This looks like it might indeed be it! I'll apply it to our internal 1.8.0
packages and give it a shot. Thanks!
-Dustin
On Jul 15, 2023 at 2:42 AM -0500, Otto Moerbeek <o...@drijf.net>, wrote:
> On Fri, Jul 14, 2023 at 03:06:12PM -0500, Dustin Marquess via dnsdist wrote:
>
> > So far we've had instances with dnsdist 1.8.0 having a thread in a tight
> > loop. OS versions seem to vary widely, so I don't believe it's a glibc bug.
> >
> > Config on both is the same plain config:
> >
> > setLocal("127.0.0.1:53", {reusePort=true})
> > addLocal("127.0.0.1:53", {reusePort=true})
> > addLocal("127.0.0.1:53", {reusePort=true})
> > addLocal("127.0.0.1:53", {reusePort=true})
> > addACL('10.0.0.0/8')
> > newServer({address="10.112.104.116", checkType="A", checkClass=DNSClass.IN,
> > checkName="hc.xxx.local", mustResolve=true, checkInterval=30})
> > newServer({address="10.112.106.177", checkType="A", checkClass=DNSClass.IN,
> > checkName="hc.xxx.local", mustResolve=true, checkInterval=30})
> > newServer({address="10.9.41.68", checkType="A", checkClass=DNSClass.IN,
> > checkName="hc.xxx.local", mustResolve=true, checkInterval=30})
> > setServerPolicy(firstAvailable)
> >
> > -- Tuning
> > setRingBuffersSize(1000000, 100)
> > setMaxTCPClientThreads(20)
> >
> > -- Caching
> > -- We should make these tunables configurable
> > pc = newPacketCache(100000, {maxTTL=86400, minTTL=0,
> > temporaryFailureTTL=60, staleTTL=60, dontAge=false})
> > getPool(""):setCache(pc)
> >
> > -- Don't try and hit the internet
> > setSecurityPollSuffix("")
> >
> > [pid 2990] recvfrom(-1, 0x7f3d9c0008c0, 4368, 0, NULL, NULL) = -1 EBADF
> > (Bad file descriptor)
> > [pid 2990] recvfrom(-1, 0x7f3d9c0008c0, 4368, 0, NULL, NULL) = -1 EBADF
> > (Bad file descriptor)
> > [pid 2990] recvfrom(-1, 0x7f3d9c0008c0, 4368, 0, NULL, NULL) = -1 EBADF
> > (Bad file descriptor)
> > [pid 2990] recvfrom(-1, 0x7f3d9c0008c0, 4368, 0, NULL, NULL) = -1 EBADF
> > (Bad file descriptor)
> >
> > In each case, a strace shows a bad recvfrom() call in a tight loop:
> >
> > Obviously -1 is a bad fd! Restarting dnsdist seems to resolve it. The only
> > idea I can come up with is that when dnsdist first starts, it's unable to
> > contact the upstream DNS servers and that somehow causes the issue. When we
> > restart it, it IS able to contact them, and so works fine.
> >
> > Any ideas?
> >
> > Thanks!
> > -Dustin
>
> This is likely https://github.com/PowerDNS/pdns/pull/12726
>
> ATM this is not marked for backporting to 1.8.x. Don't know if that is
> an omission.
>
> -Otto
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