Bug#953019: udev: unexpected network interface name changes on upgrade from stretch

[Sergio Gelato]

* Michael Biebl [2020-03-03 14:34:37 +0100]:
> > stretch# udevadm test-builtin net_id /sys/class/net/enp94s0f0
> 
> > ID_NET_NAME_PATH=enp94s0f0
> 
> ...
> 
> > buster# udevadm test-builtin net_id /sys/class/net/ens1f0np0 
> 
> > ID_NET_NAME_PATH=enp94s0f0np0
> > ID_NET_NAME_SLOT=ens1f0np0
> 
> 
> Are you using the same kernel?

I've run "udevadm test-builtin net_id /sys/class/net/enp94s0f0" after
"apt-get dist-upgrade" and before rebooting into the new kernel and
seen the new values of ID_NET_NAME_PATH and ID_NET_NAME_SLOT.
(I have several servers with this hardware configuration. I would not
have known to check this the first time; this is an observation from
the second upgrade.)

> Do you get different names if you boot
> your buster system with the stretch kernel?

That I haven't tried yet. I have two more servers of this type to upgrade.
For a quick test, I've now upgraded systemd from stretch-backports…

# apt-get install --only-upgrade -t stretch-backports udev
[...]
The following additional packages will be installed:
  libpam-systemd libsystemd0 libsystemd0:i386 libudev1 systemd
Suggested packages:
  systemd-container
The following packages will be upgraded:
  libpam-systemd libsystemd0 libsystemd0:i386 libudev1 systemd udev
6 upgraded, 0 newly installed, 0 to remove and 193 not upgraded.
[...]
# udevadm test-builtin net_id /sys/class/net/enp94s0f0
Load module index
Parsed configuration file /lib/systemd/network/99-default.link
Created link configuration context.
Using default interface naming scheme 'v240'.
ID_NET_NAMING_SCHEME=v240
ID_NET_NAME_MAC=enxd09466xxxxxx
ID_OUI_FROM_DATABASE=Dell Inc.
ID_NET_NAME_PATH=enp94s0f0
ID_NET_NAME_SLOT=ens1f0
Unload module index
Unloaded link configuration context.
# reboot

After the reboot into kernel 4.9.210-1, the new interface name is ens1f0. 
So the switch to the slot-based name follows the systemd upgrade, while
the np0 suffix seems kernel-related.