nixos/network-interfaces-systemd: improve default ethernet network matching (#347283)

  genericDhcpNetworks = initrd: mkIf cfg.useDHCP {

    networks."99-ethernet-default-dhcp" = {

      # We want to match physical ethernet interfaces as commonly

      # found on laptops, desktops and servers, to provide an

      # "out-of-the-box" setup that works for common cases.  This

      # heuristic isn't perfect (it could match interfaces with

      # custom names that _happen_ to start with en or eth), but

      # should be good enough to make the common case easy and can

      # be overridden on a case-by-case basis using

      # higher-priority networks or by disabling useDHCP.

      # Type=ether matches veth interfaces as well, and this is

      # more likely to result in interfaces being configured to

      # use DHCP when they shouldn't.

      matchConfig.Name = ["en*" "eth*"];

      matchConfig = {

        Type = "ether";

        Kind = "!*"; # physical interfaces have no kind

      };

      DHCP = "yes";

      networkConfig.IPv6PrivacyExtensions = "kernel";

    };

    networks."99-wireless-client-dhcp" = {

      # Like above, but this is much more likely to be correct.

      matchConfig.WLANInterfaceType = "station";

      DHCP = "yes";

      networkConfig.IPv6PrivacyExtensions = "kernel";