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Groups > linux.debian.bugs.dist > #763840

Bug#836236: prosody: doesn't try IPv4 when IPv6 fails

From Matthew Wild <mwild1@gmail.com>
Newsgroups linux.debian.bugs.dist
Subject Bug#836236: prosody: doesn't try IPv4 when IPv6 fails
Date 2016-09-01 10:40 +0200
Message-ID <scvHs-78u-29@gated-at.bofh.it> (permalink)
References <sclf4-7DL-7@gated-at.bofh.it> <sclI6-7NG-39@gated-at.bofh.it> <sclRL-86A-7@gated-at.bofh.it> <scmb7-8fs-7@gated-at.bofh.it>
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On 31 August 2016 at 23:25, Cyril Brulebois <kibi@debian.org> wrote:
> So it looks to me like it could be an initial DNS issue (partial and/or
> no resolution depending on the domain) which happened at start-up time,
> and failed/incomplete resolutions weren't attempted again later on.
>
> Would this seem even remotely plausible?

Yes, this is plausible. I've seen this issue before on some servers,
but I haven't been able to track it down to a cause. One theory is
that if you log into a freshly-started server, and you have a lot of
contacts on remote domains, it triggers a burst of DNS requests. DNS
being UDP, which is lossy, some of the DNS requests fail due to packet
loss caused by temporary network congestion.

Whether that theory is plausible I'm not sure - it doesn't seem like
it would be *that* much traffic to deal with. Perhaps there are some
queue sizes or something we could tweak if that is the problem though.

Eventually the failed s2s connections do establish - they will be
retried as soon as you change status for example, or if any of your
remote contacts change status or try to send you a message.

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Thread

Bug#836236: prosody: doesn't try IPv4 when IPv6 fails Cyril Brulebois <kibi@debian.org> - 2016-08-31 23:30 +0200
  Bug#836236: prosody: doesn't try IPv4 when IPv6 fails Matthew Wild <mwild1@gmail.com> - 2016-09-01 00:00 +0200
    Bug#836236: prosody: doesn't try IPv4 when IPv6 fails Cyril Brulebois <kibi@debian.org> - 2016-09-01 00:10 +0200
      Bug#836236: prosody: doesn't try IPv4 when IPv6 fails Cyril Brulebois <kibi@debian.org> - 2016-09-01 00:30 +0200
        Bug#836236: prosody: doesn't try IPv4 when IPv6 fails Matthew Wild <mwild1@gmail.com> - 2016-09-01 10:40 +0200
          Bug#836236: prosody: doesn't try IPv4 when IPv6 fails Cyril Brulebois <kibi@debian.org> - 2016-09-01 17:20 +0200

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