[Bug 2032824] Re: Veth pairs fail activation on Jammy

[Lukas Märdian]

The changes landed in upstream NetworkManager between 1.39.10-dev and
1.41.8-dev all of which is included in Noble.

** Changed in: network-manager (Ubuntu)
       Status: Triaged => Fix Released

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Title:
  Veth pairs fail activation on Jammy

Status in network-manager package in Ubuntu:
  Fix Released
Status in network-manager source package in Jammy:
  Triaged

Bug description:
  Network Manager 1.36 has a bug that prevents it to activate veth
  pairs. The problem was found in the Netplan's CI with the new support
  for veths in Netplan (because we run the tests on Jammy).

  How to reproduce the problem:

  1) Launch a Jammy VM and install network-manager

  lxc launch  ubuntu:jammy jammy --vm
  lxc shell jammy
  apt -y install network-manager

  2) Set the default Netplan's renderer to NetworkManager so NM can
  manage interfaces (it will make Netplan create the file
  /var/run/NetworkManager/conf.d/10-globally-managed-devices.conf)

  netplan set --origin-hint=50-cloud-init network.renderer=NetworkManager
  netplan apply

  3) Create the veth pair

  nmcli con add type veth ifname veth0 peer veth1 ipv4.method disabled ipv6.method disabled
  nmcli con add type veth ifname veth1 peer veth0 ipv4.method disabled ipv6.method disabled

  4) Reboot

  5) Check with "nmcli con show" that the new connections were not
  activated, even though both interfaces were created in the system.
  Also, check the systemd journal and you should see this error message:

  <error> [1692805758.9025] manager: (veth-veth0) couldn't create the
  device: Failed to create veth interface 'veth0' for 'veth-veth0':
  exists

  
  Try the very same steps on Lunar and you'll see that the connections will be activated just fine.

  
  This issue appears to be fixed by this commit https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/commit/4655b7c308461ae1f86d592ea6d45e00a2820423

  I created a PPA with the fix here
  https://launchpad.net/~danilogondolfo/+archive/ubuntu/network-manager

  If you run the same steps again on Jammy with this PPA you'll see it
  fixes this issue. In fact, Netplan's integration tests will work on
  Jammy using the PPA.

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