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[Bug 1527902] Re: 3.13.0-71: IPv6 UDP DNS packets are not received


For reproducing just try to use Kopete IM client and try to connect to
some jabber server. Kopete must use IPv6 recursive DNS server for
translating jabber SRV or A records. DNS server address is read from
standard file /etc/resolv.conf.

So if you do not have IPv6 connectivity, you can you start some
recursive (or forward) DNS server on IPv6 localhost and set nameserver
::1 in /etc/resolv.conf. This is quick hack, but should work.

I see that NetworkManager on Ubuntu is already using dnsmasq (as
forwarder), but does not have enabled IPv6 support on localhost. It
automatically add "nameserver" line into /etc/resolv.conf.

To tell dnsmasq to listen also on IPv6 localhost add configuration like:
$ echo listen-address=::1 > /etc/NetworkManager/dnsmasq.d/ipv6
(and reboot)

And set "nameserver ::1" in /etc/resolv.conf (note that NetworkManager
is changing that file when reconnecting...)

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  3.13.0-71: IPv6 UDP DNS packets are not received

Status in linux package in Ubuntu:
  In Progress
Status in linux-lts-trusty package in Ubuntu:
  In Progress

Bug description:
  After upgrading linux kernel from version 3.13.0-68 to 3.13.0-71 then
  Kopete (IM messenger) stopped working, cannot connect to any jabber

  I started debugging this problem and found out that, problem resolve
  when I boot back 3.13.0-68 kernel version (without touching any system
  files or packages). When I boot 3.13.0-71 Kopete always does not

  Next I debugged that problem on 3.13.0-71 is just when
  /etc/resolv.conf contains only IPv6 addresses of DNS servers.

  Problem is comes down to dns resolver (jabber in Kopete has its own
  for SRV records) and syscall recvfrom() (on IPv6 socket) always return
  error -EAGAIN without any data returned. But wireshark see that DNS
  response was recevied.

  So it looks like that after 3.13.0-68 kernel was included some change
  which broke receiving UDP packets via IPv6 socket. IPv4 is OK.

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