fix: Fixed an issue where BatchedSendQueue was including the HeadIndex twice when copying data, which was causing stream corruption when the data exceeded a certain throughput. [NCCBUG-187] (#2332)

fix: Fixed an issue where BatchedSendQueue was including the HeadIndex twice when copying data, which was causing stream corruption when the data exceeded a certain throughput. [NCCBUG-187] (#2332)

Author: ShadauxCat

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -17,6 +17,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 
 ### Fixed
 - Fixed server side issue where, depending upon component ordering, some NetworkBehaviour components might not have their OnNetworkDespawn method invoked if the client side disconnected. (#2323)
+- Fixed a case where data corruption could occur when using UnityTransport when reaching a certain level of send throughput. (#2332)
 
 - Fixed an issue in `UnityTransport` where an exception would be thrown if starting a Relay host/server on WebGL. This exception should only be thrown if using direct connections (where WebGL can't act as a host/server). (#2321)
 

com.unity.netcode.gameobjects/Runtime/Transports/UTP/BatchedSendQueue.cs

@@ -226,7 +226,7 @@ public int FillWriterWithMessages(ref DataStreamWriter writer)
                     {
                         writer.WriteInt(messageLength);
 
-                        var messageOffset = HeadIndex + reader.GetBytesRead();
+                        var messageOffset = reader.GetBytesRead();
                         WriteBytes(ref writer, (byte*)m_Data.GetUnsafePtr() + messageOffset, messageLength);
 
                         writerAvailable -= sizeof(int) + messageLength;

com.unity.netcode.gameobjects/Tests/Editor/Transports/BatchedSendQueueTests.cs

@@ -229,6 +229,12 @@ public void BatchedSendQueue_FillWriterWithMessages_PartialPushedMessages()
             var writer = new DataStreamWriter(data);
             Assert.AreEqual(messageLength, q.FillWriterWithMessages(ref writer));
             AssertIsTestMessage(data);
+
+            q.Consume(messageLength);
+
+            writer = new DataStreamWriter(data);
+            Assert.AreEqual(messageLength, q.FillWriterWithMessages(ref writer));
+            AssertIsTestMessage(data);
         }
 
         [Test]