[Bug 1224007] Re: mtu not always set properly on bond/vlan interface

[Dan Streetman]

** Patch added: "lp1224007-xenial.debdiff"
   https://bugs.launchpad.net/debian/+source/vlan/+bug/1224007/+attachment/4750478/+files/lp1224007-xenial.debdiff

** Patch removed: "debdiffv2 for yakkety vlan"
   https://bugs.launchpad.net/debian/+source/vlan/+bug/1224007/+attachment/4739534/+files/lp1224007-yakkety-v2.debdiff

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Title:
  mtu not always set properly on bond/vlan interface

Status in vlan package in Ubuntu:
  New
Status in vlan package in Debian:
  New

Bug description:
  * Description

  When configuring a network with bonding+vlan and setting the MTU,
  occasionally the MTU doesn't get set properly on the vlan interface.

  In addition if one checks /var/log/upstart/networking.log whenever there is a failure the following message is printed:
  SIOCSIFMTU: Numerical result out of range

  I've tested the latest ifupdown package (0.7.44) and the problem still exists.
  Multi/single CPU settings both exhibit the issue.

  * Versions
  This affects latest ifupdown and ubuntu p/q/r/s.

  * Test Case

  # Create a p/q/r/s server vm with two network interfaces
  # This is reproducible on real hardware as well

  # Install the following
  sudo apt-get install vlan ifenslave-2.6 bridge-utils
  sudo modprobe bonding 8021q

  # Edit the interfaces file
  /etc/networking/interfaces:

  auto bond0
  iface bond0 inet manual
    bond-mode 802.3ad
    bond-miimon 100
    bond-lacp-rate 1
    bond-slaves eth0 eth1
    post-up ifconfig bond0 mtu 9000

  auto eth0
  iface eth0 inet manual
    bond-master bond0
    post-up ifconfig eth0 mtu 9000

  auto eth1
  iface eth1 inet manual
    bond-master bond0
    post-up ifconfig eth1 mtu 9000

  auto bond0.123
  iface bond0.123 inet static
    address 192.168.122.68
    netmask 255.255.255.0
    gateway 192.168.122.1
    post-up ifconfig bond0.123 mtu 9000

  # edit rc.local (or another startup script) so we reboot until we hit the error
  /etc/rc.local:

  DEVS="eth0 eth1 bond0 bond0.123"
  for d in $DEVS; do
          mtu=$(cat /sys/class/net/$d/mtu)
          if [ $mtu != 9000 ]; then
                  echo "FAIL"
                  exit 1
          fi
  done

  reboot
  exit 0

  # Now reboot the machine, within 10m or so you should be at the login prompt
  # if you ifconfig | grep MTU you will see some of our interfaces did not get 
  # the MTU properly set and the test failed.
  # Essentially we want to ensure that all MTU's (except lo) were set to 9000

  * Workaround

  Change the bond0.123 post-up command to:
    post-up sleep 2 && ifconfig bond0.123 mtu 9000

  Now when rebooting the interfaces will all be brought up with the
  proper MTU.

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