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

[Chris J Arges]

Public bug reported:

* 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.

** Affects: ifupdown (Ubuntu)
     Importance: High
         Status: New

** Affects: ifupdown (Debian)
     Importance: Unknown
         Status: Unknown

** Bug watch added: Debian Bug tracker #722496
   http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=722496

** Also affects: ifupdown (Debian) via
   http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=722496
   Importance: Unknown
       Status: Unknown

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https://bugs.launchpad.net/bugs/1224007

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

Status in “ifupdown” package in Ubuntu:
  New
Status in “ifupdown” package in Debian:
  Unknown

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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