Stop rejecting packages from the tunnel

Appears that firewall rejects packages before they are getting unwrapped by GRE

Signed-off-by: Egor Savkin <es@m-labs.hk>

nixbld-etc-nixos/configuration.nix

@@ -92,8 +92,11 @@ in
     firewall = {
       allowedTCPPorts = [ 53 80 443 2222 7402 ];
       allowedUDPPorts = [ 53 67 500 4500 ];
-      trustedInterfaces = [ netifLan netifUSA ];
+      trustedInterfaces = [ netifLan ];
       logRefusedConnections = false;
+      extraCommands = ''
+        iptables -A INPUT -s 5.78.86.156 -j ACCEPT
+      '';
     };
     useDHCP = false;
     interfaces."${netifWan}".useDHCP = true;  # PCCW - always wants active DHCP lease or cuts you off