nixos/wireguard: add metric option

This new option, networking.wireguard.interfaces.NAME.metric, allows
increasing the metric of the routes, effectively lowering priority.

(I'm using high metric to allow having the Wireguard interface always
up, even when the client machines are on their home network. Before I
had to stop the interface when home to avoid packet routing issues.)

1 files changed, 10 insertions, 1 deletions

diff --git a/nixos/modules/services/networking/wireguard.nix b/nixos/modules/services/networking/wireguard.nix
index 21473388d76e..d4099be12a27 100644
--- a/nixos/modules/services/networking/wireguard.nix
+++ b/nixos/modules/services/networking/wireguard.nix
@@ -164,6 +164,15 @@ let
           of the wireguard network has to be adjusted as well.
         '';
       };
+
+      metric = mkOption {
+        default = null;
+        type = with types; nullOr int;
+        example = 700;
+        description = lib.mdDoc ''
+          Set the metric of routes related to this Wireguard interface.
+        '';
+      };
     };
 
   };
@@ -395,7 +404,7 @@ let
             optionalString interfaceCfg.allowedIPsAsRoutes
               (concatMapStringsSep "\n"
                 (allowedIP:
-                  ''${ip} route replace "${allowedIP}" dev "${interfaceName}" table "${interfaceCfg.table}"''
+                  ''${ip} route replace "${allowedIP}" dev "${interfaceName}" table "${interfaceCfg.table}" ${optionalString (interfaceCfg.metric != null) "metric ${toString interfaceCfg.metric}"}''
                 ) peer.allowedIPs);
         in ''
           ${wg_setup}