@enr0n and @daniloegea would you mind taking a look at this PR? I'll still keep it as a draft (please don't merge yet), as we need wider availability of the upstream systemd changes, especially in our test runners (i.e. systemd v258+ or backports).

But besides that, the PR should be ready for review and comply with the spec linked above.

Danilo, do you have any clue what's wrong with the CodeQL (cpp) workflow? Just upgrading from v2 to v3 doesn't seem to do the trick.

The systemd part of this work was landed upstream and backported to https://launchpad.net/ubuntu/+source/systemd/257.2-3ubuntu1, thanks to @enr0n !

I've now finished implementation of the Netplan side and tested it in Ubuntu Plucky (by uncommenting the line after # XXX: Enable extra testing once systemd#34640 is available on the SUT (i.e. systemd v258+). in ethernets.py autopkgtest), so this should be ready for review!

Before merging it, we need to make sure the CI is ready (i.e. systemd v258+ or backport of the feature) and we should also run the full autopkgtest, as described above.

@enr0n WDYT?

This is now included in Ubuntu Plucky: https://launchpad.net/ubuntu/+source/netplan.io/1.1.2-1ubuntu1

This was deployed to Ubuntu Plucky in early February and didn't show any issues. Let's keep the integration test disabled, as the upstream Netplan CI does not yet provide the required systemd v258, but get it merged.