xfrm interfaces not supported

[Jean-Sébastien Frerot]

for VPN connections, in my case using strongswan, I'm not able to setup xfrm interfaces with netplan. I have to go back to ifupdown and use pre-up command:
"ip link add ipsec0 type xfrm dev eth0 if_id 42"

It would be nice for netplan to support such interfaces.

strongswan ref: https://wiki.strongswan.org/projects/strongswan/wiki/RouteBasedVPN#XFRM-Interfaces-on-Linux

[Junien F (axino)]

xfrm is supported by networkd by the way
https://www.freedesktop.org/software/systemd/man/systemd.network.html | grep xfrm

[adamretter (adam-retter)]

+1 for this. I would also prefer to configure my XFRM interface and its routing via Netplan.

[adamretter (adam-retter)]

For the time being I have worked around the deficiency by using the networkd-dispatcher. I created the script `/etc/networkd-dispatcher/routable.d/50-xfrm`:

```
#!/bin/sh

ip link add xfrm0 type xfrm dev eno3 if_id 0xabcd
ip address add 10.0.1.254/32 dev xfrm0
ip link set xfrm0 up
ip route add 10.0.2.254/32 dev xfrm0
```

[Junien F (axino)]

@adam-retter If you're using systemd-networkd, I suggest using the native xfrm implementation - see https://systemd.network/systemd.netdev.html and https://systemd.network/systemd.network.html (grep xfrm in these pages)

[Mike Brown (mikebrown345)]

Another +1 for this.

A note for others - the systemd-networkd version-237 which comes with Ubuntu 18.04 does not support XFRM in the [netdev] spec. So options seem to be:

A) On Ubuntu 18.04 use a network-dispatcher script (as @adamretter put down)
B) On Ubuntu 18.04 upgrade systemd to gain access to xfrm**
C) Use Ubuntu 20.04 systemd-networkd
D) Hop onto launchpad.net to leave a +1 for netplan to support the explosion of new network features in systemd

**I wanted to see how irksome this would be so I upgraded 237 to 245.4 mostly following these instructions https://gist.github.com/Jiab77/7df6e80804567f6f599b227cf2fafd00
On an AWS t2.micro it took 20 minutes for dpkg to compile everything.

[NWhisper (night-whisper)]

+100500 for this.