fix: 32bit-ARMv7 crashes on android (#2654)

* fix
Word alignment applied to batch message.
Adjusted MaximumTransmissionUnitSize setter to round down to nearest word aligned size
Adjusted DefaultNonFragmentedMessageMaxSize  to round down to nearest word aligned size

* Fixed tests
The tools bytes measured tests were slightly modified

---------

Co-authored-by: Kitty Draper <kitty.draper@unity3d.com>

Author: NoelStephensUnity

com.unity.netcode.gameobjects/Runtime/Core/NetworkManager.cs

@@ -586,7 +586,7 @@ private void OnEnable()
         /// <param name="size"></param>
         public int MaximumTransmissionUnitSize
         {
-            set => MessageManager.NonFragmentedMessageMaxSize = value;
+            set => MessageManager.NonFragmentedMessageMaxSize = value & ~7; // Round down to nearest word aligned size
             get => MessageManager.NonFragmentedMessageMaxSize;
         }
 

com.unity.netcode.gameobjects/Runtime/Messaging/NetworkBatchHeader.cs

@@ -12,6 +12,11 @@ internal struct NetworkBatchHeader : INetworkSerializeByMemcpy
         /// </summary>
         public ushort Magic;
 
+        /// <summary>
+        /// Total number of messages in the batch.
+        /// </summary>
+        public ushort BatchCount;
+
         /// <summary>
         /// Total number of bytes in the batch.
         /// </summary>
@@ -22,9 +27,5 @@ internal struct NetworkBatchHeader : INetworkSerializeByMemcpy
         /// </summary>
         public ulong BatchHash;
 
-        /// <summary>
-        /// Total number of messages in the batch.
-        /// </summary>
-        public ushort BatchCount;
     }
 }

com.unity.netcode.gameobjects/Runtime/Messaging/NetworkMessageManager.cs

@@ -95,7 +95,7 @@ internal uint GetMessageType(Type t)
             return m_MessageTypes[t];
         }
 
-        public const int DefaultNonFragmentedMessageMaxSize = 1300;
+        public const int DefaultNonFragmentedMessageMaxSize = 1300 & ~7; // Round down to nearest word aligned size (1296)
         public int NonFragmentedMessageMaxSize = DefaultNonFragmentedMessageMaxSize;
         public int FragmentedMessageMaxSize = int.MaxValue;
 
@@ -829,11 +829,17 @@ internal unsafe void ProcessSendQueues()
                     // Skipping the Verify and sneaking the write mark in because we know it's fine.
                     queueItem.Writer.Handle->AllowedWriteMark = sizeof(NetworkBatchHeader);
 #endif
-                    queueItem.BatchHeader.BatchHash = XXHash.Hash64(queueItem.Writer.GetUnsafePtr() + sizeof(NetworkBatchHeader), queueItem.Writer.Length - sizeof(NetworkBatchHeader));
 
-                    queueItem.BatchHeader.BatchSize = queueItem.Writer.Length;
+
+                    var alignedLength = (queueItem.Writer.Length + 7) & ~7;
+                    queueItem.Writer.TryBeginWrite(alignedLength);
+
+                    queueItem.BatchHeader.BatchHash = XXHash.Hash64(queueItem.Writer.GetUnsafePtr() + sizeof(NetworkBatchHeader), alignedLength - sizeof(NetworkBatchHeader));
+
+                    queueItem.BatchHeader.BatchSize = alignedLength;
 
                     queueItem.Writer.WriteValue(queueItem.BatchHeader);
+                    queueItem.Writer.Seek(alignedLength);
 
 
                     try

com.unity.netcode.gameobjects/Tests/Runtime/Metrics/TransportBytesMetricsTests.cs

@@ -41,7 +41,7 @@ public IEnumerator TrackTotalNumberOfBytesSent()
             }
 
             Assert.True(observer.Found);
-            Assert.AreEqual(FastBufferWriter.GetWriteSize(messageName) + k_MessageOverhead, observer.Value);
+            Assert.AreEqual(((FastBufferWriter.GetWriteSize(messageName) + k_MessageOverhead) + 7) & ~7, observer.Value);
         }
 
         [UnityTest]
@@ -61,8 +61,6 @@ public IEnumerator TrackTotalNumberOfBytesReceived()
                 writer.Dispose();
             }
 
-
-
             var nbFrames = 0;
             while (!observer.Found || nbFrames < 10)
             {
@@ -71,7 +69,7 @@ public IEnumerator TrackTotalNumberOfBytesReceived()
             }
 
             Assert.True(observer.Found);
-            Assert.AreEqual(FastBufferWriter.GetWriteSize(messageName) + k_MessageOverhead, observer.Value);
+            Assert.AreEqual(((FastBufferWriter.GetWriteSize(messageName) + k_MessageOverhead) + 7) & ~7, observer.Value);
         }
 
         private class TotalBytesObserver : IMetricObserver
@@ -89,12 +87,22 @@ public TotalBytesObserver(IMetricDispatcher dispatcher, DirectionalMetricInfo me
 
             public long Value { get; private set; }
 
+            private int m_BytesFoundCounter;
+            private long m_TotalBytes;
+
             public void Observe(MetricCollection collection)
             {
                 if (collection.TryGetCounter(m_MetricInfo.Id, out var counter) && counter.Value > 0)
                 {
-                    Found = true;
-                    Value = counter.Value;
+                    // Don't assign another observed value once one is already observed
+                    if (!Found)
+                    {
+                        Found = true;
+                        Value = counter.Value;
+                        m_TotalBytes += ((counter.Value + 7) & ~7);
+                        m_BytesFoundCounter++;
+                        UnityEngine.Debug.Log($"[{m_BytesFoundCounter}] Bytes Observed {counter.Value} | Total Bytes Observed: {m_TotalBytes}");
+                    }
                 }
             }
         }