[Bug 1940860] Re: Mellanox NIC interface names change between 5.4 and 5.8

[dann frazier]

@ddstreet I agree that systemd is behaving as designed. But I'm not sure
what the proper fix for this is, and therefore where changes would be
required.

My initial thought is that perhaps subiquity installs should do what
MAAS installs do and configure netplan to always use the install-time
names. I've added a subiquity for that consideration. Note that if that
is the chosen solution, we should be careful to ignore NICs with
randomly generated MACs (see bug 1936972).

** Also affects: subiquity
   Importance: Undecided
       Status: New

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to systemd in Ubuntu.
https://bugs.launchpad.net/bugs/1940860

Title:
  Mellanox NIC interface names change between 5.4 and 5.8

Status in subiquity:
  New
Status in linux package in Ubuntu:
  Confirmed
Status in systemd package in Ubuntu:
  New

Bug description:
  I noticed on a couple of systems that my network interface names
  change when upgrading from the focal LTS (5.4) kernel to the focal HWE
  (both 5.8 & 5.11) kernels. Both systems have Mellanox Connect-X 5
  NICs.

  dannf at bizzy:~$ uname -a
  Linux bizzy 5.4.0-81-generic #91-Ubuntu SMP Thu Jul 15 19:10:30 UTC 2021 aarch64 aarch64 aarch64 GNU/Linux
  dannf at bizzy:~$ ls /sys/class/net
  enp1s0f0  enp1s0f1  enx3e8734bc294f  lo

  dannf at bizzy:~$ uname -a
  Linux bizzy 5.8.0-63-generic #71~20.04.1-Ubuntu SMP Thu Jul 15 17:46:44 UTC 2021 aarch64 aarch64 aarch64 GNU/Linux
  dannf at bizzy:~$ ls /sys/class/net
  enp1s0f0np0  enp1s0f1np1  enx3e8734bc294f  lo

  dannf at bizzy:~$ uname -a
  Linux bizzy 5.11.0-27-generic #29~20.04.1-Ubuntu SMP Wed Aug 11 15:58:08 UTC 2021 aarch64 aarch64 aarch64 GNU/Linux
  dannf at bizzy:~$ ls /sys/class/net
  enp1s0f0np0  enp1s0f1np1  enx3e8734bc294f  lo

  I bisected this down to a kernel change:
  # first bad commit: [c6acd629eec754a9679f922d51f90e44c769b80c] net/mlx5e: Add support for devlink-port in non-representors mode

  The impact is that your network can fail to come up after
  transitioning from the LTS kernel to the HWE kernel. Now, this isn't a
  huge problem for MAAS installs because MAAS configures netplan to
  always use the same names as were used at commissioning. It does
  impact subiquity based installs however, which do not.

To manage notifications about this bug go to:
https://bugs.launchpad.net/subiquity/+bug/1940860/+subscriptions