriate file state on the server.
	To allow for this type of client recovery, the server MAY extend the
	period for delegation recovery beyond the typical lease expiration
	period. This implies that requests from other clients that conflict
	with these delegations will need to wait. Because the normal recall
	process may require significant time for the client to flush changed
	state to the server, other clients need be prepared for delays that
	occur because of a conflicting delegation. This longer interval
	would increase the window for clients to reboot and consult stable
	storage so that the delegations can be reclaimed. For open
	delegations, such delegations are reclaimed using OPEN with a claim
	type of CLAIM_DELEGATE_PREV. (See the sections on "Data Caching and
	Revocation" and "Operation 18: OPEN" for discussion of open
	delegation and the details of OPEN respectively).
	A server MAY support a claim type of CLAIM_DELEGATE_PREV, but if it
	does, it MUST NOT remove delegations upon SETCLIENTID_CONFIRM, and
	instead MUST, for a period of time no less than that of the value of
	the lease_time attribute, maintain the client's delegations to allow
	time for the client to issue CLAIM_DELEGATE_PREV requests. The server
	that supports CLAIM_DELEGATE_PREV MUST support the DELEGPURGE
	operation.
	When the server reboots or restarts, delegations are reclaimed (using
	the OPEN operation with CLAIM_PREVIOUS) in a similar fashion to
	record locks and share reservations. However, there is a slight
	semantic difference. In the normal case if the server decides that a
	delegation should not be granted, it performs the requested action
	(e.g. OPEN) without granting any delegation. For reclaim, the server
	grants the delegation but a special designation is applied so that
	the client treats the delegation as having been granted but recalled
	by the server. Because of this, the client has the duty to write all
	modified state to the server and then return the delegation. This
	process of handling delegation reclaim reconciles three principles of
	the NFS version 4 protocol:
	o Upon reclaim, a client reporting resources assigned to it by an
	earlier server instance must be granted those resources.
	o The server has unquestionable authority to determine whether
	delegations are to be granted and, once granted, whether they
	are to be continued.
	Draft Specification NFS version 4 Protocol October 2002
	o The use of callbacks is not to be depended upon until the client
	has proven its ability to receive them.
	When a network partition occurs, delegations are subject to freeing
	by the server when the lease renewal period expires. This is similar
	to the behavior for locks and share reservations. For delegations,
	however, the server may extend the period in which conflicting
	requests are held off. Eventually the occurrence of a conflicting
	request from another client will cause revocation of the delegation.
	A loss of the callback path (e.g. by later network configuration
	change) will have the same effect. A recall request will fail and
	revocation of the delegation will result.
	A client normally finds out about revocation of a delegation when it
	uses a stateid associated with a delegation and receives the error
	NFS4ERR_EXPIRED. It also may find out about delegation revocation
	after a client reboot when it attempts to reclaim a delegation and
	receives that same error. Note that in the case of a revoked write
	open delegation, there are issues because data may have been modified
	by the client whose delegation is revoked and separately by other
	clients. See the section "Revocation Recovery for Write Open
	Delegation" for a discussion of such issues. Note also that when
	delegations are revoked, information about the revoked delegation
	will be written by the server to stable storage (as described in the
	section "Crash Recovery"). This is done to deal with the case in
	which a server reboots after revoking a delegation but before the
	client holding the revoked delegation is notified about the
	revocation.
	9.3. Data Caching
	When applications share access to a set of files, they need to be
	implemented so as to take account of the possibility of conflicting
	access by another application. This is true whether the applications
	in question execute on different clients or reside on the same
	client.
	Share reservations and record locks are the facilities the NFS
	version 4 protocol provides to allow applications to coordinate
	access by providing mutual exclusion facilities. The NFS version 4
	protocol's data caching must be implemented such that it does not
	invalidate the assumptions that those using these facilities depend
	upon.
	9.3.1. Data Caching and OPENs
	In order to avoid invalidating the sharing assumptions that
	applications rely on, NFS version 4 clients should not provide cached
	data to applications or modify it on behalf of an application when it
	would not be valid to obtain or modify that same data via a READ or
	Draft Specification NFS version 4 Protocol October 2002
	WRITE operation.
	Furthermore, in the absence of open delegation (see the section "Open
	Delegation") two additional rules apply. Note that these rules are
	obeyed in practice by many NFS version 2 and version 3 clients.
	o First, cached data present on a client must be revalidated after
	doing an OPEN. Revalidating means that the client fetches the
	change attribute from the server, compares it with the cached
	change attribute, and if different, declares the cached data (as
	well as the cached attributes) as invalid. This is to ensure
	that the data for the OPENed file is still correctly reflected
	in the client's cache. This validation must be done at least
	when the client's OPEN operation includes DENY=WRITE or BOTH
	thus terminating a period in which other clients may have had
	the opportunity to open the file with WRITE access. Clients may
	choose to do the revalidation more often (i.e. at OPENs
	specifying DENY=NONE) to parallel the NFS version 3 protocol's
	practice for the benefit of users assuming this degree of cache
	revalidation.
	Since the change attribute is updated for data and metadata
	modifications, some client implementors may be tempted to use
	the time_modify attribute and not change to validate cached
	data, so that metadata changes do not spuriously invalidate
	clean data. The implementor is cautioned in this approach. The
	change attribute is guaranteed to change for each update to the
	file, whereas time_modify is guaranteed to change only at the
	granularity of the time_delta attribute. Use by the client's
	data cache validation logic of time_modify and not change runs
	the risk of the client incorrectly marking stale data as valid.
	o Second, modified data must be flushed to the server before
	closing a file OPENed for write. This is complementary to the
	first rule. If the data is not flushed at CLOSE, the
	revalidation done after client OPENs as file is unable to
	achieve its purpose. The other aspect to flushing the data
	before close is that the data must be committed to stable
	storage, at the server, before the CLOSE operation is requested
	by the client. In the case of a server reboot or restart and a
	CLOSEd file, it may not be possible to retransmit the data to be
	written to the file. Hence, this requirement.
	9.3.2. Data Caching and File Locking
	For those applications that choose to use file locking instead of
	share reservations to exclude inconsistent file access, there is an
	analogous set of constraints that apply to client side data caching.
	These rules are effective only if the file locking is used in a way
	that matches in an equivalent way the actual READ and WRITE
	Draft Specification NFS version 4 Protocol October 2002
	operations executed. This is as opposed to file locking that is
	based on pure convention. For example, it is possible to manipulate
	a two-megabyte file by dividing the file into two one-megabyte
	regions and protecting access to the two regions by file locks on
	bytes zero and one. A lock for write on byte zero of the file would
	represent the right to do READ and WRITE operations on the first
	region. A lock for write on byte one of the file would represent the
	right to do READ and WRITE operations on the second region. As long
	as all applications manipulating the file obey this convention, they
	will work on a local filesystem. However, they may not work with the
	NFS version 4 protocol unless clients refrain from data caching.
	The rules for data caching in the file locking environment are:
	o First, when a client obtains a file lock for a particular
	region, the data cache corresponding to that region (if any
	cache data exists) must be revalidated. If the change attribute
	indicates that the file may have been updated since the cached
	data was obtained, the client must flush or invalidate the
	cached data for the newly locked region. A client might choose
	to invalidate all of non-modified cached data that it has for
	the file but the only requirement for correct operation is to
	invalidate all of the data in the newly locked region.
	o Second, before releasing a write lock for a region, all modified
	data for that region must be flushed to the server. The
	modified data must also be written to stable storage.
	Note that flushing data to the server and the invalidation of cached
	data must reflect the actual byte ranges locked or unlocked.
	Rounding these up or down to reflect client cache block boundaries
	will cause problems if not carefully done. For example, writing a
	modified block when only half of that block is within an area being
	unlocked may cause invalid modification to the region outside the
	unlocked area. This, in turn, may be part of a region locked by
	another client. Clients can avoid this situation by synchronously
	performing portions of write operations that overlap that portion
	(initial or final) that is not a full block. Similarly, invalidating
	a locked area which is not an integral number of full buffer blocks
	would require the client to read one or two partial blocks from the
	server if the revalidation procedure shows that the data which the
	client possesses may not be valid.
	The data that is written to the server as a prerequisite to the
	unlocking of a region must be written, at the server, to stable
	storage. The client may accomplish this either with synchronous
	writes or by following asynchronous writes with a COMMIT operation.
	This is required because retransmission of the modified data after a
	server reboot might conflict with a lock held by another client.
	A client implementation may choose to accommodate applications which
	use record locking in non-standard ways (e.g. using a record lock as
	Draft Specification NFS version 4 Protocol October 2002
	a global semaphore) by flushing to the server more data upon an LOCKU
	than is covered by the locked range. This may include modified data
	within files other than the one for which the unlocks are being done.
	In such cases, the client must not interfere with applications whose
	READs and WRITEs are being done only within the bounds of record
	locks which the application holds. For example, an application locks
	a single byte of a file and proceeds to write that single byte. A
	client that chose to handle a LOCKU by flushing all modified data to
	the server could validly write that single byte in response to an
	unrelated unlock. However, it would not be valid to write the entire
	block in which that single written byte was located since it includes
	an area that is not locked and might be locked by another client.
	Client implementations can avoid this problem by dividing files with
	modified data into those for which all modifications are done to
	areas covered by an appropriate record lock and those for which there
	are modifications not covered by a record lock. Any writes done for
	the former class of files must not include areas not locked and thus
	not modified on the client.
	9.3.3. Data Caching and Mandatory File Locking
	Client side data caching needs to respect mandatory file locking when
	it is in effect. The presence of mandatory file locking for a given
	file is indicated when the client gets back NFS4ERR_LOCKED from a
	READ or WRITE on a file it has an appropriate share reservation for.
	When mandatory locking is in effect for a file, the client must check
	for an appropriate file lock for data being read or written. If a
	lock exists for the range being read or written, the client may
	satisfy the request using the client's validated cache. If an
	appropriate file lock is not held for the range of the read or write,
	the read or write request must not be satisfied by the client's cache
	and the request must be sent to the server for processing. When a
	read or write request partially overlaps a locked region, the request
	should be subdivided into multiple pieces with each region (locked or
	not) treated appropriately.
	9.3.4. Data Caching and File Identity
	When clients cache data, the file data needs to be organized
	according to the filesystem object to which the data belongs. For
	NFS version 3 clients, the typical practice has been to assume for
	the purpose of caching that distinct filehandles represent distinct
	filesystem objects. The client then has the choice to organize and
	maintain the data cache on this basis.
	In the NFS version 4 protocol, there is now the possibility to have
	significant deviations from a "one filehandle per object" model
	because a filehandle may be constructed on the basis of the object's
	pathname. Therefore, clients need a reliable method to determine if
	two filehandles designate the same filesystem object. If clients
	Draft Specification NFS version 4 Protocol October 2002
	were simply to assume that all distinct filehandles denote distinct
	objects and proceed to do data caching on this basis, caching
	inconsistencies would arise between the distinct client side objects
	which mapped to the same server side object.
	By providing a method to differentiate filehandles, the NFS version 4
	protocol alleviates a potential functional regression in comparison
	with the NFS version 3 protocol. Without this method, caching
	inconsistencies within the same client could occur and this has not
	been present in previous versions of the NFS protocol. Note that it
	is possible to have such inconsistencies with applications executing
	on multiple clients but that is not the issue being addressed here.
	For the purposes of data caching, the following steps allow an NFS
	version 4 client to determine whether two distinct filehandles denote
	the same server side object:
	o If GETATTR directed to two filehandles returns different values
	of the fsid attribute, then the filehandles represent distinct
	objects.
	o If GETATTR for any file with an fsid that matches the fsid of
	the two filehandles in question returns a unique_handles
	attribute with a value of TRUE, then the two objects are
	distinct.
	o If GETATTR directed to the two filehandles does not return the
	fileid attribute for both of the handles, then it cannot be
	determined whether the two objects are the same. Therefore,
	operations which depend on that knowledge (e.g. client side data
	caching) cannot be done reliably.
	o If GETATTR directed to the two filehandles returns different
	values for the fileid attribute, then they are distinct objects.
	o Otherwise they are the same object.
	9.4. Open Delegation
	When a file is being OPENed, the server may delegate further handling
	of opens and closes for that file to the opening client. Any such
	delegation is recallable, since the circumstances that allowed for
	the delegation are subject to change. In particular, the server may
	receive a conflicting OPEN from another client, the server must
	recall the delegation before deciding whether the OPEN from the other
	client may be granted. Making a delegation is up to the server and
	clients should not assume that any particular OPEN either will or
	will not result in an open delegation. The following is a typical
	set of conditions that servers might use in deciding whether OPEN
	should be delegated:
	Draft Specification NFS version 4 Protocol October 2002
	o The client must be able to respond to the server's callback
	requests. The server will use the CB_NULL procedure for a test
	of callback ability.
	o The client must have responded properly to previous recalls.
	o There must be no current open conflicting with the requested
	delegation.
	o There should be no current delegation that conflicts with the
	delegation being requested.
	o The probability of future conflicting open requests should be
	low based on the recent history of the file.
	o The existence of any server-specific semantics of OPEN/CLOSE
	that would make the required handling incompatible with the
	prescribed handling that the delegated client would apply (see
	below).
	There are two types of open delegations, read and write. A read open
	delegation allows a client to handle, on its own, requests to open a
	file for reading that do not deny read access to others. Multiple
	read open delegations may be outstanding simultaneously and do not
	conflict. A write open delegation allows the client to handle, on
	its own, all opens. Only one write open delegation may exist for a
	given file at a given time and it is inconsistent with any read open
	delegations.
	When a client has a read open delegation, it may not make any changes
	to the contents or attributes of the file but it is assured that no
	other client may do so. When a client has a write open delegation,
	it may modify the file data since no other client will be accessing
	the file's data. The client holding a write delegation may only
	affect file attributes which are intimately connected with the file
	data: size, time_modify, change.
	When a client has an open delegation, it does not send OPENs or
	CLOSEs to the server but updates the appropriate status internally.
	For a read open delegation, opens that cannot be handled locally
	(opens for write or that deny read access) must be sent to the
	server.
	When an open delegation is made, the response to the OPEN contains an
	open delegation structure which specifies the following:
	o the type of delegation (read or write)
	o space limitation information to control flushing of data on
	close (write open delegation only, see the section "Open
	Delegation and Data Caching")
	Draft Specification NFS version 4 Protocol October 2002
	o an nfsace4 specifying read and write permissions
	o a stateid to represent the delegation for READ and WRITE
	The delegation stateid is separate and distinct from the stateid for
	the OPEN proper. The standard stateid, unlike the delegation
	stateid, is associated with a particular lock_owner and will continue
	to be valid after the delegation is recalled and the file remains
	open.
	When a request internal to the client is made to open a file and open
	delegation is in effect, it will be accepted or rejected solely on
	the basis of the following conditions. Any requirement for other
	checks to be made by the delegate should result in open delegation
	being denied so that the checks can be made by the server itself.
	o The access and deny bits for the request and the file as
	described in the section "Share Reservations".
	o The read and write permissions as determined below.
	The nfsace4 passed with delegation can be used to avoid frequent
	ACCESS calls. The permission check should be as follows:
	o If the nfsace4 indicates that the open may be done, then it
	should be granted without reference to the server.
	o If the nfsace4 indicates that the open may not be done, then an
	ACCESS request must be sent to the server to obtain the
	definitive answer.
	The server may return an nfsace4 that is more restrictive than the
	actual ACL of the file. This includes an nfsace4 that specifies
	denial of all access. Note that some common practices such as
	mapping the traditional user "root" to the user "nobody" may make it
	incorrect to return the actual ACL of the file in the delegation
	response.
	The use of delegation together with various other forms of caching
	creates the possibility that no server authentication will ever be
	performed for a given user since all of the user's requests might be
	satisfied locally. Where the client is depending on the server for
	authentication, the client should be sure authentication occurs for
	each user by use of the ACCESS operation. This should be the case
	even if an ACCESS operation would not be required otherwise. As
	mentioned before, the server may enforce frequent authentication by
	returning an nfsace4 denying all access with every open delegation.
	Draft Specification NFS version 4 Protocol October 2002
	9.4.1. Open Delegation and Data Caching
	OPEN delegation allows much of the message overhead associated with
	the opening and closing files to be eliminated. An open when an open
	delegation is in effect does not require that a validation message be
	sent to the server. The continued endurance of the "read open
	delegation" provides a guarantee that no OPEN for write and thus no
	write has occurred. Similarly, when closing a file opened for write
	and if write open delegation is in effect, the data written does not
	have to be flushed to the server until the open delegation is
	recalled. The continued endurance of the open delegation provides a
	guarantee that no open and thus no read or write has been done by
	another client.
	For the purposes of open delegation, READs and WRITEs done without an
	OPEN are treated as the functional equivalents of a corresponding
	type of OPEN. This refers to the READs and WRITEs that use the
	special stateids consisting of all zero bits or all one bits.
	Therefore, READs or WRITEs with a special stateid done by another
	client will force the server to recall a write open delegation. A
	WRITE with a special stateid done by another client will force a
	recall of read open delegations.
	With delegations, a client is able to avoid writing data to the
	server when the CLOSE of a file is serviced. The file close system
	call is the usual point at which the client is notified of a lack of
	stable storage for the modified file data generated by the
	application. At the close, file data is written to the server and
	through normal accounting the server is able to determine if the
	available filesystem space for the data has been exceeded (i.e.
	server returns NFS4ERR_NOSPC or NFS4ERR_DQUOT). This accounting
	includes quotas. The introduction of delegations requires that a
	alternative method be in place for the same type of communication to
	occur between client and server.
	In the delegation response, the server provides either the limit of
	the size of the file or the number of modified blocks and associated
	block size. The server must ensure that the client will be able to
	flush data to the server of a size equal to that provided in the
	original delegation. The server must make this assurance for all
	outstanding delegations. Therefore, the server must be careful in
	its management of available space for new or modified data taking
	into account available filesystem space and any applicable quotas.
	The server can recall delegations as a result of managing the
	available filesystem space. The client should abide by the server's
	state space limits for delegations. If the client exceeds the stated
	limits for the delegation, the server's behavior is undefined.
	Based on server conditions, quotas or available filesystem space, the
	server may grant write open delegations with very restrictive space
	limitations. The limitations may be defined in a way that will
	always force modified data to be flushed to the server on close.
	Draft Specification NFS version 4 Protocol October 2002
	With respect to authentication, flushing modified data to the server
	after a CLOSE has occurred may be problematic. For example, the user
	of the application may have logged off the client and unexpired
	authentication credentials may not be present. In this case, the
	client may need to take special care to ensure that local unexpired
	credentials will in fact be available. This may be accomplished by
	tracking the expiration time of credentials and flushing data well in
	advance of their expiration or by making private copies of
	credentials to assure their availability when needed.
	9.4.2. Open Delegation and File Locks
	When a client holds a write open delegation, lock operations are
	performed locally. This includes those required for mandatory file
	locking. This can be done since the delegation implies that there
	can be no conflicting locks. Similarly, all of the revalidations
	that would normally be associated with obtaining locks and the
	flushing of data associated with the releasing of locks need not be
	done.
	When a client holds a read open delegation, lock operations are not
	performed locally. All lock operations, including those requesting
	non-exclusive locks, are sent to the server for resolution.
	9.4.3. Handling of CB_GETATTR
	The server needs to employ special handling for a GETATTR where the
	target is a file that has a write open delegation in effect. The
	reason for this is that the client holding the write delegation may
	have modified the data and the server needs to reflect this change to
	the second client that submitted the GETATTR. Therefore, the client
	holding the write delegation needs to be interrogated. The server
	will use the CB_GETATTR operation. The only attributes that the
	server can reliably query via CB_GETATTR are size and change.
	Since CB_GETATTR is being used to satisfy another client's GETATTR
	request, the server only needs to know if the client holding the
	delegation has a modified version of the file. If the client's copy
	of the delegated file is not modified (data or size), the server can
	satisfy the second client's GETATTR request from the attributes
	stored locally at the server. If the file is modified, the server
	only needs to know about this modified state. If the server
	determines that the file is currently modified, it will respond to
	the second client's GETATTR as if the file had been modified locally
	at the server.
	Since the form of the change attribute is determined by the server
	and is opaque to the client, the client and server need to agree on a
	method of communicating the modified state of the file. For the size
	attribute, the client will report its current view of the file size.
	Draft Specification NFS version 4 Protocol October 2002
	For the change attribute, the handling is more involved.
	For the client, the following steps will be taken when receiving a
	write delegation:
	o The value of the change attribute will be obtained from the
	server and cached. Let this value be represented by c.
	o The client will create a value greater than c that will be used
	for communicating modified data is held at the client. Let this
	value be represented by d.
	o When the client is queried via CB_GETATTR for the change
	attribute, it checks to see if it holds modified data. If the
	file is modified, the value d is returned for the change
	attribute value. If this file is not currently modified, the
	client returns the value c for the change attribute.
	For simplicity of implementation, the client MAY for each CB_GETATTR
	return the same value d. This is true even if, between successive
	CB_GETATTR operations, the client again modifies in the file's data
	or metadata in its cache. The client can return the same value
	because the only requirement is that the client be able to indicate
	to the server that the client holds modified data. Therefore, the
	value of d may always be c + 1.
	While the change attribute is opaque to the client in the sense that
	it has no idea what units of time, if any, the server is counting
	change with, it is not opaque in that the client has to treat it as
	an unsigned integer, and the server has to be able to see the results
	of the client's changes to that integer. Therefore, the server MUST
	encode the change attribute in network order when sending it to the
	client. The client MUST decode it from network order to its native
	order when receiving it and the client MUST encode it network order
	when sending it to the server. For this reason, change is defined as
	an unsigned integer rather than an opaque array of octets.
	For the server, the following steps will be taken when providing a
	write delegation:
	o Upon providing a write delegation, the server will cache a copy
	of the change attribute in the data structure it uses to record
	the delegation. Let this value be represented by sc.
	o When a second client sends a GETATTR operation on the same file
	to the server, the server obtains the change attribute from the
	first client. Let this value be cc.
	o If the value cc is equal to sc, the file is not modified and the
	server returns the current values for change, time_metadata, and
	time_modify (for example) to the second client.
	Draft Specification NFS version 4 Protocol October 2002
	o If the value cc is NOT equal to sc, the file is currently
	modified at the first client and most likely will be modified at
	the server at a future time. The server then uses its current
	time to construct attribute values for time_metadata and
	time_modify. A new value of sc, which we will call nsc, is
	computed by the server, such that nsc >= sc + 1. The server
	then returns the constructed time_metadata, time_modify, and nsc
	values to the requester. The server replaces sc in the
	delegation record with nsc. To prevent the possibility of
	time_modify, time_metadata, and change from appearing to go
	backward (which would happen if the client holding the
	delegation fails to write its modified data to the server before
	the delegation is revoked or returned), the server SHOULD update
	the file's metadata record with the constructed attribute
	values. For reasons of reasonable performance, committing the
	constructed attribute values to stable storage is OPTIONAL.
	As discussed earlier in this section, the client MAY return the
	same cc value on subsequent CB_GETATTR calls, even if the file
	was modified in the client's cache yet again between successive
	CB_GETATTR calls. Therefore, the server must assume that the
	file has been modified yet again, and MUST take care to ensure
	that the new nsc it constructs and returns is greater than the
	previous nsc it returned. An example implementation's
	delegation record would satisfy this mandate by including a
	boolean field (let us call it "modified") that is set to false
	when the delegation is granted, and an sc value set at the time
	of grant to the change attribute value. The modified field would
	be set to true the first time cc != sc, and would stay true
	until the delegation is returned or revoked. The processing for
	constructing nsc, time_modify, and time_metadata would use this
	pseudo code:
	if (!modified) {
	do CB_GETATTR for change and size;
	if (cc != sc)
	modified = TRUE; } else {
	do CB_GETATTR for size; }
	if (modified) {
	sc = sc + 1;
	time_modify = time_metadata = current_time;
	update sc, time_modify, time_metadata into file's metadata;
	}
	return to client (that sent GETATTR) the attributes
	it requested, but make sure size comes from what
	CB_GETATTR returned. Do not update the file's metadata
	with the client's modified size.
	o In the case that the file attribute size is different than the
	Draft Specification NFS version 4 Protocol October 2002
	server's current value, the server treats this as a modification
	regardless of the value of the change attribute retrieved via
	CB_GETATTR and responds to the second client as in the last
	step.
	This methodology resolves issues of clock differences between client
	and server and other scenarios where the use of CB_GETATTR break
	down.
	It should be noted that the server is under no obligation to use
	CB_GETATTR and therefore the server MAY simply recall the delegation
	to avoid its use.
	9.4.4. Recall of Open Delegation
	The following events necessitate recall of an open delegation:
	o Potentially conflicting OPEN request (or READ/WRITE done with
	"special" stateid)
	o SETATTR issued by another client
	o REMOVE request for the file
	o RENAME request for the file as either source or target of the
	RENAME
	Whether a RENAME of a directory in the path leading to the file
	results in recall of an open delegation depends on the semantics of
	the server filesystem. If that filesystem denies such RENAMEs when a
	file is open, the recall must be performed to determine whether the
	file in question is, in fact, open.
	In addition to the situations above, the server may choose to recall
	open delegations at any time if resource constraints make it
	advisable to do so. Clients should always be prepared for the
	possibility of recall.
	When a client receives a recall for an open delegation, it needs to
	update state on the server before returning the delegation. These
	same updates must be done whenever a client chooses to return a
	delegation voluntarily. The following items of state need to be
	dealt with:
	o If the file associated with the delegation is no longer open and
	no previous CLOSE operation has been sent to the server, a CLOSE
	operation must be sent to the server.
	o If a file has other open references at the client, then OPEN
	operations must be sent to the server. The appropriate stateids
	Draft Specification NFS version 4 Protocol October 2002
	will be provided by the server for subsequent use by the client
	since the delegation stateid will not longer be valid. These
	OPEN requests are done with the claim type of
	CLAIM_DELEGATE_CUR. This will allow the presentation of the
	delegation stateid so that the client can establish the
	appropriate rights to perform the OPEN. (see the section
	"Operation 18: OPEN" for details.)
	o If there are granted file locks, the corresponding LOCK
	operations need to be performed. This applies to the write open
	delegation case only.
	o For a write open delegation, if at the time of recall the file
	is not open for write, all modified data for the file must be
	flushed to the server. If the delegation had not existed, the
	client would have done this data flush before the CLOSE
	operation.
	o For a write open delegation when a file is still open at the
	time of recall, any modified data for the file needs to be
	flushed to the server.
	o With the write open delegation in place, it is possible that the
	file was truncated during the duration of the delegation. For
	example, the truncation could have occurred as a result of an
	OPEN UNCHECKED with a size attribute value of zero. Therefore,
	if a truncation of the file has occurred and this operation has
	not been propagated to the server, the truncation must occur
	before any modified data is written to the server.
	In the case of write open delegation, file locking imposes some
	additional requirements. To precisely maintain the associated
	invariant, it is required to flush any modified data in any region
	for which a write lock was released while the write delegation was in
	effect. However, because the write open delegation implies no other
	locking by other clients, a simpler implementation is to flush all
	modified data for the file (as described just above) if any write
	lock has been released while the write open delegation was in effect.
	An implementation need not wait until delegation recall (or deciding
	to voluntarily return a delegation) to perform any of the above
	actions, if implementation considerations (e.g. resource availability
	constraints) make that desirable. Generally, however, the fact that
	the actual open state of the file may continue to change makes it not
	worthwhile to send information about opens and closes to the server,
	except as part of delegation return. Only in the case of closing the
	open that resulted in obtaining the delegation would clients be
	likely to do this early, since, in that case, the close once done
	will not be undone. Regardless of the client's choices on scheduling
	these actions, all must be performed before the delegation is
	returned, including (when applicable) the close that corresponds to
	the open that resulted in the delegation. These actions can be
	Draft Specification NFS version 4 Protocol October 2002
	performed either in previous requests or in previous operations in
	the same COMPOUND request.
	9.4.5. Clients that Fail to Honor Delegation Recalls
	A client may fail to respond to a recall for various reasons, such as
	a failure of the callback path from server to the client. The client
	may be unaware of a failure in the callback path. This lack of
	awareness could result in the client finding out long after the
	failure that its delegation has been revoked, and another client has
	modified the data for which the client had a delegation. This is
	especially a problem for the client that held a write delegation.
	The server also has a dilemma in that the client that fails to
	respond to the recall might also be sending other NFS requests,
	including those that renew the lease before the lease expires.
	Without returning an error for those lease renewing operations, the
	server leads the client to believe that the delegation it has is in
	force.
	This difficulty is solved by the following rules:
	o When the callback path is down, the server MUST NOT revoke the
	delegation if one of the following occurs:
	- The client has issued a RENEW operation and the server has
	returned an NFS4ERR_CB_PATH_DOWN error. The server MUST renew
	the lease for any record locks and share reservations the
	client has that the server has known about (as opposed to those
	locks and share reservations the client has established but not
	yet sent to the server, due to the delegation). The server
	SHOULD give the client a reasonable time to return its
	delegations to the server before revoking the client's
	delegations.
	- The client has not issued a RENEW operation for some period of
	time after the server attempted to recall the delegation. This
	period of time MUST NOT be less than the value of the
	lease_time attribute.
	o When the client holds a delegation, it can not rely on operations,
	except for RENEW, that take a stateid, to renew delegation leases
	across callback path failures. The client that wants to keep
	delegations in force across callback path failures must use RENEW
	to do so.
	9.4.6. Delegation Revocation
	At the point a delegation is revoked, if there are associated opens
	on the client, the applications holding these opens need to be
	Draft Specification NFS version 4 Protocol October 2002
	notified. This notification usually occurs by returning errors for
	READ/WRITE operations or when a close is attempted for the open file.
	If no opens exist for the file at the point the delegation is
	revoked, then notification of the revocation is unnecessary.
	However, if there is modified data present at the client for the
	file, the user of the application should be notified. Unfortunately,
	it may not be possible to notify the user since active applications
	may not be present at the client. See the section "Revocation
	Recovery for Write Open Delegation" for additional details.
	9.5. Data Caching and Revocation
	When locks and delegations are revoked, the assumptions upon which
	successful caching depend are no longer guaranteed. For any locks or
	share reservations that have been revoked, the corresponding owner
	needs to be notified. This notification includes applications with a
	file open that has a corresponding delegation which has been revoked.
	Cached data associated with the revocation must be removed from the
	client. In the case of modified data existing in the client's cache,
	that data must be removed from the client without it being written to
	the server. As mentioned, the assumptions made by the client are no
	longer valid at the point when a lock or delegation has been revoked.
	For example, another client may have been granted a conflicting lock
	after the revocation of the lock at the first client. Therefore, the
	data within the lock range may have been modified by the other
	client. Obviously, the first client is unable to guarantee to the
	application what has occurred to the file in the case of revocation.
	Notification to a lock owner will in many cases consist of simply
	returning an error on the next and all subsequent READs/WRITEs to the
	open file or on the close. Where the methods available to a client
	make such notification impossible because errors for certain
	operations may not be returned, more drastic action such as signals
	or process termination may be appropriate. The justification for
	this is that an invariant for which an application depends on may be
	violated. Depending on how errors are typically treated for the
	client operating environment, further levels of notification
	including logging, console messages, and GUI pop-ups may be
	appropriate.
	9.5.1. Revocation Recovery for Write Open Delegation
	Revocation recovery for a write open delegation poses the special
	issue of modified data in the client cache while the file is not
	open. In this situation, any client which does not flush modified
	data to the server on each close must ensure that the user receives
	appropriate notification of the failure as a result of the
	revocation. Since such situations may require human action to
	correct problems, notification schemes in which the appropriate user
	Draft Specification NFS version 4 Protocol October 2002
	or administrator is notified may be necessary. Logging and console
	messages are typical examples.
	If there is modified data on the client, it must not be flushed
	normally to the server. A client may attempt to provide a copy of
	the file data as modified during the delegation under a different
	name in the filesystem name space to ease recovery. Note that when
	the client can determine that the file has not been modified by any
	other client, or when the client has a complete cached copy of file
	in question, such a saved copy of the client's view of the file may
	be of particular value for recovery. In other case, recovery using a
	copy of the file based partially on the client's cached data and
	partially on the server copy as modified by other clients, will be
	anything but straightforward, so clients may avoid saving file
	contents in these situations or mark the results specially to warn
	users of possible problems.
	Saving of such modified data in delegation revocation situations may
	be limited to files of a certain size or might be used only when
	sufficient disk space is available within the target filesystem.
	Such saving may also be restricted to situations when the client has
	sufficient buffering resources to keep the cached copy available
	until it is properly stored to the target filesystem.
	9.6. Attribute Caching
	The attributes discussed in this section do not include named
	attributes. Individual named attributes are analogous to files and
	caching of the data for these needs to be handled just as data
	caching is for ordinary files. Similarly, LOOKUP results from an
	OPENATTR directory are to be cached on the same basis as any other
	pathnames and similarly for directory contents.
	Clients may cache file attributes obtained from the server and use
	them to avoid subsequent GETATTR requests. Such caching is write
	through in that modification to file attributes is always done by
	means of requests to the server and should not be done locally and
	cached. The exception to this are modifications to attributes that
	are intimately connected with data caching. Therefore, extending a
	file by writing data to the local data cache is reflected immediately
	in the size as seen on the client without this change being
	immediately reflected on the server. Normally such changes are not
	propagated directly to the server but when the modified data is
	flushed to the server, analogous attribute changes are made on the
	server. When open delegation is in effect, the modified attributes
	may be returned to the server in the response to a CB_RECALL call.
	The result of local caching of attributes is that the attribute
	caches maintained on individual clients will not be coherent. Changes
	made in one order on the server may be seen in a different order on
	Draft Specification NFS version 4 Protocol October 2002
	one client and in a third order on a different client.
	The typical filesystem application programming interfaces do not
	provide means to atomically modify or interrogate attributes for
	multiple files at the same time. The following rules provide an
	environment where the potential incoherences mentioned above can be
	reasonably managed. These rules are derived from the practice of
	previous NFS protocols.
	o All attributes for a given file (per-fsid attributes excepted)
	are cached as a unit at the client so that no non-
	serializability can arise within the context of a single file.
	o An upper time boundary is maintained on how long a client cache
	entry can be kept without being refreshed from the server.
	o When operations are performed that change attributes at the
	server, the updated attribute set is requested as part of the
	containing RPC. This includes directory operations that update
	attributes indirectly. This is accomplished by following the
	modifying operation with a GETATTR operation and then using the
	results of the GETATTR to update the client's cached attributes.
	Note that if the full set of attributes to be cached is requested by
	READDIR, the results can be cached by the client on the same basis as
	attributes obtained via GETATTR.
	A client may validate its cached version of attributes for a file by
	fetching just both the change and time_access attributes and assuming
	that if the change attribute has the same value as it did when the
	attributes were cached, then no attributes other than time_access
	have changed. The reason why time_access is also fetched is because
	many servers operate in environments where the operation that updates
	change does not update time_access. For example, POSIX file
	semantics do not update access time when a file is modified by the
	write system call. Therefore, the client that wants a current
	time_access value should fetch it with change during the attribute
	cache validation processing and update its cached time_access.
	The client may maintain a cache of modified attributes for those
	attributes intimately connected with data of modified regular files
	(size, time_modify, and change). Other than those three attributes,
	the client MUST NOT maintain a cache of modified attributes. Instead,
	attribute changes are immediately sent to the server.
	In some operating environments, the equivalent to time_access is
	expected to be implicitly updated by each read of the content of the
	file object. If an NFS client is caching the content of a file
	object, whether it is a regular file, directory, or symbolic link,
	the client SHOULD NOT update the time_access attribute (via SETATTR
	or a small READ or READDIR request) on the server with each read that
	is satisfied from cache. The reason is that this can defeat the
	Draft Specification NFS version 4 Protocol October 2002
	performance benefits of caching content, especially since an explicit
	SETATTR of time_access may alter the change attribute on the server.
	If the change attribute changes, clients that are caching the content
	will think the content has changed, and will re-read unmodified data
	from the server. Nor is the client encouraged to maintain a modified
	version of time_access in its cache, since this would mean that the
	client will either eventually have to write the access time to the
	server with bad performance effects, or it would never update the
	server's time_access, thereby resulting in a situation where an
	application that caches access time between a close and open of the
	same file observes the access time oscillating between the past and
	present. The time_access attribute always means the time of last
	access to a file by a read that was satisfied by the server. This way
	clients will tend to see only time_access changes that go forward in
	time.
	9.7. Data and Metadata Caching and Memory Mapped Files
	Some operating environments include the capability for an application
	to map a file's content into the application's address space. Each
	time the application accesses a memory location that corresponds to a
	block that has not been loaded into the address space, a page fault
	occurs and the file is read (or if the block does not exist in the
	file, the block is allocated and then instantiated in the
	application's address space).
	As long as each memory mapped access to the file requires a page
	fault, the relevant attributes of the file that are used to detect
	access and modification (time_access, time_metadata, time_modify, and
	change) will be updated. However, in many operating environments,
	when page faults are not required these attributes will not be
	updated on reads or updates to the file via memory access (regardless
	whether the file is local file or is being access remotely). A
	client or server MAY fail to update attributes of a file that is
	being accessed via memory mapped I/O. This has several implications:
	o If there is an application on the server that has memory mapped
	a file that a client is also accessing, the client may not be
	able to get a consistent value of the change attribute to
	determine whether its cache is stale or not. A server that
	knows that the file is memory mapped could always
	pessimistically return updated values for change so as to force
	the application to always get the most up to date data and
	metadata for the file. However, due to the negative performance
	implications of this, such behavior is OPTIONAL.
	o If the memory mapped file is not being modified on the server,
	and instead is just being read by an application via the memory
	mapped interface, the client will not see an updated time_access
	attribute. However, in many operating environments, neither
	will any process running on the server. Thus NFS clients are at
	Draft Specification NFS version 4 Protocol October 2002
	no disadvantage with respect to local processes.
	o If there is another client that is memory mapping the file, and
	if that client is holding a write delegation, the same set of
	issues as discussed in the previous two bullet items apply. So,
	when a server does a CB_GETATTR to a file that the client has
	modified in its cache, the response from CB_GETATTR will not
	necessarily be accurate. As discussed earlier, the client's
	obligation is to report that the file has been modified since
	the delegation was granted, not whether it has been modified
	again between successive CB_GETATTR calls, and the server MUST
	assume that any file the client has modified in cache has been
	modified again between successive CB_GETATTR calls. Depending
	on the nature of the client's memory management system, this
	weak obligation may not be possible. A client MAY return stale
	information in CB_GETATTR whenever the file is memory mapped.
	o The mixture of memory mapping and file locking on the same file
	is problematic. Consider the following scenario, where a page
	size on each client is 8192 bytes.
	- Client A memory maps first page (8192 bytes) of file X
	- Client B memory maps first page (8192 bytes) of file X
	- Client A write locks first 4096 bytes
	- Client B write locks second 4096 bytes
	- Client A, via a STORE instruction modifies part of its
	locked region.
	- Simultaneous to client A, client B issues a STORE on part
	of its locked region.
	Here the challenge is for each client to resynchronize to get a
	correct view of the first page. In many operating environments,
	the virtual memory management systems on each client only know a
	page is modified, not that a subset of the page corresponding to
	the respective lock regions has been modified. So it is not
	possible for each client to do the right thing, which is to only
	write to the server that portion of the page that is locked.
	For example, if client A simply writes out the page, and then
	client B writes out the page, client A's data is lost.
	Moreover, if mandatory locking is enabled on the file, then we
	have a different problem. When clients A and B issue the STORE
	instructions, the resulting page faults require a record lock on
	the entire page. Each client then tries to extend their locked
	range to the entire page, which results in a deadlock.
	Draft Specification NFS version 4 Protocol October 2002
	Communicating the NFS4ERR_DEADLOCK error to a STORE instruction
	is difficult at best.
	If a client is locking the entire memory mapped file, there is
	no problem with advisory or mandatory record locking, at least
	until the client unlocks a region in the middle of the file.
	Given the above issues the following are permitted:
	- Clients and servers MAY deny memory mapping a file they
	know there are record locks for.
	- Clients and servers MAY deny a record lock on a file they
	know is memory mapped.
	- A client MAY deny memory mapping a file that it knows
	requires mandatory locking for I/O. If mandatory locking
	is enabled after the file is opened and mapped, the client
	MAY deny the application further access to its mapped file.
	9.8. Name Caching
	The results of LOOKUP and READDIR operations may be cached to avoid
	the cost of subsequent LOOKUP operations. Just as in the case of
	attribute caching, inconsistencies may arise among the various client
	caches. To mitigate the effects of these inconsistencies and given
	the context of typical filesystem APIs, an upper time boundary is
	maintained on how long a client name cache entry can be kept without
	verifying that the entry has not been made invalid by a directory
	change operation performed by another client.
	When a client is not making changes to a directory for which there
	exist name cache entries, the client needs to periodically fetch
	attributes for that directory to ensure that it is not being
	modified. After determining that no modification has occurred, the
	expiration time for the associated name cache entries may be updated
	to be the current time plus the name cache staleness bound.
	When a client is making changes to a given directory, it needs to
	determine whether there have been changes made to the directory by
	other clients. It does this by using the change attribute as
	reported before and after the directory operation in the associated
	change_info4 value returned for the operation. The server is able to
	communicate to the client whether the change_info4 data is provided
	atomically with respect to the directory operation. If the change
	values are provided atomically, the client is then able to compare
	the pre-operation change value with the change value in the client's
	name cache. If the comparison indicates that the directory was
	updated by another client, the name cache associated with the
	Draft Specification NFS version 4 Protocol October 2002
	modified directory is purged from the client. If the comparison
	indicates no modification, the name cache can be updated on the
	client to reflect the directory operation and the associated timeout
	extended. The post-operation change value needs to be saved as the
	basis for future change_info4 comparisons.
	As demonstrated by the scenario above, name caching requires that the
	client revalidate name cache data by inspecting the change attribute
	of a directory at the point when the name cache item was cached.
	This requires that the server update the change attribute for
	directories when the contents of the corresponding directory is
	modified. For a client to use the change_info4 information
	appropriately and correctly, the server must report the pre and post
	operation change attribute values atomically. When the server is
	unable to report the before and after values atomically with respect
	to the directory operation, the server must indicate that fact in the
	change_info4 return value. When the information is not atomically
	reported, the client should not assume that other clients have not
	changed the directory.
	9.9. Directory Caching
	The results of READDIR operations may be used to avoid subsequent
	READDIR operations. Just as in the cases of attribute and name
	caching, inconsistencies may arise among the various client caches.
	To mitigate the effects of these inconsistencies, and given the
	context of typical filesystem APIs, the following rules should be
	followed:
	o Cached READDIR information for a directory which is not obtained
	in a single READDIR operation must always be a consistent
	snapshot of directory contents. This is determined by using a
	GETATTR before the first READDIR and after the last of READDIR
	that contributes to the cache.
	o An upper time boundary is maintained to indicate the length of
	time a directory cache entry is considered valid before the
	client must revalidate the cached information.
	The revalidation technique parallels that discussed in the case of
	name caching. When the client is not changing the directory in
	question, checking the change attribute of the directory with GETATTR
	is adequate. The lifetime of the cache entry can be extended at
	these checkpoints. When a client is modifying the directory, the
	client needs to use the change_info4 data to determine whether there
	are other clients modifying the directory. If it is determined that
	no other client modifications are occurring, the client may update
	its directory cache to reflect its own changes.
	As demonstrated previously, directory caching requires that the
	client revalidate directory cache data by inspecting the change
	Draft Specification NFS version 4 Protocol October 2002
	attribute of a directory at the point when the directory was cached.
	This requires that the server update the change attribute for
	directories when the contents of the corresponding directory is
	modified. For a client to use the change_info4 information
	appropriately and correctly, the server must report the pre and post
	operation change attribute values atomically. When the server is
	unable to report the before and after values atomically with respect
	to the directory operation, the server must indicate that fact in the
	change_info4 return value. When the information is not atomically
	reported, the client should not assume that other clients have not
	changed the directory.
	Draft Specification NFS version 4 Protocol October 2002
	10. Minor Versioning
	To address the requirement of an NFS protocol that can evolve as the
	need arises, the NFS version 4 protocol contains the rules and
	framework to allow for future minor changes or versioning.
	The base assumption with respect to minor versioning is that any
	future accepted minor version must follow the IETF process and be
	documented in a standards track RFC. Therefore, each minor version
	number will correspond to an RFC. Minor version zero of the NFS
	version 4 protocol is represented by this RFC. The COMPOUND
	procedure will support the encoding of the minor version being
	requested by the client.
	The following items represent the basic rules for the development of
	minor versions. Note that a future minor version may decide to
	modify or add to the following rules as part of the minor version
	definition.
	1 Procedures are not added or deleted
	To maintain the general RPC model, NFS version 4 minor versions
	will not add to or delete procedures from the NFS program.
	2 Minor versions may add operations to the COMPOUND and
	CB_COMPOUND procedures.
	The addition of operations to the COMPOUND and CB_COMPOUND
	procedures does not affect the RPC model.
	2.1 Minor versions may append attributes to GETATTR4args, bitmap4,
	and GETATTR4res.
	This allows for the expansion of the attribute model to allow
	for future growth or adaptation.
	2.2 Minor version X must append any new attributes after the last
	documented attribute.
	Since attribute results are specified as an opaque array of
	per-attribute XDR encoded results, the complexity of adding new
	attributes in the midst of the current definitions will be too
	burdensome.
	3 Minor versions must not modify the structure of an existing
	operation's arguments or results.
	Draft Specification NFS version 4 Protocol October 2002
	Again the complexity of handling multiple structure definitions
	for a single operation is too burdensome. New operations should
	be added instead of modifying existing structures for a minor
	version.
	This rule does not preclude the following adaptations in a minor
	version.
	o adding bits to flag fields such as new attributes to
	GETATTR's bitmap4 data type
	o adding bits to existing attributes like ACLs that have flag
	words
	o extending enumerated types (including NFS4ERR_*) with new
	values
	4 Minor versions may not modify the structure of existing
	attributes.
	5 Minor versions may not delete operations.
	This prevents the potential reuse of a particular operation
	"slot" in a future minor version.
	6 Minor versions may not delete attributes.
	7 Minor versions may not delete flag bits or enumeration values.
	8 Minor versions may declare an operation as mandatory to NOT
	implement.
	Specifying an operation as "mandatory to not implement" is
	equivalent to obsoleting an operation. For the client, it means
	that the operation should not be sent to the server. For the
	server, an NFS error can be returned as opposed to "dropping"
	the request as an XDR decode error. This approach allows for
	the obsolescence of an operation while maintaining its structure
	so that a future minor version can reintroduce the operation.
	8.1 Minor versions may declare attributes mandatory to NOT
	implement.
	8.2 Minor versions may declare flag bits or enumeration values as
	mandatory to NOT implement.
	Draft Specification NFS version 4 Protocol October 2002
	9 Minor versions may downgrade features from mandatory to
	recommended, or recommended to optional.
	10 Minor versions may upgrade features from optional to recommended
	or recommended to mandatory.
	11 A client and server that support minor version X must support
	minor versions 0 (zero) through X-1 as well.
	12 No new features may be introduced as mandatory in a minor
	version.
	This rule allows for the introduction of new functionality and
	forces the use of implementation experience before designating a
	feature as mandatory.
	13 A client MUST NOT attempt to use a stateid, filehandle, or
	similar returned object from the COMPOUND procedure with minor
	version X for another COMPOUND procedure with minor version Y,
	where X != Y.
	Draft Specification NFS version 4 Protocol October 2002
	11. Internationalization
	The primary issue in which NFS needs to deal with
	internationalization, or I18N, is with respect to file names and
	other strings as used within the protocol. The choice of string
	representation must allow reasonable name/string access to clients
	which use various languages. The UTF-8 encoding of the UCS as
	defined by [ISO10646] allows for this type of access and follows the
	policy described in "IETF Policy on Character Sets and Languages",
	[RFC2277]. This choice is explained further in the following.
	11.1. Universal Versus Local Character Sets
	[RFC1345] describes a table of 16 bit characters for many different
	languages (the bit encodings match Unicode, though of course
	[RFC1345] is somewhat out of date with respect to current Unicode
	assignments). Each character from each language has a unique 16 bit
	value in the 16 bit character set. Thus this table can be thought of
	as a universal character set. [RFC1345] then talks about groupings
	of subsets of the entire 16 bit character set into "Charset Tables".
	For example one might take all the Greek characters from the 16 bit
	table (which are consecutively allocated), and normalize their
	offsets to a table that fits in 7 bits. Thus it is determined that
	"lower case alpha" is in the same position as "upper case a" in the
	US-ASCII table, and "upper case alpha" is in the same position as
	"lower case a" in the US-ASCII table.
	These normalized subset character sets can be thought of as "local
	character sets", suitable for an operating system locale.
	Local character sets are not suitable for the NFS protocol. Consider
	someone who creates a file with a name in a Swedish character set.
	If someone else later goes to access the file with their locale set
	to the Swedish language, then there are no problems. But if someone
	in say the US-ASCII locale goes to access the file, the file name
	will look very different, because the Swedish characters in the 7 bit
	table will now be represented in US-ASCII characters on the display.
	It would be preferable to give the US-ASCII user a way to display the
	file name using Swedish glyphs. In order to do that, the NFS protocol
	would have to include the locale with the file name on each operation
	to create a file.
	However, the complexity burden of defining such locales in a way that
	could be understood by all clients and servers, and maintaining them
	in the face of changes would be considerable. A better solution is
	desirable.
	If the NFS version 4 protocol used a universal 16 bit or 32 bit
	character set (or an encoding of a 16 bit or 32 bit character set
	into octets), then the server and client need not care if the locale
	of the user accessing the file is different than the locale of the
	user who created the file. The unique 16 bit or 32 bit encoding of
	Draft Specification NFS version 4 Protocol October 2002
	the character allows for determination of what language the character
	is from and also how to display that character on the client. The
	server need not know what locales are used.
	11.2. Overview of Universal Character Set Standards
	The previous section makes a case for using a universal character
	set. This section makes the case for using UTF-8 as the specific
	universal character set for the NFS version 4 protocol.
	[RFC2279] discusses UTF-* (UTF-8 and other UTF-XXX encodings),
	Unicode, and UCS-*. There are two standards bodies managing
	universal code sets:
	o ISO/IEC which has the standard 10646-1
	o Unicode which has the Unicode standard
	Both standards bodies have pledged to track each other's assignments
	of character codes.
	The following is a brief analysis of the various standards.
	UCS Universal Character Set. This is ISO/IEC 10646-1: "a
	multi-octet character set called the Universal Character
	Set (UCS), which encompasses most of the world's writing
	systems."
	UCS-2 a two octet per character encoding that addresses the first
	2^16 characters of UCS. Currently there are no UCS
	characters beyond that range.
	UCS-4 a four octet per character encoding that permits the
	encoding of up to 2^31 characters.
	UTF UTF is an abbreviation of the term "UCS transformation
	format" and is used in the naming of various standards for
	encoding of UCS characters as described below.
	UTF-1 Only historical interest; it has been removed from 10646-1
	UTF-7 Encodes the entire "repertoire" of UCS "characters using
	only octets with the higher order bit clear". [RFC2152]
	describes UTF-7. UTF-7 accomplishes this by reserving one
	of the 7bit US-ASCII characters as a "shift" character to
	indicate non-US-ASCII characters.
	Draft Specification NFS version 4 Protocol October 2002
	UTF-8 Unlike UTF-7, uses all 8 bits of the octets. US-ASCII
	characters are encoded as before unchanged. Any octet with
	the high bit cleared can only mean a US-ASCII character.
	The high bit set means that a UCS character is being
	encoded.
	UTF-16 Encodes UCS-4 characters into UCS-2 characters using a
	reserved range in UCS-2.
	Unicode Unicode and UCS-2 are the same; [RFC2279] states:
	Up to the present time, changes in Unicode and amendments
	to ISO/IEC 10646 have tracked each other, so that the
	character repertoires and code point assignments have
	remained in sync. The relevant standardization committees
	have committed to maintain this very useful synchronism.
	11.3. Difficulties with UCS-4, UCS-2, Unicode
	Adapting existing applications, and filesystems to multi-octet
	schemes like UCS and Unicode can be difficult. A significant amount
	of code has been written to process streams of bytes. Also there are
	many existing stored objects described with 7 bit or 8 bit
	characters. Doubling or quadrupling the bandwidth and storage
	requirements seems like an expensive way to accomplish I18N.
	UCS-2 and Unicode are "only" 16 bits long. That might seem to be
	enough but, according to [Unicode1], 49,194 Unicode characters are
	already assigned. According to [Unicode2] there are still more
	languages that need to be added.
	11.4. UTF-8 and its solutions
	UTF-8 solves problems for NFS that exist with the use of UCS and
	Unicode. UTF-8 will encode 16 bit and 32 bit characters in a way
	that will be compact for most users. The encoding table from UCS-4 to
	UTF-8, as copied from [RFC2279]:
	UCS-4 range (hex.) UTF-8 octet sequence (binary)
	0000 0000-0000 007F 0xxxxxxx
	0000 0080-0000 07FF 110xxxxx 10xxxxxx
	0000 0800-0000 FFFF 1110xxxx 10xxxxxx 10xxxxxx
	0001 0000-001F FFFF 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
	0020 0000-03FF FFFF 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
	0400 0000-7FFF FFFF 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
	10xxxxxx
	See [RFC2279] for precise encoding and decoding rules. Note because
	Draft Specification NFS version 4 Protocol October 2002
	of UTF-16, the algorithm from Unicode/UCS-2 to UTF-8 needs to account
	for the reserved range between D800 and DFFF.
	Note that the 16 bit UCS or Unicode characters require no more than 3
	octets to encode into UTF-8
	Interestingly, UTF-8 has room to handle characters larger than 31
	bits, because the leading octet of form:
	1111111x
	is not defined. If needed, ISO could either use that octet to
	indicate a sequence of an encoded 8 octet character, or perhaps use
	11111110 to permit the next octet to indicate an even more expandable
	character set.
	So using UTF-8 to represent character encodings means never having to
	run out of room.
	11.5. Normalization
	The client and server operating environments may differ in their
	policies and operational methods with respect to character
	normalization (See [Unicode1] for a discussion of normalization
	forms). This difference may also exist between applications on the
	same client. This adds to the difficulty of providing a single
	normalization policy for the protocol that allows for maximal
	interoperability. This issue is similar to the character case issues
	where the server may or may not support case insensitive file name
	matching and may or may not preserve the character case when storing
	file names. The protocol does not mandate a particular behavior but
	allows for the various permutations.
	The NFS version 4 protocol does not mandate the use of a particular
	normalization form at this time. A later revision of this
	specification may specify a particular normalization form.
	Therefore, the server and client can expect that they may receive
	unnormalized characters within protocol requests and responses. If
	the operating environment requires normalization, then the
	implementation must normalize the various UTF-8 encoded strings
	within the protocol before presenting the information to an
	application (at the client) or local filesystem (at the server).
	11.6. UTF-8 Related Errors
	Where the client sends an invalid UTF-8 string, the server should
	return an NFS4ERR_INVAL error. This includes cases in which
	inappropriate prefixes are detected and where the count includes
	trailing bytes that do not constitute a full UCS character.
	Where the client supplied string is valid UTF-8 but contains
	Draft Specification NFS version 4 Protocol October 2002
	characters that are not supported by the server as a value for that
	string (e.g. names containing characters that have more than two
	octets on a filesystem that supports Unicode characters only), the
	server should return an NFS4ERR_BADCHAR error.
	Where a UTF-8 string is used as a file name, and the filesystem,
	while supporting all of the characters within the name, does not
	allow that particular name to be used, the error should return the
	error NFS4ERR_BADNAME. This includes situations in which the server
	filesystem imposes a normalization constraint on name strings, but
	will also include such situations as filesystem prohibitions of "."
	and ".." as file names for certain operations, and other such
	constraints.
	Draft Specification NFS version 4 Protocol October 2002
	12. Error Definitions
	NFS error numbers are assigned to failed operations within a compound
	request. A compound request contains a number of NFS operations that
	have their results encoded in sequence in a compound reply. The
	results of successful operations will consist of an NFS4_OK status
	followed by the encoded results of the operation. If an NFS
	operation fails, an error status will be entered in the reply and the
	compound request will be terminated.
	A description of each defined error follows:
	NFS4_OK Indicates the operation completed successfully.
	NFS4ERR_ACCESS Permission denied. The caller does not have the
	correct permission to perform the requested
	operation. Contrast this with NFS4ERR_PERM,
	which restricts itself to owner or privileged
	user permission failures.
	NFS4ERR_ATTRNOTSUPP An attribute specified is not supported by the
	server. Does not apply to the GETATTR
	operation.
	NFS4ERR_ADMIN_REVOKED Due to administrator intervention, the
	lockowner's record locks, share reservations,
	and delegations have been revoked by the
	server.
	NFS4ERR_BADCHAR A UTF-8 string contains a character which is
	not supported by the server in the context in
	which it being used.
	NFS4ERR_BAD_COOKIE READDIR cookie is stale.
	NFS4ERR_BADHANDLE Illegal NFS filehandle. The filehandle failed
	internal consistency checks.
	NFS4ERR_BADNAME A name string in a request consists of valid
	UTF-8 characters supported by the server but
	the name is not supported by the server as a
	valid name for current operation.
	NFS4ERR_BADOWNER An owner, owner_group, or ACL attribute value
	can not be translated to local representation.
	NFS4ERR_BADTYPE An attempt was made to create an object of a
	type not supported by the server.
	NFS4ERR_BAD_RANGE The range for a LOCK, LOCKT, or LOCKU operation
	Draft Specification NFS version 4 Protocol October 2002
	is not appropriate to the allowable range of
	offsets for the server.
	NFS4ERR_BAD_SEQID The sequence number in a locking request is
	neither the next expected number or the last
	number processed.
	NFS4ERR_BAD_STATEID A stateid generated by the current server
	instance, but which does not designate any
	locking state (either current or superseded)
	for a current lockowner-file pair, was used.
	NFS4ERR_BADXDR The server encountered an XDR decoding error
	while processing an operation.
	NFS4ERR_CLID_INUSE The SETCLIENTID operation has found that a
	client id is already in use by another client.
	NFS4ERR_DEADLOCK The server has been able to determine a file
	locking deadlock condition for a blocking lock
	request.
	NFS4ERR_DELAY The server initiated the request, but was not
	able to complete it in a timely fashion. The
	client should wait and then try the request
	with a new RPC transaction ID. For example,
	this error should be returned from a server
	that supports hierarchical storage and receives
	a request to process a file that has been
	migrated. In this case, the server should start
	the immigration process and respond to client
	with this error. This error may also occur
	when a necessary delegation recall makes
	processing a request in a timely fashion
	impossible.
	NFS4ERR_DENIED An attempt to lock a file is denied. Since
	this may be a temporary condition, the client
	is encouraged to retry the lock request until
	the lock is accepted.
	NFS4ERR_DQUOT Resource (quota) hard limit exceeded. The
	user's resource limit on the server has been
	exceeded.
	NFS4ERR_EXIST File exists. The file specified already exists.
	NFS4ERR_EXPIRED A lease has expired that is being used in the
	current operation.
	NFS4ERR_FBIG File too large. The operation would have caused
	a file to grow beyond the server's limit.
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_FHEXPIRED The filehandle provided is volatile and has
	expired at the server.
	NFS4ERR_FILE_OPEN The operation can not be successfully processed
	because a file involved in the operation is
	currently open.
	NFS4ERR_GRACE The server is in its recovery or grace period
	which should match the lease period of the
	server.
	NFS4ERR_INVAL Invalid argument or unsupported argument for an
	operation. Two examples are attempting a
	READLINK on an object other than a symbolic
	link or specifying a value for an enum field
	that is not defined in the protocol (e.g.
	nfs_ftype4).
	NFS4ERR_IO I/O error. A hard error (for example, a disk
	error) occurred while processing the requested
	operation.
	NFS4ERR_ISDIR Is a directory. The caller specified a
	directory in a non-directory operation.
	NFS4ERR_LEASE_MOVED A lease being renewed is associated with a
	filesystem that has been migrated to a new
	server.
	NFS4ERR_LOCKED A read or write operation was attempted on a
	locked file.
	NFS4ERR_LOCK_NOTSUPP Server does not support atomic upgrade or
	downgrade of locks.
	NFS4ERR_LOCK_RANGE A lock request is operating on a sub-range of a
	current lock for the lock owner and the server
	does not support this type of request.
	NFS4ERR_LOCKS_HELD A CLOSE was attempted and file locks would
	exist after the CLOSE.
	NFS4ERR_MINOR_VERS_MISMATCH
	The server has received a request that
	specifies an unsupported minor version. The
	server must return a COMPOUND4res with a zero
	length operations result array.
	NFS4ERR_MLINK Too many hard links.
	NFS4ERR_MOVED The filesystem which contains the current
	filehandle object has been relocated or
	Draft Specification NFS version 4 Protocol October 2002
	migrated to another server. The client may
	obtain the new filesystem location by obtaining
	the "fs_locations" attribute for the current
	filehandle. For further discussion, refer to
	the section "Filesystem Migration or
	Relocation".
	NFS4ERR_NAMETOOLONG The filename in an operation was too long.
	NFS4ERR_NOENT No such file or directory. The file or
	directory name specified does not exist.
	NFS4ERR_NOFILEHANDLE The logical current filehandle value (or, in
	the case of RESTOREFH, the saved filehandle
	value) has not been set properly. This may be
	a result of a malformed COMPOUND operation
	(i.e. no PUTFH or PUTROOTFH before an operation
	that requires the current filehandle be set).
	NFS4ERR_NO_GRACE A reclaim of client state has fallen outside of
	the grace period of the server. As a result,
	the server can not guarantee that conflicting
	state has not been provided to another client.
	NFS4ERR_NOSPC No space left on device. The operation would
	have caused the server's filesystem to exceed
	its limit.
	NFS4ERR_NOTDIR Not a directory. The caller specified a non-
	directory in a directory operation.
	NFS4ERR_NOTEMPTY An attempt was made to remove a directory that
	was not empty.
	NFS4ERR_NOTSUPP Operation is not supported.
	NFS4ERR_NOT_SAME This error is returned by the VERIFY operation
	to signify that the attributes compared were
	not the same as provided in the client's
	request.
	NFS4ERR_NXIO I/O error. No such device or address.
	NFS4ERR_OLD_STATEID A stateid which designates the locking state
	for a lockowner-file at an earlier time was
	used.
	NFS4ERR_OPENMODE The client attempted a READ, WRITE, LOCK or
	SETATTR operation not sanctioned by the stateid
	passed (e.g. writing to a file opened only for
	read).
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_OP_ILLEGAL An illegal operation value has been specified
	in the argop field of a COMPOUND or CB_COMPOUND
	procedure.
	NFS4ERR_PERM Not owner. The operation was not allowed
	because the caller is either not a privileged
	user (root) or not the owner of the target of
	the operation.
	NFS4ERR_RECLAIM_BAD The reclaim provided by the client does not
	match any of the server's state consistency
	checks and is bad.
	NFS4ERR_RECLAIM_CONFLICT
	The reclaim provided by the client has
	encountered a conflict and can not be provided.
	Potentially indicates a misbehaving client.
	NFS4ERR_RESOURCE For the processing of the COMPOUND procedure,
	the server may exhaust available resources and
	can not continue processing operations within
	the COMPOUND procedure. This error will be
	returned from the server in those instances of
	resource exhaustion related to the processing
	of the COMPOUND procedure.
	NFS4ERR_RESTOREFH The RESTOREFH operation does not have a saved
	filehandle (identified by SAVEFH) to operate
	upon.
	NFS4ERR_ROFS Read-only filesystem. A modifying operation was
	attempted on a read-only filesystem.
	NFS4ERR_SAME This error is returned by the NVERIFY operation
	to signify that the attributes compared were
	the same as provided in the client's request.
	NFS4ERR_SERVERFAULT An error occurred on the server which does not
	map to any of the legal NFS version 4 protocol
	error values. The client should translate this
	into an appropriate error. UNIX clients may
	choose to translate this to EIO.
	NFS4ERR_SHARE_DENIED An attempt to OPEN a file with a share
	reservation has failed because of a share
	conflict.
	NFS4ERR_STALE Invalid filehandle. The filehandle given in the
	arguments was invalid. The file referred to by
	that filehandle no longer exists or access to
	it has been revoked.
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_STALE_CLIENTID A clientid not recognized by the server was
	used in a locking or SETCLIENTID_CONFIRM
	request.
	NFS4ERR_STALE_STATEID A stateid generated by an earlier server
	instance was used.
	NFS4ERR_SYMLINK The current filehandle provided for a LOOKUP is
	not a directory but a symbolic link. Also used
	if the final component of the OPEN path is a
	symbolic link.
	NFS4ERR_TOOSMALL The encoded response to a READDIR request
	exceeds the size limit set by the initial
	request.
	NFS4ERR_WRONGSEC The security mechanism being used by the client
	for the operation does not match the server's
	security policy. The client should change the
	security mechanism being used and retry the
	operation.
	NFS4ERR_XDEV Attempt to do an operation between different
	fsids.
	Draft Specification NFS version 4 Protocol October 2002
	13. NFS version 4 Requests
	For the NFS version 4 RPC program, there are two traditional RPC
	procedures: NULL and COMPOUND. All other functionality is defined as
	a set of operations and these operations are defined in normal
	XDR/RPC syntax and semantics. However, these operations are
	encapsulated within the COMPOUND procedure. This requires that the
	client combine one or more of the NFS version 4 operations into a
	single request.
	The NFS4_CALLBACK program is used to provide server to client
	signaling and is constructed in a similar fashion as the NFS version
	4 program. The procedures CB_NULL and CB_COMPOUND are defined in the
	same way as NULL and COMPOUND are within the NFS program. The
	CB_COMPOUND request also encapsulates the remaining operations of the
	NFS4_CALLBACK program. There is no predefined RPC program number for
	the NFS4_CALLBACK program. It is up to the client to specify a
	program number in the "transient" program range. The program and
	port number of the NFS4_CALLBACK program are provided by the client
	as part of the SETCLIENTID/SETCLIENTID_CONFIRM sequence. The program
	and port can be changed by another SETCLIENTID/SETCLIENTID_CONFIRM
	sequence, and it is possible to use the sequence to change them
	within a client incarnation without removing relevant leased client
	state.
	13.1. Compound Procedure
	The COMPOUND procedure provides the opportunity for better
	performance within high latency networks. The client can avoid
	cumulative latency of multiple RPCs by combining multiple dependent
	operations into a single COMPOUND procedure. A compound operation
	may provide for protocol simplification by allowing the client to
	combine basic procedures into a single request that is customized for
	the client's environment.
	The CB_COMPOUND procedure precisely parallels the features of
	COMPOUND as described above.
	The basic structure of the COMPOUND procedure is:
	+-----+--------------+--------+-----------+-----------+-----------+--
	| tag | minorversion | numops | op + args | op + args | op + args |
	+-----+--------------+--------+-----------+-----------+-----------+--
	and the reply's structure is:
	+------------+-----+--------+-----------------------+--
	|last status | tag | numres | status + op + results |
	+------------+-----+--------+-----------------------+--
	The numops and numres fields, used in the depiction above, represent
	Draft Specification NFS version 4 Protocol October 2002
	the count for the counted array encoding use to signify the number of
	arguments or results encoded in the request and response. As per the
	XDR encoding, these counts must match exactly the number of operation
	arguments or results encoded.
	13.2. Evaluation of a Compound Request
	The server will process the COMPOUND procedure by evaluating each of
	the operations within the COMPOUND procedure in order. Each
	component operation consists of a 32 bit operation code, followed by
	the argument of length determined by the type of operation. The
	results of each operation are encoded in sequence into a reply
	buffer. The results of each operation are preceded by the opcode and
	a status code (normally zero). If an operation results in a non-zero
	status code, the status will be encoded and evaluation of the
	compound sequence will halt and the reply will be returned. Note
	that evaluation stops even in the event of "non error" conditions
	such as NFS4ERR_SAME.
	There are no atomicity requirements for the operations contained
	within the COMPOUND procedure. The operations being evaluated as
	part of a COMPOUND request may be evaluated simultaneously with other
	COMPOUND requests that the server receives.
	It is the client's responsibility for recovering from any partially
	completed COMPOUND procedure. Partially completed COMPOUND
	procedures may occur at any point due to errors such as
	NFS4ERR_RESOURCE and NFS4ERR_DELAY. This may occur even given an
	otherwise valid operation string. Further, a server reboot which
	occurs in the middle of processing a COMPOUND procedure may leave the
	client with the difficult task of determining how far COMPOUND
	processing has proceeded. Therefore, the client should avoid overly
	complex COMPOUND procedures in the event of the failure of an
	operation within the procedure.
	Each operation assumes a "current" and "saved" filehandle that is
	available as part of the execution context of the compound request.
	Operations may set, change, or return the current filehandle. The
	"saved" filehandle is used for temporary storage of a filehandle
	value and as operands for the RENAME and LINK operations.
	13.3. Synchronous Modifying Operations
	NFS version 4 operations that modify the filesystem are synchronous.
	When an operation is successfully completed at the server, the client
	can depend that any data associated with the request is now on stable
	storage (the one exception is in the case of the file data in a WRITE
	operation with the UNSTABLE option specified).
	This implies that any previous operations within the same compound
	Draft Specification NFS version 4 Protocol October 2002
	request are also reflected in stable storage. This behavior enables
	the client's ability to recover from a partially executed compound
	request which may resulted from the failure of the server. For
	example, if a compound request contains operations A and B and the
	server is unable to send a response to the client, depending on the
	progress the server made in servicing the request the result of both
	operations may be reflected in stable storage or just operation A may
	be reflected. The server must not have just the results of operation
	B in stable storage.
	13.4. Operation Values
	The operations encoded in the COMPOUND procedure are identified by
	operation values. To avoid overlap with the RPC procedure numbers,
	operations 0 (zero) and 1 are not defined. Operation 2 is not
	defined but reserved for future use with minor versioning.
	Draft Specification NFS version 4 Protocol October 2002
	14. NFS version 4 Procedures
	14.1. Procedure 0: NULL - No Operation
	SYNOPSIS
	<null>
	ARGUMENT
	void;
	RESULT
	void;
	DESCRIPTION
	Standard NULL procedure. Void argument, void response. This
	procedure has no functionality associated with it. Because of this
	it is sometimes used to measure the overhead of processing a
	service request. Therefore, the server should ensure that no
	unnecessary work is done in servicing this procedure.
	ERRORS
	None.
	Draft Specification NFS version 4 Protocol October 2002
	14.2. Procedure 1: COMPOUND - Compound Operations
	SYNOPSIS
	compoundargs -> compoundres
	ARGUMENT
	union nfs_argop4 switch (nfs_opnum4 argop) {
	case <OPCODE>: <argument>;
	...
	};
	struct COMPOUND4args {
	utf8string tag;
	uint32_t minorversion;
	nfs_argop4 argarray<>;
	};
	RESULT
	union nfs_resop4 switch (nfs_opnum4 resop){
	case <OPCODE>: <result>;
	...
	};
	struct COMPOUND4res {
	nfsstat4 status;
	utf8string tag;
	nfs_resop4 resarray<>;
	};
	DESCRIPTION
	The COMPOUND procedure is used to combine one or more of the NFS
	operations into a single RPC request. The main NFS RPC program has
	two main procedures: NULL and COMPOUND. All other operations use
	the COMPOUND procedure as a wrapper.
	The COMPOUND procedure is used to combine individual operations
	into a single RPC request. The server interprets each of the
	operations in turn. If an operation is executed by the server and
	the status of that operation is NFS4_OK, then the next operation in
	the COMPOUND procedure is executed. The server continues this
	process until there are no more operations to be executed or one of
	the operations has a status value other than NFS4_OK.
	Draft Specification NFS version 4 Protocol October 2002
	In the processing of the COMPOUND procedure, the server may find
	that it does not have the available resources to execute any or all
	of the operations within the COMPOUND sequence. In this case, the
	error NFS4ERR_RESOURCE will be returned for the particular
	operation within the COMPOUND procedure where the resource
	exhaustion occurred. This assumes that all previous operations
	within the COMPOUND sequence have been evaluated successfully. The
	results for all of the evaluated operations must be returned to the
	client.
	The server will generally choose between two methods of decoding
	the client's request. The first would be the traditional one pass
	XDR decode. If there is an XDR decoding error in this case, the
	RPC XDR decode error would be returned. The second method would be
	to make an initial pass to decode the basic COMPOUND request and
	then to XDR decode the individual operations; the most interesting
	is the decode of attributes. In this case, the server may
	encounter an XDR decode error during the second pass. In this
	case, the server would return the error NFS4ERR_BADXDR to signify
	the decode error.
	The COMPOUND arguments contain a "minorversion" field. The initial
	and default value for this field is 0 (zero). This field will be
	used by future minor versions such that the client can communicate
	to the server what minor version is being requested. If the server
	receives a COMPOUND procedure with a minorversion field value that
	it does not support, the server MUST return an error of
	NFS4ERR_MINOR_VERS_MISMATCH and a zero length resultdata array.
	Contained within the COMPOUND results is a "status" field. If the
	results array length is non-zero, this status must be equivalent to
	the status of the last operation that was executed within the
	COMPOUND procedure. Therefore, if an operation incurred an error
	then the "status" value will be the same error value as is being
	returned for the operation that failed.
	Note that operations, 0 (zero) and 1 (one) are not defined for the
	COMPOUND procedure. Operation 2 is not defined but reserved for
	future definition and use with minor versioning. If the server
	receives a operation array that contains operation 2 and the
	minorversion field has a value of 0 (zero), an error of
	NFS4ERR_OP_ILLEGAL, as described in the next paragraph, is returned
	to the client. If an operation array contains an operation 2 and
	the minorversion field is non-zero and the server does not support
	the minor version, the server returns an error of
	NFS4ERR_MINOR_VERS_MISMATCH. Therefore, the
	NFS4ERR_MINOR_VERS_MISMATCH error takes precedence over all other
	errors.
	It is possible that the server receives a request that contains an
	operation that is less than the first legal operation (OP_ACCESS)
	or greater than the last legal operation (OP_RELEASE_LOCKOWNER).
	Draft Specification NFS version 4 Protocol October 2002
	In this case, the server's response will encode the opcode
	OP_ILLEGAL rather than the illegal opcode of the request. The
	status field in the ILLEGAL return results will set to
	NFS4ERR_OP_ILLEGAL. The COMPOUND procedure's return results will
	also be NFS4ERR_OP_ILLEGAL.
	The definition of the "tag" in the request is left to the
	implementor. It may be used to summarize the content of the
	compound request for the benefit of packet sniffers and engineers
	debugging implementations. However, the value of "tag" in the
	response SHOULD be the same value as provided in the request. This
	applies to the tag field of the CB_COMPOUND procedure as well.
	IMPLEMENTATION
	Since an error of any type may occur after only a portion of the
	operations have been evaluated, the client must be prepared to
	recover from any failure. If the source of an NFS4ERR_RESOURCE
	error was a complex or lengthy set of operations, it is likely that
	if the number of operations were reduced the server would be able
	to evaluate them successfully. Therefore, the client is
	responsible for dealing with this type of complexity in recovery.
	ERRORS
	All errors defined in the protocol
	Draft Specification NFS version 4 Protocol October 2002
	14.2.1. Operation 3: ACCESS - Check Access Rights
	SYNOPSIS
	(cfh), accessreq -> supported, accessrights
	ARGUMENT
	const ACCESS4_READ = 0x00000001;
	const ACCESS4_LOOKUP = 0x00000002;
	const ACCESS4_MODIFY = 0x00000004;
	const ACCESS4_EXTEND = 0x00000008;
	const ACCESS4_DELETE = 0x00000010;
	const ACCESS4_EXECUTE = 0x00000020;
	struct ACCESS4args {
	/* CURRENT_FH: object */
	uint32_t access;
	};
	RESULT
	struct ACCESS4resok {
	uint32_t supported;
	uint32_t access;
	};
	union ACCESS4res switch (nfsstat4 status) {
	case NFS4_OK:
	ACCESS4resok resok4;
	default:
	void;
	};
	DESCRIPTION
	ACCESS determines the access rights that a user, as identified by
	the credentials in the RPC request, has with respect to the file
	system object specified by the current filehandle. The client
	encodes the set of access rights that are to be checked in the bit
	mask "access". The server checks the permissions encoded in the
	bit mask. If a status of NFS4_OK is returned, two bit masks are
	included in the response. The first, "supported", represents the
	access rights for which the server can verify reliably. The
	second, "access", represents the access rights available to the
	user for the filehandle provided. On success, the current
	filehandle retains its value.
	Draft Specification NFS version 4 Protocol October 2002
	Note that the supported field will contain only as many values as
	was originally sent in the arguments. For example, if the client
	sends an ACCESS operation with only the ACCESS4_READ value set and
	the server supports this value, the server will return only
	ACCESS4_READ even if it could have reliably checked other values.
	The results of this operation are necessarily advisory in nature.
	A return status of NFS4_OK and the appropriate bit set in the bit
	mask does not imply that such access will be allowed to the file
	system object in the future. This is because access rights can be
	revoked by the server at any time.
	The following access permissions may be requested:
	ACCESS4_READ Read data from file or read a directory.
	ACCESS4_LOOKUP Look up a name in a directory (no meaning for non-
	directory objects).
	ACCESS4_MODIFY Rewrite existing file data or modify existing
	directory entries.
	ACCESS4_EXTEND Write new data or add directory entries.
	ACCESS4_DELETE Delete an existing directory entry.
	ACCESS4_EXECUTE Execute file (no meaning for a directory).
	On success, the current filehandle retains its value.
	IMPLEMENTATION
	In general, it is not sufficient for the client to attempt to
	deduce access permissions by inspecting the uid, gid, and mode
	fields in the file attributes or by attempting to interpret the
	contents of the ACL attribute. This is because the server may
	perform uid or gid mapping or enforce additional access control
	restrictions. It is also possible that the server may not be in
	the same ID space as the client. In these cases (and perhaps
	others), the client can not reliably perform an access check with
	only current file attributes.
	In the NFS version 2 protocol, the only reliable way to determine
	whether an operation was allowed was to try it and see if it
	succeeded or failed. Using the ACCESS operation in the NFS version
	4 protocol, the client can ask the server to indicate whether or
	not one or more classes of operations are permitted. The ACCESS
	operation is provided to allow clients to check before doing a
	series of operations which will result in an access failure. The
	OPEN operation provides a point where the server can verify access
	to the file object and method to return that information to the
	Draft Specification NFS version 4 Protocol October 2002
	client. The ACCESS operation is still useful for directory
	operations or for use in the case the UNIX API "access" is used on
	the client.
	The information returned by the server in response to an ACCESS
	call is not permanent. It was correct at the exact time that the
	server performed the checks, but not necessarily afterwards. The
	server can revoke access permission at any time.
	The client should use the effective credentials of the user to
	build the authentication information in the ACCESS request used to
	determine access rights. It is the effective user and group
	credentials that are used in subsequent read and write operations.
	Many implementations do not directly support the ACCESS4_DELETE
	permission. Operating systems like UNIX will ignore the
	ACCESS4_DELETE bit if set on an access request on a non-directory
	object. In these systems, delete permission on a file is
	determined by the access permissions on the directory in which the
	file resides, instead of being determined by the permissions of the
	file itself. Therefore, the mask returned enumerating which access
	rights can be determined will have the ACCESS4_DELETE value set to
	0. This indicates to the client that the server was unable to
	check that particular access right. The ACCESS4_DELETE bit in the
	access mask returned will then be ignored by the client.
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_BADHANDLE
	NFS4ERR_BADXDR
	NFS4ERR_DELAY
	NFS4ERR_FHEXPIRED
	NFS4ERR_INVAL
	NFS4ERR_IO
	NFS4ERR_MOVED
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	Draft Specification NFS version 4 Protocol October 2002
	14.2.2. Operation 4: CLOSE - Close File
	SYNOPSIS
	(cfh), seqid, open_stateid -> open_stateid
	ARGUMENT
	struct CLOSE4args {
	/* CURRENT_FH: object */
	seqid4 seqid
	stateid4 open_stateid;
	};
	RESULT
	union CLOSE4res switch (nfsstat4 status) {
	case NFS4_OK:
	stateid4 open_stateid;
	default:
	void;
	};
	DESCRIPTION
	The CLOSE operation releases share reservations for the regular or
	named attribute file as specified by the current filehandle. The
	share reservations and other state information released at the
	server as a result of this CLOSE is only associated with the
	supplied stateid. The sequence id provides for the correct
	ordering. State associated with other OPENs is not affected.
	If record locks are held, the client SHOULD release all locks
	before issuing a CLOSE. The server MAY free all outstanding locks
	on CLOSE but some servers may not support the CLOSE of a file that
	still has record locks held. The server MUST return failure if any
	locks would exist after the CLOSE.
	On success, the current filehandle retains its value.
	IMPLEMENTATION
	Even though CLOSE returns a stateid, this stateid is not useful to
	the client and should be treated as deprecated. CLOSE "shuts down"
	the state associated with all OPENs for the file by a single
	Draft Specification NFS version 4 Protocol October 2002
	open_owner. As noted above, CLOSE will either release all file
	locking state or return an error. Therefore, the stateid returned
	by CLOSE is not useful for operations that follow.
	ERRORS
	NFS4ERR_ADMIN_REVOKED
	NFS4ERR_BADHANDLE
	NFS4ERR_BAD_SEQID
	NFS4ERR_BAD_STATEID
	NFS4ERR_BADXDR
	NFS4ERR_DELAY
	NFS4ERR_EXPIRED
	NFS4ERR_FHEXPIRED
	NFS4ERR_INVAL
	NFS4ERR_ISDIR
	NFS4ERR_LEASE_MOVED
	NFS4ERR_LOCKS_HELD
	NFS4ERR_MOVED
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_OLD_STATEID
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	NFS4ERR_STALE_STATEID
	Draft Specification NFS version 4 Protocol October 2002
	14.2.3. Operation 5: COMMIT - Commit Cached Data
	SYNOPSIS
	(cfh), offset, count -> verifier
	ARGUMENT
	struct COMMIT4args {
	/* CURRENT_FH: file */
	offset4 offset;
	count4 count;
	};
	RESULT
	struct COMMIT4resok {
	verifier4 writeverf;
	};
	union COMMIT4res switch (nfsstat4 status) {
	case NFS4_OK:
	COMMIT4resok resok4;
	default:
	void;
	};
	DESCRIPTION
	The COMMIT operation forces or flushes data to stable storage for
	the file specified by the current filehandle. The flushed data is
	that which was previously written with a WRITE operation which had
	the stable field set to UNSTABLE4.
	The offset specifies the position within the file where the flush
	is to begin. An offset value of 0 (zero) means to flush data
	starting at the beginning of the file. The count specifies the
	number of bytes of data to flush. If count is 0 (zero), a flush
	from offset to the end of the file is done.
	The server returns a write verifier upon successful completion of
	the COMMIT. The write verifier is used by the client to determine
	if the server has restarted or rebooted between the initial
	WRITE(s) and the COMMIT. The client does this by comparing the
	write verifier returned from the initial writes and the verifier
	returned by the COMMIT operation. The server must vary the value
	of the write verifier at each server event or instantiation that
	may lead to a loss of uncommitted data. Most commonly this occurs
	when the server is rebooted; however, other events at the server
	Draft Specification NFS version 4 Protocol October 2002
	may result in uncommitted data loss as well.
	On success, the current filehandle retains its value.
	IMPLEMENTATION
	The COMMIT operation is similar in operation and semantics to the
	POSIX fsync(2) system call that synchronizes a file's state with
	the disk (file data and metadata is flushed to disk or stable
	storage). COMMIT performs the same operation for a client, flushing
	any unsynchronized data and metadata on the server to the server's
	disk or stable storage for the specified file. Like fsync(2), it
	may be that there is some modified data or no modified data to
	synchronize. The data may have been synchronized by the server's
	normal periodic buffer synchronization activity. COMMIT should
	return NFS4_OK, unless there has been an unexpected error.
	COMMIT differs from fsync(2) in that it is possible for the client
	to flush a range of the file (most likely triggered by a buffer-
	reclamation scheme on the client before file has been completely
	written).
	The server implementation of COMMIT is reasonably simple. If the
	server receives a full file COMMIT request, that is starting at
	offset 0 and count 0, it should do the equivalent of fsync()'ing
	the file. Otherwise, it should arrange to have the cached data in
	the range specified by offset and count to be flushed to stable
	storage. In both cases, any metadata associated with the file must
	be flushed to stable storage before returning. It is not an error
	for there to be nothing to flush on the server. This means that
	the data and metadata that needed to be flushed have already been
	flushed or lost during the last server failure.
	The client implementation of COMMIT is a little more complex.
	There are two reasons for wanting to commit a client buffer to
	stable storage. The first is that the client wants to reuse a
	buffer. In this case, the offset and count of the buffer are sent
	to the server in the COMMIT request. The server then flushes any
	cached data based on the offset and count, and flushes any metadata
	associated with the file. It then returns the status of the flush
	and the write verifier. The other reason for the client to
	generate a COMMIT is for a full file flush, such as may be done at
	close. In this case, the client would gather all of the buffers
	for this file that contain uncommitted data, do the COMMIT
	operation with an offset of 0 and count of 0, and then free all of
	those buffers. Any other dirty buffers would be sent to the server
	in the normal fashion.
	After a buffer is written by the client with the stable parameter
	set to UNSTABLE4, the buffer must be considered as modified by the
	client until the buffer has either been flushed via a COMMIT
	Draft Specification NFS version 4 Protocol October 2002
	operation or written via a WRITE operation with stable parameter
	set to FILE_SYNC4 or DATA_SYNC4. This is done to prevent the buffer
	from being freed and reused before the data can be flushed to
	stable storage on the server.
	When a response is returned from either a WRITE or a COMMIT
	operation and it contains a write verifier that is different than
	previously returned by the server, the client will need to
	retransmit all of the buffers containing uncommitted cached data to
	the server. How this is to be done is up to the implementor. If
	there is only one buffer of interest, then it should probably be
	sent back over in a WRITE request with the appropriate stable
	parameter. If there is more than one buffer, it might be
	worthwhile retransmitting all of the buffers in WRITE requests with
	the stable parameter set to UNSTABLE4 and then retransmitting the
	COMMIT operation to flush all of the data on the server to stable
	storage. The timing of these retransmissions is left to the
	implementor.
	The above description applies to page-cache-based systems as well
	as buffer-cache-based systems. In those systems, the virtual
	memory system will need to be modified instead of the buffer cache.
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_BADHANDLE
	NFS4ERR_BADXDR
	NFS4ERR_FHEXPIRED
	NFS4ERR_INVAL
	NFS4ERR_IO
	NFS4ERR_ISDIR
	NFS4ERR_MOVED
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_RESOURCE
	NFS4ERR_ROFS
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	Draft Specification NFS version 4 Protocol October 2002
	14.2.4. Operation 6: CREATE - Create a Non-Regular File Object
	SYNOPSIS
	(cfh), name, type, attrs -> (cfh), change_info, attrs_set
	ARGUMENT
	union createtype4 switch (nfs_ftype4 type) {
	case NF4LNK:
	linktext4 linkdata;
	case NF4BLK:
	case NF4CHR:
	specdata4 devdata;
	case NF4SOCK:
	case NF4FIFO:
	case NF4DIR:
	void;
	};
	struct CREATE4args {
	/* CURRENT_FH: directory for creation */
	createtype4 objtype;
	component4 objname;
	fattr4 createattrs;
	};
	RESULT
	struct CREATE4resok {
	change_info4 cinfo;
	bitmap4 attrset; /* attributes set */
	};
	union CREATE4res switch (nfsstat4 status) {
	case NFS4_OK:
	CREATE4resok resok4;
	default:
	void;
	};
	DESCRIPTION
	The CREATE operation creates a non-regular file object in a
	directory with a given name. The OPEN operation MUST be used to
	create a regular file.
	The objname specifies the name for the new object. The objtype
	determines the type of object to be created: directory, symlink,
	Draft Specification NFS version 4 Protocol October 2002
	etc.
	If an object of the same name already exists in the directory, the
	server will return the error NFS4ERR_EXIST.
	For the directory where the new file object was created, the server
	returns change_info4 information in cinfo. With the atomic field
	of the change_info4 struct, the server will indicate if the before
	and after change attributes were obtained atomically with respect
	to the file object creation.
	If the objname has a length of 0 (zero), or if objname does not
	obey the UTF-8 definition, the error NFS4ERR_INVAL will be
	returned.
	The current filehandle is replaced by that of the new object.
	The createattrs specifies the initial set of attributes for the
	object. The set of attributes may include any writable attribute
	valid for the object type. When the operation is successful, the
	server will return to the client an attribute mask signifying which
	attributes were successfully set for the object.
	If createattrs includes neither the owner attribute nor an ACL with
	an ACE for the owner, and if the server's filesystem both supports
	and requires an owner attribute (or an owner ACE) then the server
	MUST derive the owner (or the owner ACE). This would typically be
	from the principal indicated in the RPC credentials of the call,
	but the server's operating environment or filesystem semantics may
	dictate other methods of derivation. Similarly, if createattrs
	includes neither the group attribute nor a group ACE, and if the
	server's filesystem both supports and requires the notion of a
	group attribute (or group ACE), the server MUST derive the group
	attribute (or the corresponding owner ACE) for the file. This could
	be from the RPC call's credentials, such as the group principal if
	the credentials include it (such as with AUTH_SYS), from the group
	identifier associated with the principal in the credentials (for
	e.g., POSIX systems have a passwd database that has the group
	identifier for every user identifier), inherited from directory the
	object is created in, or whatever else the server's operating
	environment or filesystem semantics dictate. This applies to the
	OPEN operation too.
	Conversely, it is possible the client will specify in createattrs
	an owner attribute or group attribute or ACL that the principal
	indicated the RPC call's credentials does not have permissions to
	create files for. The error to be returned in this instance is
	NFS4ERR_PERM. This applies to the OPEN operation too.
	IMPLEMENTATION
	Draft Specification NFS version 4 Protocol October 2002
	If the client desires to set attribute values after the create, a
	SETATTR operation can be added to the COMPOUND request so that the
	appropriate attributes will be set.
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_ATTRNOTSUPP
	NFS4ERR_BADCHAR
	NFS4ERR_BADHANDLE
	NFS4ERR_BADNAME
	NFS4ERR_BADOWNER
	NFS4ERR_BADTYPE
	NFS4ERR_BADXDR
	NFS4ERR_DELAY
	NFS4ERR_DQUOT
	NFS4ERR_EXIST
	NFS4ERR_FHEXPIRED
	NFS4ERR_INVAL
	NFS4ERR_IO
	NFS4ERR_MOVED
	NFS4ERR_NAMETOOLONG
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_NOSPC
	NFS4ERR_NOTDIR
	NFS4ERR_PERM
	NFS4ERR_RESOURCE
	NFS4ERR_ROFS
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	Draft Specification NFS version 4 Protocol October 2002
	14.2.5. Operation 7: DELEGPURGE - Purge Delegations Awaiting Recovery
	SYNOPSIS
	clientid ->
	ARGUMENT
	struct DELEGPURGE4args {
	clientid4 clientid;
	};
	RESULT
	struct DELEGPURGE4res {
	nfsstat4 status;
	};
	DESCRIPTION
	Purges all of the delegations awaiting recovery for a given client.
	This is useful for clients which do not commit delegation
	information to stable storage to indicate that conflicting requests
	need not be delayed by the server awaiting recovery of delegation
	information.
	This operation should be used by clients that record delegation
	information on stable storage on the client. In this case,
	DELEGPURGE should be issued immediately after doing delegation
	recovery on all delegations known to the client. Doing so will
	notify the server that no additional delegations for the client
	will be recovered allowing it to free resources, and avoid delaying
	other clients who make requests that conflict with the unrecovered
	delegations. The set of delegations known to the server and the
	client may be different. The reason for this is that a client may
	fail after making a request which resulted in delegation but before
	it received the results and committed them to the client's stable
	storage.
	The server MAY support DELEGPURGE, but if it does not, it MUST NOT
	support CLAIM_DELEGATE_PREV.
	ERRORS
	NFS4ERR_BADXDR
	NFS4ERR_NOTSUPP
	NFS4ERR_LEASE_MOVED
	NFS4ERR_MOVED
	NFS4ERR_RESOURCE
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE_CLIENTID
	Draft Specification NFS version 4 Protocol October 2002
	14.2.6. Operation 8: DELEGRETURN - Return Delegation
	SYNOPSIS
	(cfh), stateid ->
	ARGUMENT
	struct DELEGRETURN4args {
	/* CURRENT_FH: delegated file */
	stateid4 stateid;
	};
	RESULT
	struct DELEGRETURN4res {
	nfsstat4 status;
	};
	DESCRIPTION
	Returns the delegation represented by the current filehandle and
	stateid.
	Delegations may be returned when recalled or voluntarily (i.e.
	before the server has recalled them). In either case the client
	must properly propagate state changed under the context of the
	delegation to the server before returning the delegation.
	ERRORS
	NFS4ERR_ADMIN_REVOKED
	NFS4ERR_BAD_STATEID
	NFS4ERR_BADXDR
	NFS4ERR_EXPIRED
	NFS4ERR_INVAL
	NFS4ERR_LEASE_MOVED
	NFS4ERR_MOVED
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_NOTSUPP
	NFS4ERR_OLD_STATEID
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	NFS4ERR_STALE_STATEID
	Draft Specification NFS version 4 Protocol October 2002
	14.2.7. Operation 9: GETATTR - Get Attributes
	SYNOPSIS
	(cfh), attrbits -> attrbits, attrvals
	ARGUMENT
	struct GETATTR4args {
	/* CURRENT_FH: directory or file */
	bitmap4 attr_request;
	};
	RESULT
	struct GETATTR4resok {
	fattr4 obj_attributes;
	};
	union GETATTR4res switch (nfsstat4 status) {
	case NFS4_OK:
	GETATTR4resok resok4;
	default:
	void;
	};
	DESCRIPTION
	The GETATTR operation will obtain attributes for the filesystem
	object specified by the current filehandle. The client sets a bit
	in the bitmap argument for each attribute value that it would like
	the server to return. The server returns an attribute bitmap that
	indicates the attribute values for which it was able to return,
	followed by the attribute values ordered lowest attribute number
	first.
	The server must return a value for each attribute that the client
	requests if the attribute is supported by the server. If the
	server does not support an attribute or cannot approximate a useful
	value then it must not return the attribute value and must not set
	the attribute bit in the result bitmap. The server must return an
	error if it supports an attribute but cannot obtain its value. In
	that case no attribute values will be returned.
	All servers must support the mandatory attributes as specified in
	the section "File Attributes".
	On success, the current filehandle retains its value.
	Draft Specification NFS version 4 Protocol October 2002
	IMPLEMENTATION
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_BADHANDLE
	NFS4ERR_BADXDR
	NFS4ERR_DELAY
	NFS4ERR_FHEXPIRED
	NFS4ERR_INVAL
	NFS4ERR_IO
	NFS4ERR_MOVED
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	Draft Specification NFS version 4 Protocol October 2002
	14.2.8. Operation 10: GETFH - Get Current Filehandle
	SYNOPSIS
	(cfh) -> filehandle
	ARGUMENT
	/* CURRENT_FH: */
	void;
	RESULT
	struct GETFH4resok {
	nfs_fh4 object;
	};
	union GETFH4res switch (nfsstat4 status) {
	case NFS4_OK:
	GETFH4resok resok4;
	default:
	void;
	};
	DESCRIPTION
	This operation returns the current filehandle value.
	On success, the current filehandle retains its value.
	IMPLEMENTATION
	Operations that change the current filehandle like LOOKUP or CREATE
	do not automatically return the new filehandle as a result. For
	instance, if a client needs to lookup a directory entry and obtain
	its filehandle then the following request is needed.
	PUTFH (directory filehandle)
	LOOKUP (entry name)
	GETFH
	ERRORS
	NFS4ERR_BADHANDLE
	NFS4ERR_FHEXPIRED
	NFS4ERR_MOVED
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	Draft Specification NFS version 4 Protocol October 2002
	14.2.9. Operation 11: LINK - Create Link to a File
	SYNOPSIS
	(sfh), (cfh), newname -> (cfh), change_info
	ARGUMENT
	struct LINK4args {
	/* SAVED_FH: source object */
	/* CURRENT_FH: target directory */
	component4 newname;
	};
	RESULT
	struct LINK4resok {
	change_info4 cinfo;
	};
	union LINK4res switch (nfsstat4 status) {
	case NFS4_OK:
	LINK4resok resok4;
	default:
	void;
	};
	DESCRIPTION
	The LINK operation creates an additional newname for the file
	represented by the saved filehandle, as set by the SAVEFH
	operation, in the directory represented by the current filehandle.
	The existing file and the target directory must reside within the
	same filesystem on the server. On success, the current filehandle
	will continue to be the target directory. If an object exists in
	the target directory with the same name as newname, the server must
	return NFS4ERR_EXIST.
	For the target directory, the server returns change_info4
	information in cinfo. With the atomic field of the change_info4
	struct, the server will indicate if the before and after change
	attributes were obtained atomically with respect to the link
	creation.
	If the newname has a length of 0 (zero), or if newname does not
	obey the UTF-8 definition, the error NFS4ERR_INVAL will be
	returned.
	Draft Specification NFS version 4 Protocol October 2002
	IMPLEMENTATION
	Changes to any property of the "hard" linked files are reflected in
	all of the linked files. When a link is made to a file, the
	attributes for the file should have a value for numlinks that is
	one greater than the value before the LINK operation.
	The statement "file and the target directory must reside within the
	same filesystem on the server" means that the fsid fields in the
	attributes for the objects are the same. If they reside on
	different filesystems, the error, NFS4ERR_XDEV, is returned. On
	some servers, the filenames, "." and "..", are illegal as newname.
	In the case that newname is already linked to the file represented
	by the saved filehandle, the server will return NFS4ERR_EXIST.
	Note that symbolic links are created with the CREATE operation.
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_BADCHAR
	NFS4ERR_BADHANDLE
	NFS4ERR_BADNAME
	NFS4ERR_BADXDR
	NFS4ERR_DELAY
	NFS4ERR_DQUOT
	NFS4ERR_EXIST
	NFS4ERR_FHEXPIRED
	NFS4ERR_FILE_OPEN
	NFS4ERR_INVAL
	NFS4ERR_IO
	NFS4ERR_ISDIR
	NFS4ERR_MLINK
	NFS4ERR_MOVED
	NFS4ERR_NAMETOOLONG
	NFS4ERR_NOENT
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_NOSPC
	NFS4ERR_NOTDIR
	NFS4ERR_NOTSUPP
	NFS4ERR_RESOURCE
	NFS4ERR_ROFS
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	NFS4ERR_WRONGSEC
	NFS4ERR_XDEV
	Draft Specification NFS version 4 Protocol October 2002
	14.2.10. Operation 12: LOCK - Create Lock
	SYNOPSIS
	(cfh) locktype, reclaim, offset, length, locker -> stateid
	ARGUMENT
	struct open_to_lock_owner4 {
	seqid4 open_seqid;
	stateid4 open_stateid;
	seqid4 lock_seqid;
	lock_owner4 lock_owner;
	};
	struct exist_lock_owner4 {
	stateid4 lock_stateid;
	seqid4 lock_seqid;
	};
	union locker4 switch (bool new_lock_owner) {
	case TRUE:
	open_to_lock_owner4 open_owner;
	case FALSE:
	exist_lock_owner4 lock_owner;
	};
	enum nfs_lock_type4 {
	READ_LT = 1,
	WRITE_LT = 2,
	READW_LT = 3, /* blocking read */
	WRITEW_LT = 4 /* blocking write */
	};
	struct LOCK4args {
	/* CURRENT_FH: file */
	nfs_lock_type4 locktype;
	bool reclaim;
	offset4 offset;
	length4 length;
	locker4 locker;
	};
	RESULT
	struct LOCK4denied {
	offset4 offset;
	length4 length;
	nfs_lock_type4 locktype;
	Draft Specification NFS version 4 Protocol October 2002
	lock_owner4 owner;
	};
	struct LOCK4resok {
	stateid4 lock_stateid;
	};
	union LOCK4res switch (nfsstat4 status) {
	case NFS4_OK:
	LOCK4resok resok4;
	case NFS4ERR_DENIED:
	LOCK4denied denied;
	default:
	void;
	};
	DESCRIPTION
	The LOCK operation requests a record lock for the byte range
	specified by the offset and length parameters. The lock type is
	also specified to be one of the nfs_lock_type4s. If this is a
	reclaim request, the reclaim parameter will be TRUE;
	Bytes in a file may be locked even if those bytes are not currently
	allocated to the file. To lock the file from a specific offset
	through the end-of-file (no matter how long the file actually is)
	use a length field with all bits set to 1 (one). If the length is
	zero, or if a length which is not all bits set to one is specified,
	and length when added to the offset exceeds the maximum 64-bit
	unsigned integer value, the error NFS4ERR_INVAL will result.
	Some servers may only support locking for byte offsets that fit
	within 32 bits. If the client specifies a range that includes a
	byte beyond the last byte offset of the 32-bit range, but does not
	include the last byte offset of the 32-bit and all of the byte
	offsets beyond it, up to the end of the valid 64-bit range, such a
	32-bit server MUST return the error NFS4ERR_BAD_RANGE.
	In the case that the lock is denied, the owner, offset, and length
	of a conflicting lock are returned.
	On success, the current filehandle retains its value.
	IMPLEMENTATION
	If the server is unable to determine the exact offset and length of
	the conflicting lock, the same offset and length that were provided
	in the arguments should be returned in the denied results. The
	File Locking section contains a full description of this and the
	other file locking operations.
	Draft Specification NFS version 4 Protocol October 2002
	LOCK operations are subject to permission checks and to checks
	against the access type of the associated file. However, the
	specific right and modes required for various type of locks,
	reflect the semantics of the server-exported filesystem, and are
	not specified by the protocol. For example, Windows 2000 allows a
	write lock of a file open for READ, while a POSIX-compliant system
	does not.
	When the client makes a lock request that corresponds to a range
	that the lockowner has locked already (with the same or different
	lock type), or to a sub-region of such a range, or to a region
	which includes multiple locks already granted to that lockowner, in
	whole or in part, and the server does not support such locking
	operations (i.e. does not support POSIX locking semantics), the
	server will return the error NFS4ERR_LOCK_RANGE. In that case, the
	client may return an error, or it may emulate the required
	operations, using only LOCK for ranges that do not include any
	bytes already locked by that lock_owner and LOCKU of locks held by
	that lock_owner (specifying an exactly-matching range and type).
	Similarly, when the client makes a lock request that amounts to
	upgrading (changing from a read lock to a write lock) or
	downgrading (changing from write lock to a read lock) an existing
	record lock, and the server does not support such a lock, the
	server will return NFS4ERR_LOCK_NOTSUPP. Such operations may not
	perfectly reflect the required semantics in the face of conflicting
	lock requests from other clients.
	The locker argument specifies the lock_owner that is associated
	with the LOCK request. The locker4 structure is a switched union
	that indicates whether the lock_owner is known to the server or if
	the lock_owner is new to the server. In the case that the
	lock_owner is known to the server and has an established
	lock_seqid, the argument is just the lock_owner and lock_seqid. In
	the case that the lock_owner is not known to the server, the
	argument contains not only the lock_owner and lock_seqid but also
	the open_stateid and open_seqid. The new lock_owner case covers
	the very first lock done by the lock_owner and offers a method to
	use the established state of the open_stateid to transition to the
	use of the lock_owner.
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_ADMIN_REVOKED
	NFS4ERR_BADHANDLE
	NFS4ERR_BAD_RANGE
	NFS4ERR_BAD_SEQID
	NFS4ERR_BAD_STATEID
	NFS4ERR_BADXDR
	NFS4ERR_DEADLOCK
	NFS4ERR_DELAY
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_DENIED
	NFS4ERR_EXPIRED
	NFS4ERR_FHEXPIRED
	NFS4ERR_GRACE
	NFS4ERR_INVAL
	NFS4ERR_ISDIR
	NFS4ERR_LEASE_MOVED
	NFS4ERR_LOCK_NOTSUPP
	NFS4ERR_LOCK_RANGE
	NFS4ERR_MOVED
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_NO_GRACE
	NFS4ERR_OLD_STATEID
	NFS4ERR_OPENMODE
	NFS4ERR_RECLAIM_BAD
	NFS4ERR_RECLAIM_CONFLICT
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	NFS4ERR_STALE_CLIENTID
	NFS4ERR_STALE_STATEID
	Draft Specification NFS version 4 Protocol October 2002
	14.2.11. Operation 13: LOCKT - Test For Lock
	SYNOPSIS
	(cfh) locktype, offset, length owner -> {void, NFS4ERR_DENIED ->
	owner}
	ARGUMENT
	struct LOCKT4args {
	/* CURRENT_FH: file */
	nfs_lock_type4 locktype;
	offset4 offset;
	length4 length;
	lock_owner4 owner;
	};
	RESULT
	struct LOCK4denied {
	offset4 offset;
	length4 length;
	nfs_lock_type4 locktype;
	lock_owner4 owner;
	};
	union LOCKT4res switch (nfsstat4 status) {
	case NFS4ERR_DENIED:
	LOCK4denied denied;
	case NFS4_OK:
	void;
	default:
	void;
	};
	DESCRIPTION
	The LOCKT operation tests the lock as specified in the arguments.
	If a conflicting lock exists, the owner, offset, length, and type
	of the conflicting lock are returned; if no lock is held, nothing
	other than NFS4_OK is returned. Lock types READ_LT and READW_LT
	are processed in the same way in that a conflicting lock test is
	done without regard to blocking or non-blocking. The same is true
	for WRITE_LT and WRITEW_LT.
	The ranges are specified as for LOCK. The NFS4ERR_INVAL and
	NFS4ERR_BAD_RANGE errors are returned under the same circumstances
	as for LOCK.
	Draft Specification NFS version 4 Protocol October 2002
	On success, the current filehandle retains its value.
	IMPLEMENTATION
	If the server is unable to determine the exact offset and length of
	the conflicting lock, the same offset and length that were provided
	in the arguments should be returned in the denied results. The
	File Locking section contains further discussion of the file
	locking mechanisms.
	LOCKT uses a lock_owner4 rather a stateid4, as is used in LOCK to
	identify the owner. This is because the client does not have to
	open the file to test for the existence of a lock, so a stateid may
	not be available.
	The test for conflicting locks should exclude locks for the current
	lockowner. Note that since such locks are not examined the
	possible existence of overlapping ranges may not affect the results
	of LOCKT. If the server does examine locks that match the
	lockowner for the purpose of range checking, NFS4ERR_LOCK_RANGE may
	be returned.. In the event that it returns NFS4_OK, clients may do
	a LOCK and receive NFS4ERR_LOCK_RANGE on the LOCK request because
	of the flexibility provided to the server.
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_BADHANDLE
	NFS4ERR_BAD_RANGE
	NFS4ERR_BADXDR
	NFS4ERR_DELAY
	NFS4ERR_DENIED
	NFS4ERR_FHEXPIRED
	NFS4ERR_GRACE
	NFS4ERR_INVAL
	NFS4ERR_ISDIR
	NFS4ERR_LEASE_MOVED
	NFS4ERR_LOCK_RANGE
	NFS4ERR_MOVED
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	NFS4ERR_STALE_CLIENTID
	Draft Specification NFS version 4 Protocol October 2002
	14.2.12. Operation 14: LOCKU - Unlock File
	SYNOPSIS
	(cfh) type, seqid, stateid, offset, length -> stateid
	ARGUMENT
	struct LOCKU4args {
	/* CURRENT_FH: file */
	nfs_lock_type4 locktype;
	seqid4 seqid;
	stateid4 stateid;
	offset4 offset;
	length4 length;
	};
	RESULT
	union LOCKU4res switch (nfsstat4 status) {
	case NFS4_OK:
	stateid4 stateid;
	default:
	void;
	};
	DESCRIPTION
	The LOCKU operation unlocks the record lock specified by the
	parameters. The client may set the locktype field to any value that
	is legal for the nfs_lock_type4 enumerated type, and the server
	MUST accept any legal value for locktype. Any legal value for
	locktype has no effect on the success or failure of the LOCKU
	operation.
	The ranges are specified as for LOCK. The NFS4ERR_INVAL and
	NFS4ERR_BAD_RANGE errors are returned under the same circumstances
	as for LOCK.
	On success, the current filehandle retains its value.
	IMPLEMENTATION
	If the area to be unlocked does not correspond exactly to a lock
	actually held by the lockowner the server may return the error
	NFS4ERR_LOCK_RANGE. This includes the case in which the area is
	not locked, where the area is a sub-range of the area locked, where
	it overlaps the area locked without matching exactly or the area
	Draft Specification NFS version 4 Protocol October 2002
	specified includes multiple locks held by the lockowner. In all of
	these cases, allowed by POSIX locking semantics, a client receiving
	this error, should if it desires support for such operations,
	simulate the operation using LOCKU on ranges corresponding to locks
	it actually holds, possibly followed by LOCK requests for the sub-
	ranges not being unlocked.
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_ADMIN_REVOKED
	NFS4ERR_BADHANDLE
	NFS4ERR_BAD_RANGE
	NFS4ERR_BAD_SEQID
	NFS4ERR_BAD_STATEID
	NFS4ERR_BADXDR
	NFS4ERR_EXPIRED
	NFS4ERR_FHEXPIRED
	NFS4ERR_GRACE
	NFS4ERR_INVAL
	NFS4ERR_ISDIR
	NFS4ERR_LEASE_MOVED
	NFS4ERR_LOCK_RANGE
	NFS4ERR_MOVED
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_OLD_STATEID
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	NFS4ERR_STALE_STATEID
	Draft Specification NFS version 4 Protocol October 2002
	14.2.13. Operation 15: LOOKUP - Lookup Filename
	SYNOPSIS
	(cfh), component -> (cfh)
	ARGUMENT
	struct LOOKUP4args {
	/* CURRENT_FH: directory */
	component4 objname;
	};
	RESULT
	struct LOOKUP4res {
	/* CURRENT_FH: object */
	nfsstat4 status;
	};
	DESCRIPTION
	This operation LOOKUPs or finds a filesystem object using the
	directory specified by the current filehandle. LOOKUP evaluates
	the component and if the object exists the current filehandle is
	replaced with the component's filehandle.
	If the component cannot be evaluated either because it does not
	exist or because the client does not have permission to evaluate
	the component, then an error will be returned and the current
	filehandle will be unchanged.
	If the component is a zero length string or if any component does
	not obey the UTF-8 definition, the error NFS4ERR_INVAL will be
	returned.
	IMPLEMENTATION
	If the client wants to achieve the effect of a multi-component
	lookup, it may construct a COMPOUND request such as (and obtain
	each filehandle):
	Draft Specification NFS version 4 Protocol October 2002
	PUTFH (directory filehandle)
	LOOKUP "pub"
	GETFH
	LOOKUP "foo"
	GETFH
	LOOKUP "bar"
	GETFH
	NFS version 4 servers depart from the semantics of previous NFS
	versions in allowing LOOKUP requests to cross mountpoints on the
	server. The client can detect a mountpoint crossing by comparing
	the fsid attribute of the directory with the fsid attribute of the
	directory looked up. If the fsids are different then the new
	directory is a server mountpoint. UNIX clients that detect a
	mountpoint crossing will need to mount the server's filesystem.
	This needs to be done to maintain the file object identity checking
	mechanisms common to UNIX clients.
	Servers that limit NFS access to "shares" or "exported" filesystems
	should provide a pseudo-filesystem into which the exported
	filesystems can be integrated, so that clients can browse the
	server's name space. The clients view of a pseudo filesystem will
	be limited to paths that lead to exported filesystems.
	Note: previous versions of the protocol assigned special semantics
	to the names "." and "..". NFS version 4 assigns no special
	semantics to these names. The LOOKUPP operator must be used to
	lookup a parent directory.
	Note that this operation does not follow symbolic links. The
	client is responsible for all parsing of filenames including
	filenames that are modified by symbolic links encountered during
	the lookup process.
	If the current filehandle supplied is not a directory but a
	symbolic link, the error NFS4ERR_SYMLINK is returned as the error.
	For all other non-directory file types, the error NFS4ERR_NOTDIR is
	returned.
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_BADCHAR
	NFS4ERR_BADHANDLE
	NFS4ERR_BADNAME
	NFS4ERR_BADXDR
	NFS4ERR_FHEXPIRED
	NFS4ERR_INVAL
	NFS4ERR_IO
	NFS4ERR_MOVED
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_NAMETOOLONG
	NFS4ERR_NOENT
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_NOTDIR
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	NFS4ERR_SYMLINK
	NFS4ERR_WRONGSEC
	Draft Specification NFS version 4 Protocol October 2002
	14.2.14. Operation 16: LOOKUPP - Lookup Parent Directory
	SYNOPSIS
	(cfh) -> (cfh)
	ARGUMENT
	/* CURRENT_FH: object */
	void;
	RESULT
	struct LOOKUPP4res {
	/* CURRENT_FH: directory */
	nfsstat4 status;
	};
	DESCRIPTION
	The current filehandle is assumed to refer to a regular directory
	or a named attribute directory. LOOKUPP assigns the filehandle for
	its parent directory to be the current filehandle. If there is no
	parent directory an NFS4ERR_NOENT error must be returned.
	Therefore, NFS4ERR_NOENT will be returned by the server when the
	current filehandle is at the root or top of the server's file tree.
	IMPLEMENTATION
	As for LOOKUP, LOOKUPP will also cross mountpoints.
	If the current filehandle is not a directory or named attribute
	directory, the error NFS4ERR_NOTDIR is returned.
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_BADHANDLE
	NFS4ERR_FHEXPIRED
	NFS4ERR_IO
	NFS4ERR_MOVED
	NFS4ERR_NOENT
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_NOTDIR
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	Draft Specification NFS version 4 Protocol October 2002
	14.2.15. Operation 17: NVERIFY - Verify Difference in Attributes
	SYNOPSIS
	(cfh), fattr -> -
	ARGUMENT
	struct NVERIFY4args {
	/* CURRENT_FH: object */
	fattr4 obj_attributes;
	};
	RESULT
	struct NVERIFY4res {
	nfsstat4 status;
	};
	DESCRIPTION
	This operation is used to prefix a sequence of operations to be
	performed if one or more attributes have changed on some filesystem
	object. If all the attributes match then the error NFS4ERR_SAME
	must be returned.
	On success, the current filehandle retains its value.
	IMPLEMENTATION
	This operation is useful as a cache validation operator. If the
	object to which the attributes belong has changed then the
	following operations may obtain new data associated with that
	object. For instance, to check if a file has been changed and
	obtain new data if it has:
	PUTFH (public)
	LOOKUP "foobar"
	NVERIFY attrbits attrs
	READ 0 32767
	In the case that a recommended attribute is specified in the
	NVERIFY operation and the server does not support that attribute
	for the filesystem object, the error NFS4ERR_ATTRNOTSUPP is
	returned to the client.
	When the attribute rdattr_error or any write-only attribute (e.g.
	Draft Specification NFS version 4 Protocol October 2002
	time_modify_set) is specified, the error NFS4ERR_INVAL is returned
	to the client.
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_ATTRNOTSUPP
	NFS4ERR_BADCHAR
	NFS4ERR_BADHANDLE
	NFS4ERR_BADXDR
	NFS4ERR_DELAY
	NFS4ERR_FHEXPIRED
	NFS4ERR_INVAL
	NFS4ERR_IO
	NFS4ERR_MOVED
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_RESOURCE
	NFS4ERR_SAME
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	Draft Specification NFS version 4 Protocol October 2002
	14.2.16. Operation 18: OPEN - Open a Regular File
	SYNOPSIS
	(cfh), seqid, share_access, share_deny, owner, openhow, claim ->
	(cfh), stateid, cinfo, rflags, open_confirm, attrset delegation
	ARGUMENT
	struct OPEN4args {
	seqid4 seqid;
	uint32_t share_access;
	uint32_t share_deny;
	open_owner4 owner;
	openflag4 openhow;
	open_claim4 claim;
	};
	enum createmode4 {
	UNCHECKED4 = 0,
	GUARDED4 = 1,
	EXCLUSIVE4 = 2
	};
	union createhow4 switch (createmode4 mode) {
	case UNCHECKED4:
	case GUARDED4:
	fattr4 createattrs;
	case EXCLUSIVE4:
	verifier4 createverf;
	};
	enum opentype4 {
	OPEN4_NOCREATE = 0,
	OPEN4_CREATE = 1
	};
	union openflag4 switch (opentype4 opentype) {
	case OPEN4_CREATE:
	createhow4 how;
	default:
	void;
	};
	/* Next definitions used for OPEN delegation */
	enum limit_by4 {
	NFS_LIMIT_SIZE = 1,
	NFS_LIMIT_BLOCKS = 2
	/* others as needed */
	};
	Draft Specification NFS version 4 Protocol October 2002
	struct nfs_modified_limit4 {
	uint32_t num_blocks;
	uint32_t bytes_per_block;
	};
	union nfs_space_limit4 switch (limit_by4 limitby) {
	/* limit specified as file size */
	case NFS_LIMIT_SIZE:
	uint64_t filesize;
	/* limit specified by number of blocks */
	case NFS_LIMIT_BLOCKS:
	nfs_modified_limit4 mod_blocks;
	} ;
	enum open_delegation_type4 {
	OPEN_DELEGATE_NONE = 0,
	OPEN_DELEGATE_READ = 1,
	OPEN_DELEGATE_WRITE = 2
	};
	enum open_claim_type4 {
	CLAIM_NULL = 0,
	CLAIM_PREVIOUS = 1,
	CLAIM_DELEGATE_CUR = 2,
	CLAIM_DELEGATE_PREV = 3
	};
	struct open_claim_delegate_cur4 {
	stateid4 delegate_stateid;
	component4 file;
	};
	union open_claim4 switch (open_claim_type4 claim) {
	/*
	* No special rights to file. Ordinary OPEN of the specified file.
	*/
	case CLAIM_NULL:
	/* CURRENT_FH: directory */
	component4 file;
	/*
	* Right to the file established by an open previous to server
	* reboot. File identified by filehandle obtained at that time
	* rather than by name.
	*/
	case CLAIM_PREVIOUS:
	/* CURRENT_FH: file being reclaimed */
	open_delegation_type4 delegate_type;
	/*
	* Right to file based on a delegation granted by the server.
	* File is specified by name.
	Draft Specification NFS version 4 Protocol October 2002
	*/
	case CLAIM_DELEGATE_CUR:
	/* CURRENT_FH: directory */
	open_claim_delegate_cur4 delegate_cur_info;
	/* Right to file based on a delegation granted to a previous boot
	* instance of the client. File is specified by name.
	*/
	case CLAIM_DELEGATE_PREV:
	/* CURRENT_FH: directory */
	component4 file_delegate_prev;
	};
	RESULT
	struct open_read_delegation4 {
	stateid4 stateid; /* Stateid for delegation*/
	bool recall; /* Pre-recalled flag for
	delegations obtained
	by reclaim
	(CLAIM_PREVIOUS) */
	nfsace4 permissions; /* Defines users who don't
	need an ACCESS call to
	open for read */
	};
	struct open_write_delegation4 {
	stateid4 stateid; /* Stateid for delegation*/
	bool recall; /* Pre-recalled flag for
	delegations obtained
	by reclaim
	(CLAIM_PREVIOUS) */
	nfs_space_limit4 space_limit; /* Defines condition that
	the client must check to
	determine whether the
	file needs to be flushed
	to the server on close.
	*/
	nfsace4 permissions; /* Defines users who don't
	need an ACCESS call as
	part of a delegated
	open. */
	};
	union open_delegation4
	switch (open_delegation_type4 delegation_type) {
	case OPEN_DELEGATE_NONE:
	void;
	case OPEN_DELEGATE_READ:
	open_read_delegation4 read;
	Draft Specification NFS version 4 Protocol October 2002
	case OPEN_DELEGATE_WRITE:
	open_write_delegation4 write;
	};
	const OPEN4_RESULT_CONFIRM = 0x00000002;
	const OPEN4_RESULT_LOCKTYPE_POSIX = 0x00000004;
	struct OPEN4resok {
	stateid4 stateid; /* Stateid for open */
	change_info4 cinfo; /* Directory Change Info */
	uint32_t rflags; /* Result flags */
	bitmap4 attrset; /* attributes on create */
	open_delegation4 delegation; /* Info on any open
	delegation */
	};
	union OPEN4res switch (nfsstat4 status) {
	case NFS4_OK:
	/* CURRENT_FH: opened file */
	OPEN4resok resok4;
	default:
	void;
	};
	WARNING TO CLIENT IMPLEMENTORS
	OPEN resembles LOOKUP in that it generates a filehandle for the
	client to use. Unlike LOOKUP though, OPEN creates server state on
	the filehandle. In normal circumstances, the client can only
	release this state with a CLOSE operation. CLOSE uses the current
	filehandle to determine which file to close. Therefore the client
	MUST follow every OPEN operation with a GETFH operation in the same
	COMPOUND procedure. This will supply the client with the
	filehandle such that CLOSE can be used appropriately.
	Simply waiting for the lease on the file to expire is insufficient
	because the server may maintain the state indefinitely as long as
	another client does not attempt to make a conflicting access to the
	same file.
	DESCRIPTION
	The OPEN operation creates and/or opens a regular file in a
	directory with the provided name. If the file does not exist at
	the server and creation is desired, specification of the method of
	creation is provided by the openhow parameter. The client has the
	choice of three creation methods: UNCHECKED, GUARDED, or EXCLUSIVE.
	If the current filehandle is a named attribute directory, OPEN will
	then create or open a named attribute file. Note that exclusive
	Draft Specification NFS version 4 Protocol October 2002
	create of a named attribute is not supported. If the createmode is
	EXCLUSIVE4 and the current filehandle is a named attribute
	directory, the server will return EINVAL.
	UNCHECKED means that the file should be created if a file of that
	name does not exist and encountering an existing regular file of
	that name is not an error. For this type of create, createattrs
	specifies the initial set of attributes for the file. The set of
	attributes may include any writable attribute valid for regular
	files. When an UNCHECKED create encounters an existing file, the
	attributes specified by createattrs are not used, except that when
	an size of zero is specified, the existing file is truncated. If
	GUARDED is specified, the server checks for the presence of a
	duplicate object by name before performing the create. If a
	duplicate exists, an error of NFS4ERR_EXIST is returned as the
	status. If the object does not exist, the request is performed as
	described for UNCHECKED. For each of these cases (UNCHECKED and
	GUARDED) where the operation is successful, the server will return
	to the client an attribute mask signifying which attributes were
	successfully set for the object.
	EXCLUSIVE specifies that the server is to follow exclusive creation
	semantics, using the verifier to ensure exclusive creation of the
	target. The server should check for the presence of a duplicate
	object by name. If the object does not exist, the server creates
	the object and stores the verifier with the object. If the object
	does exist and the stored verifier matches the client provided
	verifier, the server uses the existing object as the newly created
	object. If the stored verifier does not match, then an error of
	NFS4ERR_EXIST is returned. No attributes may be provided in this
	case, since the server may use an attribute of the target object to
	store the verifier. If the server uses an attribute to store the
	exclusive create verifier, it will signify which attribute by
	setting the appropriate bit in the attribute mask that is returned
	in the results.
	For the target directory, the server returns change_info4
	information in cinfo. With the atomic field of the change_info4
	struct, the server will indicate if the before and after change
	attributes were obtained atomically with respect to the link
	creation.
	Upon successful creation, the current filehandle is replaced by
	that of the new object.
	The OPEN operation provides for Windows share reservation
	capability with the use of the share_access and share_deny fields
	of the OPEN arguments. The client specifies at OPEN the required
	share_access and share_deny modes. For clients that do not
	directly support SHAREs (i.e. UNIX), the expected deny value is
	DENY_NONE. In the case that there is a existing SHARE reservation
	that conflicts with the OPEN request, the server returns the error
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_SHARE_DENIED. For a complete SHARE request, the client
	must provide values for the owner and seqid fields for the OPEN
	argument. For additional discussion of SHARE semantics see the
	section on 'Share Reservations'.
	In the case that the client is recovering state from a server
	failure, the claim field of the OPEN argument is used to signify
	that the request is meant to reclaim state previously held.
	The "claim" field of the OPEN argument is used to specify the file
	to be opened and the state information which the client claims to
	possess. There are four basic claim types which cover the various
	situations for an OPEN. They are as follows:
	CLAIM_NULL
	For the client, this is a new OPEN
	request and there is no previous state
	associate with the file for the client.
	CLAIM_PREVIOUS
	The client is claiming basic OPEN state
	for a file that was held previous to a
	server reboot. Generally used when a
	server is returning persistent
	filehandles; the client may not have the
	file name to reclaim the OPEN.
	CLAIM_DELEGATE_CUR
	The client is claiming a delegation for
	OPEN as granted by the server.
	Generally this is done as part of
	recalling a delegation.
	CLAIM_DELEGATE_PREV
	The client is claiming a delegation
	granted to a previous client instance;
	used after the client reboots. The
	server MAY support CLAIM_DELEGATE_PREV.
	If it does support CLAIM_DELEGATE_PREV,
	SETCLIENTID_CONFIRM MUST NOT remove the
	client's delegation state, and the
	server MUST support the DELEGPURGE
	operation.
	For OPEN requests whose claim type is other than CLAIM_PREVIOUS
	(i.e. requests other than those devoted to reclaiming opens after a
	server reboot) that reach the server during its grace or lease
	expiration period, the server returns an error of NFS4ERR_GRACE.
	For any OPEN request, the server may return an open delegation,
	which allows further opens and closes to be handled locally on the
	client as described in the section Open Delegation. Note that
	delegation is up to the server to decide. The client should never
	assume that delegation will or will not be granted in a particular
	instance. It should always be prepared for either case. A partial
	Draft Specification NFS version 4 Protocol October 2002
	exception is the reclaim (CLAIM_PREVIOUS) case, in which a
	delegation type is claimed. In this case, delegation will always
	be granted, although the server may specify an immediate recall in
	the delegation structure.
	The rflags returned by a successful OPEN allow the server to return
	information governing how the open file is to be handled.
	OPEN4_RESULT_CONFIRM indicates that the client MUST execute an
	OPEN_CONFIRM operation before using the open file.
	OPEN4_RESULT_LOCKTYPE_POSIX indicates the server's file locking
	behavior supports the complete set of Posix locking techniques.
	From this the client can choose to manage file locking state in a
	way to handle a mis-match of file locking management.
	If the component is of zero length, NFS4ERR_INVAL will be returned.
	The component is also subject to the normal UTF-8, character
	support, and name checks. See the section "UTF-8 Related Errors"
	for further discussion.
	When an OPEN is done and the specified lockowner already has the
	resulting filehandle open, the result is to "OR" together the new
	share and deny status together with the existing status. In this
	case, only a single CLOSE need be done, even though multiple OPENs
	were completed. When such an OPEN is done, checking of share
	reservations for the new OPEN proceeds normally, with no exception
	for the existing OPEN held by the same lockowner.
	If the underlying filesystem at the server is only accessible in a
	read-only mode and the OPEN request has specified ACCESS_WRITE or
	ACCESS_BOTH, the server will return NFS4ERR_ROFS to indicate a
	read-only filesystem.
	As with the CREATE operation, the server MUST derive the owner,
	owner ACE, group, or group ACE if any of the four attributes are
	required and supported by the server's filesystem. For an OPEN
	with the EXCLUSIVE4 createmode, the server has no choice, since
	such OPEN calls do not include the createattrs field. Conversely,
	if createattrs is specified, and includes owner or group (or
	corresponding ACEs) that the principal in the RPC call's
	credentials does not have authorization to create files for, then
	the server may return NFS4ERR_PERM.
	In the case of a OPEN which specifies a size of zero (e.g.
	truncation) and the file has named attributes, the named attributes
	are left as is. They are not removed.
	IMPLEMENTATION
	The OPEN operation contains support for EXCLUSIVE create. The
	mechanism is similar to the support in NFS version 3 [RFC1813]. As
	in NFS version 3, this mechanism provides reliable exclusive
	Draft Specification NFS version 4 Protocol October 2002
	creation. Exclusive create is invoked when the how parameter is
	EXCLUSIVE. In this case, the client provides a verifier that can
	reasonably be expected to be unique. A combination of a client
	identifier, perhaps the client network address, and a unique number
	generated by the client, perhaps the RPC transaction identifier,
	may be appropriate.
	If the object does not exist, the server creates the object and
	stores the verifier in stable storage. For filesystems that do not
	provide a mechanism for the storage of arbitrary file attributes,
	the server may use one or more elements of the object meta-data to
	store the verifier. The verifier must be stored in stable storage
	to prevent erroneous failure on retransmission of the request. It
	is assumed that an exclusive create is being performed because
	exclusive semantics are critical to the application. Because of the
	expected usage, exclusive CREATE does not rely solely on the
	normally volatile duplicate request cache for storage of the
	verifier. The duplicate request cache in volatile storage does not
	survive a crash and may actually flush on a long network partition,
	opening failure windows. In the UNIX local filesystem environment,
	the expected storage location for the verifier on creation is the
	meta-data (time stamps) of the object. For this reason, an
	exclusive object create may not include initial attributes because
	the server would have nowhere to store the verifier.
	If the server can not support these exclusive create semantics,
	possibly because of the requirement to commit the verifier to
	stable storage, it should fail the OPEN request with the error,
	NFS4ERR_NOTSUPP.
	During an exclusive CREATE request, if the object already exists,
	the server reconstructs the object's verifier and compares it with
	the verifier in the request. If they match, the server treats the
	request as a success. The request is presumed to be a duplicate of
	an earlier, successful request for which the reply was lost and
	that the server duplicate request cache mechanism did not detect.
	If the verifiers do not match, the request is rejected with the
	status, NFS4ERR_EXIST.
	Once the client has performed a successful exclusive create, it
	must issue a SETATTR to set the correct object attributes. Until
	it does so, it should not rely upon any of the object attributes,
	since the server implementation may need to overload object meta-
	data to store the verifier. The subsequent SETATTR must not occur
	in the same COMPOUND request as the OPEN. This separation will
	guarantee that the exclusive create mechanism will continue to
	function properly in the face of retransmission of the request.
	Use of the GUARDED attribute does not provide exactly-once
	semantics. In particular, if a reply is lost and the server does
	not detect the retransmission of the request, the operation can
	fail with NFS4ERR_EXIST, even though the create was performed
	Draft Specification NFS version 4 Protocol October 2002
	successfully. The client would use this behavior in the case that
	the application has not requested an exclusive create but has asked
	to have the file truncated when the file is opened. In the case of
	the client timing out and retransmitting the create request, the
	client can use GUARDED to prevent against a sequence like: create,
	write, create (retransmitted) from occurring.
	For SHARE reservations, the client must specify a value for
	share_access that is one of READ, WRITE, or BOTH. For share_deny,
	the client must specify one of NONE, READ, WRITE, or BOTH. If the
	client fails to do this, the server must return NFS4ERR_INVAL.
	Based on the share_access value (READ, WRITE, or BOTH) the client
	should check that the requester has the proper access rights to
	perform the specified operation. This would generally be the
	results of applying the ACL access rules to the file for the
	current requester. However, just as with the ACCESS operation, the
	client should not attempt to second-guess the server's decisions,
	as access rights may change and may be subject to server
	administrative controls outside the ACL framework. If the
	requester is not authorized to READ or WRITE (depending on the
	share_access value), the server must return NFS4ERR_ACCESS. Note
	that since the NFS version 4 protocol does not impose any
	requirement that READs and WRITEs issued for an open file have the
	same credentials as the OPEN itself, the server still must do
	appropriate access checking on the READs and WRITEs themselves.
	If the component provided to OPEN is a symbolic link, the error
	NFS4ERR_SYMLINK will be returned to the client. If the current
	filehandle is not a directory, the error NFS4ERR_NOTDIR will be
	returned.
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_ADMIN_REVOKED
	NFS4ERR_ATTRNOTSUPP
	NFS4ERR_BADCHAR
	NFS4ERR_BADHANDLE
	NFS4ERR_BADNAME
	NFS4ERR_BADOWNER
	NFS4ERR_BAD_SEQID
	NFS4ERR_BADXDR
	NFS4ERR_DELAY
	NFS4ERR_DQUOT
	NFS4ERR_EXIST
	NFS4ERR_EXPIRED
	NFS4ERR_FHEXPIRED
	NFS4ERR_GRACE
	NFS4ERR_IO
	NFS4ERR_INVAL
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_ISDIR
	NFS4ERR_LEASE_MOVED
	NFS4ERR_MOVED
	NFS4ERR_NAMETOOLONG
	NFS4ERR_NOENT
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_NOSPC
	NFS4ERR_NOTDIR
	NFS4ERR_NO_GRACE
	NFS4ERR_PERM
	NFS4ERR_RECLAIM_BAD
	NFS4ERR_RECLAIM_CONFLICT
	NFS4ERR_RESOURCE
	NFS4ERR_ROFS
	NFS4ERR_SERVERFAULT
	NFS4ERR_SHARE_DENIED
	NFS4ERR_STALE
	NFS4ERR_STALE_CLIENTID
	NFS4ERR_SYMLINK
	NFS4ERR_WRONGSEC
	Draft Specification NFS version 4 Protocol October 2002
	14.2.17. Operation 19: OPENATTR - Open Named Attribute Directory
	SYNOPSIS
	(cfh) createdir -> (cfh)
	ARGUMENT
	struct OPENATTR4args {
	/* CURRENT_FH: object */
	bool createdir;
	};
	RESULT
	struct OPENATTR4res {
	/* CURRENT_FH: named attr directory*/
	nfsstat4 status;
	};
	DESCRIPTION
	The OPENATTR operation is used to obtain the filehandle of the
	named attribute directory associated with the current filehandle.
	The result of the OPENATTR will be a filehandle to an object of
	type NF4ATTRDIR. From this filehandle, READDIR and LOOKUP
	operations can be used to obtain filehandles for the various named
	attributes associated with the original filesystem object.
	Filehandles returned within the named attribute directory will have
	a type of NF4NAMEDATTR.
	The createdir argument allows the client to signify if a named
	attribute directory should be created as a result of the OPENATTR
	operation. Some clients may use the OPENATTR operation with a
	value of FALSE for createdir to determine if any named attributes
	exist for the object. If none exist, then NFS4ERR_NOENT will be
	returned. If createdir has a value of TRUE and no named attribute
	directory exists, one is created. The creation of a named
	attribute directory assumes that the server has implemented named
	attribute support in this fashion and is not required to do so by
	this definition.
	IMPLEMENTATION
	If the server does not support named attributes for the current
	filehandle, an error of NFS4ERR_NOTSUPP will be returned to the
	client.
	Draft Specification NFS version 4 Protocol October 2002
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_BADHANDLE
	NFS4ERR_BADXDR
	NFS4ERR_DELAY
	NFS4ERR_DQUOT
	NFS4ERR_FHEXPIRED
	NFS4ERR_IO
	NFS4ERR_MOVED
	NFS4ERR_NOENT
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_NOSPC
	NFS4ERR_NOTSUPP
	NFS4ERR_RESOURCE
	NFS4ERR_ROFS
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	Draft Specification NFS version 4 Protocol October 2002
	14.2.18. Operation 20: OPEN_CONFIRM - Confirm Open
	SYNOPSIS
	(cfh), seqid, stateid-> stateid
	ARGUMENT
	struct OPEN_CONFIRM4args {
	/* CURRENT_FH: opened file */
	seqid4 seqid;
	stateid4 stateid;
	};
	RESULT
	struct OPEN_CONFIRM4resok {
	stateid4 stateid;
	};
	union OPEN_CONFIRM4res switch (nfsstat4 status) {
	case NFS4_OK:
	OPEN_CONFIRM4resok resok4;
	default:
	void;
	};
	DESCRIPTION
	This operation is used to confirm the sequence id usage for the
	first time that a open_owner is used by a client. The stateid
	returned from the OPEN operation is used as the argument for this
	operation along with the next sequence id for the open_owner. The
	sequence id passed to the OPEN_CONFIRM must be 1 (one) greater than
	the seqid passed to the OPEN operation from which the open_confirm
	value was obtained. If the server receives an unexpected sequence
	id with respect to the original open, then the server assumes that
	the client will not confirm the original OPEN and all state
	associated with the original OPEN is released by the server.
	On success, the current filehandle retains its value.
	IMPLEMENTATION
	A given client might generate many open_owner4 data structures for
	a given clientid. The client will periodically either dispose of
	its open_owner4s or stop using them for indefinite periods of time.
	The latter situation is why the NFS version 4 protocol does not
	Draft Specification NFS version 4 Protocol October 2002
	have an explicit operation to exit an open_owner4: such an
	operation is of no use in that situation. Instead, to avoid
	unbounded memory use, the server needs to implement a strategy for
	disposing of open_owner4s that have no current lock, open, or
	delegation state for any files and have not been used recently.
	The time period used to determine when to dispose of open_owner4s
	is an implementation choice. The time period should certainly be
	no less than the lease time plus any grace period the server wishes
	to implement beyond a lease time. The OPEN_CONFIRM operation
	allows the server to safely dispose of unused open_owner4 data
	structures.
	In the case that a client issues an OPEN operation and the server
	no longer has a record of the open_owner4, the server needs ensure
	that this is a new OPEN and not a replay or retransmission.
	Servers must not require confirmation on OPENs that grant
	delegations or are doing reclaim operations. See section "Use of
	Open Confirmation" for details. The server can easily avoid this
	by noting whether it has disposed of one open_owner4 for the given
	clientid. If the server does not support delegation, it might
	simply maintain a single bit that notes whether any open_owner4
	(for any client) has been disposed of.
	The server must hold unconfirmed OPEN state until one of three
	events occur. First, the client sends an OPEN_CONFIRM request with
	the appropriate sequence id and stateid within the lease period.
	In this case, the OPEN state on the server goes to confirmed, and
	the open_owner4 on the server is fully established.
	Second, the client sends another OPEN request with a sequence id
	that is incorrect for the open_owner4 (out of sequence). In this
	case, the server assumes the second OPEN request is valid and the
	first one is a replay. The server cancels the OPEN state of the
	first OPEN request, establishes an unconfirmed OPEN state for the
	second OPEN request, and responds to the second OPEN request with
	an indication that an OPEN_CONFIRM is needed. The process then
	repeats itself. While there is a potential for a denial of service
	attack on the client, it is mitigated if the client and server
	require the use of a security flavor based on Kerberos V5, LIPKEY,
	or some other flavor that uses cryptography.
	What if the server is in the unconfirmed OPEN state for a given
	open_owner4, and it receives an operation on the open_owner4 that
	has a stateid but the operation is not OPEN, or it is OPEN_CONFIRM
	but with the wrong stateid? Then, even if the seqid is correct,
	the server returns NFS4ERR_BAD_STATEID, because the server assumes
	the operation is a replay: if the server has no established OPEN
	state, then there is no way, for example, a LOCK operation could be
	valid.
	Third, neither of the two aforementioned events occur for the
	Draft Specification NFS version 4 Protocol October 2002
	open_owner4 within the lease period. In this case, the OPEN state
	is canceled and disposal of the open_owner4 can occur.
	ERRORS
	NFS4ERR_ADMIN_REVOKED
	NFS4ERR_BADHANDLE
	NFS4ERR_BAD_SEQID
	NFS4ERR_BAD_STATEID
	NFS4ERR_BADXDR
	NFS4ERR_EXPIRED
	NFS4ERR_FHEXPIRED
	NFS4ERR_INVAL
	NFS4ERR_ISDIR
	NFS4ERR_MOVED
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_OLD_STATEID
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	NFS4ERR_STALE_STATEID
	Draft Specification NFS version 4 Protocol October 2002
	14.2.19. Operation 21: OPEN_DOWNGRADE - Reduce Open File Access
	SYNOPSIS
	(cfh), stateid, seqid, access, deny -> stateid
	ARGUMENT
	struct OPEN_DOWNGRADE4args {
	/* CURRENT_FH: opened file */
	stateid4 stateid;
	seqid4 seqid;
	uint32_t share_access;
	uint32_t share_deny;
	};
	RESULT
	struct OPEN_DOWNGRADE4resok {
	stateid4 stateid;
	};
	union OPEN_DOWNGRADE4res switch(nfsstat4 status) {
	case NFS4_OK:
	OPEN_DOWNGRADE4resok resok4;
	default:
	void;
	};
	DESCRIPTION
	This operation is used to adjust the share_access and share_deny
	bits for a given open. This is necessary when a given lockowner
	opens the same file multiple times with different share_access and
	share_deny flags. In this situation, a close of one of the opens
	may change the appropriate share_access and share_deny flags to
	remove bits associated with opens no longer in effect.
	The share_access and share_deny bits specified in this operation
	replace the current ones for the specified open file. The
	share_access and share_deny bits specified must be exactly equal to
	the union of the share_access and share_deny bits specified for
	some subset of the OPENs in effect for current openowner on the
	current file. If that constraint is not respected, the error
	NFS4ERR_INVAL should be returned. Since share_access and
	share_deny bits are subsets of those already granted, it is not
	possible for this request to be denied because of conflicting share
	reservations.
	Draft Specification NFS version 4 Protocol October 2002
	On success, the current filehandle retains its value.
	ERRORS
	NFS4ERR_ADMIN_REVOKED
	NFS4ERR_BADHANDLE
	NFS4ERR_BAD_SEQID
	NFS4ERR_BAD_STATEID
	NFS4ERR_BADXDR
	NFS4ERR_EXPIRED
	NFS4ERR_FHEXPIRED
	NFS4ERR_INVAL
	NFS4ERR_MOVED
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_OLD_STATEID
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	NFS4ERR_STALE_STATEID
	Draft Specification NFS version 4 Protocol October 2002
	14.2.20. Operation 22: PUTFH - Set Current Filehandle
	SYNOPSIS
	filehandle -> (cfh)
	ARGUMENT
	struct PUTFH4args {
	nfs_fh4 object;
	};
	RESULT
	struct PUTFH4res {
	/* CURRENT_FH: */
	nfsstat4 status;
	};
	DESCRIPTION
	Replaces the current filehandle with the filehandle provided as an
	argument.
	If the security mechanism used by the requester does not meet the
	requirements of the filehandle provided to this operation, the
	server MUST return NFS4ERR_WRONGSEC.
	IMPLEMENTATION
	Commonly used as the first operator in an NFS request to set the
	context for following operations.
	ERRORS
	NFS4ERR_BADHANDLE
	NFS4ERR_BADXDR
	NFS4ERR_FHEXPIRED
	NFS4ERR_MOVED
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	NFS4ERR_WRONGSEC
	Draft Specification NFS version 4 Protocol October 2002
	14.2.21. Operation 23: PUTPUBFH - Set Public Filehandle
	SYNOPSIS
	- -> (cfh)
	ARGUMENT
	void;
	RESULT
	struct PUTPUBFH4res {
	/* CURRENT_FH: public fh */
	nfsstat4 status;
	};
	DESCRIPTION
	Replaces the current filehandle with the filehandle that represents
	the public filehandle of the server's name space. This filehandle
	may be different from the "root" filehandle which may be associated
	with some other directory on the server.
	The public filehandle represents the concepts embodied in
	[RFC2054], [RFC2055], [RFC2224]. The intent for NFS version 4 is
	that the public filehandle (represented by the PUTPUBFH operation)
	be used as a method of providing WebNFS server compatibility with
	NFS versions 2 and 3.
	The public filehandle and the root filehandle (represented by the
	PUTROOTFH operation) should be equivalent. If the public and root
	filehandles are not equivalent, then the public filehandle MUST be
	a descendant of the root filehandle.
	IMPLEMENTATION
	Used as the first operator in an NFS request to set the context for
	following operations.
	With the NFS version 2 and 3 public filehandle, the client is able
	to specify whether the path name provided in the LOOKUP should be
	evaluated as either an absolute path relative to the server's root
	or relative to the public filehandle. [RFC2224] contains further
	discussion of the functionality. With NFS version 4, that type of
	specification is not directly available in the LOOKUP operation.
	The reason for this is because the component separators needed to
	specify absolute vs. relative are not allowed in NFS version 4.
	Draft Specification NFS version 4 Protocol October 2002
	Therefore, the client is responsible for constructing its request
	such that the use of either PUTROOTFH or PUTPUBFH are used to
	signify absolute or relative evaluation of an NFS URL respectively.
	Note that there are warnings mentioned in [RFC2224] with respect to
	the use of absolute evaluation and the restrictions the server may
	place on that evaluation with respect to how much of its namespace
	has been made available. These same warnings apply to NFS version
	4. It is likely, therefore that because of server implementation
	details, an NFS version 3 absolute public filehandle lookup may
	behave differently than an NFS version 4 absolute resolution.
	There is a form of security negotiation as described in [RFC2755]
	that uses the public filehandle a method of employing SNEGO. This
	method is not available with NFS version 4 as filehandles are not
	overloaded with special meaning and therefore do not provide the
	same framework as NFS versions 2 and 3. Clients should therefore
	use the security negotiation mechanisms described in this RFC.
	ERRORS
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_WRONGSEC
	Draft Specification NFS version 4 Protocol October 2002
	14.2.22. Operation 24: PUTROOTFH - Set Root Filehandle
	SYNOPSIS
	- -> (cfh)
	ARGUMENT
	void;
	RESULT
	struct PUTROOTFH4res {
	/* CURRENT_FH: root fh */
	nfsstat4 status;
	};
	DESCRIPTION
	Replaces the current filehandle with the filehandle that represents
	the root of the server's name space. From this filehandle a LOOKUP
	operation can locate any other filehandle on the server. This
	filehandle may be different from the "public" filehandle which may
	be associated with some other directory on the server.
	IMPLEMENTATION
	Commonly used as the first operator in an NFS request to set the
	context for following operations.
	ERRORS
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_WRONGSEC
	Draft Specification NFS version 4 Protocol October 2002
	14.2.23. Operation 25: READ - Read from File
	SYNOPSIS
	(cfh), stateid, offset, count -> eof, data
	ARGUMENT
	struct READ4args {
	/* CURRENT_FH: file */
	stateid4 stateid;
	offset4 offset;
	count4 count;
	};
	RESULT
	struct READ4resok {
	bool eof;
	opaque data<>;
	};
	union READ4res switch (nfsstat4 status) {
	case NFS4_OK:
	READ4resok resok4;
	default:
	void;
	};
	DESCRIPTION
	The READ operation reads data from the regular file identified by
	the current filehandle.
	The client provides an offset of where the READ is to start and a
	count of how many bytes are to be read. An offset of 0 (zero)
	means to read data starting at the beginning of the file. If
	offset is greater than or equal to the size of the file, the
	status, NFS4_OK, is returned with a data length set to 0 (zero) and
	eof is set to TRUE. The READ is subject to access permissions
	checking.
	If the client specifies a count value of 0 (zero), the READ
	succeeds and returns 0 (zero) bytes of data again subject to access
	permissions checking. The server may choose to return fewer bytes
	than specified by the client. The client needs to check for this
	condition and handle the condition appropriately.
	The stateid value for a READ request represents a value returned
	Draft Specification NFS version 4 Protocol October 2002
	from a previous record lock or share reservation request. The
	stateid is used by the server to verify that the associated share
	reservation and any record locks are still valid and to update
	lease timeouts for the client.
	If the read ended at the end-of-file (formally, in a correctly
	formed READ request, if offset + count is equal to the size of the
	file), or the read request extends beyond the size of the file (if
	offset + count is greater than the size of the file), eof is
	returned as TRUE; otherwise it is FALSE. A successful READ of an
	empty file will always return eof as TRUE.
	If the current filehandle is not a regular file, an error will be
	returned to the client. In the case the current filehandle
	represents a directory, NFS4ERR_ISDIR is return; otherwise,
	NFS4ERR_INVAL is returned.
	For a READ with a stateid value of all bits 0, the server MAY allow
	the READ to be serviced subject to mandatory file locks or the
	current share deny modes for the file. For a READ with a stateid
	value of all bits 1, the server MAY allow READ operations to bypass
	locking checks at the server.
	On success, the current filehandle retains its value.
	IMPLEMENTATION
	It is possible for the server to return fewer than count bytes of
	data. If the server returns less than the count requested and eof
	is set to FALSE, the client should issue another READ to get the
	remaining data. A server may return less data than requested under
	several circumstances. The file may have been truncated by another
	client or perhaps on the server itself, changing the file size from
	what the requesting client believes to be the case. This would
	reduce the actual amount of data available to the client. It is
	possible that the server may back off the transfer size and reduce
	the read request return. Server resource exhaustion may also occur
	necessitating a smaller read return.
	If mandatory file locking is on for the file, and if the region
	corresponding to the data to be read from file is write locked by
	an owner not associated the stateid, the server will return the
	NFS4ERR_LOCKED error. The client should try to get the appropriate
	read record lock via the LOCK operation before re-attempting the
	READ. When the READ completes, the client should release the
	record lock via LOCKU.
	ERRORS
	NFS4ERR_ACCESS
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_ADMIN_REVOKED
	NFS4ERR_BADHANDLE
	NFS4ERR_BAD_STATEID
	NFS4ERR_BADXDR
	NFS4ERR_DELAY
	NFS4ERR_EXPIRED
	NFS4ERR_FHEXPIRED
	NFS4ERR_GRACE
	NFS4ERR_IO
	NFS4ERR_INVAL
	NFS4ERR_ISDIR
	NFS4ERR_LEASE_MOVED
	NFS4ERR_LOCKED
	NFS4ERR_MOVED
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_NXIO
	NFS4ERR_OLD_STATEID
	NFS4ERR_OPENMODE
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	NFS4ERR_STALE_STATEID
	Draft Specification NFS version 4 Protocol October 2002
	14.2.24. Operation 26: READDIR - Read Directory
	SYNOPSIS
	(cfh), cookie, cookieverf, dircount, maxcount, attr_request ->
	cookieverf { cookie, name, attrs }
	ARGUMENT
	struct READDIR4args {
	/* CURRENT_FH: directory */
	nfs_cookie4 cookie;
	verifier4 cookieverf;
	count4 dircount;
	count4 maxcount;
	bitmap4 attr_request;
	};
	RESULT
	struct entry4 {
	nfs_cookie4 cookie;
	component4 name;
	fattr4 attrs;
	entry4 *nextentry;
	};
	struct dirlist4 {
	entry4 *entries;
	bool eof;
	};
	struct READDIR4resok {
	verifier4 cookieverf;
	dirlist4 reply;
	};
	union READDIR4res switch (nfsstat4 status) {
	case NFS4_OK:
	READDIR4resok resok4;
	default:
	void;
	};
	DESCRIPTION
	The READDIR operation retrieves a variable number of entries from a
	filesystem directory and returns client requested attributes for
	each entry along with information to allow the client to request
	Draft Specification NFS version 4 Protocol October 2002
	additional directory entries in a subsequent READDIR.
	The arguments contain a cookie value that represents where the
	READDIR should start within the directory. A value of 0 (zero) for
	the cookie is used to start reading at the beginning of the
	directory. For subsequent READDIR requests, the client specifies a
	cookie value that is provided by the server on a previous READDIR
	request.
	The cookieverf value should be set to 0 (zero) when the cookie
	value is 0 (zero) (first directory read). On subsequent requests,
	it should be a cookieverf as returned by the server. The
	cookieverf must match that returned by the READDIR in which the
	cookie was acquired. If the server determines that the cookieverf
	is no longer valid for the directory, the error NFS4ERR_NOT_SAME
	must be returned.
	The dircount portion of the argument is a hint of the maximum
	number of bytes of directory information that should be returned.
	This value represents the length of the names of the directory
	entries and the cookie value for these entries. This length
	represents the XDR encoding of the data (names and cookies) and not
	the length in the native format of the server.
	The maxcount value of the argument is the maximum number of bytes
	for the result. This maximum size represents all of the data being
	returned within the READDIR4resok structure and includes the XDR
	overhead. The server may return less data. If the server is
	unable to return a single directory entry within the maxcount
	limit, the error NFS4ERR_TOOSMALL will be returned to the client.
	Finally, attr_request represents the list of attributes to be
	returned for each directory entry supplied by the server.
	On successful return, the server's response will provide a list of
	directory entries. Each of these entries contains the name of the
	directory entry, a cookie value for that entry, and the associated
	attributes as requested. The "eof" flag has a value of TRUE if
	there are no more entries in the directory.
	The cookie value is only meaningful to the server and is used as a
	"bookmark" for the directory entry. As mentioned, this cookie is
	used by the client for subsequent READDIR operations so that it may
	continue reading a directory. The cookie is similar in concept to
	a READ offset but should not be interpreted as such by the client.
	Ideally, the cookie value should not change if the directory is
	modified since the client may be caching these values.
	In some cases, the server may encounter an error while obtaining
	the attributes for a directory entry. Instead of returning an
	error for the entire READDIR operation, the server can instead
	return the attribute 'fattr4_rdattr_error'. With this, the server
	Draft Specification NFS version 4 Protocol October 2002
	is able to communicate the failure to the client and not fail the
	entire operation in the instance of what might be a transient
	failure. Obviously, the client must request the
	fattr4_rdattr_error attribute for this method to work properly. If
	the client does not request the attribute, the server has no choice
	but to return failure for the entire READDIR operation.
	For some filesystem environments, the directory entries "." and
	".." have special meaning and in other environments, they may not.
	If the server supports these special entries within a directory,
	they should not be returned to the client as part of the READDIR
	response. To enable some client environments, the cookie values of
	0, 1, and 2 are to be considered reserved. Note that the UNIX
	client will use these values when combining the server's response
	and local representations to enable a fully formed UNIX directory
	presentation to the application.
	For READDIR arguments, cookie values of 1 and 2 should not be used
	and for READDIR results cookie values of 0, 1, and 2 should not be
	returned.
	On success, the current filehandle retains its value.
	IMPLEMENTATION
	The server's filesystem directory representations can differ
	greatly. A client's programming interfaces may also be bound to
	the local operating environment in a way that does not translate
	well into the NFS protocol. Therefore the use of the dircount and
	maxcount fields are provided to allow the client the ability to
	provide guidelines to the server. If the client is aggressive
	about attribute collection during a READDIR, the server has an idea
	of how to limit the encoded response. The dircount field provides
	a hint on the number of entries based solely on the names of the
	directory entries. Since it is a hint, it may be possible that a
	dircount value is zero. In this case, the server is free to ignore
	the dircount value and return directory information based on the
	specified maxcount value.
	The cookieverf may be used by the server to help manage cookie
	values that may become stale. It should be a rare occurrence that
	a server is unable to continue properly reading a directory with
	the provided cookie/cookieverf pair. The server should make every
	effort to avoid this condition since the application at the client
	may not be able to properly handle this type of failure.
	The use of the cookieverf will also protect the client from using
	READDIR cookie values that may be stale. For example, if the file
	system has been migrated, the server may or may not be able to use
	the same cookie values to service READDIR as the previous server
	used. With the client providing the cookieverf, the server is able
	Draft Specification NFS version 4 Protocol October 2002
	to provide the appropriate response to the client. This prevents
	the case where the server may accept a cookie value but the
	underlying directory has changed and the response is invalid from
	the client's context of its previous READDIR.
	Since some servers will not be returning "." and ".." entries as
	has been done with previous versions of the NFS protocol, the
	client that requires these entries be present in READDIR responses
	must fabricate them.
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_BADHANDLE
	NFS4ERR_BAD_COOKIE
	NFS4ERR_BADXDR
	NFS4ERR_DELAY
	NFS4ERR_FHEXPIRED
	NFS4ERR_INVAL
	NFS4ERR_IO
	NFS4ERR_MOVED
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_NOTDIR
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	NFS4ERR_TOOSMALL
	Draft Specification NFS version 4 Protocol October 2002
	14.2.25. Operation 27: READLINK - Read Symbolic Link
	SYNOPSIS
	(cfh) -> linktext
	ARGUMENT
	/* CURRENT_FH: symlink */
	void;
	RESULT
	struct READLINK4resok {
	linktext4 link;
	};
	union READLINK4res switch (nfsstat4 status) {
	case NFS4_OK:
	READLINK4resok resok4;
	default:
	void;
	};
	DESCRIPTION
	READLINK reads the data associated with a symbolic link. The data
	is a UTF-8 string that is opaque to the server. That is, whether
	created by an NFS client or created locally on the server, the data
	in a symbolic link is not interpreted when created, but is simply
	stored.
	On success, the current filehandle retains its value.
	IMPLEMENTATION
	A symbolic link is nominally a pointer to another file. The data
	is not necessarily interpreted by the server, just stored in the
	file. It is possible for a client implementation to store a path
	name that is not meaningful to the server operating system in a
	symbolic link. A READLINK operation returns the data to the client
	for interpretation. If different implementations want to share
	access to symbolic links, then they must agree on the
	interpretation of the data in the symbolic link.
	The READLINK operation is only allowed on objects of type NF4LNK.
	The server should return the error, NFS4ERR_INVAL, if the object is
	not of type, NF4LNK.
	Draft Specification NFS version 4 Protocol October 2002
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_BADHANDLE
	NFS4ERR_DELAY
	NFS4ERR_FHEXPIRED
	NFS4ERR_INVAL
	NFS4ERR_IO
	NFS4ERR_ISDIR
	NFS4ERR_MOVED
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_NOTSUPP
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	Draft Specification NFS version 4 Protocol October 2002
	14.2.26. Operation 28: REMOVE - Remove Filesystem Object
	SYNOPSIS
	(cfh), filename -> change_info
	ARGUMENT
	struct REMOVE4args {
	/* CURRENT_FH: directory */
	component4 target;
	};
	RESULT
	struct REMOVE4resok {
	change_info4 cinfo;
	}
	union REMOVE4res switch (nfsstat4 status) {
	case NFS4_OK:
	REMOVE4resok resok4;
	default:
	void;
	}
	DESCRIPTION
	The REMOVE operation removes (deletes) a directory entry named by
	filename from the directory corresponding to the current
	filehandle. If the entry in the directory was the last reference
	to the corresponding filesystem object, the object may be
	destroyed.
	For the directory where the filename was removed, the server
	returns change_info4 information in cinfo. With the atomic field
	of the change_info4 struct, the server will indicate if the before
	and after change attributes were obtained atomically with respect
	to the removal.
	If the target has a length of 0 (zero), or if target does not obey
	the UTF-8 definition, the error NFS4ERR_INVAL will be returned.
	On success, the current filehandle retains its value.
	IMPLEMENTATION
	NFS versions 2 and 3 required a different operator RMDIR for
	Draft Specification NFS version 4 Protocol October 2002
	directory removal and REMOVE for non-directory removal. This
	allowed clients to skip checking the file type when being passed a
	non-directory delete system call (e.g. unlink() in POSIX) to remove
	a directory, as well as the converse (e.g. a rmdir() on a non-
	directory) because they knew the server would check the file type.
	NFS version 4 REMOVE can be used to delete any directory entry
	independent of its file type. The implementor of an NFS version 4
	client's entry points from the unlink() and rmdir() system calls
	should first check the file type against the types the system call
	is allowed to remove before issuing a REMOVE. Alternatively, the
	implementor can produce a COMPOUND call that includes a
	LOOKUP/VERIFY sequence to verify the file type before a REMOVE
	operation in the same COMPOUND call.
	The concept of last reference is server specific. However, if the
	numlinks field in the previous attributes of the object had the
	value 1, the client should not rely on referring to the object via
	a filehandle. Likewise, the client should not rely on the resources
	(disk space, directory entry, and so on) formerly associated with
	the object becoming immediately available. Thus, if a client needs
	to be able to continue to access a file after using REMOVE to
	remove it, the client should take steps to make sure that the file
	will still be accessible. The usual mechanism used is to RENAME
	the file from its old name to a new hidden name.
	If the server finds that the file is still open when the REMOVE
	arrives:
	o The server SHOULD NOT delete the file's directory entry if the
	file was opened with OPEN4_SHARE_DENY_WRITE or
	OPEN4_SHARE_DENY_BOTH.
	o If the file was not opened with OPEN4_SHARE_DENY_WRITE or
	OPEN4_SHARE_DENY_BOTH, the server SHOULD delete the file's
	directory entry. However, until last CLOSE of the file, the
	server MAY continue to allow access to the file via its
	filehandle.
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_BADCHAR
	NFS4ERR_BADHANDLE
	NFS4ERR_BADNAME
	NFS4ERR_BADXDR
	NFS4ERR_DELAY
	NFS4ERR_FHEXPIRED
	NFS4ERR_FILE_OPEN
	NFS4ERR_INVAL
	NFS4ERR_IO
	NFS4ERR_MOVED
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_NAMETOOLONG
	NFS4ERR_NOENT
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_NOTDIR
	NFS4ERR_NOTEMPTY
	NFS4ERR_RESOURCE
	NFS4ERR_ROFS
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	Draft Specification NFS version 4 Protocol October 2002
	14.2.27. Operation 29: RENAME - Rename Directory Entry
	SYNOPSIS
	(sfh), oldname, (cfh), newname -> source_change_info,
	target_change_info
	ARGUMENT
	struct RENAME4args {
	/* SAVED_FH: source directory */
	component4 oldname;
	/* CURRENT_FH: target directory */
	component4 newname;
	};
	RESULT
	struct RENAME4resok {
	change_info4 source_cinfo;
	change_info4 target_cinfo;
	};
	union RENAME4res switch (nfsstat4 status) {
	case NFS4_OK:
	RENAME4resok resok4;
	default:
	void;
	};
	DESCRIPTION
	The RENAME operation renames the object identified by oldname in
	the source directory corresponding to the saved filehandle, as set
	by the SAVEFH operation, to newname in the target directory
	corresponding to the current filehandle. The operation is required
	to be atomic to the client. Source and target directories must
	reside on the same filesystem on the server. On success, the
	current filehandle will continue to be the target directory.
	If the target directory already contains an entry with the name,
	newname, the source object must be compatible with the target:
	either both are non-directories or both are directories and the
	target must be empty. If compatible, the existing target is
	removed before the rename occurs (See the IMPLEMENTATION subsection
	of the section "Operation 28: REMOVE - Remove Filesystem Object"
	for client and server actions whenever a target is removed). If
	they are not compatible or if the target is a directory but not
	empty, the server will return the error, NFS4ERR_EXIST.
	Draft Specification NFS version 4 Protocol October 2002
	If oldname and newname both refer to the same file (they might be
	hard links of each other), then RENAME should perform no action and
	return success.
	For both directories involved in the RENAME, the server returns
	change_info4 information. With the atomic field of the
	change_info4 struct, the server will indicate if the before and
	after change attributes were obtained atomically with respect to
	the rename.
	If the oldname refers to a named attribute and the saved and
	current filehandles refer to different filesystem objects, the
	server will return NFS4ERR_XDEV just as if the saved and current
	filehandles represented directories on different filesystems.
	If the oldname or newname has a length of 0 (zero), or if oldname
	or newname does not obey the UTF-8 definition, the error
	NFS4ERR_INVAL will be returned.
	IMPLEMENTATION
	The RENAME operation must be atomic to the client. The statement
	"source and target directories must reside on the same filesystem
	on the server" means that the fsid fields in the attributes for the
	directories are the same. If they reside on different filesystems,
	the error, NFS4ERR_XDEV, is returned.
	Based on the value of the fh_expire_type attribute for the object,
	the filehandle may or may not expire on a RENAME. However, server
	implementors are strongly encouraged to attempt to keep filehandles
	from expiring in this fashion.
	On some servers, the file names "." and ".." are illegal as either
	oldname or newname, and will result in the error NFS4ERR_BADNAME.
	In addition, on many servers the case of oldname or newname being
	an alias for the source directory will be checked for. Such
	servers will return the error NFS4ERR_INVAL in these cases.
	If either of the source or target filehandles are not directories,
	the server will return NFS4ERR_NOTDIR.
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_BADCHAR
	NFS4ERR_BADHANDLE
	NFS4ERR_BADNAME
	NFS4ERR_BADXDR
	NFS4ERR_DELAY
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_DQUOT
	NFS4ERR_EXIST
	NFS4ERR_FHEXPIRED
	NFS4ERR_FILE_OPEN
	NFS4ERR_INVAL
	NFS4ERR_IO
	NFS4ERR_MOVED
	NFS4ERR_NAMETOOLONG
	NFS4ERR_NOENT
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_NOSPC
	NFS4ERR_NOTDIR
	NFS4ERR_NOTEMPTY
	NFS4ERR_RESOURCE
	NFS4ERR_ROFS
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	NFS4ERR_WRONGSEC
	NFS4ERR_XDEV
	Draft Specification NFS version 4 Protocol October 2002
	14.2.28. Operation 30: RENEW - Renew a Lease
	SYNOPSIS
	clientid -> ()
	ARGUMENT
	struct RENEW4args {
	clientid4 clientid;
	};
	RESULT
	struct RENEW4res {
	nfsstat4 status;
	};
	DESCRIPTION
	The RENEW operation is used by the client to renew leases which it
	currently holds at a server. In processing the RENEW request, the
	server renews all leases associated with the client. The
	associated leases are determined by the clientid provided via the
	SETCLIENTID operation.
	IMPLEMENTATION
	When the client holds delegations, it needs to use RENEW to detect
	when the server has determined that the callback path is down.
	When the server has made such a determination, only the RENEW
	operation will renew the lease on delegations. If the server
	determines the callback path is down, it returns
	NFS4ERR_CB_PATH_DOWN. Even though it returns NFS4ERR_CB_PATH_DOWN,
	the server MUST renew the lease on the record locks and share
	reservations that the client has established on the server. If for
	some reason the lock and share reservation lease cannot be renewed,
	then the server MUST return an error other than
	NFS4ERR_CB_PATH_DOWN, even if the callback path is also down.
	ERRORS
	NFS4ERR_ADMIN_REVOKED
	NFS4ERR_BADXDR
	NFS4ERR_CB_PATH_DOWN
	NFS4ERR_EXPIRED
	NFS4ERR_LEASE_MOVED
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE_CLIENTID
	Draft Specification NFS version 4 Protocol October 2002
	14.2.29. Operation 31: RESTOREFH - Restore Saved Filehandle
	SYNOPSIS
	(sfh) -> (cfh)
	ARGUMENT
	/* SAVED_FH: */
	void;
	RESULT
	struct RESTOREFH4res {
	/* CURRENT_FH: value of saved fh */
	nfsstat4 status;
	};
	DESCRIPTION
	Set the current filehandle to the value in the saved filehandle.
	If there is no saved filehandle then return the error
	NFS4ERR_RESTOREFH.
	IMPLEMENTATION
	Operations like OPEN and LOOKUP use the current filehandle to
	represent a directory and replace it with a new filehandle.
	Assuming the previous filehandle was saved with a SAVEFH operator,
	the previous filehandle can be restored as the current filehandle.
	This is commonly used to obtain post-operation attributes for the
	directory, e.g.
	PUTFH (directory filehandle)
	SAVEFH
	GETATTR attrbits (pre-op dir attrs)
	CREATE optbits "foo" attrs
	GETATTR attrbits (file attributes)
	RESTOREFH
	GETATTR attrbits (post-op dir attrs)
	ERRORS
	NFS4ERR_BADHANDLE
	NFS4ERR_FHEXPIRED
	NFS4ERR_MOVED
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_RESOURCE
	NFS4ERR_RESTOREFH
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	NFS4ERR_WRONGSEC
	Draft Specification NFS version 4 Protocol October 2002
	14.2.30. Operation 32: SAVEFH - Save Current Filehandle
	SYNOPSIS
	(cfh) -> (sfh)
	ARGUMENT
	/* CURRENT_FH: */
	void;
	RESULT
	struct SAVEFH4res {
	/* SAVED_FH: value of current fh */
	nfsstat4 status;
	};
	DESCRIPTION
	Save the current filehandle. If a previous filehandle was saved
	then it is no longer accessible. The saved filehandle can be
	restored as the current filehandle with the RESTOREFH operator.
	On success, the current filehandle retains its value.
	IMPLEMENTATION
	ERRORS
	NFS4ERR_BADHANDLE
	NFS4ERR_FHEXPIRED
	NFS4ERR_MOVED
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	Draft Specification NFS version 4 Protocol October 2002
	14.2.31. Operation 33: SECINFO - Obtain Available Security
	SYNOPSIS
	(cfh), name -> { secinfo }
	ARGUMENT
	struct SECINFO4args {
	/* CURRENT_FH: directory */
	component4 name;
	};
	RESULT
	enum rpc_gss_svc_t {/* From RFC 2203 */
	RPC_GSS_SVC_NONE = 1,
	RPC_GSS_SVC_INTEGRITY = 2,
	RPC_GSS_SVC_PRIVACY = 3
	};
	struct rpcsec_gss_info {
	sec_oid4 oid;
	qop4 qop;
	rpc_gss_svc_t service;
	};
	union secinfo4 switch (uint32_t flavor) {
	case RPCSEC_GSS:
	rpcsec_gss_info flavor_info;
	default:
	void;
	};
	typedef secinfo4 SECINFO4resok<>;
	union SECINFO4res switch (nfsstat4 status) {
	case NFS4_OK:
	SECINFO4resok resok4;
	default:
	void;
	};
	DESCRIPTION
	The SECINFO operation is used by the client to obtain a list of
	valid RPC authentication flavors for a specific directory
	filehandle, file name pair. SECINFO should apply the same access
	Draft Specification NFS version 4 Protocol October 2002
	methodology used for LOOKUP when evaluating the name. Therefore,
	if the requester does not have the appropriate access to LOOKUP the
	name then SECINFO must behave the same way and return
	NFS4ERR_ACCESS.
	The result will contain an array which represents the security
	mechanisms available, with an order corresponding to server's
	preferences, the most preferred being first in the array. The
	client is free to pick whatever security mechanism it both desires
	and supports, or to pick in the server's preference order the first
	one it supports. The array entries are represented by the secinfo4
	structure. The field 'flavor' will contain a value of AUTH_NONE,
	AUTH_SYS (as defined in [RFC1831]), or RPCSEC_GSS (as defined in
	[RFC2203]).
	For the flavors AUTH_NONE and AUTH_SYS, no additional security
	information is returned. For a return value of RPCSEC_GSS, a
	security triple is returned that contains the mechanism object id
	(as defined in [RFC2743]), the quality of protection (as defined in
	[RFC2743]) and the service type (as defined in [RFC2203]). It is
	possible for SECINFO to return multiple entries with flavor equal
	to RPCSEC_GSS with different security triple values.
	On success, the current filehandle retains its value.
	If the name has a length of 0 (zero), or if name does not obey the
	UTF-8 definition, the error NFS4ERR_INVAL will be returned.
	IMPLEMENTATION
	The SECINFO operation is expected to be used by the NFS client when
	the error value of NFS4ERR_WRONGSEC is returned from another NFS
	operation. This signifies to the client that the server's security
	policy is different from what the client is currently using. At
	this point, the client is expected to obtain a list of possible
	security flavors and choose what best suits its policies.
	As mentioned, the server's security policies will determine when a
	client request receives NFS4ERR_WRONGSEC. The operations which may
	receive this error are: LINK, LOOKUP, OPEN, PUTFH, PUTPUBFH,
	PUTROOTFH, RESTOREFH, RENAME, and indirectly READDIR. LINK and
	RENAME will only receive this error if the security used for the
	operation is inappropriate for saved filehandle. With the
	exception of READDIR, these operations represent the point at which
	the client can instantiate a filehandle into the "current
	filehandle" at the server. The filehandle is either provided by
	the client (PUTFH, PUTPUBFH, PUTROOTFH) or generated as a result of
	a name to filehandle translation (LOOKUP and OPEN). RESTOREFH is
	different because the filehandle is a result of a previous SAVEFH.
	Even though the filehandle, for RESTOREFH, might have previously
	passed the server's inspection for a security match, the server
	Draft Specification NFS version 4 Protocol October 2002
	will check it again on RESTOREFH to ensure that the security policy
	has not changed.
	If the client wants to resolve an error return of NFS4ERR_WRONGSEC,
	the following will occur:
	o For LOOKUP and OPEN, the client will use SECINFO with the same
	current filehandle and name as provided in the original LOOKUP
	or OPEN to enumerate the available security triples.
	o For LINK, PUTFH, RENAME, and RESTOREFH, the client will use
	SECINFO and provide the parent directory filehandle and object
	name which corresponds to the filehandle originally provided by
	the PUTFH RESTOREFH, or for LINK and RENAME, the SAVEFH.
	o For PUTROOTFH and PUTPUBFH, the client will be unable to use
	the SECINFO operation since SECINFO requires a current
	filehandle and none exist for these two operations. Therefore,
	the client must iterate through the security triples available
	at the client and reattempt the PUTROOTFH or PUTPUBFH
	operation. In the unfortunate event none of the MANDATORY
	security triples are supported by the client and server, the
	client SHOULD try using others that support integrity. Failing
	that, the client can try using AUTH_NONE, but because such
	forms lack integrity checks, this puts the client at risk.
	Nonetheless, the server SHOULD allow the client to use whatever
	security form the client requests and the server supports,
	since the risks of doing so are on the client.
	The READDIR operation will not directly return the NFS4ERR_WRONGSEC
	error. However, if the READDIR request included a request for
	attributes, it is possible that the READDIR request's security
	triple does not match that of a directory entry. If this is the
	case and the client has requested the rdattr_error attribute, the
	server will return the NFS4ERR_WRONGSEC error in rdattr_error for
	the entry.
	See the section "Security Considerations" for a discussion on the
	recommendations for security flavor used by SECINFO.
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_BADCHAR
	NFS4ERR_BADHANDLE
	NFS4ERR_BADNAME
	NFS4ERR_BADXDR
	NFS4ERR_FHEXPIRED
	NFS4ERR_INVAL
	NFS4ERR_MOVED
	NFS4ERR_NAMETOOLONG
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_NOENT
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_NOTDIR
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	Draft Specification NFS version 4 Protocol October 2002
	14.2.32. Operation 34: SETATTR - Set Attributes
	SYNOPSIS
	(cfh), stateid, attrmask, attr_vals -> attrsset
	ARGUMENT
	struct SETATTR4args {
	/* CURRENT_FH: target object */
	stateid4 stateid;
	fattr4 obj_attributes;
	};
	RESULT
	struct SETATTR4res {
	nfsstat4 status;
	bitmap4 attrsset;
	};
	DESCRIPTION
	The SETATTR operation changes one or more of the attributes of a
	filesystem object. The new attributes are specified with a bitmap
	and the attributes that follow the bitmap in bit order.
	The stateid argument for SETATTR is used to provide file locking
	context that is necessary for SETATTR requests that set the size
	attribute. Since setting the size attribute modifies the file's
	data, it has the same locking requirements as a corresponding
	WRITE. Any SETATTR that sets the size attribute is incompatible
	with a share reservation that specifies DENY_WRITE. The area
	between the old end-of-file and the new end-of-file is considered
	to be modified just as would have been the case had the area in
	question been specified as the target of WRITE, for the purpose of
	checking conflicts with record locks, for those cases in which a
	server is implementing mandatory record locking behavior. A valid
	stateid should always be specified. When the file size attribute
	is not set, the special stateid consisting of all bits zero should
	be passed.
	On either success or failure of the operation, the server will
	return the attrsset bitmask to represent what (if any) attributes
	were successfully set. The attrsset in the response is a subset of
	the bitmap4 that is part of the obj_attributes in the argument.
	On success, the current filehandle retains its value.
	Draft Specification NFS version 4 Protocol October 2002
	IMPLEMENTATION
	If the request specifies the owner attribute to be set, the server
	should allow the operation to succeed if the current owner of the
	object matches the value specified in the request. Some servers
	may be implemented in a way as to prohibit the setting of the owner
	attribute unless the requester has privilege to do so. If the
	server is lenient in this one case of matching owner values, the
	client implementation may be simplified in cases of creation of an
	object followed by a SETATTR.
	The file size attribute is used to request changes to the size of a
	file. A value of 0 (zero) causes the file to be truncated, a value
	less than the current size of the file causes data from new size to
	the end of the file to be discarded, and a size greater than the
	current size of the file causes logically zeroed data bytes to be
	added to the end of the file. Servers are free to implement this
	using holes or actual zero data bytes. Clients should not make any
	assumptions regarding a server's implementation of this feature,
	beyond that the bytes returned will be zeroed. Servers must
	support extending the file size via SETATTR.
	SETATTR is not guaranteed atomic. A failed SETATTR may partially
	change a file's attributes.
	Changing the size of a file with SETATTR indirectly changes the
	time_modify. A client must account for this as size changes can
	result in data deletion.
	The attributes time_access_set and time_modify_set are write-only
	attributes constructed as a switched union so the client can direct
	the server in setting the time values. If the switched union
	specifies SET_TO_CLIENT_TIME4, the client has provided an nfstime4
	to be used for the operation. If the switch union does not specify
	SET_TO_CLIENT_TIME4, the server is to use its current time for the
	SETATTR operation.
	If server and client times differ, programs that compare client
	time to file times can break. A time maintenance protocol should be
	used to limit client/server time skew.
	Use of a COMPOUND containing a VERIFY operation specifying only the
	change attribute, immediately followed by a SETATTR, provides a
	means whereby a client may specify a request that emulates the
	functionality of the SETATTR guard mechanism of NFS version 3.
	Since the function of the guard mechanism is to avoid changes to
	the file attributes based on stale information, delays between
	checking of the guard condition and the setting of the attributes
	have the potential to compromise this function, as would the
	corresponding delay in the NFS version 4 emulation. Therefore, NFS
	version 4 servers should take care to avoid such delays, to the
	degree possible, when executing such a request.
	Draft Specification NFS version 4 Protocol October 2002
	If the server does not support an attribute as requested by the
	client, the server should return NFS4ERR_ATTRNOTSUPP.
	A mask of the attributes actually set is returned by SETATTR in all
	cases. That mask must not include attributes bits not requested to
	be set by the client, and must be equal to the mask of attributes
	requested to be set only if the SETATTR completes without error.
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_ADMIN_REVOKED
	NFS4ERR_ATTRNOTSUPP
	NFS4ERR_BADCHAR
	NFS4ERR_BADHANDLE
	NFS4ERR_BADOWNER
	NFS4ERR_BAD_STATEID
	NFS4ERR_BADXDR
	NFS4ERR_DELAY
	NFS4ERR_DQUOT
	NFS4ERR_EXPIRED
	NFS4ERR_FBIG
	NFS4ERR_FHEXPIRED
	NFS4ERR_GRACE
	NFS4ERR_INVAL
	NFS4ERR_IO
	NFS4ERR_ISDIR
	NFS4ERR_LOCKED
	NFS4ERR_MOVED
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_NOSPC
	NFS4ERR_OLD_STATEID
	NFS4ERR_OPENMODE
	NFS4ERR_PERM
	NFS4ERR_RESOURCE
	NFS4ERR_ROFS
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	NFS4ERR_STALE_STATEID
	Draft Specification NFS version 4 Protocol October 2002
	14.2.33. Operation 35: SETCLIENTID - Negotiate Clientid
	SYNOPSIS
	client, callback, callback_ident -> clientid, setclientid_confirm
	ARGUMENT
	struct SETCLIENTID4args {
	nfs_client_id4 client;
	cb_client4 callback;
	uint32_t callback_ident;
	};
	RESULT
	struct SETCLIENTID4resok {
	clientid4 clientid;
	verifier4 setclientid_confirm;
	};
	union SETCLIENTID4res switch (nfsstat4 status) {
	case NFS4_OK:
	SETCLIENTID4resok resok4;
	case NFS4ERR_CLID_INUSE:
	clientaddr4 client_using;
	default:
	void;
	};
	DESCRIPTION
	The client uses the SETCLIENTID operation to notify the server of
	its intention to use a particular client identifier, callback, and
	callback_ident for subsequent requests that entail creating lock,
	share reservation, and delegation state on the server. Upon
	successful completion the server will return a short hand clientid
	which, if confirmed via a separate step, will be used in subsequent
	file locking and file open requests. Confirmation of the clientid
	must be done via the SETCLIENTID_CONFIRM operation to return the
	clientid and setclientid_confirm values, as verifiers, to the
	server. The reason why two verifiers are necessary is that it is
	possible to use SETCLIENTID and SETCLIENTID_CONFIRM to modify the
	callback and callback_ident information but not the short hand
	clientid. In that event, the setclientid_confirm value is
	effectively the only verifier.
	The callback information provided in this operation will be used if
	the client is provided an open delegation at a future point.
	Draft Specification NFS version 4 Protocol October 2002
	Therefore, the client must correctly reflect the program and port
	numbers for the callback program at the time SETCLIENTID is used.
	The callback_ident value is used by the server on the callback.
	The client can use leverage the callback_ident eliminate the need
	for more than one callback RPC program number while still being
	able to determine which server is initiating the callback.
	IMPLEMENTATION
	To understand how to implement SETCLIENTID, make the following
	notations. Let:
	x be the value of the client.id subfield of the SETCLIENTID4args
	structure.
	v be the value of the client.verifier subfield of the
	SETCLIENTID4args structure.
	c be the value of the clientid field returned in the
	SETCLIENTID4resok structure.
	k represent the value combination of the fields callback and
	callback_ident fields of the SETCLIENTID4args structure.
	s be the setclientid_confirm value returned in the
	SETCLIENTID4resok structure.
	{ x, v, c, k, s }
	be a quintuple for a client record. A client record is
	confirmed if there has been a SETCLIENTID_CONFIRM operation to
	confirm it. Otherwise it is unconfirmed. An unconfirmed
	record is established by a SETCLIENTID call.
	Since SETCLIENTID is a non-idempotent operation, let us assume that
	the server is implementing the duplicate request cache (DRC).
	When the server gets a SETCLIENTID { v, x, k } request, it
	processes it in the following manner.
	o It first looks up the request in the DRC. If there is a hit, it
	returns the result cached in the DRC. The server does NOT remove
	client state (locks, shares, delegations) nor does it modify any
	recorded callback and callback_ident information for client { x
	}.
	For any DRC miss, the server takes the client id string x, and
	searches for client records for x that the server may have
	recorded from previous SETCLIENTID calls. For any confirmed
	Draft Specification NFS version 4 Protocol October 2002
	record with the same id string x, if the recorded principal does
	not match that of SETCLIENTID call, then the server returns a
	NFS4ERR_CLID_INUSE error.
	For brevity of discussion, the remaining description of the
	processing assumes that there was a DRC miss, and that where the
	server has previously recorded a confirmed record for client x,
	the aforementioned principal check has successfully passed.
	o The server checks if it has recorded a confirmed recorded for {
	v, x, c, l, s }, where l may or may not equal k. If so, and since
	the id verifier v of the request matches that which is confirmed
	and recorded, the server treats this as a probable callback
	information update and records an unconfirmed { v, x, c, k, t }
	and leaves the confirmed { v, x, c, l, s } in place, such that t
	!= s. It does not matter if k equals l or not. Any pre-existing
	unconfirmed { v, x, c, *, * } is removed.
	The server returns { c, t }. It is indeed returning the old
	clientid4 value c, because the client apparently only wants to
	update callback value k to value l. It's possible this request
	is one from the Byzantine router that has stale callback
	information, but this is not a problem. The callback information
	update is only confirmed if followed up by a SETCLIENTID_CONFIRM
	{ c, t }.
	The server awaits confirmation of k via SETCLIENTID_CONFIRM { c,
	t }.
	The server does NOT remove client (lock/share/delegation) state
	for x.
	o The server has previously recorded a confirmed { u, x, c, l, s }
	record such that v != u, l may or may not equal k, and has not
	recorded any unconfirmed { *, x, *, *, * } record for x. The
	server records an unconfirmed { v, x, d, k, t } (d != c, t != s).
	The server returns { d, t }.
	The server awaits confirmation of { d, k } via
	SETCLIENTID_CONFIRM { d, t }.
	The server does NOT remove client (lock/share/delegation) state
	for x.
	o The server has previously recorded a confirmed { u, x, c, l, s }
	record such that v != u, l may or may not equal k, and recorded
	an unconfirmed { w, x, d, m, t } record such that c != d, t != s,
	m may or may not equal k, m may or may not equal l, and k may or
	Draft Specification NFS version 4 Protocol October 2002
	may not equal l. Whether w == v or w != v makes no difference.
	The server simply removes the unconfirmed { w, x, d, m, t }
	record and replaces it with an unconfirmed { v, x, e, k, r }
	record, such that e != d, e != c, r != t, r != s.
	The server returns { e, r }.
	The server awaits confirmation of { e, k } via
	SETCLIENTID_CONFIRM { e, r }.
	The server does NOT remove client (lock/share/delegation) state
	for x.
	o The server has no confirmed { *, x, *, *, * } for x. It may or
	may not have recorded an unconfirmed { u, x, c, l, s }, where l
	may or may not equal k, and u may or may not equal v. Any
	unconfirmed record { u, x, c, l, * }, regardless whether u == v
	or l == k, is replaced with an unconfirmed record { v, x, d, k, t
	} where d != c, t != s.
	The server returns { d, t }.
	The server awaits confirmation of { d, k } via
	SETCLIENTID_CONFIRM { d, t }. The server does NOT remove client
	(lock/share/delegation) state for x.
	The server generates the clientid and setclientid_confirm values
	and must take care to ensure that these values are extremely
	unlikely to ever be regenerated.
	ERRORS
	NFS4ERR_BADXDR
	NFS4ERR_CLID_INUSE
	NFS4ERR_INVAL
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	Draft Specification NFS version 4 Protocol October 2002
	14.2.34. Operation 36: SETCLIENTID_CONFIRM - Confirm Clientid
	SYNOPSIS
	clientid, verifier -> -
	ARGUMENT
	struct SETCLIENTID_CONFIRM4args {
	clientid4 clientid;
	verifier4 setclientid_confirm;
	};
	RESULT
	struct SETCLIENTID_CONFIRM4res {
	nfsstat4 status;
	};
	DESCRIPTION
	This operation is used by the client to confirm the results from a
	previous call to SETCLIENTID. The client provides the server
	supplied (from a SETCLIENTID response) clientid. The server
	responds with a simple status of success or failure.
	IMPLEMENTATION
	The client must use the SETCLIENTID_CONFIRM operation to confirm
	the following two distinct cases:
	o The client's use of a new shorthand client identifier (as
	returned from the server in the response to SETCLIENTID), a new
	callback value (as specified in the arguments to SETCLIENTID) and
	a new callback_ident (as specified in the arguments to
	SETCLIENTID) value. The client's use of SETCLIENTID_CONFIRM in
	this case also confirms the removal of any of the client's
	previous relevant leased state. Relevant leased client state
	includes record locks, share reservations, and where the server
	does not support the CLAIM_DELEGATE_PREV claim type, delegations.
	If the server supports CLAIM_DELEGATE_PREV, then
	SETCLIENTID_CONFIRM MUST NOT remove delegations for this client;
	relevant leased client state would then just include record locks
	and share reservations.
	o The client's re-use of an old, previously confirmed, shorthand
	client identifier, a new callback value, and a new callback_ident
	Draft Specification NFS version 4 Protocol October 2002
	value. The client's use of SETCLIENTID_CONFIRM in this case MUST
	NOT result in the removal of any previous leased state (locks,
	share reservations, and delegations)
	We use the same notation and definitions for v, x, c, k, s, and
	unconfirmed and confirmed client records as introduced in the
	description of the SETCLIENTID operation. The arguments to
	SETCLIENTID_CONFIRM are indicated by the notation { c, s }, where c
	is a value of type clientid4, and s is a value of type verifier4
	corresponding to the setclientid_confirm field.
	As with SETCLIENTID, SETCLIENTID_CONFIRM is a non-idempotent
	operation, and we assume that the server is implementing the
	duplicate request cache (DRC).
	When the server gets a SETCLIENTID_CONFIRM { c, s } request, it
	processes it in the following manner.
	o It first looks up the request in the DRC. If there is a hit, it
	returns the result cached in the DRC. The server does not remove
	any relevant leased client state nor does it modify any recorded
	callback and callback_ident information for client { x } as
	represented by the short hand value c.
	For a DRC miss, the server checks for client records that match the
	short hand value c. The processing cases are as follows:
	o The server has recorded an unconfirmed { v, x, c, k, s } record
	and a confirmed { v, x, c, l, t } record, such that s != t. If
	the principals of the records do not match that of the
	SETCLIENTID_CONFIRM, the server returns NFS4ERR_CLID_INUSE, and
	no relevant leased client state is removed and no recorded
	callback and callback_ident information for client { x } is
	changed. Otherwise, the confirmed { v, x, c, l, t } record is
	removed and the unconfirmed { v, x, c, k, s } is marked as
	confirmed, thereby modifying recorded and confirmed callback and
	callback_ident information for client { x }.
	The server does not remove any relevant leased client state.
	The server returns NFS4_OK.
	o The server has not recorded an unconfirmed { v, x, c, *, * } and
	has recorded a confirmed { v, x, c, *, s }. If the principals of
	the record and of SETCLIENTID_CONFIRM do not match, the server
	returns NFS4ERR_CLID_INUSE without removing any relevant leased
	client state and without changing recorded callback and
	callback_ident values for client { x }.
	If the principals match, then what has likely happened is that
	the client never got the response from the SETCLIENTID_CONFIRM,
	and the DRC entry has been purged. Whatever the scenario, since
	Draft Specification NFS version 4 Protocol October 2002
	the principals match, as well as { c, s } matching a confirmed
	record, the server leaves client x's relevant leased client state
	intact, leaves its callback and callback_ident values unmodified,
	and returns NFS4_OK.
	o The server has not recorded a confirmed { *, *, c, *, * }, and
	has recorded an unconfirmed { *, x, c, k, s }. Even if this is a
	retry from client, nonetheless the client's first
	SETCLIENTID_CONFIRM attempt was not received by the server.
	Retry or not, the server doesn't know, but it processes it as if
	were a first try. If the principal of the unconfirmed { *, x, c,
	k, s } record mismatches that of the SETCLIENTID_CONFIRM request
	the server returns NFS4ERR_CLID_INUSE without removing any
	relevant leased client state.
	Otherwise, the server records a confirmed { *, x, c, k, s }. If
	there is also a confirmed { *, x, d, *, t }, the server MUST
	remove the client x's relevant leased client state, and overwrite
	the callback state with k. The confirmed record { *, x, d, *, t }
	is removed.
	Server returns NFS4_OK.
	o The server has no record of a confirmed or unconfirmed { *, *, c,
	*, s }. The server returns NFS4ERR_STALE_CLIENTID. The server
	does not remove any relevant leased client state, nor does it
	modify any recorded callback and callback_ident information for
	any client.
	The server needs to cache unconfirmed { v, x, c, k, s } client
	records and await for some time their confirmation. As should be
	clear from the record processing discussions for SETCLIENTID and
	SETCLIENTID_CONFIRM, there are cases where the server does not
	deterministically remove unconfirmed client records. To avoid
	running out of resources, the server is not required to hold
	unconfirmed records indefinitely. One strategy the server might
	use is to set a limit on how many unconfirmed client records it
	will maintain, and then when the limit would be exceeded, remove
	the oldest record. Another strategy might be to remove an
	unconfirmed record when some amount of time has elapsed. The choice
	of the amount of time is fairly arbitrary but it is surely no
	higher than the server's lease time period. Consider that leases
	need to be renewed before the lease time expires via an operation
	from the client. If the client cannot issue a SETCLIENTID_CONFIRM
	after a SETCLIENTID before a period of time equal to that of a
	lease expires, then the client is unlikely to be able maintain
	state on the server during steady state operation.
	If the client does send a SETCLIENTID_CONFIRM for an unconfirmed
	record that the server has already deleted, the client will get
	NFS4ERR_STALE_CLIENTID back. If so, the client should then start
	over, and send SETCLIENTID to reestablish an unconfirmed client
	Draft Specification NFS version 4 Protocol October 2002
	record and get back an unconfirmed clientid and setclientid_confirm
	verifier. The client should then send the SETCLIENTID_CONFIRM to
	confirm the clientid.
	SETCLIENTID_CONFIRM does not establish or renew a lease. However,
	if SETCLIENTID_CONFIRM removes relevant leased client state, and
	that state does not include existing delegations, the server MUST
	allow the client a period of time no less than the value of
	lease_time attribute, to reclaim, (via the CLAIM_DELEGATE_PREV
	claim type of the OPEN operation) its delegations before removing
	unreclaimed delegations.
	ERRORS
	NFS4ERR_BADXDR
	NFS4ERR_CLID_INUSE
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE_CLIENTID
	Draft Specification NFS version 4 Protocol October 2002
	14.2.35. Operation 37: VERIFY - Verify Same Attributes
	SYNOPSIS
	(cfh), fattr -> -
	ARGUMENT
	struct VERIFY4args {
	/* CURRENT_FH: object */
	fattr4 obj_attributes;
	};
	RESULT
	struct VERIFY4res {
	nfsstat4 status;
	};
	DESCRIPTION
	The VERIFY operation is used to verify that attributes have a value
	assumed by the client before proceeding with following operations
	in the compound request. If any of the attributes do not match
	then the error NFS4ERR_NOT_SAME must be returned. The current
	filehandle retains its value after successful completion of the
	operation.
	IMPLEMENTATION
	One possible use of the VERIFY operation is the following compound
	sequence. With this the client is attempting to verify that the
	file being removed will match what the client expects to be
	removed. This sequence can help prevent the unintended deletion of
	a file.
	PUTFH (directory filehandle)
	LOOKUP (file name)
	VERIFY (filehandle == fh)
	PUTFH (directory filehandle)
	REMOVE (file name)
	This sequence does not prevent a second client from removing and
	creating a new file in the middle of this sequence but it does help
	avoid the unintended result.
	In the case that a recommended attribute is specified in the VERIFY
	operation and the server does not support that attribute for the
	filesystem object, the error NFS4ERR_ATTRNOTSUPP is returned to the
	Draft Specification NFS version 4 Protocol October 2002
	client.
	When the attribute rdattr_error or any write-only attribute (e.g.
	time_modify_set) is specified, the error NFS4ERR_INVAL is returned
	to the client.
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_ATTRNOTSUPP
	NFS4ERR_BADCHAR
	NFS4ERR_BADHANDLE
	NFS4ERR_BADXDR
	NFS4ERR_DELAY
	NFS4ERR_FHEXPIRED
	NFS4ERR_INVAL
	NFS4ERR_MOVED
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_NOT_SAME
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	Draft Specification NFS version 4 Protocol October 2002
	14.2.36. Operation 38: WRITE - Write to File
	SYNOPSIS
	(cfh), stateid, offset, stable, data -> count, committed, writeverf
	ARGUMENT
	enum stable_how4 {
	UNSTABLE4 = 0,
	DATA_SYNC4 = 1,
	FILE_SYNC4 = 2
	};
	struct WRITE4args {
	/* CURRENT_FH: file */
	stateid4 stateid;
	offset4 offset;
	stable_how4 stable;
	opaque data<>;
	};
	RESULT
	struct WRITE4resok {
	count4 count;
	stable_how4 committed;
	verifier4 writeverf;
	};
	union WRITE4res switch (nfsstat4 status) {
	case NFS4_OK:
	WRITE4resok resok4;
	default:
	void;
	};
	DESCRIPTION
	The WRITE operation is used to write data to a regular file. The
	target file is specified by the current filehandle. The offset
	specifies the offset where the data should be written. An offset
	of 0 (zero) specifies that the write should start at the beginning
	of the file. The count, as encoded as part of the opaque data
	parameter, represents the number of bytes of data that are to be
	written. If the count is 0 (zero), the WRITE will succeed and
	return a count of 0 (zero) subject to permissions checking. The
	server may choose to write fewer bytes than requested by the
	client.
	Draft Specification NFS version 4 Protocol October 2002
	Part of the write request is a specification of how the write is to
	be performed. The client specifies with the stable parameter the
	method of how the data is to be processed by the server. If stable
	is FILE_SYNC4, the server must commit the data written plus all
	filesystem metadata to stable storage before returning results.
	This corresponds to the NFS version 2 protocol semantics. Any
	other behavior constitutes a protocol violation. If stable is
	DATA_SYNC4, then the server must commit all of the data to stable
	storage and enough of the metadata to retrieve the data before
	returning. The server implementor is free to implement DATA_SYNC4
	in the same fashion as FILE_SYNC4, but with a possible performance
	drop. If stable is UNSTABLE4, the server is free to commit any
	part of the data and the metadata to stable storage, including all
	or none, before returning a reply to the client. There is no
	guarantee whether or when any uncommitted data will subsequently be
	committed to stable storage. The only guarantees made by the server
	are that it will not destroy any data without changing the value of
	verf and that it will not commit the data and metadata at a level
	less than that requested by the client.
	The stateid value for a WRITE request represents a value returned
	from a previous record lock or share reservation request. The
	stateid is used by the server to verify that the associated share
	reservation and any record locks are still valid and to update
	lease timeouts for the client.
	Upon successful completion, the following results are returned.
	The count result is the number of bytes of data written to the
	file. The server may write fewer bytes than requested. If so, the
	actual number of bytes written starting at location, offset, is
	returned.
	The server also returns an indication of the level of commitment of
	the data and metadata via committed. If the server committed all
	data and metadata to stable storage, committed should be set to
	FILE_SYNC4. If the level of commitment was at least as strong as
	DATA_SYNC4, then committed should be set to DATA_SYNC4. Otherwise,
	committed must be returned as UNSTABLE4. If stable was FILE4_SYNC,
	then committed must also be FILE_SYNC4: anything else constitutes a
	protocol violation. If stable was DATA_SYNC4, then committed may be
	FILE_SYNC4 or DATA_SYNC4: anything else constitutes a protocol
	violation. If stable was UNSTABLE4, then committed may be either
	FILE_SYNC4, DATA_SYNC4, or UNSTABLE4.
	The final portion of the result is the write verifier. The write
	verifier is a cookie that the client can use to determine whether
	the server has changed instance (boot) state between a call to
	WRITE and a subsequent call to either WRITE or COMMIT. This cookie
	must be consistent during a single instance of the NFS version 4
	protocol service and must be unique between instances of the NFS
	version 4 protocol server, where uncommitted data may be lost.
	Draft Specification NFS version 4 Protocol October 2002
	If a client writes data to the server with the stable argument set
	to UNSTABLE4 and the reply yields a committed response of
	DATA_SYNC4 or UNSTABLE4, the client will follow up some time in the
	future with a COMMIT operation to synchronize outstanding
	asynchronous data and metadata with the server's stable storage,
	barring client error. It is possible that due to client crash or
	other error that a subsequent COMMIT will not be received by the
	server.
	For a WRITE with a stateid value of all bits 0, the server MAY
	allow the WRITE to be serviced subject to mandatory file locks or
	the current share deny modes for the file. For a WRITE with a
	stateid value of all bits 1, the server MUST NOT allow the WRITE
	operation to bypass locking checks at the server and are treated
	exactly the same as if a stateid of all bits 0 were used.
	On success, the current filehandle retains its value.
	IMPLEMENTATION
	It is possible for the server to write fewer bytes of data than
	requested by the client. In this case, the server should not
	return an error unless no data was written at all. If the server
	writes less than the number of bytes specified, the client should
	issue another WRITE to write the remaining data.
	It is assumed that the act of writing data to a file will cause the
	time_modified of the file to be updated. However, the
	time_modified of the file should not be changed unless the contents
	of the file are changed. Thus, a WRITE request with count set to 0
	should not cause the time_modified of the file to be updated.
	The definition of stable storage has been historically a point of
	contention. The following expected properties of stable storage
	may help in resolving design issues in the implementation. Stable
	storage is persistent storage that survives:
	1. Repeated power failures.
	2. Hardware failures (of any board, power supply, etc.).
	3. Repeated software crashes, including reboot cycle.
	This definition does not address failure of the stable storage
	module itself.
	The verifier is defined to allow a client to detect different
	instances of an NFS version 4 protocol server over which cached,
	uncommitted data may be lost. In the most likely case, the verifier
	allows the client to detect server reboots. This information is
	required so that the client can safely determine whether the server
	Draft Specification NFS version 4 Protocol October 2002
	could have lost cached data. If the server fails unexpectedly and
	the client has uncommitted data from previous WRITE requests (done
	with the stable argument set to UNSTABLE4 and in which the result
	committed was returned as UNSTABLE4 as well) it may not have
	flushed cached data to stable storage. The burden of recovery is on
	the client and the client will need to retransmit the data to the
	server.
	A suggested verifier would be to use the time that the server was
	booted or the time the server was last started (if restarting the
	server without a reboot results in lost buffers).
	The committed field in the results allows the client to do more
	effective caching. If the server is committing all WRITE requests
	to stable storage, then it should return with committed set to
	FILE_SYNC4, regardless of the value of the stable field in the
	arguments. A server that uses an NVRAM accelerator may choose to
	implement this policy. The client can use this to increase the
	effectiveness of the cache by discarding cached data that has
	already been committed on the server.
	Some implementations may return NFS4ERR_NOSPC instead of
	NFS4ERR_DQUOT when a user's quota is exceeded. In the case that
	the current filehandle is a directory, the server will return
	NFS4ERR_ISDIR. If the current filehandle is not a regular file or
	a directory, the server will return NFS4ERR_INVAL.
	If mandatory file locking is on for the file, and corresponding
	record of the data to be written file is read or write locked by an
	owner that is not associated with the stateid, the server will
	return NFS4ERR_LOCKED. If so, the client must check if the owner
	corresponding to the stateid used with the WRITE operation has a
	conflicting read lock that overlaps with the region that was to be
	written. If the stateid's owner has no conflicting read lock, then
	the client should try to get the appropriate write record lock via
	the LOCK operation before re-attempting the WRITE. When the WRITE
	completes, the client should release the record lock via LOCKU.
	If the stateid's owner had a conflicting read lock, then the client
	has no choice but to return an error to the application that
	attempted the WRITE. The reason is that since the stateid's owner
	had a read lock, the server either attempted to temporarily
	effectively upgrade this read lock to a write lock, or the server
	has no upgrade capability. If the server attempted to upgrade the
	read lock and failed, it is pointless for the client to re-attempt
	the upgrade via the LOCK operation, because there might be another
	client also trying to upgrade. If two clients are blocked trying
	upgrade the same lock, the clients deadlock. If the server has no
	upgrade capability, then it is pointless to try a LOCK operation to
	upgrade.
	Draft Specification NFS version 4 Protocol October 2002
	ERRORS
	NFS4ERR_ACCESS
	NFS4ERR_ADMIN_REVOKED
	NFS4ERR_BADHANDLE
	NFS4ERR_BAD_STATEID
	NFS4ERR_BADXDR
	NFS4ERR_DELAY
	NFS4ERR_DQUOT
	NFS4ERR_EXPIRED
	NFS4ERR_FBIG
	NFS4ERR_FHEXPIRED
	NFS4ERR_GRACE
	NFS4ERR_INVAL
	NFS4ERR_IO
	NFS4ERR_ISDIR
	NFS4ERR_LEASE_MOVED
	NFS4ERR_LOCKED
	NFS4ERR_MOVED
	NFS4ERR_NOFILEHANDLE
	NFS4ERR_NOSPC
	NFS4ERR_NXIO
	NFS4ERR_OLD_STATEID
	NFS4ERR_OPENMODE
	NFS4ERR_RESOURCE
	NFS4ERR_ROFS
	NFS4ERR_SERVERFAULT
	NFS4ERR_STALE
	NFS4ERR_STALE_STATEID
	Draft Specification NFS version 4 Protocol October 2002
	14.2.37. Operation 39: RELEASE_LOCKOWNER - Release Lockowner State
	SYNOPSIS
	lockowner -> ()
	ARGUMENT
	struct RELEASE_LOCKOWNER4args {
	lock_owner4 lock_owner;
	};
	RESULT
	struct RELEASE_LOCKOWNER4res {
	nfsstat4 status;
	};
	DESCRIPTION
	This operation is used to notify the server that the lock_owner is
	no longer in use by the client. This allows the server to release
	cached state related to the specified lock_owner. If file locks,
	associated with the lock_owner, are held at the server, the error
	NFS4ERR_LOCKS_HELD will be returned and no further action will be
	taken.
	IMPLEMENTATION
	The client may choose to use this operation to ease the amount of
	server state that is held. Depending on behavior of applications
	at the client, it may be important for the client to use this
	operation since the server has certain obligations with respect to
	holding a reference to a lock_owner as long as the associated file
	is open. Therefore, if the client knows for certain that the
	lock_owner will no longer be used under the context of the
	associated open_owner4, it should use RELEASE_LOCKOWNER.
	ERRORS
	NFS4ERR_ADMIN_REVOKED
	NFS4ERR_BADXDR
	NFS4ERR_EXPIRED
	NFS4ERR_LEASE_MOVED
	NFS4ERR_LOCKS_HELD
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_STALE_CLIENTID
	Draft Specification NFS version 4 Protocol October 2002
	14.2.38. Operation 10044: ILLEGAL - Illegal operation
	SYNOPSIS
	<null> -> ()
	ARGUMENT
	void;
	RESULT
	struct ILLEGAL4res {
	nfsstat4 status;
	};
	DESCRIPTION
	This operation is a placeholder for encoding a result to handle the
	case of the client sending an operation code within COMPOUND that
	is not supported. See the COMPOUND procedure description for more
	details.
	The status field of ILLEGAL4res MUST be set to NFS4ERR_OP_ILLEGAL.
	IMPLEMENTATION
	A client will probably not send an operation with code OP_ILLEGAL
	but if it does, the response will be ILLEGAL4res just as it would
	be with any other invalid operation code. Note that if the server
	gets an illegal operation code that is not OP_ILLEGAL, and if the
	server checks for legal operation codes during the XDR decode
	phase, then the ILLEGAL4res would not be returned.
	ERRORS
	NFS4ERR_OP_ILLEGAL
	Draft Specification NFS version 4 Protocol October 2002
	15. NFS version 4 Callback Procedures
	The procedures used for callbacks are defined in the following
	sections. In the interest of clarity, the terms "client" and
	"server" refer to NFS clients and servers, despite the fact that for
	an individual callback RPC, the sense of these terms would be
	precisely the opposite.
	15.1. Procedure 0: CB_NULL - No Operation
	SYNOPSIS
	<null>
	ARGUMENT
	void;
	RESULT
	void;
	DESCRIPTION
	Standard NULL procedure. Void argument, void response. Even
	though there is no direct functionality associated with this
	procedure, the server will use CB_NULL to confirm the existence of
	a path for RPCs from server to client.
	ERRORS
	None.
	Draft Specification NFS version 4 Protocol October 2002
	15.2. Procedure 1: CB_COMPOUND - Compound Operations
	SYNOPSIS
	compoundargs -> compoundres
	ARGUMENT
	enum nfs_cb_opnum4 {
	OP_CB_GETATTR = 3,
	OP_CB_RECALL = 4,
	OP_CB_ILLEGAL = 10044
	};
	union nfs_cb_argop4 switch (unsigned argop) {
	case OP_CB_GETATTR: CB_GETATTR4args opcbgetattr;
	case OP_CB_RECALL: CB_RECALL4args opcbrecall;
	case OP_CB_ILLEGAL: void opcbillegal;
	};
	struct CB_COMPOUND4args {
	utf8string tag;
	uint32_t minorversion;
	uint32_t callback_ident;
	nfs_cb_argop4 argarray<>;
	};
	RESULT
	union nfs_cb_resop4 switch (unsigned resop){
	case OP_CB_GETATTR: CB_GETATTR4res opcbgetattr;
	case OP_CB_RECALL: CB_RECALL4res opcbrecall;
	};
	struct CB_COMPOUND4res {
	nfsstat4 status;
	utf8string tag;
	nfs_cb_resop4 resarray<>;
	};
	DESCRIPTION
	The CB_COMPOUND procedure is used to combine one or more of the
	callback procedures into a single RPC request. The main callback
	RPC program has two main procedures: CB_NULL and CB_COMPOUND. All
	other operations use the CB_COMPOUND procedure as a wrapper.
	In the processing of the CB_COMPOUND procedure, the client may find
	that it does not have the available resources to execute any or all
	Draft Specification NFS version 4 Protocol October 2002
	of the operations within the CB_COMPOUND sequence. In this case,
	the error NFS4ERR_RESOURCE will be returned for the particular
	operation within the CB_COMPOUND procedure where the resource
	exhaustion occurred. This assumes that all previous operations
	within the CB_COMPOUND sequence have been evaluated successfully.
	Contained within the CB_COMPOUND results is a 'status' field. This
	status must be equivalent to the status of the last operation that
	was executed within the CB_COMPOUND procedure. Therefore, if an
	operation incurred an error then the 'status' value will be the
	same error value as is being returned for the operation that
	failed.
	For the definition of the "tag" field, see the section "Procedure
	1: COMPOUND - Compound Operations".
	The value of callback_ident is supplied by the client during
	SETCLIENTID. The server must use the client supplied
	callback_ident during the CB_COMPOUND to allow the client to
	properly identify the server.
	Illegal operation codes are handled in the same way as they are
	handled for the COMPOUND procedure.
	IMPLEMENTATION
	The CB_COMPOUND procedure is used to combine individual operations
	into a single RPC request. The client interprets each of the
	operations in turn. If an operation is executed by the client and
	the status of that operation is NFS4_OK, then the next operation in
	the CB_COMPOUND procedure is executed. The client continues this
	process until there are no more operations to be executed or one of
	the operations has a status value other than NFS4_OK.
	ERRORS
	NFS4ERR_BADHANDLE
	NFS4ERR_BAD_STATEID
	NFS4ERR_BADXDR
	NFS4ERR_OP_ILLEGAL
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	Draft Specification NFS version 4 Protocol October 2002
	15.2.1. Operation 3: CB_GETATTR - Get Attributes
	SYNOPSIS
	fh, attr_request -> attrmask, attr_vals
	ARGUMENT
	struct CB_GETATTR4args {
	nfs_fh4 fh;
	bitmap4 attr_request;
	};
	RESULT
	struct CB_GETATTR4resok {
	fattr4 obj_attributes;
	};
	union CB_GETATTR4res switch (nfsstat4 status) {
	case NFS4_OK:
	CB_GETATTR4resok resok4;
	default:
	void;
	};
	DESCRIPTION
	The CB_GETATTR operation is used by the server to obtain the
	current modified state of a file that has been write delegated.
	The attributes size and change are the only ones guaranteed to be
	serviced by the client. See the section "Handling of CB_GETATTR"
	for a full description of how the client and server are to interact
	with the use of CB_GETATTR.
	If the filehandle specified is not one for which the client holds a
	write open delegation, an NFS4ERR_BADHANDLE error is returned.
	IMPLEMENTATION
	The client returns attrmask bits and the associated attribute
	values only for the change attribute, and attributes that it may
	change (time_modify, and size).
	ERRORS
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_BADHANDLE
	NFS4ERR_BADXDR
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	Draft Specification NFS version 4 Protocol October 2002
	15.2.2. Operation 4: CB_RECALL - Recall an Open Delegation
	SYNOPSIS
	stateid, truncate, fh -> ()
	ARGUMENT
	struct CB_RECALL4args {
	stateid4 stateid;
	bool truncate;
	nfs_fh4 fh;
	};
	RESULT
	struct CB_RECALL4res {
	nfsstat4 status;
	};
	DESCRIPTION
	The CB_RECALL operation is used to begin the process of recalling
	an open delegation and returning it to the server.
	The truncate flag is used to optimize recall for a file which is
	about to be truncated to zero. When it is set, the client is freed
	of obligation to propagate modified data for the file to the
	server, since this data is irrelevant.
	If the handle specified is not one for which the client holds an
	open delegation, an NFS4ERR_BADHANDLE error is returned.
	If the stateid specified is not one corresponding to an open
	delegation for the file specified by the filehandle, an
	NFS4ERR_BAD_STATEID is returned.
	IMPLEMENTATION
	The client should reply to the callback immediately. Replying does
	not complete the recall except when an error was returned. The
	recall is not complete until the delegation is returned using a
	DELEGRETURN.
	ERRORS
	NFS4ERR_BADHANDLE
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_BAD_STATEID
	NFS4ERR_BADXDR
	NFS4ERR_RESOURCE
	NFS4ERR_SERVERFAULT
	Draft Specification NFS version 4 Protocol October 2002
	15.2.3. Operation 10044: CB_ILLEGAL - Illegal Callback Operation
	SYNOPSIS
	<null> -> ()
	ARGUMENT
	void;
	RESULT
	struct CB_ILLEGAL4res {
	nfsstat4 status;
	};
	DESCRIPTION
	This operation is a placeholder for encoding a result to handle the
	case of the client sending an operation code within COMPOUND that
	is not supported. See the COMPOUND procedure description for more
	details.
	The status field of CB_ILLEGAL4res MUST be set to
	NFS4ERR_OP_ILLEGAL.
	IMPLEMENTATION
	A server will probably not send an operation with code
	OP_CB_ILLEGAL but if it does, the response will be CB_ILLEGAL4res
	just as it would be with any other invalid operation code. Note
	that if the client gets an illegal operation code that is not
	OP_ILLEGAL, and if the client checks for legal operation codes
	during the XDR decode phase, then the CB_ILLEGAL4res would not be
	returned.
	ERRORS
	NFS4ERR_OP_ILLEGAL
	Draft Specification NFS version 4 Protocol October 2002
	16. Security Considerations
	The major security feature to consider is the authentication of the
	user making the request of NFS service. Consideration should also be
	given to the integrity and privacy of this NFS request. These
	specific issues are discussed as part of the section on "RPC and
	Security Flavor".
	For reasons of reduced administration overhead, better performance
	and/or reduction of CPU utilization, users of NFS version 4
	implementations may choose to not use security mechanisms that enable
	integrity protection on each remote procedure call and response. The
	use of mechanisms without integrity leaves the customer vulnerable to
	an attacker in between the NFS client and server that modifies the
	RPC request and/or the response. While implementations are free to
	provide the option to use weaker security mechanisms, there are two
	operations in particular that warrant the implementation overriding
	user choices.
	The first such operation is SECINFO. It is recommended that the
	client issue the SECINFO call such that it is protected with a
	security flavor that has integrity protection, such as RPCSEC_GSS
	with a security triple that uses either rpc_gss_svc_integrity or
	rpc_gss_svc_privacy (rpc_gss_svc_privacy includes integrity
	protection) service. Without integrity protection encapsulating
	SECINFO and therefore its results, an attacker in the middle could
	modify results such that the client might select a weaker algorithm
	in the set allowed by server, making the client and/or server
	vulnerable to further attacks.
	The second operation that should definitely use integrity protection
	is any GETATTR for the fs_locations attribute. The attack has two
	steps. First the attacker modifies the unprotected results of some
	operation to return NFS4ERR_MOVED. Second, when the client follows up
	with a GETATTR for the fs_locations attribute, the attacker modifies
	the results to cause the client migrate its traffic to a server
	controlled by the attacker.
	Because the operations SETCLIENTID/SETCLIENTID_CONFIRM are
	responsible for the release of client state, it is imperative that
	the principal used for these operations is checked against and match
	the previous use of these operations. See the section "Client ID"
	for further discussion.
	Draft Specification NFS version 4 Protocol October 2002
	17. IANA Considerations
	17.1. Named Attribute Definition
	The NFS version 4 protocol provides for the association of named
	attributes to files. The name space identifiers for these attributes
	are defined as string names. The protocol does not define the
	specific assignment of the name space for these file attributes; the
	application developer or system vendor is allowed to define the
	attribute, its semantics, and the associated name. Even though this
	name space will not be specifically controlled to prevent collisions,
	the application developer or system vendor is strongly encouraged
	register its named attributes with IANA, and provide the name
	assignment and associated semantics for attributes via an
	Informational RFC. This will provide for interoperability where
	common interests exist.
	17.2. ONC RPC Network Identifiers (netids)
	The section "Structured Data Types" discussed the r_netid field and
	the corresponding r_addr field of a clientaddr4 structure. There
	should be a registry at IANA for netids and the corresponding
	universal address format corresponding to the native address format
	for the transport represented by a netid.
	Draft Specification NFS version 4 Protocol October 2002
	18. RPC definition file
	/*
	* Copyright (C) The Internet Society (1998,1999,2000,2001,2002).
	* All Rights Reserved.
	*/
	/*
	* nfs4_prot.x
	*
	*/
	%#pragma ident "@(#)nfs4_prot.x 1.119"
	/*
	* Basic typedefs for RFC 1832 data type definitions
	*/
	typedef int int32_t;
	typedef unsigned int uint32_t;
	typedef hyper int64_t;
	typedef unsigned hyper uint64_t;
	/*
	* Sizes
	*/
	const NFS4_FHSIZE = 128;
	const NFS4_VERIFIER_SIZE = 8;
	const NFS4_OPAQUE_LIMIT = 1024;
	/*
	* File types
	*/
	enum nfs_ftype4 {
	NF4REG = 1, /* Regular File */
	NF4DIR = 2, /* Directory */
	NF4BLK = 3, /* Special File - block device */
	NF4CHR = 4, /* Special File - character device */
	NF4LNK = 5, /* Symbolic Link */
	NF4SOCK = 6, /* Special File - socket */
	NF4FIFO = 7, /* Special File - fifo */
	NF4ATTRDIR = 8, /* Attribute Directory */
	NF4NAMEDATTR = 9 /* Named Attribute */
	};
	/*
	* Error status
	*/
	enum nfsstat4 {
	NFS4_OK = 0, /* everything is okay */
	NFS4ERR_PERM = 1, /* caller not privileged */
	NFS4ERR_NOENT = 2, /* no such file/directory */
	NFS4ERR_IO = 5, /* hard I/O error */
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_NXIO = 6, /* no such device */
	NFS4ERR_ACCESS = 13, /* access denied */
	NFS4ERR_EXIST = 17, /* file already exists */
	NFS4ERR_XDEV = 18, /* different filesystems */
	/* Unused/reserved 19 */
	NFS4ERR_NOTDIR = 20, /* should be a directory */
	NFS4ERR_ISDIR = 21, /* should not be directory */
	NFS4ERR_INVAL = 22, /* invalid argument */
	NFS4ERR_FBIG = 27, /* file exceeds server max */
	NFS4ERR_NOSPC = 28, /* no space on filesystem */
	NFS4ERR_ROFS = 30, /* read-only filesystem */
	NFS4ERR_MLINK = 31, /* too many hard links */
	NFS4ERR_NAMETOOLONG = 63, /* name exceeds server max */
	NFS4ERR_NOTEMPTY = 66, /* directory not empty */
	NFS4ERR_DQUOT = 69, /* hard quota limit reached*/
	NFS4ERR_STALE = 70, /* file no longer exists */
	NFS4ERR_BADHANDLE = 10001,/* Illegal filehandle */
	NFS4ERR_BAD_COOKIE = 10003,/* READDIR cookie is stale */
	NFS4ERR_NOTSUPP = 10004,/* operation not supported */
	NFS4ERR_TOOSMALL = 10005,/* response limit exceeded */
	NFS4ERR_SERVERFAULT = 10006,/* undefined server error */
	NFS4ERR_BADTYPE = 10007,/* type invalid for CREATE */
	NFS4ERR_DELAY = 10008,/* file "busy" - retry */
	NFS4ERR_SAME = 10009,/* nverify says attrs same */
	NFS4ERR_DENIED = 10010,/* lock unavailable */
	NFS4ERR_EXPIRED = 10011,/* lock lease expired */
	NFS4ERR_LOCKED = 10012,/* I/O failed due to lock */
	NFS4ERR_GRACE = 10013,/* in grace period */
	NFS4ERR_FHEXPIRED = 10014,/* filehandle expired */
	NFS4ERR_SHARE_DENIED = 10015,/* share reserve denied */
	NFS4ERR_WRONGSEC = 10016,/* wrong security flavor */
	NFS4ERR_CLID_INUSE = 10017,/* clientid in use */
	NFS4ERR_RESOURCE = 10018,/* resource exhaustion */
	NFS4ERR_MOVED = 10019,/* filesystem relocated */
	NFS4ERR_NOFILEHANDLE = 10020,/* current FH is not set */
	NFS4ERR_MINOR_VERS_MISMATCH = 10021,/* minor vers not supp */
	NFS4ERR_STALE_CLIENTID = 10022,/* server has rebooted */
	NFS4ERR_STALE_STATEID = 10023,/* server has rebooted */
	NFS4ERR_OLD_STATEID = 10024,/* state is out of sync */
	NFS4ERR_BAD_STATEID = 10025,/* incorrect stateid */
	NFS4ERR_BAD_SEQID = 10026,/* request is out of seq. */
	NFS4ERR_NOT_SAME = 10027,/* verify - attrs not same */
	NFS4ERR_LOCK_RANGE = 10028,/* lock range not supported*/
	NFS4ERR_SYMLINK = 10029,/* should be file/directory*/
	NFS4ERR_RESTOREFH = 10030,/* no saved filehandle */
	NFS4ERR_LEASE_MOVED = 10031,/* some filesystem moved */
	NFS4ERR_ATTRNOTSUPP = 10032,/* recommended attr not sup*/
	NFS4ERR_NO_GRACE = 10033,/* reclaim outside of grace*/
	NFS4ERR_RECLAIM_BAD = 10034,/* reclaim error at server */
	NFS4ERR_RECLAIM_CONFLICT = 10035,/* conflict on reclaim */
	NFS4ERR_BADXDR = 10036,/* XDR decode failed */
	NFS4ERR_LOCKS_HELD = 10037,/* file locks held at CLOSE*/
	Draft Specification NFS version 4 Protocol October 2002
	NFS4ERR_OPENMODE = 10038,/* conflict in OPEN and I/O*/
	NFS4ERR_BADOWNER = 10039,/* owner translation bad */
	NFS4ERR_BADCHAR = 10040,/* utf-8 char not supported*/
	NFS4ERR_BADNAME = 10041,/* name not supported */
	NFS4ERR_BAD_RANGE = 10042,/* lock range not supported*/
	NFS4ERR_LOCK_NOTSUPP = 10043,/* no atomic up/downgrade */
	NFS4ERR_OP_ILLEGAL = 10044,/* undefined operation */
	NFS4ERR_DEADLOCK = 10045,/* file locking deadlock */
	NFS4ERR_FILE_OPEN = 10046,/* open file blocks op. */
	NFS4ERR_ADMIN_REVOKED = 10047,/* lockowner state revoked */
	NFS4ERR_CB_PATH_DOWN = 10048 /* callback path down */
	};
	/*
	* Basic data types
	*/
	typedef uint32_t bitmap4<>;
	typedef uint64_t offset4;
	typedef uint32_t count4;
	typedef uint64_t length4;
	typedef uint64_t clientid4;
	typedef uint32_t seqid4;
	typedef opaque utf8string<>;
	typedef utf8string component4;
	typedef component4 pathname4<>;
	typedef uint64_t nfs_lockid4;
	typedef uint64_t nfs_cookie4;
	typedef utf8string linktext4;
	typedef opaque sec_oid4<>;
	typedef uint32_t qop4;
	typedef uint32_t mode4;
	typedef uint64_t changeid4;
	typedef opaque verifier4[NFS4_VERIFIER_SIZE];
	/*
	* Timeval
	*/
	struct nfstime4 {
	int64_t seconds;
	uint32_t nseconds;
	};
	enum time_how4 {
	SET_TO_SERVER_TIME4 = 0,
	SET_TO_CLIENT_TIME4 = 1
	};
	union settime4 switch (time_how4 set_it) {
	case SET_TO_CLIENT_TIME4:
	nfstime4 time;
	default:
	void;
	Draft Specification NFS version 4 Protocol October 2002
	};
	/*
	* File access handle
	*/
	typedef opaque nfs_fh4<NFS4_FHSIZE>;
	/*
	* File attribute definitions
	*/
	/*
	* FSID structure for major/minor
	*/
	struct fsid4 {
	uint64_t major;
	uint64_t minor;
	};
	/*
	* Filesystem locations attribute for relocation/migration
	*/
	struct fs_location4 {
	utf8string server<>;
	pathname4 rootpath;
	};
	struct fs_locations4 {
	pathname4 fs_root;
	fs_location4 locations<>;
	};
	/*
	* Various Access Control Entry definitions
	*/
	/*
	* Mask that indicates which Access Control Entries are supported.
	* Values for the fattr4_aclsupport attribute.
	*/
	const ACL4_SUPPORT_ALLOW_ACL = 0x00000001;
	const ACL4_SUPPORT_DENY_ACL = 0x00000002;
	const ACL4_SUPPORT_AUDIT_ACL = 0x00000004;
	const ACL4_SUPPORT_ALARM_ACL = 0x00000008;
	typedef uint32_t acetype4;
	/*
	* acetype4 values, others can be added as needed.
	*/
	Draft Specification NFS version 4 Protocol October 2002
	const ACE4_ACCESS_ALLOWED_ACE_TYPE = 0x00000000;
	const ACE4_ACCESS_DENIED_ACE_TYPE = 0x00000001;
	const ACE4_SYSTEM_AUDIT_ACE_TYPE = 0x00000002;
	const ACE4_SYSTEM_ALARM_ACE_TYPE = 0x00000003;
	/*
	* ACE flag
	*/
	typedef uint32_t aceflag4;
	/*
	* ACE flag values
	*/
	const ACE4_FILE_INHERIT_ACE = 0x00000001;
	const ACE4_DIRECTORY_INHERIT_ACE = 0x00000002;
	const ACE4_NO_PROPAGATE_INHERIT_ACE = 0x00000004;
	const ACE4_INHERIT_ONLY_ACE = 0x00000008;
	const ACE4_SUCCESSFUL_ACCESS_ACE_FLAG = 0x00000010;
	const ACE4_FAILED_ACCESS_ACE_FLAG = 0x00000020;
	const ACE4_IDENTIFIER_GROUP = 0x00000040;
	/*
	* ACE mask
	*/
	typedef uint32_t acemask4;
	/*
	* ACE mask values
	*/
	const ACE4_READ_DATA = 0x00000001;
	const ACE4_LIST_DIRECTORY = 0x00000001;
	const ACE4_WRITE_DATA = 0x00000002;
	const ACE4_ADD_FILE = 0x00000002;
	const ACE4_APPEND_DATA = 0x00000004;
	const ACE4_ADD_SUBDIRECTORY = 0x00000004;
	const ACE4_READ_NAMED_ATTRS = 0x00000008;
	const ACE4_WRITE_NAMED_ATTRS = 0x00000010;
	const ACE4_EXECUTE = 0x00000020;
	const ACE4_DELETE_CHILD = 0x00000040;
	const ACE4_READ_ATTRIBUTES = 0x00000080;
	const ACE4_WRITE_ATTRIBUTES = 0x00000100;
	const ACE4_DELETE = 0x00010000;
	const ACE4_READ_ACL = 0x00020000;
	const ACE4_WRITE_ACL = 0x00040000;
	const ACE4_WRITE_OWNER = 0x00080000;
	const ACE4_SYNCHRONIZE = 0x00100000;
	/*
	* ACE4_GENERIC_READ -- defined as combination of
	Draft Specification NFS version 4 Protocol October 2002
	* ACE4_READ_ACL |
	* ACE4_READ_DATA |
	* ACE4_READ_ATTRIBUTES |
	* ACE4_SYNCHRONIZE
	*/
	const ACE4_GENERIC_READ = 0x00120081;
	/*
	* ACE4_GENERIC_WRITE -- defined as combination of
	* ACE4_READ_ACL |
	* ACE4_WRITE_DATA |
	* ACE4_WRITE_ATTRIBUTES |
	* ACE4_WRITE_ACL |
	* ACE4_APPEND_DATA |
	* ACE4_SYNCHRONIZE
	*/
	const ACE4_GENERIC_WRITE = 0x00160106;
	/*
	* ACE4_GENERIC_EXECUTE -- defined as combination of
	* ACE4_READ_ACL
	* ACE4_READ_ATTRIBUTES
	* ACE4_EXECUTE
	* ACE4_SYNCHRONIZE
	*/
	const ACE4_GENERIC_EXECUTE = 0x001200A0;
	/*
	* Access Control Entry definition
	*/
	struct nfsace4 {
	acetype4 type;
	aceflag4 flag;
	acemask4 access_mask;
	utf8string who;
	};
	/*
	* Field definitions for the fattr4_mode attribute
	*/
	const MODE4_SUID = 0x800; /* set user id on execution */
	const MODE4_SGID = 0x400; /* set group id on execution */
	const MODE4_SVTX = 0x200; /* save text even after use */
	const MODE4_RUSR = 0x100; /* read permission: owner */
	const MODE4_WUSR = 0x080; /* write permission: owner */
	const MODE4_XUSR = 0x040; /* execute permission: owner */
	const MODE4_RGRP = 0x020; /* read permission: group */
	const MODE4_WGRP = 0x010; /* write permission: group */
	const MODE4_XGRP = 0x008; /* execute permission: group */
	Draft Specification NFS version 4 Protocol October 2002
	const MODE4_ROTH = 0x004; /* read permission: other */
	const MODE4_WOTH = 0x002; /* write permission: other */
	const MODE4_XOTH = 0x001; /* execute permission: other */
	/*
	* Special data/attribute associated with
	* file types NF4BLK and NF4CHR.
	*/
	struct specdata4 {
	uint32_t specdata1; /* major device number */
	uint32_t specdata2; /* minor device number */
	};
	/*
	* Values for fattr4_fh_expire_type
	*/
	const FH4_PERSISTENT = 0x00000000;
	const FH4_NOEXPIRE_WITH_OPEN = 0x00000001;
	const FH4_VOLATILE_ANY = 0x00000002;
	const FH4_VOL_MIGRATION = 0x00000004;
	const FH4_VOL_RENAME = 0x00000008;
	typedef bitmap4 fattr4_supported_attrs;
	typedef nfs_ftype4 fattr4_type;
	typedef uint32_t fattr4_fh_expire_type;
	typedef changeid4 fattr4_change;
	typedef uint64_t fattr4_size;
	typedef bool fattr4_link_support;
	typedef bool fattr4_symlink_support;
	typedef bool fattr4_named_attr;
	typedef fsid4 fattr4_fsid;
	typedef bool fattr4_unique_handles;
	typedef uint32_t fattr4_lease_time;
	typedef nfsstat4 fattr4_rdattr_error;
	typedef nfsace4 fattr4_acl<>;
	typedef uint32_t fattr4_aclsupport;
	typedef bool fattr4_archive;
	typedef bool fattr4_cansettime;
	typedef bool fattr4_case_insensitive;
	typedef bool fattr4_case_preserving;
	typedef bool fattr4_chown_restricted;
	typedef uint64_t fattr4_fileid;
	typedef uint64_t fattr4_files_avail;
	typedef nfs_fh4 fattr4_filehandle;
	typedef uint64_t fattr4_files_free;
	typedef uint64_t fattr4_files_total;
	typedef fs_locations4 fattr4_fs_locations;
	typedef bool fattr4_hidden;
	typedef bool fattr4_homogeneous;
	typedef uint64_t fattr4_maxfilesize;
	Draft Specification NFS version 4 Protocol October 2002
	typedef uint32_t fattr4_maxlink;
	typedef uint32_t fattr4_maxname;
	typedef uint64_t fattr4_maxread;
	typedef uint64_t fattr4_maxwrite;
	typedef utf8string fattr4_mimetype;
	typedef mode4 fattr4_mode;
	typedef uint64_t fattr4_mounted_on_fileid;
	typedef bool fattr4_no_trunc;
	typedef uint32_t fattr4_numlinks;
	typedef utf8string fattr4_owner;
	typedef utf8string fattr4_owner_group;
	typedef uint64_t fattr4_quota_avail_hard;
	typedef uint64_t fattr4_quota_avail_soft;
	typedef uint64_t fattr4_quota_used;
	typedef specdata4 fattr4_rawdev;
	typedef uint64_t fattr4_space_avail;
	typedef uint64_t fattr4_space_free;
	typedef uint64_t fattr4_space_total;
	typedef uint64_t fattr4_space_used;
	typedef bool fattr4_system;
	typedef nfstime4 fattr4_time_access;
	typedef settime4 fattr4_time_access_set;
	typedef nfstime4 fattr4_time_backup;
	typedef nfstime4 fattr4_time_create;
	typedef nfstime4 fattr4_time_delta;
	typedef nfstime4 fattr4_time_metadata;
	typedef nfstime4 fattr4_time_modify;
	typedef settime4 fattr4_time_modify_set;
	/*
	* Mandatory Attributes
	*/
	const FATTR4_SUPPORTED_ATTRS = 0;
	const FATTR4_TYPE = 1;
	const FATTR4_FH_EXPIRE_TYPE = 2;
	const FATTR4_CHANGE = 3;
	const FATTR4_SIZE = 4;
	const FATTR4_LINK_SUPPORT = 5;
	const FATTR4_SYMLINK_SUPPORT = 6;
	const FATTR4_NAMED_ATTR = 7;
	const FATTR4_FSID = 8;
	const FATTR4_UNIQUE_HANDLES = 9;
	const FATTR4_LEASE_TIME = 10;
	const FATTR4_RDATTR_ERROR = 11;
	const FATTR4_FILEHANDLE = 19;
	/*
	* Recommended Attributes
	*/
	const FATTR4_ACL = 12;
	const FATTR4_ACLSUPPORT = 13;
	Draft Specification NFS version 4 Protocol October 2002
	const FATTR4_ARCHIVE = 14;
	const FATTR4_CANSETTIME = 15;
	const FATTR4_CASE_INSENSITIVE = 16;
	const FATTR4_CASE_PRESERVING = 17;
	const FATTR4_CHOWN_RESTRICTED = 18;
	const FATTR4_FILEID = 20;
	const FATTR4_FILES_AVAIL = 21;
	const FATTR4_FILES_FREE = 22;
	const FATTR4_FILES_TOTAL = 23;
	const FATTR4_FS_LOCATIONS = 24;
	const FATTR4_HIDDEN = 25;
	const FATTR4_HOMOGENEOUS = 26;
	const FATTR4_MAXFILESIZE = 27;
	const FATTR4_MAXLINK = 28;
	const FATTR4_MAXNAME = 29;
	const FATTR4_MAXREAD = 30;
	const FATTR4_MAXWRITE = 31;
	const FATTR4_MIMETYPE = 32;
	const FATTR4_MODE = 33;
	const FATTR4_NO_TRUNC = 34;
	const FATTR4_NUMLINKS = 35;
	const FATTR4_OWNER = 36;
	const FATTR4_OWNER_GROUP = 37;
	const FATTR4_QUOTA_AVAIL_HARD = 38;
	const FATTR4_QUOTA_AVAIL_SOFT = 39;
	const FATTR4_QUOTA_USED = 40;
	const FATTR4_RAWDEV = 41;
	const FATTR4_SPACE_AVAIL = 42;
	const FATTR4_SPACE_FREE = 43;
	const FATTR4_SPACE_TOTAL = 44;
	const FATTR4_SPACE_USED = 45;
	const FATTR4_SYSTEM = 46;
	const FATTR4_TIME_ACCESS = 47;
	const FATTR4_TIME_ACCESS_SET = 48;
	const FATTR4_TIME_BACKUP = 49;
	const FATTR4_TIME_CREATE = 50;
	const FATTR4_TIME_DELTA = 51;
	const FATTR4_TIME_METADATA = 52;
	const FATTR4_TIME_MODIFY = 53;
	const FATTR4_TIME_MODIFY_SET = 54;
	const FATTR4_MOUNTED_ON_FILEID = 55;
	typedef opaque attrlist4<>;
	/*
	* File attribute container
	*/
	struct fattr4 {
	bitmap4 attrmask;
	attrlist4 attr_vals;
	};
	Draft Specification NFS version 4 Protocol October 2002
	/*
	* Change info for the client
	*/
	struct change_info4 {
	bool atomic;
	changeid4 before;
	changeid4 after;
	};
	struct clientaddr4 {
	/* see struct rpcb in RFC 1833 */
	string r_netid<>; /* network id */
	string r_addr<>; /* universal address */
	};
	/*
	* Callback program info as provided by the client
	*/
	struct cb_client4 {
	uint32_t cb_program;
	clientaddr4 cb_location;
	};
	/*
	* Stateid
	*/
	struct stateid4 {
	uint32_t seqid;
	opaque other[12];
	};
	/*
	* Client ID
	*/
	struct nfs_client_id4 {
	verifier4 verifier;
	opaque id<NFS4_OPAQUE_LIMIT>;
	};
	struct open_owner4 {
	clientid4 clientid;
	opaque owner<NFS4_OPAQUE_LIMIT>;
	};
	struct lock_owner4 {
	clientid4 clientid;
	opaque owner<NFS4_OPAQUE_LIMIT>;
	};
	enum nfs_lock_type4 {
	READ_LT = 1,
	WRITE_LT = 2,
	Draft Specification NFS version 4 Protocol October 2002
	READW_LT = 3, /* blocking read */
	WRITEW_LT = 4 /* blocking write */
	};
	/*
	* ACCESS: Check access permission
	*/
	const ACCESS4_READ = 0x00000001;
	const ACCESS4_LOOKUP = 0x00000002;
	const ACCESS4_MODIFY = 0x00000004;
	const ACCESS4_EXTEND = 0x00000008;
	const ACCESS4_DELETE = 0x00000010;
	const ACCESS4_EXECUTE = 0x00000020;
	struct ACCESS4args {
	/* CURRENT_FH: object */
	uint32_t access;
	};
	struct ACCESS4resok {
	uint32_t supported;
	uint32_t access;
	};
	union ACCESS4res switch (nfsstat4 status) {
	case NFS4_OK:
	ACCESS4resok resok4;
	default:
	void;
	};
	/*
	* CLOSE: Close a file and release share reservations
	*/
	struct CLOSE4args {
	/* CURRENT_FH: object */
	seqid4 seqid;
	stateid4 open_stateid;
	};
	union CLOSE4res switch (nfsstat4 status) {
	case NFS4_OK:
	stateid4 open_stateid;
	default:
	void;
	};
	/*
	* COMMIT: Commit cached data on server to stable storage
	*/
	struct COMMIT4args {
	/* CURRENT_FH: file */
	Draft Specification NFS version 4 Protocol October 2002
	offset4 offset;
	count4 count;
	};
	struct COMMIT4resok {
	verifier4 writeverf;
	};
	union COMMIT4res switch (nfsstat4 status) {
	case NFS4_OK:
	COMMIT4resok resok4;
	default:
	void;
	};
	/*
	* CREATE: Create a non-regular file
	*/
	union createtype4 switch (nfs_ftype4 type) {
	case NF4LNK:
	linktext4 linkdata;
	case NF4BLK:
	case NF4CHR:
	specdata4 devdata;
	case NF4SOCK:
	case NF4FIFO:
	case NF4DIR:
	void;
	default:
	void; /* server should return NFS4ERR_BADTYPE */
	};
	struct CREATE4args {
	/* CURRENT_FH: directory for creation */
	createtype4 objtype;
	component4 objname;
	fattr4 createattrs;
	};
	struct CREATE4resok {
	change_info4 cinfo;
	bitmap4 attrset; /* attributes set */
	};
	union CREATE4res switch (nfsstat4 status) {
	case NFS4_OK:
	CREATE4resok resok4;
	default:
	void;
	};
	Draft Specification NFS version 4 Protocol October 2002
	/*
	* DELEGPURGE: Purge Delegations Awaiting Recovery
	*/
	struct DELEGPURGE4args {
	clientid4 clientid;
	};
	struct DELEGPURGE4res {
	nfsstat4 status;
	};
	/*
	* DELEGRETURN: Return a delegation
	*/
	struct DELEGRETURN4args {
	/* CURRENT_FH: delegated file */
	stateid4 deleg_stateid;
	};
	struct DELEGRETURN4res {
	nfsstat4 status;
	};
	/*
	* GETATTR: Get file attributes
	*/
	struct GETATTR4args {
	/* CURRENT_FH: directory or file */
	bitmap4 attr_request;
	};
	struct GETATTR4resok {
	fattr4 obj_attributes;
	};
	union GETATTR4res switch (nfsstat4 status) {
	case NFS4_OK:
	GETATTR4resok resok4;
	default:
	void;
	};
	/*
	* GETFH: Get current filehandle
	*/
	struct GETFH4resok {
	nfs_fh4 object;
	};
	union GETFH4res switch (nfsstat4 status) {
	case NFS4_OK:
	GETFH4resok resok4;
	Draft Specification NFS version 4 Protocol October 2002
	default:
	void;
	};
	/*
	* LINK: Create link to an object
	*/
	struct LINK4args {
	/* SAVED_FH: source object */
	/* CURRENT_FH: target directory */
	component4 newname;
	};
	struct LINK4resok {
	change_info4 cinfo;
	};
	union LINK4res switch (nfsstat4 status) {
	case NFS4_OK:
	LINK4resok resok4;
	default:
	void;
	};
	/*
	* For LOCK, transition from open_owner to new lock_owner
	*/
	struct open_to_lock_owner4 {
	seqid4 open_seqid;
	stateid4 open_stateid;
	seqid4 lock_seqid;
	lock_owner4 lock_owner;
	};
	/*
	* For LOCK, existing lock_owner continues to request file locks
	*/
	struct exist_lock_owner4 {
	stateid4 lock_stateid;
	seqid4 lock_seqid;
	};
	union locker4 switch (bool new_lock_owner) {
	case TRUE:
	open_to_lock_owner4 open_owner;
	case FALSE:
	exist_lock_owner4 lock_owner;
	};
	/*
	* LOCK/LOCKT/LOCKU: Record lock management
	*/
	Draft Specification NFS version 4 Protocol October 2002
	struct LOCK4args {
	/* CURRENT_FH: file */
	nfs_lock_type4 locktype;
	bool reclaim;
	offset4 offset;
	length4 length;
	locker4 locker;
	};
	struct LOCK4denied {
	offset4 offset;
	length4 length;
	nfs_lock_type4 locktype;
	lock_owner4 owner;
	};
	struct LOCK4resok {
	stateid4 lock_stateid;
	};
	union LOCK4res switch (nfsstat4 status) {
	case NFS4_OK:
	LOCK4resok resok4;
	case NFS4ERR_DENIED:
	LOCK4denied denied;
	default:
	void;
	};
	struct LOCKT4args {
	/* CURRENT_FH: file */
	nfs_lock_type4 locktype;
	offset4 offset;
	length4 length;
	lock_owner4 owner;
	};
	union LOCKT4res switch (nfsstat4 status) {
	case NFS4ERR_DENIED:
	LOCK4denied denied;
	case NFS4_OK:
	void;
	default:
	void;
	};
	struct LOCKU4args {
	/* CURRENT_FH: file */
	nfs_lock_type4 locktype;
	seqid4 seqid;
	stateid4 lock_stateid;
	offset4 offset;
	Draft Specification NFS version 4 Protocol October 2002
	length4 length;
	};
	union LOCKU4res switch (nfsstat4 status) {
	case NFS4_OK:
	stateid4 lock_stateid;
	default:
	void;
	};
	/*
	* LOOKUP: Lookup filename
	*/
	struct LOOKUP4args {
	/* CURRENT_FH: directory */
	component4 objname;
	};
	struct LOOKUP4res {
	/* CURRENT_FH: object */
	nfsstat4 status;
	};
	/*
	* LOOKUPP: Lookup parent directory
	*/
	struct LOOKUPP4res {
	/* CURRENT_FH: directory */
	nfsstat4 status;
	};
	/*
	* NVERIFY: Verify attributes different
	*/
	struct NVERIFY4args {
	/* CURRENT_FH: object */
	fattr4 obj_attributes;
	};
	struct NVERIFY4res {
	nfsstat4 status;
	};
	/*
	* Various definitions for OPEN
	*/
	enum createmode4 {
	UNCHECKED4 = 0,
	GUARDED4 = 1,
	EXCLUSIVE4 = 2
	};
	Draft Specification NFS version 4 Protocol October 2002
	union createhow4 switch (createmode4 mode) {
	case UNCHECKED4:
	case GUARDED4:
	fattr4 createattrs;
	case EXCLUSIVE4:
	verifier4 createverf;
	};
	enum opentype4 {
	OPEN4_NOCREATE = 0,
	OPEN4_CREATE = 1
	};
	union openflag4 switch (opentype4 opentype) {
	case OPEN4_CREATE:
	createhow4 how;
	default:
	void;
	};
	/* Next definitions used for OPEN delegation */
	enum limit_by4 {
	NFS_LIMIT_SIZE = 1,
	NFS_LIMIT_BLOCKS = 2
	/* others as needed */
	};
	struct nfs_modified_limit4 {
	uint32_t num_blocks;
	uint32_t bytes_per_block;
	};
	union nfs_space_limit4 switch (limit_by4 limitby) {
	/* limit specified as file size */
	case NFS_LIMIT_SIZE:
	uint64_t filesize;
	/* limit specified by number of blocks */
	case NFS_LIMIT_BLOCKS:
	nfs_modified_limit4 mod_blocks;
	} ;
	/*
	* Share Access and Deny constants for open argument
	*/
	const OPEN4_SHARE_ACCESS_READ = 0x00000001;
	const OPEN4_SHARE_ACCESS_WRITE = 0x00000002;
	const OPEN4_SHARE_ACCESS_BOTH = 0x00000003;
	const OPEN4_SHARE_DENY_NONE = 0x00000000;
	const OPEN4_SHARE_DENY_READ = 0x00000001;
	const OPEN4_SHARE_DENY_WRITE = 0x00000002;
	const OPEN4_SHARE_DENY_BOTH = 0x00000003;
	Draft Specification NFS version 4 Protocol October 2002
	enum open_delegation_type4 {
	OPEN_DELEGATE_NONE = 0,
	OPEN_DELEGATE_READ = 1,
	OPEN_DELEGATE_WRITE = 2
	};
	enum open_claim_type4 {
	CLAIM_NULL = 0,
	CLAIM_PREVIOUS = 1,
	CLAIM_DELEGATE_CUR = 2,
	CLAIM_DELEGATE_PREV = 3
	};
	struct open_claim_delegate_cur4 {
	stateid4 delegate_stateid;
	component4 file;
	};
	union open_claim4 switch (open_claim_type4 claim) {
	/*
	* No special rights to file. Ordinary OPEN of the specified file.
	*/
	case CLAIM_NULL:
	/* CURRENT_FH: directory */
	component4 file;
	/*
	* Right to the file established by an open previous to server
	* reboot. File identified by filehandle obtained at that time
	* rather than by name.
	*/
	case CLAIM_PREVIOUS:
	/* CURRENT_FH: file being reclaimed */
	open_delegation_type4 delegate_type;
	/*
	* Right to file based on a delegation granted by the server.
	* File is specified by name.
	*/
	case CLAIM_DELEGATE_CUR:
	/* CURRENT_FH: directory */
	open_claim_delegate_cur4 delegate_cur_info;
	/* Right to file based on a delegation granted to a previous boot
	* instance of the client. File is specified by name.
	*/
	case CLAIM_DELEGATE_PREV:
	/* CURRENT_FH: directory */
	component4 file_delegate_prev;
	};
	/*
	Draft Specification NFS version 4 Protocol October 2002
	* OPEN: Open a file, potentially receiving an open delegation
	*/
	struct OPEN4args {
	seqid4 seqid;
	uint32_t share_access;
	uint32_t share_deny;
	open_owner4 owner;
	openflag4 openhow;
	open_claim4 claim;
	};
	struct open_read_delegation4 {
	stateid4 stateid; /* Stateid for delegation*/
	bool recall; /* Pre-recalled flag for
	delegations obtained
	by reclaim
	(CLAIM_PREVIOUS) */
	nfsace4 permissions; /* Defines users who don't
	need an ACCESS call to
	open for read */
	};
	struct open_write_delegation4 {
	stateid4 stateid; /* Stateid for delegation */
	bool recall; /* Pre-recalled flag for
	delegations obtained
	by reclaim
	(CLAIM_PREVIOUS) */
	nfs_space_limit4 space_limit; /* Defines condition that
	the client must check to
	determine whether the
	file needs to be flushed
	to the server on close.
	*/
	nfsace4 permissions; /* Defines users who don't
	need an ACCESS call as
	part of a delegated
	open. */
	};
	union open_delegation4
	switch (open_delegation_type4 delegation_type) {
	case OPEN_DELEGATE_NONE:
	void;
	case OPEN_DELEGATE_READ:
	open_read_delegation4 read;
	case OPEN_DELEGATE_WRITE:
	open_write_delegation4 write;
	};
	/*
	* Result flags
	Draft Specification NFS version 4 Protocol October 2002
	*/
	/* Client must confirm open */
	const OPEN4_RESULT_CONFIRM = 0x00000002;
	/* Type of file locking behavior at the server */
	const OPEN4_RESULT_LOCKTYPE_POSIX = 0x00000004;
	struct OPEN4resok {
	stateid4 stateid; /* Stateid for open */
	change_info4 cinfo; /* Directory Change Info */
	uint32_t rflags; /* Result flags */
	bitmap4 attrset; /* attribute set for create*/
	open_delegation4 delegation; /* Info on any open
	delegation */
	};
	union OPEN4res switch (nfsstat4 status) {
	case NFS4_OK:
	/* CURRENT_FH: opened file */
	OPEN4resok resok4;
	default:
	void;
	};
	/*
	* OPENATTR: open named attributes directory
	*/
	struct OPENATTR4args {
	/* CURRENT_FH: object */
	bool createdir;
	};
	struct OPENATTR4res {
	/* CURRENT_FH: named attr directory */
	nfsstat4 status;
	};
	/*
	* OPEN_CONFIRM: confirm the open
	*/
	struct OPEN_CONFIRM4args {
	/* CURRENT_FH: opened file */
	stateid4 open_stateid;
	seqid4 seqid;
	};
	struct OPEN_CONFIRM4resok {
	stateid4 open_stateid;
	};
	union OPEN_CONFIRM4res switch (nfsstat4 status) {
	case NFS4_OK:
	OPEN_CONFIRM4resok resok4;
	Draft Specification NFS version 4 Protocol October 2002
	default:
	void;
	};
	/*
	* OPEN_DOWNGRADE: downgrade the access/deny for a file
	*/
	struct OPEN_DOWNGRADE4args {
	/* CURRENT_FH: opened file */
	stateid4 open_stateid;
	seqid4 seqid;
	uint32_t share_access;
	uint32_t share_deny;
	};
	struct OPEN_DOWNGRADE4resok {
	stateid4 open_stateid;
	};
	union OPEN_DOWNGRADE4res switch(nfsstat4 status) {
	case NFS4_OK:
	OPEN_DOWNGRADE4resok resok4;
	default:
	void;
	};
	/*
	* PUTFH: Set current filehandle
	*/
	struct PUTFH4args {
	nfs_fh4 object;
	};
	struct PUTFH4res {
	/* CURRENT_FH: */
	nfsstat4 status;
	};
	/*
	* PUTPUBFH: Set public filehandle
	*/
	struct PUTPUBFH4res {
	/* CURRENT_FH: public fh */
	nfsstat4 status;
	};
	/*
	* PUTROOTFH: Set root filehandle
	*/
	struct PUTROOTFH4res {
	/* CURRENT_FH: root fh */
	nfsstat4 status;
	Draft Specification NFS version 4 Protocol October 2002
	};
	/*
	* READ: Read from file
	*/
	struct READ4args {
	/* CURRENT_FH: file */
	stateid4 stateid;
	offset4 offset;
	count4 count;
	};
	struct READ4resok {
	bool eof;
	opaque data<>;
	};
	union READ4res switch (nfsstat4 status) {
	case NFS4_OK:
	READ4resok resok4;
	default:
	void;
	};
	/*
	* READDIR: Read directory
	*/
	struct READDIR4args {
	/* CURRENT_FH: directory */
	nfs_cookie4 cookie;
	verifier4 cookieverf;
	count4 dircount;
	count4 maxcount;
	bitmap4 attr_request;
	};
	struct entry4 {
	nfs_cookie4 cookie;
	component4 name;
	fattr4 attrs;
	entry4 *nextentry;
	};
	struct dirlist4 {
	entry4 *entries;
	bool eof;
	};
	struct READDIR4resok {
	verifier4 cookieverf;
	dirlist4 reply;
	};
	Draft Specification NFS version 4 Protocol October 2002
	union READDIR4res switch (nfsstat4 status) {
	case NFS4_OK:
	READDIR4resok resok4;
	default:
	void;
	};
	/*
	* READLINK: Read symbolic link
	*/
	struct READLINK4resok {
	linktext4 link;
	};
	union READLINK4res switch (nfsstat4 status) {
	case NFS4_OK:
	READLINK4resok resok4;
	default:
	void;
	};
	/*
	* REMOVE: Remove filesystem object
	*/
	struct REMOVE4args {
	/* CURRENT_FH: directory */
	component4 target;
	};
	struct REMOVE4resok {
	change_info4 cinfo;
	};
	union REMOVE4res switch (nfsstat4 status) {
	case NFS4_OK:
	REMOVE4resok resok4;
	default:
	void;
	};
	/*
	* RENAME: Rename directory entry
	*/
	struct RENAME4args {
	/* SAVED_FH: source directory */
	component4 oldname;
	/* CURRENT_FH: target directory */
	component4 newname;
	};
	struct RENAME4resok {
	Draft Specification NFS version 4 Protocol October 2002
	change_info4 source_cinfo;
	change_info4 target_cinfo;
	};
	union RENAME4res switch (nfsstat4 status) {
	case NFS4_OK:
	RENAME4resok resok4;
	default:
	void;
	};
	/*
	* RENEW: Renew a Lease
	*/
	struct RENEW4args {
	clientid4 clientid;
	};
	struct RENEW4res {
	nfsstat4 status;
	};
	/*
	* RESTOREFH: Restore saved filehandle
	*/
	struct RESTOREFH4res {
	/* CURRENT_FH: value of saved fh */
	nfsstat4 status;
	};
	/*
	* SAVEFH: Save current filehandle
	*/
	struct SAVEFH4res {
	/* SAVED_FH: value of current fh */
	nfsstat4 status;
	};
	/*
	* SECINFO: Obtain Available Security Mechanisms
	*/
	struct SECINFO4args {
	/* CURRENT_FH: directory */
	component4 name;
	};
	/*
	* From RFC 2203
	*/
	enum rpc_gss_svc_t {
	RPC_GSS_SVC_NONE = 1,
	Draft Specification NFS version 4 Protocol October 2002
	RPC_GSS_SVC_INTEGRITY = 2,
	RPC_GSS_SVC_PRIVACY = 3
	};
	struct rpcsec_gss_info {
	sec_oid4 oid;
	qop4 qop;
	rpc_gss_svc_t service;
	};
	/* RPCSEC_GSS has a value of '6' - See RFC 2203 */
	union secinfo4 switch (uint32_t flavor) {
	case RPCSEC_GSS:
	rpcsec_gss_info flavor_info;
	default:
	void;
	};
	typedef secinfo4 SECINFO4resok<>;
	union SECINFO4res switch (nfsstat4 status) {
	case NFS4_OK:
	SECINFO4resok resok4;
	default:
	void;
	};
	/*
	* SETATTR: Set attributes
	*/
	struct SETATTR4args {
	/* CURRENT_FH: target object */
	stateid4 stateid;
	fattr4 obj_attributes;
	};
	struct SETATTR4res {
	nfsstat4 status;
	bitmap4 attrsset;
	};
	/*
	* SETCLIENTID
	*/
	struct SETCLIENTID4args {
	nfs_client_id4 client;
	cb_client4 callback;
	uint32_t callback_ident;
	};
	struct SETCLIENTID4resok {
	clientid4 clientid;
	Draft Specification NFS version 4 Protocol October 2002
	verifier4 setclientid_confirm;
	};
	union SETCLIENTID4res switch (nfsstat4 status) {
	case NFS4_OK:
	SETCLIENTID4resok resok4;
	case NFS4ERR_CLID_INUSE:
	clientaddr4 client_using;
	default:
	void;
	};
	struct SETCLIENTID_CONFIRM4args {
	clientid4 clientid;
	verifier4 setclientid_confirm;
	};
	struct SETCLIENTID_CONFIRM4res {
	nfsstat4 status;
	};
	/*
	* VERIFY: Verify attributes same
	*/
	struct VERIFY4args {
	/* CURRENT_FH: object */
	fattr4 obj_attributes;
	};
	struct VERIFY4res {
	nfsstat4 status;
	};
	/*
	* WRITE: Write to file
	*/
	enum stable_how4 {
	UNSTABLE4 = 0,
	DATA_SYNC4 = 1,
	FILE_SYNC4 = 2
	};
	struct WRITE4args {
	/* CURRENT_FH: file */
	stateid4 stateid;
	offset4 offset;
	stable_how4 stable;
	opaque data<>;
	};
	struct WRITE4resok {
	count4 count;
	Draft Specification NFS version 4 Protocol October 2002
	stable_how4 committed;
	verifier4 writeverf;
	};
	union WRITE4res switch (nfsstat4 status) {
	case NFS4_OK:
	WRITE4resok resok4;
	default:
	void;
	};
	/*
	* RELEASE_LOCKOWNER: Notify server to release lockowner
	*/
	struct RELEASE_LOCKOWNER4args {
	lock_owner4 lock_owner;
	};
	struct RELEASE_LOCKOWNER4res {
	nfsstat4 status;
	};
	/*
	* ILLEGAL: Response for illegal operation numbers
	*/
	struct ILLEGAL4res {
	nfsstat4 status;
	};
	/*
	* Operation arrays
	*/
	enum nfs_opnum4 {
	OP_ACCESS = 3,
	OP_CLOSE = 4,
	OP_COMMIT = 5,
	OP_CREATE = 6,
	OP_DELEGPURGE = 7,
	OP_DELEGRETURN = 8,
	OP_GETATTR = 9,
	OP_GETFH = 10,
	OP_LINK = 11,
	OP_LOCK = 12,
	OP_LOCKT = 13,
	OP_LOCKU = 14,
	OP_LOOKUP = 15,
	OP_LOOKUPP = 16,
	OP_NVERIFY = 17,
	OP_OPEN = 18,
	OP_OPENATTR = 19,
	OP_OPEN_CONFIRM = 20,
	Draft Specification NFS version 4 Protocol October 2002
	OP_OPEN_DOWNGRADE = 21,
	OP_PUTFH = 22,
	OP_PUTPUBFH = 23,
	OP_PUTROOTFH = 24,
	OP_READ = 25,
	OP_READDIR = 26,
	OP_READLINK = 27,
	OP_REMOVE = 28,
	OP_RENAME = 29,
	OP_RENEW = 30,
	OP_RESTOREFH = 31,
	OP_SAVEFH = 32,
	OP_SECINFO = 33,
	OP_SETATTR = 34,
	OP_SETCLIENTID = 35,
	OP_SETCLIENTID_CONFIRM = 36,
	OP_VERIFY = 37,
	OP_WRITE = 38,
	OP_RELEASE_LOCKOWNER = 39,
	OP_ILLEGAL = 10044
	};
	union nfs_argop4 switch (nfs_opnum4 argop) {
	case OP_ACCESS: ACCESS4args opaccess;
	case OP_CLOSE: CLOSE4args opclose;
	case OP_COMMIT: COMMIT4args opcommit;
	case OP_CREATE: CREATE4args opcreate;
	case OP_DELEGPURGE: DELEGPURGE4args opdelegpurge;
	case OP_DELEGRETURN: DELEGRETURN4args opdelegreturn;
	case OP_GETATTR: GETATTR4args opgetattr;
	case OP_GETFH: void;
	case OP_LINK: LINK4args oplink;
	case OP_LOCK: LOCK4args oplock;
	case OP_LOCKT: LOCKT4args oplockt;
	case OP_LOCKU: LOCKU4args oplocku;
	case OP_LOOKUP: LOOKUP4args oplookup;
	case OP_LOOKUPP: void;
	case OP_NVERIFY: NVERIFY4args opnverify;
	case OP_OPEN: OPEN4args opopen;
	case OP_OPENATTR: OPENATTR4args opopenattr;
	case OP_OPEN_CONFIRM: OPEN_CONFIRM4args opopen_confirm;
	case OP_OPEN_DOWNGRADE: OPEN_DOWNGRADE4args opopen_downgrade;
	case OP_PUTFH: PUTFH4args opputfh;
	case OP_PUTPUBFH: void;
	case OP_PUTROOTFH: void;
	case OP_READ: READ4args opread;
	case OP_READDIR: READDIR4args opreaddir;
	case OP_READLINK: void;
	case OP_REMOVE: REMOVE4args opremove;
	case OP_RENAME: RENAME4args oprename;
	case OP_RENEW: RENEW4args oprenew;
	case OP_RESTOREFH: void;
	Draft Specification NFS version 4 Protocol October 2002
	case OP_SAVEFH: void;
	case OP_SECINFO: SECINFO4args opsecinfo;
	case OP_SETATTR: SETATTR4args opsetattr;
	case OP_SETCLIENTID: SETCLIENTID4args opsetclientid;
	case OP_SETCLIENTID_CONFIRM: SETCLIENTID_CONFIRM4args
	opsetclientid_confirm;
	case OP_VERIFY: VERIFY4args opverify;
	case OP_WRITE: WRITE4args opwrite;
	case OP_RELEASE_LOCKOWNER: RELEASE_LOCKOWNER4args
	oprelease_lockowner;
	case OP_ILLEGAL: void;
	};
	union nfs_resop4 switch (nfs_opnum4 resop){
	case OP_ACCESS: ACCESS4res opaccess;
	case OP_CLOSE: CLOSE4res opclose;
	case OP_COMMIT: COMMIT4res opcommit;
	case OP_CREATE: CREATE4res opcreate;
	case OP_DELEGPURGE: DELEGPURGE4res opdelegpurge;
	case OP_DELEGRETURN: DELEGRETURN4res opdelegreturn;
	case OP_GETATTR: GETATTR4res opgetattr;
	case OP_GETFH: GETFH4res opgetfh;
	case OP_LINK: LINK4res oplink;
	case OP_LOCK: LOCK4res oplock;
	case OP_LOCKT: LOCKT4res oplockt;
	case OP_LOCKU: LOCKU4res oplocku;
	case OP_LOOKUP: LOOKUP4res oplookup;
	case OP_LOOKUPP: LOOKUPP4res oplookupp;
	case OP_NVERIFY: NVERIFY4res opnverify;
	case OP_OPEN: OPEN4res opopen;
	case OP_OPENATTR: OPENATTR4res opopenattr;
	case OP_OPEN_CONFIRM: OPEN_CONFIRM4res opopen_confirm;
	case OP_OPEN_DOWNGRADE: OPEN_DOWNGRADE4res opopen_downgrade;
	case OP_PUTFH: PUTFH4res opputfh;
	case OP_PUTPUBFH: PUTPUBFH4res opputpubfh;
	case OP_PUTROOTFH: PUTROOTFH4res opputrootfh;
	case OP_READ: READ4res opread;
	case OP_READDIR: READDIR4res opreaddir;
	case OP_READLINK: READLINK4res opreadlink;
	case OP_REMOVE: REMOVE4res opremove;
	case OP_RENAME: RENAME4res oprename;
	case OP_RENEW: RENEW4res oprenew;
	case OP_RESTOREFH: RESTOREFH4res oprestorefh;
	case OP_SAVEFH: SAVEFH4res opsavefh;
	case OP_SECINFO: SECINFO4res opsecinfo;
	case OP_SETATTR: SETATTR4res opsetattr;
	case OP_SETCLIENTID: SETCLIENTID4res opsetclientid;
	case OP_SETCLIENTID_CONFIRM: SETCLIENTID_CONFIRM4res
	opsetclientid_confirm;
	case OP_VERIFY: VERIFY4res opverify;
	case OP_WRITE: WRITE4res opwrite;
	case OP_RELEASE_LOCKOWNER: RELEASE_LOCKOWNER4res
	Draft Specification NFS version 4 Protocol October 2002
	oprelease_lockowner;
	case OP_ILLEGAL: ILLEGAL4res opillegal;
	};
	struct COMPOUND4args {
	utf8string tag;
	uint32_t minorversion;
	nfs_argop4 argarray<>;
	};
	struct COMPOUND4res {
	nfsstat4 status;
	utf8string tag;
	nfs_resop4 resarray<>;
	};
	/*
	* Remote file service routines
	*/
	program NFS4_PROGRAM {
	version NFS_V4 {
	void
	NFSPROC4_NULL(void) = 0;
	COMPOUND4res
	NFSPROC4_COMPOUND(COMPOUND4args) = 1;
	} = 4;
	} = 100003;
	/*
	* NFS4 Callback Procedure Definitions and Program
	*/
	/*
	* CB_GETATTR: Get Current Attributes
	*/
	struct CB_GETATTR4args {
	nfs_fh4 fh;
	bitmap4 attr_request;
	};
	struct CB_GETATTR4resok {
	fattr4 obj_attributes;
	};
	union CB_GETATTR4res switch (nfsstat4 status) {
	case NFS4_OK:
	CB_GETATTR4resok resok4;
	default:
	Draft Specification NFS version 4 Protocol October 2002
	void;
	};
	/*
	* CB_RECALL: Recall an Open Delegation
	*/
	struct CB_RECALL4args {
	stateid4 stateid;
	bool truncate;
	nfs_fh4 fh;
	};
	struct CB_RECALL4res {
	nfsstat4 status;
	};
	/*
	* CB_ILLEGAL: Response for illegal operation numbers
	*/
	struct CB_ILLEGAL4res {
	nfsstat4 status;
	};
	/*
	* Various definitions for CB_COMPOUND
	*/
	enum nfs_cb_opnum4 {
	OP_CB_GETATTR = 3,
	OP_CB_RECALL = 4,
	OP_CB_ILLEGAL = 10044
	};
	union nfs_cb_argop4 switch (unsigned argop) {
	case OP_CB_GETATTR: CB_GETATTR4args opcbgetattr;
	case OP_CB_RECALL: CB_RECALL4args opcbrecall;
	case OP_CB_ILLEGAL: void;
	};
	union nfs_cb_resop4 switch (unsigned resop){
	case OP_CB_GETATTR: CB_GETATTR4res opcbgetattr;
	case OP_CB_RECALL: CB_RECALL4res opcbrecall;
	case OP_CB_ILLEGAL: CB_ILLEGAL4res opcbillegal;
	};
	struct CB_COMPOUND4args {
	utf8string tag;
	uint32_t minorversion;
	uint32_t callback_ident;
	nfs_cb_argop4 argarray<>;
	};
	struct CB_COMPOUND4res {
	Draft Specification NFS version 4 Protocol October 2002
	nfsstat4 status;
	utf8string tag;
	nfs_cb_resop4 resarray<>;
	};
	/*
	* Program number is in the transient range since the client
	* will assign the exact transient program number and provide
	* that to the server via the SETCLIENTID operation.
	*/
	program NFS4_CALLBACK {
	version NFS_CB {
	void
	CB_NULL(void) = 0;
	CB_COMPOUND4res
	CB_COMPOUND(CB_COMPOUND4args) = 1;
	} = 1;
	} = 0x40000000;
	Draft Specification NFS version 4 Protocol October 2002
	19. Normative References
	[ISO10646]
	"ISO/IEC 10646-1:1993. International Standard -- Information
	technology -- Universal Multiple-Octet Coded Character Set (UCS) --
	Part 1: Architecture and Basic Multilingual Plane."
	[RFC1831]
	Srinivasan, R., "RPC: Remote Procedure Call Protocol Specification
	Version 2", RFC1831, Sun Microsystems, Inc., August 1995.
	[RFC1832]
	Srinivasan, R., "XDR: External Data Representation Standard",
	RFC1832, Sun Microsystems, Inc., August 1995.
	[RFC1884]
	Hinden, R., Deering, S., "IP Version 6 Addressing Architecture",
	RFC1884, December 1995.
	[RFC1964]
	Linn, J., "The Kerberos Version 5 GSS-API Mechanism", RFC1964,
	OpenVision Technologies, June 1996.
	[RFC2025]
	Adams, C., "The Simple Public-Key GSS-API Mechanism (SPKM)", RFC2025,
	Bell-Northern Research, October 1996.
	[RFC2119]
	Bradner, S., "Key words for use in RFCs to Indicate Requirement
	Levels", RFC2119, Harvard University, March 1997
	[RFC2203]
	Eisler, M., Chiu, A., Ling, L., "RPCSEC_GSS Protocol Specification",
	RFC2203, Sun Microsystems, Inc., August 1995.
	[RFC2277]
	Alvestrand, H., "IETF Policy on Character Sets and Languages",
	RFC2277, UNINETT, January 1998.
	[RFC2279]
	Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC2279,
	Alis Technologies, January 1998.
	Draft Specification NFS version 4 Protocol October 2002
	[RFC2623]
	Eisler, M., "NFS Version 2 and Version 3 Security Issues and the NFS
	Protocol's Use of RPCSEC_GSS and Kerberos V5", RFC2623, Sun
	Microsystems, June 1999
	[RFC2743]
	Linn, J., "Generic Security Service Application Program Interface,
	Version 2, Update 1", RFC2743, RSA Laboratories, January 2000.
	[RFC2847]
	Eisler, M., "LIPKEY - A Low Infrastructure Public Key Mechanism Using
	SPKM", RFC2847, Zambeel, June 2000
	[RFC3010]
	Shepler, S., et. al., "NFS version 4 Protocol", RFC3010, December
	2000
	[Unicode1]
	The Unicode Consortium, "The Unicode Standard, Version 3.0",
	Addison-Wesley Developers Press, Reading, MA, 2000. ISBN 0-201-
	61633-5.
	More information available at: http://www.unicode.org/
	[Unicode2]
	"Unsupported Scripts" Unicode, Inc., The Unicode Consortium, P.O. Box
	700519, San Jose, CA 95710-0519 USA, September 1999
	http://www.unicode.org/unicode/standard/unsupported.html
	20. Informative References
	[Floyd]
	S. Floyd, V. Jacobson, "The Synchronization of Periodic Routing
	Messages," IEEE/ACM Transactions on Networking, 2(2), pp. 122-136,
	April 1994.
	[Gray]
	C. Gray, D. Cheriton, "Leases: An Efficient Fault-Tolerant Mechanism
	for Distributed File Cache Consistency," Proceedings of the Twelfth
	Symposium on Operating Systems Principles, p. 202-210, December 1989.
	[Juszczak]
	Draft Specification NFS version 4 Protocol October 2002
	Juszczak, Chet, "Improving the Performance and Correctness of an NFS
	Server," USENIX Conference Proceedings, USENIX Association, Berkeley,
	CA, June 1990, pages 53-63. Describes reply cache implementation
	that avoids work in the server by handling duplicate requests. More
	important, though listed as a side-effect, the reply cache aids in
	the avoidance of destructive non-idempotent operation re-application
	-- improving correctness.
	[Kazar]
	Kazar, Michael Leon, "Synchronization and Caching Issues in the
	Andrew File System," USENIX Conference Proceedings, USENIX
	Association, Berkeley, CA, Dallas Winter 1988, pages 27-36. A
	description of the cache consistency scheme in AFS. Contrasted with
	other distributed file systems.
	[Macklem]
	Macklem, Rick, "Lessons Learned Tuning the 4.3BSD Reno Implementation
	of the NFS Protocol," Winter USENIX Conference Proceedings, USENIX
	Association, Berkeley, CA, January 1991. Describes performance work
	in tuning the 4.3BSD Reno NFS implementation. Describes performance
	improvement (reduced CPU loading) through elimination of data copies.
	[Mogul]
	Mogul, Jeffrey C., "A Recovery Protocol for Spritely NFS," USENIX
	File System Workshop Proceedings, Ann Arbor, MI, USENIX Association,
	Berkeley, CA, May 1992. Second paper on Spritely NFS proposes a
	lease-based scheme for recovering state of consistency protocol.
	[Nowicki]
	Nowicki, Bill, "Transport Issues in the Network File System," ACM
	SIGCOMM newsletter Computer Communication Review, April 1989. A
	brief description of the basis for the dynamic retransmission work.
	[Pawlowski]
	Pawlowski, Brian, Ron Hixon, Mark Stein, Joseph Tumminaro, "Network
	Computing in the UNIX and IBM Mainframe Environment," Uniforum `89
	Conf. Proc., (1989) Description of an NFS server implementation for
	IBM's MVS operating system.
	[RFC1094]
	Sun Microsystems, Inc., "NFS: Network File System Protocol
	Specification", RFC1094, March 1989.
	[RFC1345]
	Simonsen, K., "Character Mnemonics & Character Sets", RFC1345,
	Draft Specification NFS version 4 Protocol October 2002
	Rationel Almen Planlaegning, June 1992.
	[RFC1813]
	Callaghan, B., Pawlowski, B., Staubach, P., "NFS Version 3 Protocol
	Specification", RFC1813, Sun Microsystems, Inc., June 1995.
	[RFC1833]
	Srinivasan, R., "Binding Protocols for ONC RPC Version 2", RFC1833,
	Sun Microsystems, Inc., August 1995.
	[RFC2054]
	Callaghan, B., "WebNFS Client Specification", RFC2054, Sun
	Microsystems, Inc., October 1996
	[RFC2055]
	Callaghan, B., "WebNFS Server Specification", RFC2055, Sun
	Microsystems, Inc., October 1996
	[RFC2152]
	Goldsmith, D., "UTF-7 A Mail-Safe Transformation Format of Unicode",
	RFC2152, Apple Computer, Inc., May 1997
	[RFC2224]
	Callaghan, B., "NFS URL Scheme", RFC2224, Sun Microsystems, Inc.,
	October 1997
	[RFC2624]
	Shepler, S., "NFS Version 4 Design Considerations", RFC2624, Sun
	Microsystems, June 1999
	[RFC2755]
	Chiu, A., Eisler, M., Callaghan, B., "Security Negotiation for
	WebNFS" , RFC2755, Sun Microsystems, June 2000
	[Sandberg]
	Sandberg, R., D. Goldberg, S. Kleiman, D. Walsh, B. Lyon, "Design
	and Implementation of the Sun Network Filesystem," USENIX Conference
	Proceedings, USENIX Association, Berkeley, CA, Summer 1985. The
	basic paper describing the SunOS implementation of the NFS version 2
	protocol, and discusses the goals, protocol specification and trade-
	offs.
	Draft Specification NFS version 4 Protocol October 2002
	[Srinivasan]
	Srinivasan, V., Jeffrey C. Mogul, "Spritely NFS: Implementation and
	Performance of Cache Consistency Protocols", WRL Research Report
	89/5, Digital Equipment Corporation Western Research Laboratory, 100
	Hamilton Ave., Palo Alto, CA, 94301, May 1989. This paper analyzes
	the effect of applying a Sprite-like consistency protocol applied to
	standard NFS. The issues of recovery in a stateful environment are
	covered in [Mogul].
	[XNFS]
	The Open Group, Protocols for Interworking: XNFS, Version 3W, The
	Open Group, 1010 El Camino Real Suite 380, Menlo Park, CA 94025, ISBN
	1-85912-184-5, February 1998.
	HTML version available: http://www.opengroup.org
	Draft Specification NFS version 4 Protocol October 2002
	21. Authors
	21.1. Editor's Address
	Spencer Shepler
	Sun Microsystems, Inc.
	7808 Moonflower Drive
	Austin, Texas 78750
	Phone: +1 512-349-9376
	E-mail: spencer.shepler@sun.com
	21.2. Authors' Addresses
	Carl Beame
	Hummingbird Ltd.
	E-mail: beame@bws.com
	Brent Callaghan
	Sun Microsystems, Inc.
	17 Network Circle
	Menlo Park, CA 94025
	Phone: +1 650-786-5067
	E-mail: brent.callaghan@sun.com
	Mike Eisler
	5765 Chase Point Circle
	Colorado Springs, CO 80919
	Phone: +1 719-599-9026
	E-mail: mike@eisler.com
	David Noveck
	Network Appliance
	375 Totten Pond Road
	Waltham, MA 02451
	Phone: +1 781-768-5347
	E-mail: dnoveck@netapp.com
	David Robinson
	Sun Microsystems, Inc.
	5300 Riata Park Court
	Austin, TX 78727
	Draft Specification NFS version 4 Protocol October 2002		Title: Network File System (NFS) version 4 Protocol
			Author(s): S. Shepler, B. Callaghan, D. Robinson, R. Thurlow,
			C. Beame, M. Eisler, D. Noveck
			Status: Standards Track
			Date: April 2003
			Mailbox: spencer.shepler@sun.com, beame@bws.com,
			brent.callaghan@sun.com, mike@eisler.com,
			dnoveck@netapp.com, david.robinson@sun.com,
			robert.thurlow@sun.com
			Pages: 275
			Characters: 600986
			Obsoletes: 3010
	Phone: +1 650-786-5088		I-D Tag: draft-ietf-nfsv4-rfc3010bis-05.txt
	E-mail: david.robinson@sun.com
	Robert Thurlow		URL: ftp://ftp.rfc-editor.org/in-notes/rfc3530.txt
	Sun Microsystems, Inc.
	500 Eldorado Blvd.
	Broomfield, CO 80021
	Phone: +1 650-786-5096		The Network File System (NFS) version 4 is a distributed filesystem
	E-mail: robert.thurlow@sun.com		protocol which owes heritage to NFS protocol version 2, RFC 1094, and
			version 3, RFC 1813. Unlike earlier versions, the NFS version 4
			protocol supports traditional file access while integrating support
			for file locking and the mount protocol. In addition, support for
			strong security (and its negotiation), compound operations, client
			caching, and internationalization have been added. Of course,
			attention has been applied to making NFS version 4 operate well in an
			Internet environment.
	21.3. Acknowledgements		This document replaces RFC 3010 as the definition of the NFS version 4
			protocol.
	The authors thank and acknowledges:		This document is a product of the Network File System Version 4
			Working Group of the IETF.
	Neil Brown for his extensive review and comments of various drafts.		This is now a Proposed Standard Protocol.
	Andy Adamson, Jim Rees, and Kendrick Smith from the CITI organization
	at the University of Michigan for their implementation efforts and
	feedback on the protocol specification. Mike Kupfer for his review
	of the file locking and ACL mechanisms. Alan Yoder for his input to
	ACL mechanisms. Peter Astrand for his close review of the protocol
	specification. Ran Atkinson for his constant reminder that users do
	matter.
	Draft Specification NFS version 4 Protocol October 2002		This document specifies an Internet standards track protocol for
			the Internet community, and requests discussion and suggestions
			for improvements. Please refer to the current edition of the
			"Internet Official Protocol Standards" (STD 1) for the
			standardization state and status of this protocol. Distribution
			of this memo is unlimited.
	22. Full Copyright Statement		This announcement is sent to the IETF list and the RFC-DIST list.
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