feat: Add methods for setting max message size limits (i.e., MTU negotiation) [MTT-6214]

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -10,6 +10,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 
 ### Added
 
+- Added: Message size limits (max single message and max fragmented message) can now be set using NetworkManager.SetMaxSingleMessageSize() and NetworkManager.SetMaxFragmentedMessageSize() for transports that don't work with the default values (#2530)
 - Added `NetworkObject.SpawnWithObservers` property (default is true) that when set to false will spawn a `NetworkObject` with no observers and will not be spawned on any client until `NetworkObject.NetworkShow` is invoked. (#2568)
 
 ### Fixed

com.unity.netcode.gameobjects/Runtime/Configuration/NetworkConfig.cs

@@ -156,7 +156,7 @@ public class NetworkConfig
         public string ToBase64()
         {
             NetworkConfig config = this;
-            var writer = new FastBufferWriter(NetworkMessageManager.NonFragmentedMessageMaxSize, Allocator.Temp);
+            var writer = new FastBufferWriter(1024, Allocator.Temp);
             using (writer)
             {
                 writer.WriteValueSafe(config.ProtocolVersion);
@@ -228,7 +228,7 @@ public ulong GetConfig(bool cache = true)
                 return m_ConfigHash.Value;
             }
 
-            var writer = new FastBufferWriter(NetworkMessageManager.NonFragmentedMessageMaxSize, Allocator.Temp, int.MaxValue);
+            var writer = new FastBufferWriter(1024, Allocator.Temp, int.MaxValue);
             using (writer)
             {
                 writer.WriteValueSafe(ProtocolVersion);

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

@@ -63,7 +63,7 @@ internal void __endSendServerRpc(ref FastBufferWriter bufferWriter, uint rpcMeth
                     networkDelivery = NetworkDelivery.ReliableFragmentedSequenced;
                     break;
                 case RpcDelivery.Unreliable:
-                    if (bufferWriter.Length > NetworkMessageManager.NonFragmentedMessageMaxSize)
+                    if (bufferWriter.Length > NetworkManager.MessageManager.NonFragmentedMessageMaxSize)
                     {
                         throw new OverflowException("RPC parameters are too large for unreliable delivery.");
                     }
@@ -144,7 +144,7 @@ internal void __endSendClientRpc(ref FastBufferWriter bufferWriter, uint rpcMeth
                     networkDelivery = NetworkDelivery.ReliableFragmentedSequenced;
                     break;
                 case RpcDelivery.Unreliable:
-                    if (bufferWriter.Length > NetworkMessageManager.NonFragmentedMessageMaxSize)
+                    if (bufferWriter.Length > NetworkManager.MessageManager.NonFragmentedMessageMaxSize)
                     {
                         throw new OverflowException("RPC parameters are too large for unreliable delivery.");
                     }
@@ -691,7 +691,7 @@ private void NetworkVariableUpdate(ulong targetClientId, int behaviourIndex)
                     // so we don't have to do this serialization work if we're not going to use the result.
                     if (IsServer && targetClientId == NetworkManager.ServerClientId)
                     {
-                        var tmpWriter = new FastBufferWriter(NetworkMessageManager.NonFragmentedMessageMaxSize, Allocator.Temp, NetworkMessageManager.FragmentedMessageMaxSize);
+                        var tmpWriter = new FastBufferWriter(NetworkManager.MessageManager.NonFragmentedMessageMaxSize, Allocator.Temp, NetworkManager.MessageManager.FragmentedMessageMaxSize);
                         using (tmpWriter)
                         {
                             message.Serialize(tmpWriter, message.Version);

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

@@ -580,6 +580,28 @@ private void OnEnable()
         /// <param name="prefab"></param>
         public void RemoveNetworkPrefab(GameObject prefab) => PrefabHandler.RemoveNetworkPrefab(prefab);
 
+        /// <summary>
+        /// Sets the maximum size of a single non-fragmented message (or message batch) passed through the transport.
+        /// This should represent the transport's MTU size, minus any transport-level overhead.
+        /// </summary>
+        /// <param name="size"></param>
+        public int MaxTransmissionUnitSize
+        {
+            set => MessageManager.NonFragmentedMessageMaxSize = value;
+            get => MessageManager.NonFragmentedMessageMaxSize;
+        }
+
+        /// <summary>
+        /// Sets the maximum size of a message (or message batch) passed through the transport with the ReliableFragmented delivery.
+        /// Warning: setting this value too low may result in the SDK becoming non-functional with projects that have a large number of NetworkBehaviours or NetworkVariables, as the SDK relies on the transport's ability to fragment some messages when they grow beyond the MTU size.
+        /// </summary>
+        /// <param name="size"></param>
+        public int MaximumFragmentedMessageSize
+        {
+            set => MessageManager.FragmentedMessageMaxSize = value;
+            get => MessageManager.FragmentedMessageMaxSize;
+        }
+
         internal void Initialize(bool server)
         {
             // Don't allow the user to start a network session if the NetworkManager is

com.unity.netcode.gameobjects/Runtime/Messaging/Messages/NetworkVariableDeltaMessage.cs

@@ -90,7 +90,7 @@ public void Serialize(FastBufferWriter writer, int targetVersion)
                 {
                     if (NetworkBehaviour.NetworkManager.NetworkConfig.EnsureNetworkVariableLengthSafety)
                     {
-                        var tempWriter = new FastBufferWriter(NetworkMessageManager.NonFragmentedMessageMaxSize, Allocator.Temp, NetworkMessageManager.FragmentedMessageMaxSize);
+                        var tempWriter = new FastBufferWriter(NetworkBehaviour.NetworkManager.MessageManager.NonFragmentedMessageMaxSize, Allocator.Temp, NetworkBehaviour.NetworkManager.MessageManager.FragmentedMessageMaxSize);
                         NetworkBehaviour.NetworkVariableFields[i].WriteDelta(tempWriter);
                         BytePacker.WriteValueBitPacked(writer, tempWriter.Length);
 

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

@@ -95,8 +95,9 @@ internal uint GetMessageType(Type t)
             return m_MessageTypes[t];
         }
 
-        public const int NonFragmentedMessageMaxSize = 1300;
-        public const int FragmentedMessageMaxSize = int.MaxValue;
+        public const int DefaultNonFragmentedMessageMaxSize = 1300;
+        public int NonFragmentedMessageMaxSize = DefaultNonFragmentedMessageMaxSize;
+        public int FragmentedMessageMaxSize = int.MaxValue;
 
         internal struct MessageWithHandler
         {

com.unity.netcode.gameobjects/Tests/Editor/Messaging/MessageSendingTests.cs

@@ -157,7 +157,7 @@ public void WhenNotExceedingBatchSize_NewBatchesAreNotCreated()
         {
             var message = GetMessage();
             var size = UnsafeUtility.SizeOf<TestMessage>() + 2; // MessageHeader packed with this message will be 2 bytes
-            for (var i = 0; i < (1300 - UnsafeUtility.SizeOf<NetworkBatchHeader>()) / size; ++i)
+            for (var i = 0; i < (m_MessageManager.NonFragmentedMessageMaxSize - UnsafeUtility.SizeOf<NetworkBatchHeader>()) / size; ++i)
             {
                 m_MessageManager.SendMessage(ref message, NetworkDelivery.Reliable, m_Clients);
             }
@@ -167,11 +167,12 @@ public void WhenNotExceedingBatchSize_NewBatchesAreNotCreated()
         }
 
         [Test]
-        public void WhenExceedingBatchSize_NewBatchesAreCreated()
+        public void WhenExceedingBatchSize_NewBatchesAreCreated([Values(500, 1000, 1300, 2000)] int maxMessageSize)
         {
             var message = GetMessage();
+            m_MessageManager.NonFragmentedMessageMaxSize = maxMessageSize;
             var size = UnsafeUtility.SizeOf<TestMessage>() + 2; // MessageHeader packed with this message will be 2 bytes
-            for (var i = 0; i < ((1300 - UnsafeUtility.SizeOf<NetworkBatchHeader>()) / size) + 1; ++i)
+            for (var i = 0; i < ((m_MessageManager.NonFragmentedMessageMaxSize - UnsafeUtility.SizeOf<NetworkBatchHeader>()) / size) + 1; ++i)
             {
                 m_MessageManager.SendMessage(ref message, NetworkDelivery.Reliable, m_Clients);
             }
@@ -181,11 +182,12 @@ public void WhenExceedingBatchSize_NewBatchesAreCreated()
         }
 
         [Test]
-        public void WhenExceedingMTUSizeWithFragmentedDelivery_NewBatchesAreNotCreated()
+        public void WhenExceedingMTUSizeWithFragmentedDelivery_NewBatchesAreNotCreated([Values(500, 1000, 1300, 2000)] int maxMessageSize)
         {
             var message = GetMessage();
+            m_MessageManager.NonFragmentedMessageMaxSize = maxMessageSize;
             var size = UnsafeUtility.SizeOf<TestMessage>() + 2; // MessageHeader packed with this message will be 2 bytes
-            for (var i = 0; i < ((1300 - UnsafeUtility.SizeOf<NetworkBatchHeader>()) / size) + 1; ++i)
+            for (var i = 0; i < ((m_MessageManager.NonFragmentedMessageMaxSize - UnsafeUtility.SizeOf<NetworkBatchHeader>()) / size) + 1; ++i)
             {
                 m_MessageManager.SendMessage(ref message, NetworkDelivery.ReliableFragmentedSequenced, m_Clients);
             }
@@ -291,7 +293,7 @@ public void WhenReceivingAMessageWithoutAHandler_ExceptionIsLogged()
 
             var message = GetMessage();
 
-            var writer = new FastBufferWriter(1300, Allocator.Temp);
+            var writer = new FastBufferWriter(m_MessageManager.NonFragmentedMessageMaxSize, Allocator.Temp);
             using (writer)
             {
                 writer.TryBeginWrite(FastBufferWriter.GetWriteSize(message));