issue with SLAAC and deprecated IPv6 addresses on recent windows versions

[Christian Hahn]

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Hi list,

In a lab I did some testing with SLAAC and different OSs and recently stumbled
upon an issue on recent windows versions. It is only present on Vista and 7, not
on XP. But let me tell you the story ...

I deprecated an formerly (by RA) announced IPv6 prefix (let's say
2001:db8:1:2::/64) by  sending some RAs with PreferredLifetime=0 and
ValidLifetime=7200 and thereafter stopped sending RAs.
All windows machines behaved correctly and deprecated the addresses derived from
that prefix. Outgoing connections no longer used it as source address, but
incoming packets (like icmpv6 echo request) where answered due to the valid
"ValidLifetime" value. ;)

Then in the second step (after some minutes of testing) I tried to re-activate
the _same_ prefix (2001:db8:1:2::/64) by sending periodic RAs with
PreferredLifetime=86400 and ValidLifetime=43200. And here the weird things
began. On Vista and 7 the values for the "Lifetimes" where updated to the new
ones derived from the RA, but the prefix status didn't change. It still was
stuck in status "deprecated". Hence the still valid IPv6 addresses from that
prefix (2001:db8:1:2::/64) wasn't used as source addresses for new connections,
only old connections used it and incoming packets where answered.

On XP it was different. The prefix came back to life, changed to status
"preferred" and the system again used it's 2001:db8:1:2::/64 IPv6 addresses as
source address for new connections.

To proof it I replicated the test, and restarted all machines beforehand. But
the result didn't change, hence it seems it is "stable" behavior.

I assume it's not the proper behavior, but found no clue in RFC4862 (SLAAC)
where I was looking for allowed status changes or similar.
Has anybody seen a similar behavior or made similar tests with different results?

BTW. I used radvd 1.1 on Ubuntu 9.04 on the router side.

cheers,
Christian
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