Close channel on TLS exception to prevent half-open connections

dubbo-remoting/dubbo-remoting-netty4/src/main/java/org/apache/dubbo/remoting/transport/netty4/ssl/SslClientTlsHandler.java

@@ -68,9 +68,10 @@ public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exc
                         INTERNAL_ERROR,
                         "unknown error in remoting module",
                         "",
-                        "TLS negotiation failed when trying to accept new connection.",
+                        "TLS negotiation failed when connecting to remote server.",
                         handshakeEvent.cause());
                 ctx.fireExceptionCaught(handshakeEvent.cause());
+                ctx.close();
             }
         }
     }

dubbo-remoting/dubbo-remoting-netty4/src/test/java/org/apache/dubbo/remoting/transport/netty4/ssl/SslHandlerExceptionTest.java

@@ -0,0 +1,60 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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
+ *
+ *     http://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.apache.dubbo.remoting.transport.netty4.ssl;
+
+import javax.net.ssl.SSLHandshakeException;
+
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.handler.ssl.SslContext;
+import io.netty.handler.ssl.SslHandshakeCompletionEvent;
+import org.junit.jupiter.api.Test;
+
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
+/**
+ * Verify that TLS handlers properly close channels on exceptions,
+ * preventing half-open connections that are TCP-alive but application-dead.
+ */
+class SslHandlerExceptionTest {
+
+    @Test
+    void serverTlsHandler_exceptionCaught_shouldCloseChannel() throws Exception {
+        ChannelHandlerContext ctx = mock(ChannelHandlerContext.class);
+
+        SslServerTlsHandler handler = new SslServerTlsHandler(null, true);
+        NoClassDefFoundError error =
+                new NoClassDefFoundError("Could not initialize class io.netty.buffer.PooledUnsafeDirectByteBuf");
+
+        handler.exceptionCaught(ctx, error);
+
+        verify(ctx).close();
+    }
+
+    @Test
+    void clientTlsHandler_handshakeFailure_shouldCloseChannel() throws Exception {
+        ChannelHandlerContext ctx = mock(ChannelHandlerContext.class);
+
+        SslClientTlsHandler handler = new SslClientTlsHandler(mock(SslContext.class));
+        SslHandshakeCompletionEvent failureEvent =
+                new SslHandshakeCompletionEvent(new SSLHandshakeException("TLS handshake timeout"));
+
+        handler.userEventTriggered(ctx, failureEvent);
+
+        verify(ctx).close();
+    }
+}