fix: prevent Owner-writable NetworkVariable from being sent to the owning client by the server and getting overwritten. NCCBUG-168 (#1871)

Author: jeffreyrainy

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

@@ -54,6 +54,14 @@ public void Serialize(FastBufferWriter writer)
                     networkVariable.CanClientRead(TargetClientId) &&
                     (NetworkBehaviour.NetworkManager.IsServer || networkVariable.CanClientWrite(NetworkBehaviour.NetworkManager.LocalClientId));
 
+                // Prevent the server from writing to the client that owns a given NetworkVariable
+                // Allowing the write would send an old value to the client and cause jitter
+                if (networkVariable.WritePerm == NetworkVariableWritePermission.Owner &&
+                    networkVariable.OwnerClientId() == TargetClientId)
+                {
+                    shouldWrite = false;
+                }
+
                 if (NetworkBehaviour.NetworkManager.NetworkConfig.EnsureNetworkVariableLengthSafety)
                 {
                     if (!shouldWrite)

com.unity.netcode.gameobjects/Runtime/NetworkVariable/NetworkVariable.cs

@@ -143,6 +143,11 @@ public override void WriteDelta(FastBufferWriter writer)
         /// <param name="keepDirtyDelta">Whether or not the container should keep the dirty delta, or mark the delta as consumed</param>
         public override void ReadDelta(FastBufferReader reader, bool keepDirtyDelta)
         {
+            // todo:
+            // keepDirtyDelta marks a variable received as dirty and causes the server to send the value to clients
+            // In a prefect world, whether a variable was A) modified locally or B) received and needs retransmit
+            // would be stored in different fields
+
             T previousValue = m_InternalValue;
             Read(reader, out m_InternalValue);
 

com.unity.netcode.gameobjects/Runtime/NetworkVariable/NetworkVariableBase.cs

@@ -94,6 +94,14 @@ public bool CanClientWrite(ulong clientId)
             }
         }
 
+        /// <summary>
+        /// Returns the ClientId of the owning client
+        /// </summary>
+        internal ulong OwnerClientId()
+        {
+            return m_NetworkBehaviour.NetworkObject.OwnerClientId;
+        }
+
         /// <summary>
         /// Writes the dirty changes, that is, the changes since the variable was last dirty, to the writer
         /// </summary>