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


I think that unlike the bug title and description suggest, this bug is
not limited to IPv6. I am having the same problem with FreeRADIUS when
RADIUS packets are received over IPv4. This problem is fixed by the
Kernel from trusty-proposed, too.

Actually, this problem looks a lot like a regression that already
appeared in 3.13.0-66 and was fixed in 3.13.0-67 (see bug #1510213 which
turned out to be the same problem as tracked in #1508510). So maybe,
some measures should be taken to ensure that this regression does not
make it into a released kernel again but it is detected during QA.

A side note regading the problem with FreeRADIUS: I only had this
problem on a multi-core multi-socket machine. On a multi-core single-
socket machine, it did not appear, but this might just have been a

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  3.13.0-71: IPv6 UDP DNS packets are not received

Status in linux package in Ubuntu:
  Fix Released
Status in linux-lts-trusty package in Ubuntu:
Status in linux-lts-utopic package in Ubuntu:
  Fix Committed
Status in linux-lts-trusty source package in Precise:
  In Progress
Status in linux source package in Trusty:
  Fix Committed
Status in linux source package in Vivid:
  Fix Released
Status in linux source package in Wily:
  Fix Released
Status in linux source package in Xenial:
  Fix Released

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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