[Bug 1630191] [NEW] MTU settings not always applied after reboot

[Dr. Jens Rosenboom]

Public bug reported:

On a node with two 10G interfaces, we configure a bond interface from
these two interfaces and then a vlan interface on top of it. The MTU of
these interfaces shall be set to be 1550 instead of the default 1500, so
we have these settings in /etc/network/interfaces.d:

root at controller-node13:~# cat /etc/network/interfaces.d/xge0
auto xge0
iface xge0 inet manual
  bond-master xiondata


root at controller-node13:~# cat /etc/network/interfaces.d/xge1
auto xge1
iface xge1 inet manual
  bond-master xiondata


root at controller-node13:~# cat /etc/network/interfaces.d/xiondata
auto xiondata
iface xiondata inet manual
  bond-slaves xge0 xge1
  bond-miimon 100
  bond-lacp-rate 1
  bond-mode 4
  mtu 1550


root at controller-node13:~# cat /etc/network/interfaces.d/xiondata.200
auto xiondata.200
iface xiondata.200 inet static
  address 10.80.1.13/24
  vlan_raw_device xiondata
  mtu 1550

After a reboot, the correct MTU is applied to the vlan interface only
50% of the time, on the other attempts, it stays at 1500, leading to
broken connectivity. If I restart the interfaces manually, by doing
"ifdown xiondata; ifup -a" the MTU settings seem to be applied correctly
every time.

root at controller-node13:~# apt policy ifupdown
ifupdown:
  Installed: 0.8.10ubuntu1
  Candidate: 0.8.10ubuntu1
  Version table:
 *** 0.8.10ubuntu1 500
        500 http://eu.archive.ubuntu.com/ubuntu xenial/main amd64 Packages
        100 /var/lib/dpkg/status

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ifupdown 0.8.10ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-38.57-generic 4.4.19
Uname: Linux 4.4.0-38-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
Date: Tue Oct  4 09:44:40 2016
ProcEnviron:
 LANGUAGE=en_US:
 TERM=screen
 PATH=(custom, no user)
 LANG=en_US.utf8
 SHELL=/bin/bash
SourcePackage: ifupdown
UpgradeStatus: No upgrade log present (probably fresh install)

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


** Tags: amd64 apport-bug third-party-packages xenial

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https://bugs.launchpad.net/bugs/1630191

Title:
  MTU settings not always applied after reboot

Status in ifupdown package in Ubuntu:
  New

Bug description:
  On a node with two 10G interfaces, we configure a bond interface from
  these two interfaces and then a vlan interface on top of it. The MTU
  of these interfaces shall be set to be 1550 instead of the default
  1500, so we have these settings in /etc/network/interfaces.d:

  root at controller-node13:~# cat /etc/network/interfaces.d/xge0
  auto xge0
  iface xge0 inet manual
    bond-master xiondata

  
  root at controller-node13:~# cat /etc/network/interfaces.d/xge1
  auto xge1
  iface xge1 inet manual
    bond-master xiondata

  
  root at controller-node13:~# cat /etc/network/interfaces.d/xiondata
  auto xiondata
  iface xiondata inet manual
    bond-slaves xge0 xge1
    bond-miimon 100
    bond-lacp-rate 1
    bond-mode 4
    mtu 1550

  
  root at controller-node13:~# cat /etc/network/interfaces.d/xiondata.200
  auto xiondata.200
  iface xiondata.200 inet static
    address 10.80.1.13/24
    vlan_raw_device xiondata
    mtu 1550

  After a reboot, the correct MTU is applied to the vlan interface only
  50% of the time, on the other attempts, it stays at 1500, leading to
  broken connectivity. If I restart the interfaces manually, by doing
  "ifdown xiondata; ifup -a" the MTU settings seem to be applied
  correctly every time.

  root at controller-node13:~# apt policy ifupdown
  ifupdown:
    Installed: 0.8.10ubuntu1
    Candidate: 0.8.10ubuntu1
    Version table:
   *** 0.8.10ubuntu1 500
          500 http://eu.archive.ubuntu.com/ubuntu xenial/main amd64 Packages
          100 /var/lib/dpkg/status

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: ifupdown 0.8.10ubuntu1
  ProcVersionSignature: Ubuntu 4.4.0-38.57-generic 4.4.19
  Uname: Linux 4.4.0-38-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2.1
  Architecture: amd64
  Date: Tue Oct  4 09:44:40 2016
  ProcEnviron:
   LANGUAGE=en_US:
   TERM=screen
   PATH=(custom, no user)
   LANG=en_US.utf8
   SHELL=/bin/bash
  SourcePackage: ifupdown
  UpgradeStatus: No upgrade log present (probably fresh install)

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