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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

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merged 3 commits into from
Dec 5, 2022
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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

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fix: Fixed an issue where BatchedSendQueue was including the HeadInde…
ShadauxCat Dec 2, 2022
5975927
Added a test
ShadauxCat Dec 5, 2022
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ShadauxCat Dec 5, 2022
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1 change: 1 addition & 0 deletions com.unity.netcode.gameobjects/CHANGELOG.md
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Expand Up @@ -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)

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2 changes: 1 addition & 1 deletion com.unity.netcode.gameobjects/Runtime/Transports/UTP/BatchedSendQueue.cs
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Expand Up @@ -226,7 +226,7 @@ public int FillWriterWithMessages(ref DataStreamWriter writer)
{
writer.WriteInt(messageLength);

var messageOffset = HeadIndex + reader.GetBytesRead();
var messageOffset = reader.GetBytesRead();
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If you look above here, there's readerOffset = HeadIndex. This was changed in #2224 from readerOffset = 0 because reader was changed from being a slice of m_data to containing all of m_data and reading from that offset. The return value of GetBytesRead() here already includes HeadIndex, so this results in HeadIndex being applied twice when calculating messageOffset.

When HeadIndex is 0 that has no effect, but when the queue gets filled more, it starts resulting in things being skipped over, data being corrupted, and - sometimes - data from completely outside the stream (i.e., garbage data) being copied into the stream.

WriteBytes(ref writer, (byte*)m_Data.GetUnsafePtr() + messageOffset, messageLength);

writerAvailable -= sizeof(int) + messageLength;
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6 changes: 6 additions & 0 deletions com.unity.netcode.gameobjects/Tests/Editor/Transports/BatchedSendQueueTests.cs
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Expand Up @@ -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]
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