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

[Dan Streetman]

systemd/udevd appears to be working exactly as advertised, using the
phys_port_name when it's provided by the device's kernel driver; should
this be marked invalid for systemd, or is there actually some change
needed there?

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Title:
  Mellanox NIC interface names change between 5.4 and 5.8

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.

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