I may have finally found a clean solution to the issues[1][2][3] with
the automatic discovery of wireless network interfaces.
[1]: https://github.com/NixOS/nixpkgs/issues/101963
[2]: https://github.com/NixOS/nixpkgs/issues/23196
[3]: https://github.com/NixOS/nixpkgs/pull/125917#issuecomment-856000426
Currently the start script fails right away if no interface is available
by the time it's running, possibly leaving the system without network.
This happens when running a little early in the boot. A solution is to
instead wait for at least one interface to appear before scanning the
/sys/class/net/ directory. This is done here by listening for the right
udev events (from the net/wlan subsystem) using the `udevadm monitor`
command and grep to match its output.
This methods guarantees the availability of at least one interface to
wpa_supplicant, but won't add additional interfaces once it has started.
However, if the current interface is lost, say unplugged, the service is
automatically stopped and will be restarted as soon as a one (not
necessarily the same) is detected. It would be possible make this fully
dynamic by running another service that continously listen for udev
events and manages the main wpa_supplicant daemon, but this is probably
overkill.
I tested the following cases:
- one interface, starting at boot, w/o predictable naming scheme
- two interfaces, starting at boot (intel wireless and a usb adapter),
w/o predictable naming scheme
- one interface after the system booted, w/o predictable naming scheme
- two interfaces after the system booted, w/o predictable naming scheme
- unplugging and plugging back the current interface
Reload only works with a static configuration path as there is no way to
pass the dynamically generated config path to a running solanum
instance, therefore we symlink the configuration to
/etc/solanum/ircd.conf.
But that will prevent reloads of the ircd, because the systemd unit
wouldn't change when the configuration changes. That is why we add the
actual location of the config file to restartTriggers and enable
reloadIfChanged, so changes will not restart, but reload on changes.
Trying to steer NixOS users away from reporting bugs to the upstream,
when they don't have the capacity to support bugs that could be the
result of our downstreaming setup.
tailscale allows to specify the interface name.
The upstream systemd unit does not expose it directly however, only
via the `FLAGS` environment variable.
I can’t be 100% sure that the escaping is correct, but this is as good
as we can do for now, unless upstream changes their unit file.
The attributes got renamed in PR #126440 and in some places this caused
evaluation errors, e.g. the tarball job was saying (locally)
> attribute 'alsaUtils' missing, at /build/source/nixos/modules/services/audio/alsa.nix:6:4
and I suspect that trunk-combined jobset's failure to evaluate was also caused.
