activate NixOS monitoring in prometheus

modules/monitoring/default.nix

@@ -23,6 +23,11 @@ in
       };
       bird = mkEnableOption "Monitor bird";
       blackbox = mkEnableOption "Monitor blackbox";
+      nixos = mkOption {
+        type = types.bool;
+        default = true;
+        description = "Monitor NixOS";
+      };
     };
   };
 
@@ -95,9 +100,13 @@ in
         User = "nixos-exporter";
         Group = "nixos-exporter";
         ExecStart = ''
-          ${pkgs.nixos-exporter}/bin/nixos-exporter
+          ${pkgs.nixos-exporter}/bin/nixos-exporter --listen [::]:9152
         '';
       };
     };
+
+    networking.firewall.extraCommands = ''
+      ip46tables -A nixos-fw -i wg-monitoring -p tcp -m tcp --dport 9152 -m comment --comment nixos-exporter -j nixos-fw-accept
+    '';
   };
 }