nixos/network: Backport systemd-networkd-wait-online@.service from 251

nixos/modules/common.nix

@@ -12,9 +12,6 @@ in
           "before accepting login.");
       };
     };
-
-    # Only present in >=22.05, so forward declare
-    documentation.nixos.options.warningsAreErrors = dummyOption;
   };
 
   imports = [

nixos/modules/network.nix

@@ -1,6 +1,35 @@
-{ lib, config, ... }:
+{ lib, pkgs, config, ... }:
 let
   inherit (lib) flatten optional mkIf mkDefault mkMerge;
+
+  # TODO: Backported from systemd 251
+  networkd-wait-online-at = pkgs.writeTextDir "lib/systemd/system/systemd-networkd-wait-online@.service" ''
+    #  SPDX-License-Identifier: LGPL-2.1-or-later
+    #
+    #  This file is part of systemd.
+    #
+    #  systemd is free software; you can redistribute it and/or modify it
+    #  under the terms of the GNU Lesser General Public License as published by
+    #  the Free Software Foundation; either version 2.1 of the License, or
+    #  (at your option) any later version.
+
+    [Unit]
+    Description=Wait for Network Interface %i to be Configured
+    Documentation=man:systemd-networkd-wait-online.service(8)
+    DefaultDependencies=no
+    Conflicts=shutdown.target
+    Requires=systemd-networkd.service
+    After=systemd-networkd.service
+    Before=network-online.target shutdown.target
+
+    [Service]
+    Type=oneshot
+    ExecStart=${pkgs.systemd}/lib/systemd/systemd-networkd-wait-online -i %i
+    RemainAfterExit=yes
+
+    [Install]
+    WantedBy=network-online.target
+  '';
 in
 {
   config = mkMerge [
@@ -12,6 +41,10 @@ in
         useNetworkd = mkDefault true;
       };
 
+      systemd = {
+        packages = [ networkd-wait-online-at ];
+      };
+
       services.resolved = {
         domains = [ config.networking.domain ];
         # Explicitly unset fallback DNS (Nix module will not allow for a blank config)