fix: Don't accept invalid connections in UnityTransport.Send [1.X] (#3383)

Backport of PR #3382.

## Changelog

- Fixed: Fixed an issue in `UnityTransport` where the transport would
accept sends on invalid connections, leading to a useless memory
allocation and confusing error message.

## Testing and Documentation

- Includes integration test.
- No documentation changes or additions were necessary.

---------

Co-authored-by: michalChrobot <michal.chrobot@unity3d.com>
Co-authored-by: Michał Chrobot <124174716+michalChrobot@users.noreply.github.com>

Author: simon-lemay-unity

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -16,6 +16,7 @@ Additional documentation and release notes are available at [Multiplayer Documen
 
 ### Fixed
 
+- Fixed an issue in `UnityTransport` where the transport would accept sends on invalid connections, leading to a useless memory allocation and confusing error message. (#3383)
 - Fixed issue where `NetworkAnimator` would log an error if there was no destination transition information. (#3384)
 - Fixed initial `NetworkTransform` spawn, ensure it uses world space. (#3361)
 - Fixed issue where `AnticipatedNetworkVariable` previous value returned by `AnticipatedNetworkVariable.OnAuthoritativeValueChanged` is updated correctly on the non-authoritative side. (#3322)

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

@@ -1342,8 +1342,13 @@ public override NetcodeNetworkEvent PollEvent(out ulong clientId, out ArraySegme
         /// <param name="networkDelivery">The delivery type (QoS) to send data with</param>
         public override void Send(ulong clientId, ArraySegment<byte> payload, NetworkDelivery networkDelivery)
         {
-            var pipeline = SelectSendPipeline(networkDelivery);
+            var connection = ParseClientId(clientId);
+            if (!m_Driver.IsCreated || m_Driver.GetConnectionState(connection) != NetworkConnection.State.Connected)
+            {
+                return;
+            }
 
+            var pipeline = SelectSendPipeline(networkDelivery);
             if (pipeline != m_ReliableSequencedPipeline && payload.Count > m_MaxPayloadSize)
             {
                 Debug.LogError($"Unreliable payload of size {payload.Count} larger than configured 'Max Payload Size' ({m_MaxPayloadSize}).");

com.unity.netcode.gameobjects/Tests/Runtime/Transports/UnityTransportTestHelpers.cs

@@ -36,6 +36,23 @@ public static IEnumerator WaitForNetworkEvent(NetworkEvent type, List<TransportE
             Assert.Fail("Timed out while waiting for network event.");
         }
 
+        // Wait to ensure no event is sent.
+        public static IEnumerator EnsureNoNetworkEvent(List<TransportEvent> events, float timeout = MaxNetworkEventWaitTime)
+        {
+            int initialCount = events.Count;
+            float startTime = Time.realtimeSinceStartup;
+
+            while (Time.realtimeSinceStartup - startTime < timeout)
+            {
+                if (events.Count > initialCount)
+                {
+                    Assert.Fail("Received unexpected network event.");
+                }
+
+                yield return new WaitForSeconds(0.01f);
+            }
+        }
+
         // Common code to initialize a UnityTransport that logs its events.
         public static void InitializeTransport(out UnityTransport transport, out List<TransportEvent> events,
             int maxPayloadSize = UnityTransport.InitialMaxPayloadSize, int maxSendQueueSize = 0, NetworkFamily family = NetworkFamily.Ipv4)

com.unity.netcode.gameobjects/Tests/Runtime/Transports/UnityTransportTests.cs

@@ -554,5 +554,22 @@ public IEnumerator DoesNotActAfterShutdown([Values] AfterShutdownAction afterShu
                 m_Server.DisconnectLocalClient();
             }
         }
+
+        [UnityTest]
+        public IEnumerator DoesNotAttemptToSendOnInvalidConnections()
+        {
+            InitializeTransport(out m_Server, out m_ServerEvents);
+            InitializeTransport(out m_Client1, out m_Client1Events);
+
+            m_Server.StartServer();
+            m_Client1.StartClient();
+
+            yield return WaitForNetworkEvent(NetworkEvent.Connect, m_Client1Events);
+
+            var data = new ArraySegment<byte>(new byte[42]);
+            m_Server.Send(0, data, NetworkDelivery.Reliable);
+
+            yield return EnsureNoNetworkEvent(m_Client1Events);
+        }
     }
 }

pvpExceptions.json

@@ -2591,6 +2591,7 @@
           "Unity.Netcode.RuntimeTests.UnityTransportTestHelpers: undocumented",
           "Unity.Netcode.RuntimeTests.UnityTransportTestHelpers: MaxNetworkEventWaitTime: undocumented",
           "Unity.Netcode.RuntimeTests.UnityTransportTestHelpers: IEnumerator WaitForNetworkEvent(NetworkEvent, List<TransportEvent>, float): undocumented",
+          "Unity.Netcode.RuntimeTests.UnityTransportTestHelpers: IEnumerator EnsureNoNetworkEvent(List<TransportEvent>, float): undocumented",
           "Unity.Netcode.RuntimeTests.UnityTransportTestHelpers: void InitializeTransport(out UnityTransport, out List<TransportEvent>, int, int, NetworkFamily): undocumented",
           "Unity.Netcode.RuntimeTests.UnityTransportTestHelpers.TransportEvent: undocumented",
           "Unity.Netcode.RuntimeTests.UnityTransportTestHelpers.TransportEvent: Type: undocumented",
@@ -2617,6 +2618,7 @@
           "Unity.Netcode.RuntimeTests.UnityTransportTests: IEnumerator SendQueuesFlushedOnRemoteClientDisconnect(NetworkDelivery): undocumented",
           "Unity.Netcode.RuntimeTests.UnityTransportTests: IEnumerator ReliablePayloadsCanBeLargerThanMaximum(): undocumented",
           "Unity.Netcode.RuntimeTests.UnityTransportTests: IEnumerator DoesNotActAfterShutdown(AfterShutdownAction): undocumented",
+          "Unity.Netcode.RuntimeTests.UnityTransportTests: IEnumerator DoesNotAttemptToSendOnInvalidConnections(): undocumented",
           "Unity.Netcode.RuntimeTests.UnityTransportTests.AfterShutdownAction: undocumented",
           "Unity.Netcode.RuntimeTests.UnityTransportTests.AfterShutdownAction: Send: undocumented",
           "Unity.Netcode.RuntimeTests.UnityTransportTests.AfterShutdownAction: DisconnectRemoteClient: undocumented",