GH-3701: Fix Possible TCP Memory Leak

Resolves #3701

Ensure `TcpSender.removeDeadConnection` is always called, for example when
intercepted and closed via `factory.closeConnectionId` or when closed
connections are harvested from the `connections` map.

**Cherry-pick to 5.4.x, 5.3.x**

Author: garyrussell

Diff for: spring-integration-ip/src/main/java/org/springframework/integration/ip/tcp/connection/AbstractConnectionFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2022 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -566,6 +566,7 @@ public void stop() {
 				TcpConnection connection = iterator.next().getValue();
 				connection.close();
 				iterator.remove();
+				getSenders().forEach(sender -> sender.removeDeadConnection(connection));
 			}
 		}
 		synchronized (this.lifecycleMonitor) {
@@ -865,6 +866,7 @@ private List<String> removeClosedConnectionsAndReturnOpenConnectionIds() {
 				TcpConnectionSupport connection = entry.getValue();
 				if (!connection.isOpen()) {
 					iterator.remove();
+					getSenders().forEach(sender -> sender.removeDeadConnection(connection));
 					logger.debug(() -> getComponentName() + ": Removed closed connection: " +
 							connection.getConnectionId());
 				}
@@ -937,11 +939,12 @@ public boolean closeConnection(String connectionId) {
 		// closed connections are removed from #connections in #harvestClosedConnections()
 		synchronized (this.connections) {
 			boolean closed = false;
-			TcpConnectionSupport connection = this.connections.get(connectionId);
+			TcpConnectionSupport connection = this.connections.remove(connectionId);
 			if (connection != null) {
 				try {
 					connection.close();
 					closed = true;
+					getSenders().forEach(sender -> sender.removeDeadConnection(connection));
 				}
 				catch (Exception ex) {
 					logger.debug(ex, () -> "Failed to close connection " + connectionId);

Diff for: spring-integration-ip/src/test/java/org/springframework/integration/ip/tcp/connection/TcpSenderTests.java

@@ -0,0 +1,108 @@
+/*
+ * Copyright 2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.integration.ip.tcp.connection;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+
+import org.junit.jupiter.api.Test;
+
+/**
+ * @author Gary Russell
+ * @since 5.3.10
+ *
+ */
+public class TcpSenderTests {
+
+	@Test
+	void senderCalledForDeadConnectionClientNet() throws InterruptedException {
+		CountDownLatch latch = new CountDownLatch(1);
+		TcpNetServerConnectionFactory server = new TcpNetServerConnectionFactory(0);
+		server.registerListener(msg -> false);
+		server.afterPropertiesSet();
+		server.setApplicationEventPublisher(event -> {
+			if (event instanceof TcpConnectionServerListeningEvent) {
+				latch.countDown();
+			}
+		});
+		server.start();
+		assertThat(latch.await(10, TimeUnit.SECONDS)).isTrue();
+		TcpNetClientConnectionFactory client = new TcpNetClientConnectionFactory("localhost", server.getPort());
+		senderCalledForDeadConnectionClient(client);
+		server.stop();
+	}
+
+	@Test
+	void senderCalledForDeadConnectionClientNio() throws InterruptedException {
+		CountDownLatch latch = new CountDownLatch(1);
+		TcpNetServerConnectionFactory server = new TcpNetServerConnectionFactory(0);
+		server.registerListener(msg -> false);
+		server.afterPropertiesSet();
+		server.setApplicationEventPublisher(event -> {
+			if (event instanceof TcpConnectionServerListeningEvent) {
+				latch.countDown();
+			}
+		});
+		server.start();
+		assertThat(latch.await(10, TimeUnit.SECONDS)).isTrue();
+		TcpNioClientConnectionFactory client = new TcpNioClientConnectionFactory("localhost", server.getPort());
+		senderCalledForDeadConnectionClient(client);
+		server.stop();
+	}
+
+	private void senderCalledForDeadConnectionClient(AbstractClientConnectionFactory client) throws InterruptedException {
+		CountDownLatch adds = new CountDownLatch(2);
+		CountDownLatch removes = new CountDownLatch(2);
+		TcpConnectionInterceptorFactoryChain chain = new TcpConnectionInterceptorFactoryChain();
+		chain.setInterceptor(new HelloWorldInterceptorFactory() {
+
+			@Override
+			public TcpConnectionInterceptorSupport getInterceptor() {
+				return new TcpConnectionInterceptorSupport() {
+				};
+			}
+
+		});
+		client.setInterceptorFactoryChain(chain);
+		client.registerSender(new TcpSender() {
+
+			@Override
+			public void addNewConnection(TcpConnection connection) {
+				adds.countDown();
+			}
+
+			@Override
+			public void removeDeadConnection(TcpConnection connection) {
+				removes.countDown();
+			}
+
+		});
+		client.setSingleUse(true);
+		client.afterPropertiesSet();
+		client.start();
+		TcpConnectionSupport conn = client.getConnection();
+		conn.close();
+		conn = client.getConnection();
+		assertThat(adds.await(10, TimeUnit.SECONDS)).isTrue();
+		conn.close();
+		client.stop();
+		assertThat(removes.await(10, TimeUnit.SECONDS)).isTrue();
+	}
+
+}