configure port forwarding

nixos/configs/robi/transmission2.nix

@@ -138,6 +138,15 @@ in
           # notify me when download finished
           script-torrent-done-enabled = true;
           script-torrent-done-filename = completionScript;
+
+          # Encryption preference.
+          # 0 = Prefer unencrypted connections,
+          # 1 = Prefer encrypted connections,
+          # 2 = Require encrypted connections;
+          # default = 1
+          # Encryption may help get around some ISP filtering, but at the cost of slightly
+          # higher CPU use
+          encryption = 2;
         };
       };
 
@@ -168,6 +177,13 @@ in
   networking.nat.enable = true;
   networking.nat.internalInterfaces = [ "ve-torrent" ];
   networking.nat.externalInterface = hostInterface;
+  networking.nat.forwardPorts = [
+    { destination = "${containerAddress}:51413"; proto = "tcp"; sourcePort = 51413; }
+  ];
+  networking.firewall = {
+    allowedTCPPorts = [ 51413 ];
+    allowedUDPPorts = [ 51413 ];
+  };
 
   # host nginx setup
   # ----------------