[tracker] Allow comparing peers using PeerId

We still default to using IPAddress/Port as some bittorrent
clients randomise their peerid, making it a little use suitable
to use as a unique identifier.

src/MonoTorrent/MonoTorrent.Tracker/IPAddressComparer.cs → src/MonoTorrent/MonoTorrent.Tracker/ClientAddressComparer.cs

@@ -1,5 +1,5 @@
 //
-// IPAddressComparer.cs
+// ClientAddressComparer.cs
 //
 // Authors:
 //   Alan McGovern <[email protected]>
@@ -29,13 +29,16 @@
 
 namespace MonoTorrent.Tracker
 {
-    public interface IPeerComparer
-    {
-        object GetKey(AnnounceRequest parameters);
-    }
-
-    class IPAddressComparer : IPeerComparer
+    /// <summary>
+    /// Uses the <see cref="AnnounceRequest.ClientAddress"/> field to compare peers when handling Announce or Scrape requests.
+    /// </summary>
+    public class ClientAddressComparer : IPeerComparer
     {
+        /// <summary>
+        /// Returns the <see cref="AnnounceRequest.ClientAddress"/> field to use to compare peers.
+        /// </summary>
+        /// <param name="parameters">The data sent as part of the Announce request</param>
+        /// <returns></returns>
         public object GetKey(AnnounceRequest parameters)
         {
             return parameters.ClientAddress;

src/MonoTorrent/MonoTorrent.Tracker/IPeerComparer.cs

@@ -0,0 +1,46 @@
+//
+// IPeerComparer.cs
+//
+// Authors:
+//   Alan McGovern <[email protected]>
+//
+// Copyright (C) 2006 Alan McGovern
+//
+// Permission is hereby granted, free of charge, to any person obtaining
+// a copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to
+// permit persons to whom the Software is furnished to do so, subject to
+// the following conditions:
+// 
+// The above copyright notice and this permission notice shall be
+// included in all copies or substantial portions of the Software.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//
+
+
+namespace MonoTorrent.Tracker
+{
+    /// <summary>
+    /// Returns one of the properties from a peers <see cref="AnnounceRequest"/>, or a value derived from
+    /// properties on the <see cref="AnnounceRequest"/>, to use when comparing peers.
+    /// </summary>
+    public interface IPeerComparer
+    {
+        /// <summary>
+        /// Returns one of the properties from the <see cref="AnnounceRequest"/> object, or a value derived from
+        /// properties on the <see cref="AnnounceRequest"/> object, to use when comparing peers.
+        /// </summary>
+        /// <param name="parameters">The data sent as part of the Announce request</param>
+        /// <returns></returns>
+        object GetKey(AnnounceRequest parameters);
+    }
+}

src/MonoTorrent/MonoTorrent.Tracker/PeerIdComparer.cs

@@ -0,0 +1,47 @@
+//
+// PeerIdComparer.cs
+//
+// Authors:
+//   Alan McGovern <[email protected]>
+//
+// Copyright (C) 2019 Alan McGovern
+//
+// Permission is hereby granted, free of charge, to any person obtaining
+// a copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to
+// permit persons to whom the Software is furnished to do so, subject to
+// the following conditions:
+// 
+// The above copyright notice and this permission notice shall be
+// included in all copies or substantial portions of the Software.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+//
+
+
+namespace MonoTorrent.Tracker
+{
+    /// <summary>
+    /// Uses the <see cref="AnnounceRequest.PeerId"/> field to compare peers when handling Announce or Scrape requests.
+    /// </summary>
+    public class PeerIdComparer : IPeerComparer
+    {
+        /// <summary>
+        /// Returns the <see cref="AnnounceRequest.PeerId"/> field to use to compare peers.
+        /// </summary>
+        /// <param name="parameters">The data sent as part of the Announce request</param>
+        /// <returns></returns>
+        public object GetKey(AnnounceRequest parameters)
+        {
+            return parameters.PeerId;
+        }
+    }
+}

src/MonoTorrent/MonoTorrent.Tracker/TrackerServer.cs

@@ -166,7 +166,7 @@ public TrackerServer(BEncodedString trackerId)
         /// <param name="trackable">The trackable to add</param>
         /// <returns></returns>
         public bool Add(ITrackable trackable)
-            => Add(trackable, new IPAddressComparer());
+            => Add(trackable, new ClientAddressComparer());
 
         /// <summary>
         /// Adds the trackable to the server