create 'lib.vpnNamespaceOpenPort'

lib.nix

@@ -54,5 +54,26 @@ inputs.nixpkgs.lib.extend (
         "-march=znver3"
         "-mtune=znver3"
       ];
+
+    vpnNamespaceOpenPort =
+      port:
+      { ... }:
+      {
+        vpnNamespaces.wg = {
+          portMappings = [
+            {
+              from = port;
+              to = port;
+            }
+          ];
+
+          openVPNPorts = [
+            {
+              port = port;
+              protocol = "both";
+            }
+          ];
+        };
+      };
   }
 )

services/bitmagnet.nix

@@ -2,24 +2,13 @@
   pkgs,
   service_configs,
   config,
+  lib,
   ...
 }:
 {
-  vpnNamespaces.wg = {
-    portMappings = [
-      {
-        from = service_configs.ports.bitmagnet;
-        to = service_configs.ports.bitmagnet;
-      }
-    ];
-
-    openVPNPorts = [
-      {
-        port = service_configs.ports.bitmagnet;
-        protocol = "both";
-      }
-    ];
-  };
+  imports = [
+    (lib.vpnNamespaceOpenPort service_configs.ports.bitmagnet)
+  ];
 
   services.bitmagnet = {
     enable = true;

services/qbittorrent.nix

@@ -13,25 +13,9 @@
       config.services.qbittorrent.serverConfig.Preferences.Downloads.TempPath
       "${config.services.qbittorrent.profileDir}/qBittorrent"
     ])
+    (lib.vpnNamespaceOpenPort config.services.qbittorrent.webuiPort)
   ];
 
-  # network namespace that is proxied through mullvad
-  vpnNamespaces.wg = {
-    portMappings = [
-      {
-        from = config.services.qbittorrent.webuiPort;
-        to = config.services.qbittorrent.webuiPort;
-      }
-    ];
-
-    openVPNPorts = [
-      {
-        port = config.services.qbittorrent.webuiPort;
-        protocol = "both";
-      }
-    ];
-  };
-
   services.qbittorrent = {
     enable = true;
     webuiPort = service_configs.ports.torrent;