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


I am able to perform dns lookups on a P+T box with -74 (and the OR has
separatly confirmed -74 as affected), so this appears to not be

mru@grovel-x-p64p5:~$ cat /proc/version_signature 
Ubuntu 3.13.0-74.118~precise1-generic 3.13.11-ckt30

mru@grovel-x-p64p5:~$ dig aaaa www.google.com @2001:4860:4860::8888

; <<>> DiG 9.8.1-P1 <<>> aaaa www.google.com @2001:4860:4860::8888
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 33031
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;www.google.com.                        IN      AAAA

www.google.com.         299     IN      AAAA    2a00:1450:4009:811::2004

;; Query time: 39 msec
;; SERVER: 2001:4860:4860::8888#53(2001:4860:4860::8888)
;; WHEN: Wed Dec 23 19:17:07 2015
;; MSG SIZE  rcvd: 60

mru@grovel-x-p64p5:~$ sudo tcpdump -n host 2001:4860:4860::8888                                
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
19:19:51.930966 IP6 2001:470:6973:2:18f8:278f:cd6d:654e.52306 > 2001:4860:4860::8888.53: 55720+ AAAA? www.google.com. (32)
19:19:51.971448 IP6 2001:4860:4860::8888.53 > 2001:470:6973:2:18f8:278f:cd6d:654e.52306: 55720 1/0/0 AAAA 2a00:1450:4009:811::2004 (60)

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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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