nixos/networkd: Add routes from interfaces to [Route] section of .network file

Closes https://github.com/NixOS/nixpkgs/pull/93635.

nixos/doc/manual/from_md/release-notes/rl-2205.section.xml

@@ -361,6 +361,18 @@
           unmaintained
         </para>
       </listitem>
+      <listitem>
+        <para>
+          The options
+          <literal>networking.interfaces.&lt;name&gt;.ipv4.routes</literal>
+          and
+          <literal>networking.interfaces.&lt;name&gt;.ipv6.routes</literal>
+          are no longer ignored when using networkd instead of the
+          default scripted network backend by setting
+          <literal>networking.useNetworkd</literal> to
+          <literal>true</literal>.
+        </para>
+      </listitem>
       <listitem>
         <para>
           MultiMC has been replaced with the fork PolyMC due to upstream

nixos/doc/manual/release-notes/rl-2205.section.md

@@ -116,6 +116,8 @@ In addition to numerous new and upgraded packages, this release has the followin
 
 - `pkgs.docbookrx` was removed since it's unmaintained
 
+- The options `networking.interfaces.<name>.ipv4.routes` and `networking.interfaces.<name>.ipv6.routes` are no longer ignored when using networkd instead of the default scripted network backend by setting `networking.useNetworkd` to `true`.
+
 - MultiMC has been replaced with the fork PolyMC due to upstream developers being hostile to 3rd party package maintainers. PolyMC removes all MultiMC branding and is aimed at providing proper 3rd party packages like the one contained in Nixpkgs. This change affects the data folder where game instances and other save and configuration files are stored. Users with existing installations should rename `~/.local/share/multimc` to `~/.local/share/polymc`. The main config file's path has also moved from `~/.local/share/multimc/multimc.cfg` to `~/.local/share/polymc/polymc.cfg`.
 
 - `pkgs.noto-fonts-cjk` is now deprecated in favor of `pkgs.noto-fonts-cjk-sans`

nixos/modules/tasks/network-interfaces-systemd.nix

@@ -12,6 +12,10 @@ let
     i.ipv4.addresses
     ++ optionals cfg.enableIPv6 i.ipv6.addresses;
 
+  interfaceRoutes = i:
+    i.ipv4.routes
+    ++ optionals cfg.enableIPv6 i.ipv6.routes;
+
   dhcpStr = useDHCP: if useDHCP == true || useDHCP == null then "yes" else "no";
 
   slaves =
@@ -94,6 +98,63 @@ in
             (if i.useDHCP != null then i.useDHCP else false));
           address = forEach (interfaceIps i)
             (ip: "${ip.address}/${toString ip.prefixLength}");
+          routes = forEach (interfaceRoutes i)
+            (route: {
+              # Most of these route options have not been tested.
+              # Please fix or report any mistakes you may find.
+              routeConfig =
+                optionalAttrs (route.prefixLength > 0) {
+                  Destination = "${route.address}/${toString route.prefixLength}";
+                } //
+                optionalAttrs (route.options ? fastopen_no_cookie) {
+                  FastOpenNoCookie = route.options.fastopen_no_cookie;
+                } //
+                optionalAttrs (route.via != null) {
+                  Gateway = route.via;
+                } //
+                optionalAttrs (route.options ? onlink) {
+                  GatewayOnLink = true;
+                } //
+                optionalAttrs (route.options ? initrwnd) {
+                  InitialAdvertisedReceiveWindow = route.options.initrwnd;
+                } //
+                optionalAttrs (route.options ? initcwnd) {
+                  InitialCongestionWindow = route.options.initcwnd;
+                } //
+                optionalAttrs (route.options ? pref) {
+                  IPv6Preference = route.options.pref;
+                } //
+                optionalAttrs (route.options ? mtu) {
+                  MTUBytes = route.options.mtu;
+                } //
+                optionalAttrs (route.options ? metric) {
+                  Metric = route.options.metric;
+                } //
+                optionalAttrs (route.options ? src) {
+                  PreferredSource = route.options.src;
+                } //
+                optionalAttrs (route.options ? protocol) {
+                  Protocol = route.options.protocol;
+                } //
+                optionalAttrs (route.options ? quickack) {
+                  QuickAck = route.options.quickack;
+                } //
+                optionalAttrs (route.options ? scope) {
+                  Scope = route.options.scope;
+                } //
+                optionalAttrs (route.options ? from) {
+                  Source = route.options.from;
+                } //
+                optionalAttrs (route.options ? table) {
+                  Table = route.options.table;
+                } //
+                optionalAttrs (route.options ? advmss) {
+                  TCPAdvertisedMaximumSegmentSize = route.options.advmss;
+                } //
+                optionalAttrs (route.options ? ttl-propagate) {
+                  TTLPropagate = route.options.ttl-propagate == "enabled";
+                };
+            });
           networkConfig.IPv6PrivacyExtensions = "kernel";
           linkConfig = optionalAttrs (i.macAddress != null) {
             MACAddress = i.macAddress;

nixos/modules/tasks/network-interfaces.nix

@@ -103,6 +103,11 @@ let
         description = ''
           Other route options. See the symbol <literal>OPTIONS</literal>
           in the <literal>ip-route(8)</literal> manual page for the details.
+          You may also specify <literal>metric</literal>,
+          <literal>src</literal>, <literal>protocol</literal>,
+          <literal>scope</literal>, <literal>from</literal>
+          and <literal>table</literal>, which are technically
+          not route options, in the sense used in the manual.
         '';
       };
 
@@ -208,6 +213,14 @@ let
         type = with types; listOf (submodule (routeOpts 4));
         description = ''
           List of extra IPv4 static routes that will be assigned to the interface.
+          <warning><para>If the route type is the default <literal>unicast</literal>, then the scope
+          is set differently depending on the value of <option>networking.useNetworkd</option>:
+          the script-based backend sets it to <literal>link</literal>, while networkd sets
+          it to <literal>global</literal>.</para></warning>
+          If you want consistency between the two implementations,
+          set the scope of the route manually with
+          <literal>networking.interfaces.eth0.ipv4.routes = [{ options.scope = "global"; }]</literal>
+          for example.
         '';
       };
 

nixos/tests/networking.nix

@@ -740,6 +740,7 @@ let
     routes = {
       name = "routes";
       machine = {
+        networking.useNetworkd = networkd;
         networking.useDHCP = false;
         networking.interfaces.eth0 = {
           ipv4.addresses = [ { address = "192.168.1.2"; prefixLength = 24; } ];
@@ -749,7 +750,13 @@ let
             { address = "2001:1470:fffd:2098::"; prefixLength = 64; via = "fdfd:b3f0::1"; }
           ];
           ipv4.routes = [
-            { address = "10.0.0.0"; prefixLength = 16; options = { mtu = "1500"; }; }
+            { address = "10.0.0.0"; prefixLength = 16; options = {
+              mtu = "1500";
+              # Explicitly set scope because iproute and systemd-networkd
+              # disagree on what the scope should be
+              # if the type is the default "unicast"
+              scope = "link";
+            }; }
             { address = "192.168.2.0"; prefixLength = 24; via = "192.168.1.1"; }
           ];
         };
@@ -798,6 +805,7 @@ let
                 ipv6Table, targetIPv6Table
             )
 
+      '' + optionalString (!networkd) ''
         with subtest("test clean-up of the tables"):
             machine.succeed("systemctl stop network-addresses-eth0")
             ipv4Residue = machine.succeed("ip -4 route list dev eth0 | head -n-3").strip()