Re: Problems with OpenBSD dhclient

> Date: Fri, 15 Jul 2005 08:23:18 -0700
> From: Sam Leffler <sam_at_errno.com>
> 
> Randy Bush wrote:
> >>>More serious is that I can't roam. When I move between APs, dhclient
> >>>exits and I need to manually re-start it. I lose my SSH sessions. Ugh!
> >>
> >>This should not be happening; dhclient should get a disassociate event, 
> >>drop the lease, then get an associate when you join the new ap and 
> >>immediately grab a new lease.
> > 
> > 
> > aiii!  this was merely a layer-2 re-association, no change at layer-3.
> 
> I mis-spoke; dhclient trys to re-acquire the current lease.  This is 
> exactly what happened before except it should now happen _immediately_ 
> on being notified of a re-association to the same ap or an association 
> to a new ap.  Actually I could check for a re-association and not 
> re-aquire the lease to reduce the overhead but regardless this should be 
> ok (so far as I understand the protocols).
> 
> The previous code polled for these events.  This made it prone to 
> missing fast re-associations (instead falling back to various timeouts) 
> and slow to respond when roaming.  The new code had been working 
> correctly; something has clearly changed and I'll fix it asap.

I'm in Vancouver at a conference and my dhclient has been dying every
few minutes. The room has 4 APs and I suspect the association is moving
between them periodically. That is just a guess, though.

In any case, several times an hour my IP address changes to 0.0.0.0 and
then disappears completely. I still see the NIC associated with the same
SSID and the signal quality is consistently excellent. Executing
'dhclient wi0' gets my connection back with the same IP address, so my
SSH session survive as long as I restart the client fairly promptly when
it goes away, but I have to watch closely. I'm now running 80211watch
and I only see:
Mon Jul 18 12:11:29 RTM_IEEE80211: disassociate
Mon Jul 18 12:12:17 RTM_IEEE80211: disassociate
Mon Jul 18 12:49:17 RTM_IEEE80211: disassociate
Mon Jul 18 12:49:52 RTM_IEEE80211: disassociate

These are interesting in that the first message occurs at some unknown
time. The second seems to occur when dhclient is re-started. I don't
understand why I never see an associate or reassociate event. Seems odd.

In any case, this is a very annoying problem and I'd be happy th help as
much as I can, but I'm trying to keep involved with the program at the
same time.
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman_at_es.net			Phone: +1 510 486-8634