Re: Resolver not always resolving hostnames

On Sun, 22 Oct 2006 11:58:12 +0200
"Simon L. Nielsen" <simon_at_FreeBSD.org> wrote:

> Hey,
> 
> I think something odd is going on in the resolver.  It seems like it
> doesn't resolve hostnames some of the time.  It's not really easily
> reproducible, but I have seen it happen several times with cvsup where
> it can't resolve the cvsup server.  If I re-run cvsup it works fine.
> 
> I see it on recent -CURRNET's (server running cvsup below is October
> 12, system running host(1) is October 15).
> 
> The cvsup log:
> 
> CVSup update begins at 2006-10-18 17:29:00
> Updating from cvsup3.dk.freebsd.org
> Name lookup failure for "cvsup3.dk.freebsd.org": Host name lookup
> failed Updating local ncvs
> CVSup update ends at 2006-10-18 17:29:01
> 
> I also seen odd things happen with host(1).  These two commands were
> run right after each other.  I don't know if it's related, but I
> suspect it is.
> 
> $ host cvsup3.dk.freebsd.org
> cvsup3.dk.freebsd.org is an alias for mirror03.inet.tele.dk.
> cvsup3.dk.freebsd.org is an alias for mirror03.inet.tele.dk.
> $ host cvsup3.dk.freebsd.org
> cvsup3.dk.freebsd.org is an alias for mirror03.inet.tele.dk.
> mirror03.inet.tele.dk has address 195.41.53.219
> cvsup3.dk.freebsd.org is an alias for mirror03.inet.tele.dk.
> cvsup3.dk.freebsd.org is an alias for mirror03.inet.tele.dk.
> 
> I only have one name-server in resolv.conf, so the problem isn't due
> to hitting different caching name-servers.
> 
> Initially I thought it was a local problem for me, but joel_at_ has seen
> the same on RELENG_6 (from July 8), and xride_at_ has seen the
> same/similar with csup where his workaround was to ping the cvsup
> server before running csup.
> 
> So, has anyone seen anything similar?  Since I can't reproduce the
> issue at will I don't really know where to look for what's going on,
> and of course it could be DNS issue...

Seen the same, I believe it started sometime around 21 Jun in RELEND_6.
At the time I believed it was due to switching to pf on that machine,
but I saw it on other machines w/o pf, all running 6-STABLE, since.

It's like the resolver it is giving up to early, if after the "Name
lookup failure ..." message I hit Ctrl+C and run it again immediately
it resolves OK.


-- 
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