[Bug 1945584] [NEW] netplan regression 19.10 to 20.04 LTS

[Brandon McDonnell]

Public bug reported:

In Ubuntu 19.10, I have a netplan config like so: 2x gigabit and 1x 10g
interface. 10g interface has several vlans. 1ge interfaces and xg vlans
are placed into bridges. For example, WAN and LAN are bridged to ge
interfaces in case 10g switch fails, then WAN and LAN will at least work
when plugged directly into server.

If I make a change to the config, I can run `netplan generate` and
`netplan apply` while system is running to update my network
configuration. However, if I run a similar (same?) config under Ubuntu
20.04, I receive the following error when running `netplan apply`:

['xg0', 'br10', 'br20', 'br200', 'xg0.20', 'xg0.181', 'xg0.180', 'xg0.10', 'xg0.200', 'xg0.182']
Cannot find unique matching interface for xg0: {'macaddress': '00:02:c9:52:7a:8e'}

The config does run correctly the first time during boot! So it seems
netplan now incorrectly picks up the VLAN interfaces (with same MAC) or
a virtual bridge interface as a physical interface??

** Affects: netplan.io (Ubuntu)
     Importance: Undecided
         Status: New

** Attachment added: "19.10 configuration, 20.04 config is similar"
   https://bugs.launchpad.net/bugs/1945584/+attachment/5529331/+files/netcfg-19.10.yaml

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https://bugs.launchpad.net/bugs/1945584

Title:
  netplan regression 19.10 to 20.04 LTS

Status in netplan.io package in Ubuntu:
  New

Bug description:
  In Ubuntu 19.10, I have a netplan config like so: 2x gigabit and 1x
  10g interface. 10g interface has several vlans. 1ge interfaces and xg
  vlans are placed into bridges. For example, WAN and LAN are bridged to
  ge interfaces in case 10g switch fails, then WAN and LAN will at least
  work when plugged directly into server.

  If I make a change to the config, I can run `netplan generate` and
  `netplan apply` while system is running to update my network
  configuration. However, if I run a similar (same?) config under Ubuntu
  20.04, I receive the following error when running `netplan apply`:

  ['xg0', 'br10', 'br20', 'br200', 'xg0.20', 'xg0.181', 'xg0.180', 'xg0.10', 'xg0.200', 'xg0.182']
  Cannot find unique matching interface for xg0: {'macaddress': '00:02:c9:52:7a:8e'}

  The config does run correctly the first time during boot! So it seems
  netplan now incorrectly picks up the VLAN interfaces (with same MAC)
  or a virtual bridge interface as a physical interface??

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