[dhcwg] Source address in Vista DHCP packets.

I've just had some tcpdump output sent to me by someone who is having
problems getting Windows Vista to work with dnsmasq. Vista is emitting
DHCP packets which look like this. There's not enough information to be
sure if they are DISCOVER or REQUEST packets (and what flavour of
REQUEST), but my guess is that they are DISCOVER.

Client Ethernet Address: 00:17:c4:10:9a:3c [|bootp]
17:36:50.527538 IP (tos 0x0, ttl 128, id 442, offset 0, flags [none],
length: 328) 169.254.194.239.68 > 255.255.255.255.67: BOOTP/DHCP,
Request from 00:17:c4:10:9a:3c, length: 300, xid:0xe014ef8f, secs:768,
flags: [Broadcast] (0x8000)

Note that the source address in the IP header is 169.254.194.239 which
is in the APIPA range. I suspect that this is the cause of the problem,
(a badly configured firewall to dumping these packets before they get to
the DHCP server because of their source address), but that is not point
of this post. I think this behaviour is a standards violation.

From RFC 2131:
   DHCP messages broadcast by a client prior to that client obtaining
   its IP address must have the source address field in the IP header
   set to 0.

It looks like the Microsoft DHCP client violates this if DHCP has timed
out at some point and an APIPA address has been selected. Further
attempts at DHCP then have a wrong source address.

So: questions.

1) Has anyone else seen this? Can you clarify the circumstances under
which it occurs?

2) Is this really a standards violation?

3) If it is, does anyone have experience of the best way to report it as
bug to Microsoft?

Cheers,

Simon.

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