netplan "match macaddress" messes up vlan IP addresses

[Brian Candler]

Using "match: macaddress:" - which is sometimes necessary (e.g. see #1724895) - causes vlan interfaces to pick up the IP address of the parent instead of the address you have defined.

To reproduce: create /etc/netplan/01-netcfg.yaml

network:
    version: 2
    renderer: networkd
    ethernets:
        ens3:
            dhcp4: false
            addresses:
                - 192.168.6.123/24
            gateway4: 192.168.6.1
            match:
                macaddress: 52:54:00:85:50:32 # << replace with your MAC address
            mtu: 9000
    vlans:
        vlan5:
            id: 5
            link: ens3
            dhcp4: false
            addresses:
                - 192.168.5.123/24

Then "netplan generate; netplan apply" (or reboot). Result:

# ip addr list | grep 192.168
    inet 192.168.6.123/24 brd 192.168.6.255 scope global ens3
    inet 192.168.6.123/24 brd 192.168.6.255 scope global vlan5

Note how vlan5 has been given the same IP address as ens3, instead of the address which was defined for it in the YAML.

WORKAROUND: adding "set-name: ens3" under the "ens3" stanza seems to make it work.

...
    ethernets:
        ens3:
            dhcp4: false
            addresses:
                - 192.168.6.123/24
            gateway4: 192.168.6.1
            match:
                macaddress: 52:54:00:85:50:32
            mtu: 9000
            set-name: ens3 # << NOTE
...

(Aside: this is a workaround to a workaround. I wouldn't have needed to match on MAC address in the first place if applying the MTU had worked without it!)

Reproduced using https://cloud-images.ubuntu.com/bionic/current/bionic-server-cloudimg-amd64.img
- image downloaded on Jan 29 2020 - under kvm/libvirt, but originally seen on real hardware.

[Alex Walender (awalende)]

This is so annoying...

My workaround is to additionally add the driver module to the match list.
VLANs run under a generic module driver, so they don't match with the parent one.

[Brian Candler (b-candler)]

@awalende: Can you click 'This bug affects me' at the top? Then it will get marked as a confirmed bug.

[Marc Gariépy (mgariepy)]

i guess it needs to add the type in the link file if there is a vlan set on top of the interface. to avoird trying to rename the vlan interface because it matches the MAC.

https://github.com/CanonicalLtd/netplan/blob/master/src/networkd.c#L101