nixos/scion: introduce package option (#327765)

nixos/modules/services/networking/scion/scion-control.nix

@@ -60,7 +60,7 @@ in
       serviceConfig = {
         Type = "simple";
         Group = if (config.services.scion.scion-dispatcher.enable == true) then "scion" else null;
-        ExecStart = "${pkgs.scion}/bin/scion-control --config ${configFile}";
+        ExecStart = "${globalCfg.package}/bin/scion-control --config ${configFile}";
         DynamicUser = true;
         Restart = "on-failure";
         BindPaths = [ "/dev/shm:/run/shm" ];

nixos/modules/services/networking/scion/scion-daemon.nix

@@ -56,7 +56,7 @@ in
       wantedBy = [ "multi-user.target" ];
       serviceConfig = {
         Type = "simple";
-        ExecStart = "${pkgs.scion}/bin/scion-daemon --config ${configFile}";
+        ExecStart = "${globalCfg.package}/bin/scion-daemon --config ${configFile}";
         Restart = "on-failure";
         DynamicUser = true;
         ${if globalCfg.stateless then "RuntimeDirectory" else "StateDirectory"} = "scion-daemon";

nixos/modules/services/networking/scion/scion-dispatcher.nix

@@ -65,7 +65,7 @@ in
         DynamicUser = true;
         BindPaths = [ "/dev/shm:/run/shm" ];
         ExecStartPre = "${pkgs.coreutils}/bin/rm -rf /run/shm/dispatcher";
-        ExecStart = "${pkgs.scion}/bin/scion-dispatcher --config ${configFile}";
+        ExecStart = "${globalCfg.package}/bin/scion-dispatcher --config ${configFile}";
         Restart = "on-failure";
         ${if globalCfg.stateless then "RuntimeDirectory" else "StateDirectory"} = "scion-dispatcher";
       };

nixos/modules/services/networking/scion/scion-router.nix

@@ -40,7 +40,7 @@ in
       wantedBy = [ "multi-user.target" ];
       serviceConfig = {
         Type = "simple";
-        ExecStart = "${pkgs.scion}/bin/scion-router --config ${configFile}";
+        ExecStart = "${globalCfg.package}/bin/scion-router --config ${configFile}";
         Restart = "on-failure";
         DynamicUser = true;
         ${if globalCfg.stateless then "RuntimeDirectory" else "StateDirectory"} = "scion-router";

nixos/modules/services/networking/scion/scion.nix

@@ -8,6 +8,7 @@ in
 {
   options.services.scion = {
     enable = mkEnableOption "all of the scion components and services";
+    package = mkPackageOption pkgs "scion" { };
     stateless = mkOption {
       type = types.bool;
       default = true;
@@ -34,7 +35,7 @@ in
   };
   config = mkIf cfg.enable {
     environment.systemPackages = [
-      pkgs.scion
+      cfg.package
     ];
     services.scion = {
       scion-dispatcher.enable = true;