Problems configuring pppoe when using netplan

Thanks for the bug report.

Currently pppoe support in networkd is unavailable at this time[1]
However, NetworkManager has support for pppoe[2], so it could be possible to work on the yaml structure needed for pppoe configuration,

Then, at least drive the NM backend, but the networkd will need an implementation.

For now, if you need pppoe support on Bionic, it's still driven from ifupdown configuration.

1. https://github.com/systemd/systemd/issues/481
2. https://developer.gnome.org/NetworkManager/stable/settings-pppoe.html

fwiw I am currently using networkd-dispatcher for this with the following scripts:

$ cat /etc/networkd-dispatcher/routable.d/ppp
#!/bin/sh

set -e

if [ "$IFACE" != wan ]; then
        exit 0
fi

pppd call centurylink

sleep 5

ip route change default dev ppp0 advmss 1482
$

$ cat /etc/networkd-dispatcher/no-carrier.d/ppp
#!/bin/sh

set -e

if [ "$IFACE" != wan ]; then
        exit 0
fi

if [ -e /run/ppp-centurylink.pid ]; then
        pid=$(cat /run/ppp-centurylink.pid)
        kill "$pid"
fi
$

With symlinks for the no-carrier.d script under dormant.d, off.d, and degraded.d.

While ideally this would be implemented directly in netplan, perhaps the above will be useful to someone who finds this bug.