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[Tero Marttila <terom@xxxxxxxx>]

The utopic kernel appears to be affected as well. Booting the same
Ubuntu 14.04 machine into the Linux 3.16.0-6-generic #11-Ubuntu kernel
installed from

   https://launchpad.net/ubuntu/+source/linux/3.16.0-6.11/+build/6217368

gives identical symptoms, i.e. dnsmasq-tftp stalls, dmesg reports "IPv6
header not found", stracing dnsmasq shows sendto() giving EPERM, and
unloading ip_vs allows the stalled tftp transfer to continue.

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https://bugs.launchpad.net/bugs/1349768

Title:
  kernel 3.13.0-32 ipvs "IPv6 header not found" related to UDP socket
  sendto() EPERM errors

Status in “linux” package in Ubuntu:
  Confirmed
Status in “linux” source package in Trusty:
  In Progress
Status in “linux” source package in Utopic:
  Confirmed

Bug description:
  I have an Ubuntu 14.04 host that I am using as both a keepalived/ipvs
  loadbalancer and dnsmasq server for pxebooting servers.

  After updating linux-image 3.13.0-29.53 -> 3.13.0-32.57 I noticed that
  dnsmasq-tftp stopped working. pxeboot clients would hang on the
  "Loading ..../linux" TFTP transfer, with the transfer stalling roughly
  ~1000 blocks into the transfer:

  10:30:51.011728 IP 10.1.1.2.43540 > 10.1.12.1.49165: UDP, length 1412
  10:30:51.011924 IP 10.1.12.1.49165 > 10.1.1.2.43540: UDP, length 4
  10:30:51.012012 IP 10.1.1.2.43540 > 10.1.12.1.49165: UDP, length 1412
  10:30:51.012183 IP 10.1.12.1.49165 > 10.1.1.2.43540: UDP, length 4

  stracing dnsmasq I noticed something very odd: sendto() on the
  socket(PF_INET, SOCK_DGRAM, IPPROTO_IP) would suddenly start
  persistently returning EPERM in mid-transfer, even when dnsmasq
  continued to periodically retry:

  select(18, [4 5 6 7 8 9 10 11 12 15 17], [], [], {0, 250000}) = 1 (in [17], left {0, 249834})
  recvfrom(17, "\0\4\3\352", 4096, 0, NULL, NULL) = 4
  lseek(16, 1410816, SEEK_SET) = 1410816
  read(16, "\25\306\345f\2{\r\4)W\276\32\336q\252_\230q\213\341U\354\25\374k7\243\32\221X+\v"..., 1408) = 1408
  sendto(17, "\0\3\3\353\25\306\345f\2{\r\4)W\276\32\336q\252_\230q\213\341U\354\25\374k7\243\32"..., 1412, 0, {sa_family=AF_INET, sin_port=htons(49165), sin_addr=inet_addr("10.1.11.3")}, 16) = 1412
  select(18, [4 5 6 7 8 9 10 11 12 15 17], [], [], {0, 250000}) = 1 (in [17], left {0, 249839})
  recvfrom(17, "\0\4\3\353", 4096, 0, NULL, NULL) = 4
  lseek(16, 1412224, SEEK_SET) = 1412224
  read(16, "*\360 <C\363l\320:\256~\307\236\26P\323\274%\260\362\341&\232\r\243\370\224\277\221\\\307\372"..., 1408) = 1408
  sendto(17, "\0\3\3\354*\360 <C\363l\320:\256~\307\236\26P\323\274%\260\362\341&\232\r\243\370\224\277"..., 1412, 0, {sa_family=AF_INET, sin_port=htons(49165), sin_addr=inet_addr("10.1.11.3")}, 16) = -1 EPERM (Operation not permitted)
  select(18, [4 5 6 7 8 9 10 11 12 15 17], [], [], {0, 250000}) = 0 (Timeout)
  select(18, [4 5 6 7 8 9 10 11 12 15 17], [], [], {0, 250000}) = 0 (Timeout)
  select(18, [4 5 6 7 8 9 10 11 12 15 17], [], [], {0, 250000}) = 0 (Timeout)
  select(18, [4 5 6 7 8 9 10 11 12 15 17], [], [], {0, 250000}) = 0 (Timeout)
  select(18, [4 5 6 7 8 9 10 11 12 15 17], [], [], {0, 250000}) = 0 (Timeout)
  select(18, [4 5 6 7 8 9 10 11 12 15 17], [], [], {0, 250000}) = 0 (Timeout)
  select(18, [4 5 6 7 8 9 10 11 12 15 17], [], [], {0, 250000}) = 0 (Timeout)
  select(18, [4 5 6 7 8 9 10 11 12 15 17], [], [], {0, 250000}) = 0 (Timeout)
  lseek(16, 1412224, SEEK_SET) = 1412224
  read(16, "*\360 <C\363l\320:\256~\307\236\26P\323\274%\260\362\341&\232\r\243\370\224\277\221\\\307\372"..., 1408) = 1408
  sendto(17, "\0\3\3\354*\360 <C\363l\320:\256~\307\236\26P\323\274%\260\362\341&\232\r\243\370\224\277"..., 1412, 0, {sa_family=AF_INET, sin_port=htons(49165), sin_addr=inet_addr("10.1.11.3")}, 16) = -1 EPERM (Operation not permitted)

  This was with all iptables rules unloaded (so no OUTPUT -j DENY) and
  apparmor profiles torn down.

  I also noticed the following dmesgs appearing at roughly similar times
  to the tftp transfers getting stuck (although not coinciding exactly
  with the stall):

  [70325.516724] IPv6 header not found

  The error pointed to ipvs (which I am using on the same host as an IPv4 NAT loadbalancer):
  http://archive.linuxvirtualserver.org/html/lvs-devel/2012-08/msg00018.html
  http://comments.gmane.org/gmane.comp.linux.lvs.devel/3614

  I then tore down the ipvs rules (service keepalived stop) and unloaded
  the modules (rmmod ip_vs_rr ip_vs), and the issue resolved itself -
  the stalled dnsmasq-tftp transfer resumed!

  This seems to be reproducible, i.e. modprobing ip_vs and starting
  keepalived will cause dnsmasq-tftp to stall again, and
  stopping/unloading will resume.

  This seems to happen reproducibly on boot with -32 and -30. This does NOT seem to happen with 3.13.0-29 which I was using up until now.
  --- 
  AlsaDevices:
   total 0
   crw-rw---- 1 root audio 116,  1 Jul 29 13:43 seq
   crw-rw---- 1 root audio 116, 33 Jul 29 13:43 timer
  AplayDevices: Error: [Errno 2] No such file or directory
  ApportVersion: 2.14.1-0ubuntu3.2
  Architecture: amd64
  ArecordDevices: Error: [Errno 2] No such file or directory
  AudioDevicesInUse: Error: command ['fuser', '-v', '/dev/snd/seq', '/dev/snd/timer'] failed with exit code 1:
  CRDA: Error: [Errno 2] No such file or directory
  DistroRelease: Ubuntu 14.04
  HibernationDevice: RESUME=/dev/mapper/catcp2-swap
  InstallationDate: Installed on 2014-06-03 (56 days ago)
  InstallationMedia: Ubuntu-Server 14.04 LTS "Trusty Tahr" - Release amd64 (20140416.2)
  MachineType: Dell Inc. PowerEdge R410
  Package: linux-image-3.13.0-32-generic 3.13.0-32.57
  PackageArchitecture: amd64
  PciMultimedia:
   
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   LANG=C.UTF-8
   SHELL=/bin/bash
  ProcFB:
   
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.13.0-32-generic root=/dev/mapper/hostname-root ro console=ttyS1,115200n8 console=tty0 nomdmonddf nomdmonisw
  ProcVersionSignature: Ubuntu 3.13.0-32.57-generic 3.13.11.4
  RelatedPackageVersions:
   linux-restricted-modules-3.13.0-32-generic N/A
   linux-backports-modules-3.13.0-32-generic  N/A
   linux-firmware                             1.127.5
  RfKill: Error: [Errno 2] No such file or directory
  Tags:  trusty
  Uname: Linux 3.13.0-32-generic x86_64
  UpgradeStatus: No upgrade log present (probably fresh install)
  UserGroups:
   
  _MarkForUpload: True
  dmi.bios.date: 07/30/2013
  dmi.bios.vendor: Dell Inc.
  dmi.bios.version: 1.12.0
  dmi.board.name: 01V648
  dmi.board.vendor: Dell Inc.
  dmi.board.version: A03
  dmi.chassis.type: 23
  dmi.chassis.vendor: Dell Inc.
  dmi.modalias: dmi:bvnDellInc.:bvr1.12.0:bd07/30/2013:svnDellInc.:pnPowerEdgeR410:pvr:rvnDellInc.:rn01V648:rvrA03:cvnDellInc.:ct23:cvr:
  dmi.product.name: PowerEdge R410
  dmi.sys.vendor: Dell Inc.

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