nixos/yggdrasil: add extraArgs option

nixos/modules/services/networking/yggdrasil.nix

@@ -121,6 +121,13 @@ in
         restarted. Keys are stored at ${keysPath}.
       '');
 
+      extraArgs = mkOption {
+        type = listOf str;
+        default = [ ];
+        example = [ "-loglevel" "info" ];
+        description = lib.mdDoc "Extra command line arguments.";
+      };
+
     };
   };
 
@@ -181,7 +188,7 @@ in
             "${binYggdrasil} -genconf") + " > /run/yggdrasil/yggdrasil.conf"}
 
           # start yggdrasil
-          ${binYggdrasil} -useconffile /run/yggdrasil/yggdrasil.conf
+          ${binYggdrasil} -useconffile /run/yggdrasil/yggdrasil.conf ${lib.strings.escapeShellArgs cfg.extraArgs}
         '';
 
         serviceConfig = {

nixos/tests/yggdrasil.nix

@@ -116,6 +116,7 @@ in import ./make-test-python.nix ({ pkgs, ...} : {
         networking.firewall.allowedTCPPorts = [ 43210 ];
         services.yggdrasil = {
           enable = true;
+          extraArgs = [ "-loglevel" "error" ];
           denyDhcpcdInterfaces = [ "ygg0" ];
           settings = {
             IfTAPMode = true;