< draft-ietf-dnsop-extended-error-09.txt		draft-ietf-dnsop-extended-error-10.txt >
	Network Working Group W. Kumari		Network Working Group W. Kumari
	Internet-Draft Google		Internet-Draft Google
	Intended status: Standards Track E. Hunt		Intended status: Standards Track E. Hunt
	Expires: March 13, 2020 ISC		Expires: March 30, 2020 ISC
	R. Arends		R. Arends
	ICANN		ICANN
	W. Hardaker		W. Hardaker
	USC/ISI		USC/ISI
	D. Lawrence		D. Lawrence
	Oracle + Dyn		Oracle + Dyn
	September 10, 2019		September 27, 2019
	Extended DNS Errors		Extended DNS Errors
	draft-ietf-dnsop-extended-error-09		draft-ietf-dnsop-extended-error-10
	Abstract		Abstract
	This document defines an extensible method to return additional		This document defines an extensible method to return additional
	information about the cause of DNS errors. Though created primarily		information about the cause of DNS errors. Though created primarily
	to extend SERVFAIL to provide additional information about the cause		to extend SERVFAIL to provide additional information about the cause
	of DNS and DNSSEC failures, the Extended DNS Errors option defined in		of DNS and DNSSEC failures, the Extended DNS Errors option defined in
	this document allows all response types to contain extended error		this document allows all response types to contain extended error
	information.		information. Extended DNS Error information does not change the
			processing of RCODEs.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on March 13, 2020.		This Internet-Draft will expire on March 30, 2020.
	Copyright Notice		Copyright Notice
	Copyright (c) 2019 IETF Trust and the persons identified as the		Copyright (c) 2019 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 2, line 24 ¶		skipping to change at page 2, line 24 ¶
	Table of Contents		Table of Contents
	1. Introduction and background . . . . . . . . . . . . . . . . . 3		1. Introduction and background . . . . . . . . . . . . . . . . . 3
	1.1. Requirements notation . . . . . . . . . . . . . . . . . . 4		1.1. Requirements notation . . . . . . . . . . . . . . . . . . 4
	2. Extended Error EDNS0 option format . . . . . . . . . . . . . 4		2. Extended Error EDNS0 option format . . . . . . . . . . . . . 4
	3. Defined Extended DNS Errors . . . . . . . . . . . . . . . . . 5		3. Defined Extended DNS Errors . . . . . . . . . . . . . . . . . 5
	3.1. Extended DNS Error Code 0 - Other . . . . . . . . . . . . 5		3.1. Extended DNS Error Code 0 - Other . . . . . . . . . . . . 5
	3.2. Extended DNS Error Code 1 -		3.2. Extended DNS Error Code 1 -
	Unsupported DNSKEY Algorithm . . . . . . . . . . . . . . 5		Unsupported DNSKEY Algorithm . . . . . . . . . . . . . . 5
	3.3. Extended DNS Error Code 2 - Unsupported		3.3. Extended DNS Error Code 2 - Unsupported DS
	DS Algorithm . . . . . . . . . . . . . . . . . . . . . . 5		Digest Type . . . . . . . . . . . . . . . . . . . . . . . 5
	3.4. Extended DNS Error Code 3 - Stale Answer . . . . . . . . 5		3.4. Extended DNS Error Code 3 - Stale Answer . . . . . . . . 5
	3.5. Extended DNS Error Code 4 - Forged Answer . . . . . . . . 5		3.5. Extended DNS Error Code 4 - Forged Answer . . . . . . . . 5
	3.6. Extended DNS Error Code 5 - DNSSEC Indeterminate . . . . 5		3.6. Extended DNS Error Code 5 - DNSSEC Indeterminate . . . . 6
	3.7. Extended DNS Error Code 6 - DNSSEC Bogus . . . . . . . . 6		3.7. Extended DNS Error Code 6 - DNSSEC Bogus . . . . . . . . 6
	3.8. Extended DNS Error Code 7 - Signature Expired . . . . . . 6		3.8. Extended DNS Error Code 7 - Signature Expired . . . . . . 6
	3.9. Extended DNS Error Code 8 - Signature Not Yet Valid . . . 6		3.9. Extended DNS Error Code 8 - Signature Not Yet Valid . . . 6
	3.10. Extended DNS Error Code 9 - DNSKEY Missing . . . . . . . 6		3.10. Extended DNS Error Code 9 - DNSKEY Missing . . . . . . . 6
	3.11. Extended DNS Error Code 10 - RRSIGs Missing . . . . . . . 6		3.11. Extended DNS Error Code 10 - RRSIGs Missing . . . . . . . 6
	3.12. Extended DNS Error Code 11 - No Zone Key Bit Set . . . . 6		3.12. Extended DNS Error Code 11 - No Zone Key Bit Set . . . . 6
	3.13. Extended DNS Error Code 12 - NSEC Missing . . . . . . . . 6		3.13. Extended DNS Error Code 12 - NSEC Missing . . . . . . . . 6
	3.14. Extended DNS Error Code 13 - Cached Error . . . . . . . . 6		3.14. Extended DNS Error Code 13 - Cached Error . . . . . . . . 6
	3.15. Extended DNS Error Code 14 - Not Ready . . . . . . . . . 6		3.15. Extended DNS Error Code 14 - Not Ready . . . . . . . . . 7
	3.16. Extended DNS Error Code 15 - Blocked . . . . . . . . . . 7		3.16. Extended DNS Error Code 15 - Blocked . . . . . . . . . . 7
	3.17. Extended DNS Error Code 16 - Censored . . . . . . . . . . 7		3.17. Extended DNS Error Code 16 - Censored . . . . . . . . . . 7
	3.18. Extended DNS Error Code 17 - Prohibited . . . . . . . . . 7		3.18. Extended DNS Error Code 17 - Filtered . . . . . . . . . . 7
	3.19. Extended DNS Error Code 18 - Filtered . . . . . . . . . . 7		3.19. Extended DNS Error Code 17 - Prohibited . . . . . . . . . 7
	3.20. Extended DNS Error Code 19 - Stale NXDOMAIN Answer . . . 7		3.20. Extended DNS Error Code 19 - Stale NXDOMAIN Answer . . . 7
	3.21. Extended DNS Error Code 20 - Lame . . . . . . . . . . . . 7		3.21. Extended DNS Error Code 20 - Not Authoritative . . . . . 7
	3.22. Extended DNS Error Code 21 - Deprecated . . . . . . . . . 8		3.22. Extended DNS Error Code 21 - Deprecated . . . . . . . . . 8
	3.23. Extended DNS Error Code 22 - No Reachable Authority . . . 8		3.23. Extended DNS Error Code 22 - No Reachable Authority . . . 8
	3.24. Extended DNS Error Code 23 - Network Error . . . . . . . 8		3.24. Extended DNS Error Code 23 - Network Error . . . . . . . 8
			3.25. Extended DNS Error Code 24 - Invalid Data . . . . . . . . 8
	4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8		4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
	4.1. A New Extended DNS Error Code EDNS Option . . . . . . . . 8		4.1. A New Extended DNS Error Code EDNS Option . . . . . . . . 8
	4.2. New Registry Table for Extended DNS Error Codes . . . . . 8		4.2. New Registry Table for Extended DNS Error Codes . . . . . 8
	5. Security Considerations . . . . . . . . . . . . . . . . . . . 11		5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
	6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11		6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
	7. References . . . . . . . . . . . . . . . . . . . . . . . . . 11		7. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
	7.1. Normative References . . . . . . . . . . . . . . . . . . 11		7.1. Normative References . . . . . . . . . . . . . . . . . . 12
	7.2. Informative References . . . . . . . . . . . . . . . . . 12		7.2. Informative References . . . . . . . . . . . . . . . . . 12
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
	1. Introduction and background		1. Introduction and background
	There are many reasons that a DNS query may fail, some of them		There are many reasons that a DNS query may fail, some of them
	transient, some permanent; some can be resolved by querying another		transient, some permanent; some can be resolved by querying another
	server, some are likely best handled by stopping resolution.		server, some are likely best handled by stopping resolution.
	Unfortunately, the error signals that a DNS server can return are		Unfortunately, the error signals that a DNS server can return are
	very limited, and are not very expressive. This means that		very limited, and are not very expressive. This means that
	applications and resolvers often have to "guess" at what the issue is		applications and resolvers often have to "guess" at what the issue is
	- e.g. was the answer marked REFUSED because of a lame delegation, or		- e.g. was the answer marked REFUSED because of a lame delegation, or
	skipping to change at page 3, line 40 ¶		skipping to change at page 3, line 41 ¶
	resolver is not a validating resolver, and the user is returned a		resolver is not a validating resolver, and the user is returned a
	potentially harmful result. With an Extended DNS Error (EDE) option		potentially harmful result. With an Extended DNS Error (EDE) option
	enclosed in the response message, the resolver is able to return a		enclosed in the response message, the resolver is able to return a
	more descriptive reason as to why any failures happened, or add		more descriptive reason as to why any failures happened, or add
	additional context to a message containing a NOERROR RCODE.		additional context to a message containing a NOERROR RCODE.
	This document specifies a mechanism to extend DNS errors to provide		This document specifies a mechanism to extend DNS errors to provide
	additional information about the cause of an error. These extended		additional information about the cause of an error. These extended
	DNS error codes described in this document and can be used by any		DNS error codes described in this document and can be used by any
	system that sends DNS queries and receives a response containing an		system that sends DNS queries and receives a response containing an
	EDE option.. Different codes are useful in different circumstances,		EDE option. Different codes are useful in different circumstances,
	and thus different systems (stub resolvers, recursive resolvers, and		and thus different systems (stub resolvers, recursive resolvers, and
	authoritative resolvers) might receive and use them.		authoritative resolvers) might receive and use them.
	This document does not allow or prohibit any particular extended		This document does not allow or prohibit any particular extended
	error codes and information be matched with any particular RCODEs.		error codes and information to be matched with any particular RCODEs.
	Some combinations of extended error codes and RCODEs may seem		Some combinations of extended error codes and RCODEs may seem
	nonsensical (such as resolver-specific extended error codes in		nonsensical (such as resolver-specific extended error codes in
	responses from authoritative servers), so systems interpreting the		responses from authoritative servers), so systems interpreting the
	extended error codes MUST NOT assume that a combination will make		extended error codes MUST NOT assume that a combination will make
	sense. Receivers MUST be able to accept EDE codes and EXTRA-TEXT in		sense. Receivers MUST be able to accept EDE codes and EXTRA-TEXT in
	all messages, including even those with a NOERROR RCODE.		all messages, including those with a NOERROR RCODE. Receivers MUST
			NOT change the processing of RCODEs in messages based on extended
			error codes.
	1.1. Requirements notation		1.1. Requirements notation
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [RFC2119].		document are to be interpreted as described in [RFC2119].
	2. Extended Error EDNS0 option format		2. Extended Error EDNS0 option format
	This draft uses an EDNS0 ([RFC2671]) option to include Extended DNS		This draft uses an EDNS0 ([RFC2671]) option to include Extended DNS
	skipping to change at page 4, line 40 ¶		skipping to change at page 4, line 43 ¶
	o OPTION-CODE, 2 octets (defined in [RFC6891]]), for EDE is TBD.		o OPTION-CODE, 2 octets (defined in [RFC6891]]), for EDE is TBD.
	[RFC Editor: change TBD to the proper code once assigned by IANA.]		[RFC Editor: change TBD to the proper code once assigned by IANA.]
	o OPTION-LENGTH, 2 octets ((defined in [RFC6891]]) contains the		o OPTION-LENGTH, 2 octets ((defined in [RFC6891]]) contains the
	length of the payload (everything after OPTION-LENGTH) in octets		length of the payload (everything after OPTION-LENGTH) in octets
	and should be 4 plus the length of the EXTRA-TEXT section (which		and should be 4 plus the length of the EXTRA-TEXT section (which
	may be a zero-length string).		may be a zero-length string).
	o INFO-CODE, 16-bits, which is the principal contribution of this		o INFO-CODE, 16-bits, which is the principal contribution of this
	document. This 16-bit value, encoded in network (MSB) byte order,		document. This 16-bit value, encoded in network (MSB) byte order,
	provides the additional context for the RESPONSE-CODE of the DNS		provides the additional context for the RESPONSE-CODE of the DNS
	message. The INFO-CODE serves as an index to the "Extended DNS		message. The INFO-CODE serves as an index into the "Extended DNS
	Errors" registry Section 4.1.		Errors" registry Section 4.1.
	o EXTRA-TEXT, a variable length, UTF-8 encoded, text field that may		o EXTRA-TEXT, a variable length, UTF-8 encoded, text field that may
	hold additional textual information. Note: EXTRA-TEXT may be zero		hold additional textual information. Note: EXTRA-TEXT may be zero
	octets in length, indicating there is no EXTRA-TEXT included.		octets in length, indicating there is no EXTRA-TEXT included.
	Care should be take not to leak private information that an		Care should be taken not to leak private information that an
	observer would not otherwise have access to, such as account		observer would not otherwise have access to, such as account
	numbers.		numbers.
	The Extended DNS Error (EDE) option can be included in any response		The Extended DNS Error (EDE) option can be included in any response
	(SERVFAIL, NXDOMAIN, REFUSED, and even NOERROR, etc) to a query that		(SERVFAIL, NXDOMAIN, REFUSED, and even NOERROR, etc) to a query that
	includes OPT Pseudo-RR [RFC6891]. This document includes a set of		includes OPT Pseudo-RR [RFC6891]. This document includes a set of
	initial codepoints (and requests to the IANA to add them to the		initial codepoints (and requests to the IANA to add them to the
	registry), but is extensible via the IANA registry to allow		registry), but is extensible via the IANA registry to allow
	additional error and information codes to be defined in the future.		additional error and information codes to be defined in the future.
	skipping to change at page 5, line 25 ¶		skipping to change at page 5, line 30 ¶
	3.1. Extended DNS Error Code 0 - Other		3.1. Extended DNS Error Code 0 - Other
	The error in question falls into a category that does not match known		The error in question falls into a category that does not match known
	extended error codes. Implementations SHOULD include a EXTRA-TEXT		extended error codes. Implementations SHOULD include a EXTRA-TEXT
	value to augment this error code with additional information.		value to augment this error code with additional information.
	3.2. Extended DNS Error Code 1 - Unsupported DNSKEY Algorithm		3.2. Extended DNS Error Code 1 - Unsupported DNSKEY Algorithm
	The resolver attempted to perform DNSSEC validation, but a DNSKEY		The resolver attempted to perform DNSSEC validation, but a DNSKEY
	RRSET contained only unknown algorithms.		RRSET contained only unsupported DNSSEC algorithms.
	3.3. Extended DNS Error Code 2 - Unsupported DS Algorithm		3.3. Extended DNS Error Code 2 - Unsupported DS Digest Type
	The resolver attempted to perform DNSSEC validation, but a DS RRSET		The resolver attempted to perform DNSSEC validation, but a DS RRSET
	contained only unknown algorithms.		contained only unsupported Digest Types.
	3.4. Extended DNS Error Code 3 - Stale Answer		3.4. Extended DNS Error Code 3 - Stale Answer
	The resolver was unable to resolve answer within its time limits and		The resolver was unable to resolve answer within its time limits and
	decided to answer with previously cached data instead of answering		decided to answer with previously cached data instead of answering
	with an error. This is typically caused by problems communicating		with an error. This is typically caused by problems communicating
	with an authoritative serever, possibly as result of a DoS attack		with an authoritative serever, possibly as result of a DoS attack
	against another network.		against another network.
	3.5. Extended DNS Error Code 4 - Forged Answer		3.5. Extended DNS Error Code 4 - Forged Answer
	For policy reasons (legal obligation, or malware filtering, for		For policy reasons (legal obligation, or malware filtering, for
	instance), an answer was forged.		instance), an answer was forged. Note that this should be used when
			an answer is still provided, not when failure codes are returned
			instead. See Blocked(15), Censored (16), and Filtered (17) for use
			when returning other response codes.
	3.6. Extended DNS Error Code 5 - DNSSEC Indeterminate		3.6. Extended DNS Error Code 5 - DNSSEC Indeterminate
	The resolver attempted to perform DNSSEC validation, but validation		The resolver attempted to perform DNSSEC validation, but validation
	ended in the Indeterminate state.		ended in the Indeterminate state [RFC4035].
	3.7. Extended DNS Error Code 6 - DNSSEC Bogus		3.7. Extended DNS Error Code 6 - DNSSEC Bogus
	The resolver attempted to perform DNSSEC validation, but validation		The resolver attempted to perform DNSSEC validation, but validation
	ended in the Bogus state.		ended in the Bogus state.
	3.8. Extended DNS Error Code 7 - Signature Expired		3.8. Extended DNS Error Code 7 - Signature Expired
	The resolver attempted to perform DNSSEC validation, but a signature		The resolver attempted to perform DNSSEC validation, but all
	in the validation chain was expired.		signatures in an RRset in the validation chain were expired.
	3.9. Extended DNS Error Code 8 - Signature Not Yet Valid		3.9. Extended DNS Error Code 8 - Signature Not Yet Valid
	The resolver attempted to perform DNSSEC validation, but the		The resolver attempted to perform DNSSEC validation, but all the
	signatures received were not yet valid.		signatures received were not yet valid.
	3.10. Extended DNS Error Code 9 - DNSKEY Missing		3.10. Extended DNS Error Code 9 - DNSKEY Missing
	A DS record existed at a parent, but no supported matching DNSKEY		A DS record existed at a parent, but no supported matching DNSKEY
	record could be found for the child.		record could be found for the child.
	3.11. Extended DNS Error Code 10 - RRSIGs Missing		3.11. Extended DNS Error Code 10 - RRSIGs Missing
	The resolver attempted to perform DNSSEC validation, but no RRSIGs		The resolver attempted to perform DNSSEC validation, but no RRSIGs
	skipping to change at page 6, line 43 ¶		skipping to change at page 6, line 48 ¶
	Bit was set in a DNSKEY.		Bit was set in a DNSKEY.
	3.13. Extended DNS Error Code 12 - NSEC Missing		3.13. Extended DNS Error Code 12 - NSEC Missing
	The resolver attempted to perform DNSSEC validation, but the		The resolver attempted to perform DNSSEC validation, but the
	requested data was missing and a covering NSEC or NSEC3 was not		requested data was missing and a covering NSEC or NSEC3 was not
	provided.		provided.
	3.14. Extended DNS Error Code 13 - Cached Error		3.14. Extended DNS Error Code 13 - Cached Error
	The resolver has cached SERVFAIL for this query.		The resolver has Cached SERVFAIL for this query.
	3.15. Extended DNS Error Code 14 - Not Ready		3.15. Extended DNS Error Code 14 - Not Ready
	The server is unable to answer the query as it is not fully		The server is unable to answer the query as it is not fully
	functional (yet).		functional (yet).
	3.16. Extended DNS Error Code 15 - Blocked		3.16. Extended DNS Error Code 15 - Blocked
	The resolver attempted to perfom a DNS query but the domain is		The server is unable to respond to the request because the domain is
	blacklisted due to a security policy implemented on the server being		blacklisted due to an internal security policy imposed by the
	directly talked to.		operator of the server being directly talked to.
	3.17. Extended DNS Error Code 16 - Censored		3.17. Extended DNS Error Code 16 - Censored
	The resolver attempted to perfom a DNS query but the domain was		The server is unable to respond to the request because the domain is
	blacklisted by a security policy imposed upon the server being talked		blacklisted by a security policy imposed upon the server being talked
	to. Note that how the imposed policy is applied is irrelevant (in-		to by an external requirement. Note that how the imposed policy is
	band DNS filtering, court order, etc).		applied is irrelevant (in-band DNS filtering, court order, etc).
	3.18. Extended DNS Error Code 17 - Prohibited		3.18. Extended DNS Error Code 17 - Filtered
			The server is unable to respond to the request because the domain is
			blacklisted as requested by the client. Functionally, this amounts
			to "you requested that we filter domains like this one."
			3.19. Extended DNS Error Code 17 - Prohibited
	An authoritative or recursive resolver that receives a query from an		An authoritative or recursive resolver that receives a query from an
	"unauthorized" client can annotate its REFUSED message with this		"unauthorized" client can annotate its REFUSED message with this
	code. Examples of "unauthorized" clients are recursive queries from		code. Examples of "unauthorized" clients are recursive queries from
	IP addresses outside the network, blacklisted IP addresses, local		IP addresses outside the network, blacklisted IP addresses, local
	policy, etc.		policy, etc.
	3.19. Extended DNS Error Code 18 - Filtered
	An authoritative or recursive resolver that receives a query from a
	client that had requested certain domains be filtered can annotate
	its REFUSED message with this code. Functionally, this amounts to
	"you requested that we filter domains like this one."
	3.20. Extended DNS Error Code 19 - Stale NXDOMAIN Answer		3.20. Extended DNS Error Code 19 - Stale NXDOMAIN Answer
	The resolver was unable to resolve an answer within its configured		The resolver was unable to resolve an answer within its configured
	time limits and decided to answer with a previously cached NXDOMAIN		time limits and decided to answer with a previously cached NXDOMAIN
	answer instead of answering with an error. This is typically caused		answer instead of answering with an error. This is typically caused
	by problems communicating with an authoritative serever, possibly as		by problems communicating with an authoritative server, possibly as
	result of a DoS attack against another network.		result of a DoS attack against another network.
	3.21. Extended DNS Error Code 20 - Lame		3.21. Extended DNS Error Code 20 - Not Authoritative
	An authoritative server that receives a query (with the RD bit clear)		An authoritative server that receives a query (with the RD bit clear,
	for a domain for which it is not authoritative SHOULD include this		or when not configured for recursion) for a domain for which it is
	EDE code in the SERVFAIL response. A resolver that receives a query		not authoritative SHOULD include this EDE code in the REFUSED
	(with the RD bit clear) SHOULD include this EDE code in the REFUSED		response. A resolver that receives a query (with the RD bit clear)
	response.		SHOULD include this EDE code in the REFUSED response.
	3.22. Extended DNS Error Code 21 - Deprecated		3.22. Extended DNS Error Code 21 - Deprecated
	The requested operation or query is not supported as its use has been		The requested operation or query is not supported as its use has been
	deprecated.		deprecated.
	3.23. Extended DNS Error Code 22 - No Reachable Authority		3.23. Extended DNS Error Code 22 - No Reachable Authority
	The resolver could not reach any of the authoritative name servers		The resolver could not reach any of the authoritative name servers
	(or they refused to reply).		(or they refused to reply).
	3.24. Extended DNS Error Code 23 - Network Error		3.24. Extended DNS Error Code 23 - Network Error
	An unrecoverable error occurred while communicating with another		An unrecoverable error occurred while communicating with another
	server.		server.
			3.25. Extended DNS Error Code 24 - Invalid Data
			An authoritative server that cannot answer with data for a zone it is
			otherwise configured to support. This may occur because its most
			recent zone is too old, or has expired, for example.
	4. IANA Considerations		4. IANA Considerations
	4.1. A New Extended DNS Error Code EDNS Option		4.1. A New Extended DNS Error Code EDNS Option
	This document defines a new EDNS(0) option, entitled "Extended DNS		This document defines a new EDNS(0) option, entitled "Extended DNS
	Error", assigned a value of TBD1 from the "DNS EDNS0 Option Codes		Error", assigned a value of TBD1 from the "DNS EDNS0 Option Codes
	(OPT)" registry [to be removed upon publication:		(OPT)" registry [to be removed upon publication:
	[http://www.iana.org/assignments/dns-parameters/dns-		[http://www.iana.org/assignments/dns-parameters/dns-
	parameters.xhtml#dns-parameters-11]		parameters.xhtml#dns-parameters-11]
	skipping to change at page 9, line 4 ¶		skipping to change at page 9, line 11 ¶
	o 0 - 32767: Expert Review [RFC2434].		o 0 - 32767: Expert Review [RFC2434].
	o 32768 - 49151: First come, first served.		o 32768 - 49151: First come, first served.
	o 49152 - 65535: Experimental / Private use.		o 49152 - 65535: Experimental / Private use.
	A starting set of entries, based on the contents of this document, is		A starting set of entries, based on the contents of this document, is
	as follows:		as follows:
	INFO-CODE: 0		INFO-CODE: 0
	Purpose: Other Error		Purpose: Other Error
	Reference: Section 3.1		Reference: Section 3.1
	INFO-CODE: 1		INFO-CODE: 1
	Purpose: Unsupported DNSKEY Algorithm		Purpose: Unsupported DNSKEY Algorithm
	Reference: Section 3.2		Reference: Section 3.2
	INFO-CODE: 2		INFO-CODE: 2
	Purpose: Unsupported DS Algorithm		Purpose: Unsupported DS Digest Type
	Reference: Section 3.3		Reference: Section 3.3
	INFO-CODE: 3		INFO-CODE: 3
	Purpose: Stale Answer		Purpose: Stale Answer
	Reference: Section 3.4		Reference: Section 3.4, [I-D.ietf-dnsop-serve-stale]
	INFO-CODE: 4		INFO-CODE: 4
	Purpose: Forged Answer		Purpose: Forged Answer
	Reference: Section 3.5		Reference: Section 3.5
	INFO-CODE: 5		INFO-CODE: 5
	Purpose: DNSSEC Indeterminate		Purpose: DNSSEC Indeterminate
	Reference: Section 3.6		Reference: Section 3.6
	INFO-CODE: 6		INFO-CODE: 6
	skipping to change at page 10, line 4 ¶		skipping to change at page 10, line 10 ¶
	Purpose: RRSIGs Missing		Purpose: RRSIGs Missing
	Reference: Section 3.11		Reference: Section 3.11
	INFO-CODE: 11		INFO-CODE: 11
	Purpose: No Zone Key Bit Set		Purpose: No Zone Key Bit Set
	Reference: Section 3.12		Reference: Section 3.12
	INFO-CODE: 12		INFO-CODE: 12
	Purpose: NSEC Missing		Purpose: NSEC Missing
	Reference: Section 3.13		Reference: Section 3.13
	INFO-CODE: 13		INFO-CODE: 13
	Purpose: Cached Error		Purpose: Cached Error
	Reference: Section 3.14		Reference: Section 3.14
	INFO-CODE: 14		INFO-CODE: 14
	Purpose: Not Ready.		Purpose: Not Ready.
	Reference: Section 3.15		Reference: Section 3.15
	INFO-CODE: 15		INFO-CODE: 15
	Purpose: Blocked		Purpose: Blocked
	Reference: Section 3.16		Reference: Section 3.16
	INFO-CODE: 16		INFO-CODE: 16
	Purpose: Censored		Purpose: Censored
	Reference: Section 3.17		Reference: Section 3.17
	INFO-CODE: 17		INFO-CODE: 17
	Purpose: Prohibited		Purpose: Filtered
	Reference: Section 3.18		Reference: Section 3.18
	INFO-CODE: 18		INFO-CODE: 18
	Purpose: Filtered		Purpose: Prohibited
	Reference: Section 3.19		Reference: Section 3.19
	INFO-CODE: 19		INFO-CODE: 19
	Purpose: Stale NXDomain Answer		Purpose: Stale NXDomain Answer
	Reference: Section 3.20		Reference: Section 3.20
	INFO-CODE: 20		INFO-CODE: 20
	Purpose: Lame		Purpose: Not Authoritative
	Reference: Section 3.21		Reference: Section 3.21
	INFO-CODE: 21		INFO-CODE: 21
	Purpose: Deprecated		Purpose: Deprecated
	Reference: Section 3.22		Reference: Section 3.22
	INFO-CODE: 22		INFO-CODE: 22
	Purpose: No Reachable Authority		Purpose: No Reachable Authority
	Reference: Section 3.23		Reference: Section 3.23
	INFO-CODE: 23		INFO-CODE: 23
	Purpose: Network Error		Purpose: Network Error
	Reference: Section 3.24		Reference: Section 3.24
			INFO-CODE: 24
			Purpose: Invalid Data
			Reference: Section 3.25
	5. Security Considerations		5. Security Considerations
	Though DNSSEC continues to be deployed, unfortunately a significant		Though DNSSEC continues to be deployed, unfortunately a significant
	number of clients (~11% according to [GeoffValidation]) that receive		number of clients (~11% according to [GeoffValidation]) that receive
	a SERVFAIL from a validating resolver because of a DNSSEC validaion		a SERVFAIL from a validating resolver because of a DNSSEC validaion
	issue will simply ask the next (potentially non-validating) resolver		issue will simply ask the next (potentially non-validating) resolver
	in their list, and thus don't get any of the protections which DNSSEC		in their list, and thus don't get any of the protections which DNSSEC
	should provide.		should provide.
	This information is unauthenticated information, and an attacker (e.g		This information is unauthenticated information, and an attacker (e.g
	a MITM or malicious recursive server) could insert an extended error		a MITM or malicious recursive server) could insert an extended error
	response into already untrusted data -- ideally clients and resolvers		response into already untrusted data -- ideally clients and resolvers
	would not trust any unauthenticated information, but until we live in		would not trust any unauthenticated information, but until we live in
	an era where all DNS answers are authenticated via DNSSEC or other		an era where all DNS answers are authenticated via DNSSEC or other
	mechanisms [RFC2845] [RFC8094], there are some tradeoffs. As an		mechanisms [RFC2845] [RFC8094], there are some tradeoffs. As an
	example, an attacker who is able to insert the DNSSEC Bogus Extended		example, an attacker who is able to insert the DNSSEC Bogus Extended
	Error into a packet could instead simply reply with a fictitious		Error into a packet could instead simply reply with a fictitious
	address (A or AAAA) record.		address (A or AAAA) record. Note that DNS Response Codes also
			contain no authentication and can be just as easily manipulated.
	6. Acknowledgements		6. Acknowledgements
	The authors wish to thank Joe Abley, Mark Andrews, Vittorio Bertola,		The authors wish to thank Joe Abley, Mark Andrews, Vittorio Bertola,
	Stephane Bortzmeyer, Vladimir Cunat, Ralph Dolmans, Peter DeVries,		Stephane Bortzmeyer, Vladimir Cunat, Ralph Dolmans, Peter DeVries,
	Peter van Dijk, Donald Eastlake, Bob Harold, Paul Hoffman, Geoff		Peter van Dijk, Mats Dufberg, Donald Eastlake, Bob Harold, Paul
	Huston, Shane Kerr, Edward Lewis, Carlos M. Martinez, George		Hoffman, Geoff Huston, Shane Kerr, Edward Lewis, Carlos M. Martinez,
	Michelson, Michael Sheldon, Puneet Sood, Petr Spacek, Ondrej Sury,		George Michelson, Eric Orth, Michael Sheldon, Puneet Sood, Petr
	Loganaden Velvindron, and Paul Vixie. They also vaguely remember		Spacek, Ondrej Sury, John Todd, Loganaden Velvindron, and Paul Vixie.
	discussing this with a number of people over the years, but have		They also vaguely remember discussing this with a number of people
	forgotten who all they were -- if you were one of them, and are not		over the years, but have forgotten who all they were -- if you were
	listed, please let us know and we'll acknowledge you.		one of them, and are not listed, please let us know and we'll
			acknowledge you.
	One author also wants to thank the band "Infected Mushroom" for		One author also wants to thank the band "Infected Mushroom" for
	providing a good background soundtrack (and to see if he can get away		providing a good background soundtrack (and to see if he can get away
	with this in an RFC!) Another author would like to thank the band		with this in an RFC!) Another author would like to thank the band
	"Mushroom Infectors". This was funny at the time we wrote it, but we		"Mushroom Infectors". This was funny at the time we wrote it, but we
	cannot remember why...		cannot remember why...
	7. References		7. References
	7.1. Normative References		7.1. Normative References
			[I-D.ietf-dnsop-serve-stale]
			Lawrence, D., Kumari, W., and P. Sood, "Serving Stale Data
			to Improve DNS Resiliency", draft-ietf-dnsop-serve-
			stale-08 (work in progress), September 2019.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997, <https://www.rfc-		DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
	editor.org/info/rfc2119>.		editor.org/info/rfc2119>.
	[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an		[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
	IANA Considerations Section in RFCs", RFC 2434,		IANA Considerations Section in RFCs", RFC 2434,
	DOI 10.17487/RFC2434, October 1998, <https://www.rfc-		DOI 10.17487/RFC2434, October 1998, <https://www.rfc-
	editor.org/info/rfc2434>.		editor.org/info/rfc2434>.
	[RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)",		[RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)",
	RFC 2671, DOI 10.17487/RFC2671, August 1999,		RFC 2671, DOI 10.17487/RFC2671, August 1999,
	<https://www.rfc-editor.org/info/rfc2671>.		<https://www.rfc-editor.org/info/rfc2671>.
			[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
			Rose, "Protocol Modifications for the DNS Security
			Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005,
			<https://www.rfc-editor.org/info/rfc4035>.
	[RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms		[RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
	for DNS (EDNS(0))", STD 75, RFC 6891,		for DNS (EDNS(0))", STD 75, RFC 6891,
	DOI 10.17487/RFC6891, April 2013, <https://www.rfc-		DOI 10.17487/RFC6891, April 2013, <https://www.rfc-
	editor.org/info/rfc6891>.		editor.org/info/rfc6891>.
	7.2. Informative References		7.2. Informative References
	[GeoffValidation]		[GeoffValidation]
	IANA, "A quick review of DNSSEC Validation in today's		IANA, "A quick review of DNSSEC Validation in today's
	Internet", June 2016, <http://www.potaroo.net/		Internet", June 2016, <http://www.potaroo.net/
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