[Bug 1695089] Re: Network Interface names differ between BIOS / UEFI

[Dimitri John Ledkov]

To further troubleshoot this, it would be interesting to see the output
of what udevadm thinks about these interfaces:

E.g. output of:
$ udevadm info -p /sys/class/net/eth0

and

$ udevadm info -p /sys/class/net/enp0s3

For the BIOS / UEFI case. Note that changing the boot type from bios to
uefi on the fly is not that well support, as different sets of packages
are installed / expected to be available by BIOS vs UEFI installations.

In general, udevd has been disabling persisten interface naming for the
virtual machines due to instability of those interfaces. But it is
interesting that "stable" names are picked for the UEFI case.

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Title:
  Network Interface names differ between BIOS / UEFI

Status in systemd package in Ubuntu:
  New

Bug description:
  Out of a discussion (with Stuart Langridge) about SystemD's new
  interface naming convention I discovered the following inconsistency
  in device naming on a BIOS vs a UEFI system...

  Using QEmu, set to act as a "440FX BIOS" system, and booting up the
  Ubuntu MATE 16.04.2 LTS ISO I get the following output from "ifconfig"
  ...

  eth0      Link encap:Ethernet  HWaddr CA:FE:15:60:0D:70
            inet addr:192.168.0.105  Bcast:192.168.0.1  Mask:255.255.255.0
            inet6 addr: fe80::b19a:de94:6e2c:37b7/64 Scope:Link
            UP BROADCAST RUNNING MULTICAST  MTU:9100  Metric:1
            RX packets:54071 errors:0 dropped:0 overruns:0 frame:0
            TX packets:48515 errors:0 dropped:0 overruns:0 carrier:0
            collisions:0 txqueuelen:1000
            RX bytes:22009423 (20.9 MiB)  TX bytes:25690847 (24.5 MiB)
            Interrupt:16

  Doing the same thing again but with QEmu being set to act as a "Q35
  UEFI" system (using the OVMF firmware) "ifconfig" gives me ...

  enp0s3    Link encap:Ethernet  HWaddr CA:FE:15:60:0D:70
            inet addr:192.168.0.105  Bcast:192.168.0.1  Mask:255.255.255.0
            inet6 addr: fe80::b19a:de94:6e2c:37b7/64 Scope:Link
            UP BROADCAST RUNNING MULTICAST  MTU:9100  Metric:1
            RX packets:27003 errors:0 dropped:0 overruns:0 frame:0
            TX packets:16171 errors:0 dropped:0 overruns:0 carrier:0
            collisions:0 txqueuelen:1000
            RX bytes:11000712 (10.2 MiB)  TX bytes:8563615 (8.1 MiB)
            Interrupt:16

  NOTE: The same is true on my desktop system (UEFI capable), the
  network interface is "enp0s5" not "eth0".

  The later one would be more like what I would expect as SystemD's
  documentation goes to great lengths to try and explain the new naming
  convention for network interfaces.

  This inconsistency could actually lead to further problems down the
  road with other packages ... for example Samba. The default example
  config reads "bind interfaces = 127.0.0.0/8 eth0" (commented out
  though) where "eth0" is not really a good example default because with
  SystemD it no longer exists (at least on a UEFI system - and I had
  that issue with several friends already where I told them "uncomment
  'bind interfaces'" to have samba only bind/listen to the desired
  interfaces ... and then it not working because there's no "eth0"). It
  might be better to determine and append the lan/subnet post-install
  (i.e. 192.168.0.0/24) or settle on a uniform device naming convention
  for the network interfaces.

  The problem should be reproducible by simply booting a installation
  ISO on a BIOS and UEFI system (or accordingly configured VM).

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