The networkd.conf file controls a variety of interesting settings
which don't seem to be configurable at the moment, including
adding names to route tables (for networkd only, although this commit
also exports them into iproute2 for convenience's sake), and
the speed metering functionality built into networkd.
Importantly, however, this also allows disabling the systemd
functionality where it likes to delete all the routes and routing rules
that haven't been configured through networkd whenever something causes
it to perform a reconfiguration.
config.boot.kernelPackages.wireguard evaluates to null on machine
closure having a > 5.6 Linux kernels, hence making the evaluation of
this test fail.
Wireguard is now part of the mainline Linux kernel, we do not need to
to add it via a additional kernel module anymore for this test.
The original idea for this test was, on top of providing a networkd
test, to provide newcomers with a sample configuration they could use
to get started with networkd.
That's precisely why we were doing this systemd tmpfile dance in the
first place. It was a convenient way to create a runtime file with a
specific mode and owner.
Sadly, this tmpfile rule made the test flaky. There's a race condition
between the wireguard interface configured by systemd-networkd and
systemd-tmpfiles-setup.
Sometimes, networkd is going to try loading the wireguard private key
file *before* the said file gets created by systemd-tmpfiles.
A perfect solution here would be to create a "After" dependency
between wg0.netdev and systemd-tmpfiles-setup.service. Sadly, it is
currently impossible to create such a dependency between a
networkd-specific unit and a service.
We're removing this tmp file in favor of pointing networkd directly to
the Nix store. This is clearly something that shouldn't be done in the
real world for a private file: the store is world-readable. However,
this is the only way I found to fix this test flakiness for now.
In `systemd-243` the option `FwMark` in the `[WireGuard]` section of
a `.netdev`-unit has been renamed to `FirewallMark`[1]. Due to the
removal of deprecated options in our `networkd` module[2] the evaluation
of this test doesn't work.
Renaming the option to its new name fixes the issue.
[1] 1c30b174ed
[2] e9d13d3751
