Fix bugs in idle timeout logic (C#) (#3156)

csharp/src/Ice/ConnectionI.cs

@@ -1941,6 +1941,9 @@ private bool validate(int operation)
                     throw new MarshalException($"Received ValidateConnection message with unexpected size {size}.");
                 }
                 TraceUtil.traceRecv(_readStream, this, _logger, _traceLevels);
+
+                // Client connection starts sending heartbeats once it's received the ValidateConnection message.
+                _idleTimeoutTransceiver?.scheduleHeartbeat();
             }
         }
 

csharp/src/Ice/Internal/IdleTimeoutTransceiverDecorator.cs

@@ -2,7 +2,6 @@
 
 #nullable enable
 
-using System.Collections;
 using System.Diagnostics;
 using System.Net.Sockets;
 
@@ -61,17 +60,8 @@ public void finishRead(Buffer buf)
 
     public ConnectionInfo getInfo() => _decoratee.getInfo();
 
-    public int initialize(Buffer readBuffer, Buffer writeBuffer, ref bool hasMoreData)
-    {
-        int op = _decoratee.initialize(readBuffer, writeBuffer, ref hasMoreData);
-
-        if (op == SocketOperation.None) // connected
-        {
-            rescheduleWriteTimer();
-        }
-
-        return op;
-    }
+    public int initialize(Buffer readBuffer, Buffer writeBuffer, ref bool hasMoreData) =>
+        _decoratee.initialize(readBuffer, writeBuffer, ref hasMoreData);
 
     public string protocol() => _decoratee.protocol();
 
@@ -108,7 +98,11 @@ public int write(Buffer buf)
         return op;
     }
 
-    internal IdleTimeoutTransceiverDecorator(Transceiver decoratee, ConnectionI connection, TimeSpan idleTimeout, bool enableIdleCheck)
+    internal IdleTimeoutTransceiverDecorator(
+        Transceiver decoratee,
+        ConnectionI connection,
+        TimeSpan idleTimeout,
+        bool enableIdleCheck)
     {
         Debug.Assert(idleTimeout > TimeSpan.Zero);
 
@@ -118,9 +112,12 @@ internal IdleTimeoutTransceiverDecorator(Transceiver decoratee, ConnectionI conn
         if (enableIdleCheck)
         {
             _readTimer = new System.Threading.Timer(_ => connection.idleCheck(_idleTimeout));
-        }
-        idleCheckEnabled = enableIdleCheck;
 
+            // idleCheckEnabled remains false for now. ConnectionI calls enableIdleCheck() when it becomes Active to
+            // schedule the first idle check and set idleCheckEnabled to true.
+            // We don't want the idle check to start when a client connection is waiting for the initial
+            // ValidateConnection message or when a server connection is in its initial StateHolding state.
+        }
         _writeTimer = new System.Threading.Timer(_ => connection.sendHeartbeat());
     }
 
@@ -142,6 +139,8 @@ internal void disableIdleCheck()
         }
     }
 
+    internal void scheduleHeartbeat() => rescheduleWriteTimer();
+
     private void cancelReadTimer() => _readTimer!.Change(Timeout.InfiniteTimeSpan, Timeout.InfiniteTimeSpan);
 
     private void cancelWriteTimer() => _writeTimer.Change(Timeout.InfiniteTimeSpan, Timeout.InfiniteTimeSpan);