Fix GCHandle leak in NetworkReachability.SetNotification

src/SystemConfiguration/NetworkReachability.cs

@@ -416,6 +416,15 @@ public NetworkReachability (IPAddress localAddress, IPAddress remoteAddress)
 		{
 		}
 
+		protected override void Dispose (bool disposing)
+		{
+			if (gchAllocated) {
+				gch.Free ();
+				gchAllocated = false;
+			}
+			base.Dispose (disposing);
+		}
+
 		[SupportedOSPlatform ("ios")]
 		[SupportedOSPlatform ("tvos")]
 		[SupportedOSPlatform ("maccatalyst")]
@@ -487,6 +496,7 @@ public StatusCode GetFlags (out NetworkReachabilityFlags flags)
 
 		Notification? notification;
 		GCHandle gch;
+		bool gchAllocated;
 
 		[UnmanagedCallersOnly]
 		static void Callback (IntPtr handle, NetworkReachabilityFlags flags, IntPtr info)
@@ -518,6 +528,7 @@ public StatusCode SetNotification (Notification? callback)
 					return StatusCode.OK;
 
 				gch = GCHandle.Alloc (this);
+				gchAllocated = true;
 				var ctx = new SCNetworkReachabilityContext (GCHandle.ToIntPtr (gch));
 
 				unsafe {
@@ -532,6 +543,11 @@ public StatusCode SetNotification (Notification? callback)
 					if (!rv)
 						return StatusCodeError.SCError ();
 
+					if (gchAllocated) {
+						gch.Free ();
+						gchAllocated = false;
+					}
+
 					return StatusCode.OK;
 				}
 			}

tests/monotouch-test/SystemConfiguration/NetworkReachabilityTest.cs

@@ -142,5 +142,98 @@ public void Schedule ()
 			Assert.IsTrue (defaultRouteReachability.Schedule (CFRunLoop.Main, CFRunLoop.ModeDefault), "Schedule");
 			Assert.IsTrue (defaultRouteReachability.Unschedule (CFRunLoop.Main, CFRunLoop.ModeDefault), "Unschedule");
 		}
+
+		[Test]
+		public void SetNotification_SetAndRemove ()
+		{
+			using var nr = new NetworkReachability (IPAddress.Loopback);
+			bool callbackInvoked = false;
+			NetworkReachability.Notification callback = (flags) => {
+				callbackInvoked = true;
+			};
+
+			// Set notification
+			var result = nr.SetNotification (callback);
+			Assert.AreEqual (StatusCode.OK, result, "SetNotification should succeed");
+
+			// Remove notification
+			result = nr.SetNotification (null);
+			Assert.AreEqual (StatusCode.OK, result, "Removing notification should succeed");
+
+			// Setting null again should be OK
+			result = nr.SetNotification (null);
+			Assert.AreEqual (StatusCode.OK, result, "Setting null when no notification is set should succeed");
+		}
+
+		[Test]
+		public void SetNotification_DisposeAfterSet ()
+		{
+			// This test ensures that disposing after setting a notification doesn't leak the GCHandle
+			var nr = new NetworkReachability (IPAddress.Loopback);
+			bool callbackInvoked = false;
+			NetworkReachability.Notification callback = (flags) => {
+				callbackInvoked = true;
+			};
+
+			var result = nr.SetNotification (callback);
+			Assert.AreEqual (StatusCode.OK, result, "SetNotification should succeed");
+
+			// Dispose without removing notification - should not leak
+			nr.Dispose ();
+		}
+
+		[Test]
+		public void SetNotification_MultipleSetRemoveCycles ()
+		{
+			using var nr = new NetworkReachability (IPAddress.Loopback);
+			bool callbackInvoked = false;
+			NetworkReachability.Notification callback = (flags) => {
+				callbackInvoked = true;
+			};
+
+			// Set notification
+			var result = nr.SetNotification (callback);
+			Assert.AreEqual (StatusCode.OK, result, "First SetNotification should succeed");
+
+			// Remove notification
+			result = nr.SetNotification (null);
+			Assert.AreEqual (StatusCode.OK, result, "First remove should succeed");
+
+			// Set notification again
+			result = nr.SetNotification (callback);
+			Assert.AreEqual (StatusCode.OK, result, "Second SetNotification should succeed");
+
+			// Remove notification again
+			result = nr.SetNotification (null);
+			Assert.AreEqual (StatusCode.OK, result, "Second remove should succeed");
+		}
+
+		[Test]
+		public void SetNotification_UpdateCallback ()
+		{
+			using var nr = new NetworkReachability (IPAddress.Loopback);
+			bool firstCallbackInvoked = false;
+			bool secondCallbackInvoked = false;
+
+			NetworkReachability.Notification firstCallback = (flags) => {
+				firstCallbackInvoked = true;
+			};
+
+			NetworkReachability.Notification secondCallback = (flags) => {
+				secondCallbackInvoked = true;
+			};
+
+			// Set first notification
+			var result = nr.SetNotification (firstCallback);
+			Assert.AreEqual (StatusCode.OK, result, "First SetNotification should succeed");
+
+			// Update with second notification
+			result = nr.SetNotification (secondCallback);
+			Assert.AreEqual (StatusCode.OK, result, "Updating notification should succeed");
+
+			// Remove notification
+			result = nr.SetNotification (null);
+			Assert.AreEqual (StatusCode.OK, result, "Removing notification should succeed");
+		}
 	}
 }