Port back to Mono.Nat and make discovery async.

OpenRA.Game/Network/Nat.cs

@@ -0,0 +1,101 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2021 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System;
+using System.Threading;
+using Mono.Nat;
+
+namespace OpenRA.Network
+{
+	public enum NatStatus { Enabled, Disabled, NotSupported }
+
+	public class Nat
+	{
+		public static NatStatus Status => NatUtility.IsSearching ? natDevice != null ? NatStatus.Enabled : NatStatus.NotSupported : NatStatus.Disabled;
+
+		static Mapping mapping;
+		static INatDevice natDevice;
+		static bool initialized;
+
+		public static void Initialize()
+		{
+			if (initialized)
+				return;
+
+			if (Game.Settings.Server.DiscoverNatDevices)
+			{
+				NatUtility.DeviceFound += DeviceFound;
+				NatUtility.StartDiscovery();
+			}
+
+			initialized = true;
+		}
+
+		static readonly SemaphoreSlim Locker = new SemaphoreSlim(1, 1);
+
+		static async void DeviceFound(object sender, DeviceEventArgs args)
+		{
+			await Locker.WaitAsync();
+			try
+			{
+				// Only interact with one at a time. Some support both UPnP and NAT-PMP.
+				natDevice = args.Device;
+
+				Log.Write("nat", "Device found: {0}", natDevice.DeviceEndpoint);
+				Log.Write("nat", "Type: {0}", natDevice.NatProtocol);
+			}
+			finally
+			{
+				Locker.Release();
+			}
+		}
+
+		public static bool TryForwardPort(int listen, int external)
+		{
+			if (natDevice == null)
+				return false;
+
+			var lifetime = Game.Settings.Server.NatPortMappingLifetime;
+			mapping = new Mapping(Protocol.Tcp, listen, external, lifetime, "OpenRA");
+			try
+			{
+				natDevice.CreatePortMap(mapping);
+			}
+			catch (Exception e)
+			{
+				Console.WriteLine("Port forwarding failed: {0}", e.Message);
+				Log.Write("nat", e.StackTrace);
+				return false;
+			}
+
+			return true;
+		}
+
+		public static bool TryRemovePortForward()
+		{
+			if (natDevice == null)
+				return false;
+
+			try
+			{
+				natDevice.DeletePortMap(mapping);
+			}
+			catch (Exception e)
+			{
+				Console.WriteLine("Port removal failed: {0}", e.Message);
+				Log.Write("nat", e.StackTrace);
+				return false;
+			}
+
+			return true;
+		}
+	}
+}