[Bug 2032824] [NEW] Veth pairs fail activation on Jammy

[Launchpad Bug Tracker]

You have been subscribed to a public bug by Lukas Märdian (slyon):

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.

** Affects: network-manager (Ubuntu)
     Importance: Low
         Status: Triaged

** Affects: network-manager (Ubuntu Jammy)
     Importance: Low
         Status: Triaged


** Tags: foundations-todo fr-8841
-- 
Veth pairs fail activation on Jammy
https://bugs.launchpad.net/bugs/2032824
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