Systemd provides some functionality to escape strings that are supposed
to be part of a unit name[1]. This seems to be used for interface names
in `sys-subsystem-net-devices-{interface}.device` and breaks
wpa_supplicant if the wireless interface name has a dash which is
encoded to \x2d.
Such an interface name is rather rare, but used i.e. when configuring
multiple wireless interfaces with `networking.wlanInterfaces`[2] to have on
interface for `wpa_supplicant` and another one for `hostapd`.
[1] https://www.freedesktop.org/software/systemd/man/systemd-escape.html
[2] https://nixos.org/nixos/options.html#networking.wlaninterfaces
This allows the user to add `wpa_supplicant` config options not yet supported by Nix without having to write the entire `wpa_supplicant.conf` file manually.
We now wait for dhcpcd to acquire a lease but dhcpcd is restarted on
system activation. As wpa_supplicant is stopped while dhcpcd is
restarting a significant delay is introduced on systems with wireless
network connections only. This changes the wpa_supplicant service to
also be restarted together with dhcpcd in case both services were
changed.
wpa_supplicant fails to start if the wireless interfaces aren't ready yet,
so we need to add a system ordering directive here to start wpa_supplicant
after the interfaces are ready. Note that Requires= is not enough since
it does not imply ordering.
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
