[Bug 1727301] Re: 229-4ubuntu20 added ARP option breaks existing bonding interfaces

[Andy Whitcroft]

Hello Markus, or anyone else affected,

Accepted systemd into xenial-proposed. The package will build now and be
available at https://launchpad.net/ubuntu/+source/systemd/229-4ubuntu21
in a few hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested and change the tag from
verification-needed-xenial to verification-done-xenial. If it does not
fix the bug for you, please add a comment stating that, and change the
tag to verification-failed-xenial. In either case, details of your
testing will help us make a better decision.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance!

** Changed in: systemd (Ubuntu Xenial)
       Status: In Progress => Fix Committed

** Tags added: verification-needed verification-needed-xenial

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https://bugs.launchpad.net/bugs/1727301

Title:
  229-4ubuntu20 added ARP option breaks existing bonding interfaces

Status in systemd:
  Fix Released
Status in systemd package in Ubuntu:
  Invalid
Status in systemd source package in Xenial:
  Fix Committed
Status in systemd source package in Zesty:
  Invalid
Status in systemd source package in Artful:
  Invalid
Status in systemd source package in Bionic:
  Invalid

Bug description:
  [Impact]

   * Setting [Link] MTUBytes= in .network file has a side-effect of
  overflowing and setting NOARP flag. This is not intended behaviour /
  regression.

   * Trying to fix above by setting ARP=on fails to work as tristate is
  incorrectly acted upon by unconditionally adding NOARP flag

   * This is a regression in -updates.

  [Test Case]

   * Configure an ethernet device with a .network file alone
   * e.g. Match by mac address and perform DHCP
   * Add [Link] section to the .network file which changes MTUBytes
   * Device brought up using this configuration should not have NOAPR flag in the output of iproute link output

   * Further add ARP=off to that .network file, the link should have NOARP flag
   * Further add ARP=on to that .network file, the link should not have NOARP flag

  A test script is attached, that given an interface can abuse it to
  validate all of the above.

  [Regression Potential]

   * These are upstream fixes for ARP= key that are part of zesty and up

  [Other Info]

   * Upstream fixes
  https://github.com/systemd/systemd/commit/b8b40317d0355bc70bb23a6240a36f3630c4952b.patch
  https://github.com/systemd/systemd/commit/1ed1f50f8277df07918e13cba3331a114eaa6fe3.patch

   * Original bug report

  this breaks existing configurations with bonding on upgrading from
  229-4ubuntu19 to 229-4ubuntu20 on xenial

  as bond interfaces are now by default configured without ARP. Hence
  you suddenly lose network connectivity on upgrade. Very bad for a SRU.

  Plus adding "ARP=yes" to the Link section of a .network file does not
  work.

  Before this update, bond interfaces (specifically 802.3ad) were
  defaulting to ARP enabled. After the upgrade, they are created with
  NOARP set on the link.

  pre-upgrade:

  eth0: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP>
  eth1: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP>
  bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP>

  post-upgrade:
  eth0: <BROADCAST,MULTICAST,NOARP,SLAVE,UP,LOWER_UP>
  eth1: <BROADCAST,MULTICAST,NOARP,SLAVE,UP,LOWER_UP>
  bond0: <BROADCAST,MULTICAST,NOARP,MASTER,UP,LOWER_UP>

  Linux cnode11 4.4.0-97-generic #120-Ubuntu SMP Tue Sep 19 17:28:18 UTC
  2017 x86_64 x86_64 x86_64 GNU/Linux

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