Devices unexpectedly renamed by netplan apply

[Daniel Axtens]

I have ens8 and ens9, currently unconfigured:

3: ens8: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 52:54:00:f9:e9:dd brd ff:ff:ff:ff:ff:ff
4: ens9: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 52:54:00:56:0d:ce brd ff:ff:ff:ff:ff:ff

I drop in the following yaml file:

network:
    version: 2
    ethernets:
        ens8:
            match:
                macaddress: 52:54:00:f9:e9:dd
            mtu: 1280
        ens9:
            match:
                macaddress: 52:54:00:56:0d:ce
            mtu: 1280
    bridges:
        br0:
            interfaces: [ens8, ens9]
            addresses:
                - 10.10.10.2/24

I then run netplan generate/netplan apply.

I observe that the links have been unexpectedly and undesirably renamed - ens8 has become eth0, and ens9 has become eth1. The mac addresses are unchanged:

5: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1280 qdisc fq_codel master br0 state UP mode DEFAULT group default qlen 1000
    link/ether 52:54:00:f9:e9:dd brd ff:ff:ff:ff:ff:ff
6: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1280 qdisc fq_codel master br0 state UP mode DEFAULT group default qlen 1000
    link/ether 52:54:00:56:0d:ce brd ff:ff:ff:ff:ff:ff
7: br0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1280 qdisc noqueue state UP mode DEFAULT group default qlen 1000
    link/ether 0e:e3:1c:83:f8:e8 brd ff:ff:ff:ff:ff:ff

I think this is some weird side-effect of the unplug/replug thing netplan does, but I don't know how to debug it further.

Adding a set-name stanza and redoing generate/apply does *not* rename the interface. (Their indexes also don't change, so I assume something is suppressing a further plug cycle?)

Rebooting works as expected - the bridge is created and the devices are not renamed.

[Daniel Axtens (daxtens)]

This goes away with replug in 0.39, so calling it fix committed for now.