#1905280 Proof of concept for xfrm_interfaces.

[max-foss]

Proof of concept to solve https://bugs.launchpad.net/netplan/+bug/1905280

network-manager rendering is not yet supported, no idea if it even works.

Duplicate if_ids are rejected because there is no sane usecase for them.

if_id = 0x2a is also a supported notation along with if_id = 42 to align with the ip -d link show output

Example interface:

   xfrm-interfaces:
     ipsec0:
       if_id: 42
       independent: true

[max-foss]

@slyon Thanks a ton for your comment on launchpad.net.

How am I supposed to resolve the ABI compatibility failure with the introduction of NetplanDefType::NETPLAN_DEF_TYPE_XFRM?

I am fairly certain the documentation check being broken is unrelated to this while I am not quite sure what causes the failed coverage-c test.