What's an xid Mismatch?

David W. Hankins dhankins at isc.org
Tue Dec 15 20:27:29 UTC 2009


On Tue, Dec 15, 2009 at 09:23:03AM -0600, Martin McCormick wrote:
> Dec 15 08:22:40 dh1 dhcpd: bind update on
> 139.78.118.164 got ack from stw: xid mismatch.  

It's cosmetic, a log line I put in because I wasn't sure how safe it
was and I wanted to see how often it fires (and if it shows up while
something else is broken), but since then we've seen it's just regular
operation.  Unfortunately we've never gotten around to removing the
log line.


There was a bug basically where the server sends two BNDUPD's and
the far side replies with a BNDACK; the server assumes the later
BNDUPD was acknowledged (which isn't the case).  The fix was to make
the server check the transaction ID on the update to ensure it
stores to database the acknowledgement of the most recent change to
the state object.

So that's the log line you're seeing, the transaction ID is older so
it's a mismatch and gets rejected.

-- 
David W. Hankins	BIND 10 needs more DHCP voices.
Software Engineer		There just aren't enough in our heads.
Internet Systems Consortium, Inc.		http://bind10.isc.org/
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