Correctly reset cached local and remote address when disconnect() is called (#9545)

Motivation:

We should correctly reset the cached local and remote address when a Channel.disconnect() is called and the channel has a notion of disconnect vs close (for example DatagramChannel implementations).

Modifications:

- Correctly reset cached kicak abd remote address
- Update testcase to cover it and so ensure all transports work in a consistent way

Result:

Correctly handle disconnect()

testsuite/src/main/java/io/netty/testsuite/transport/socket/DatagramUnicastTest.java

@@ -298,9 +298,14 @@ public class DatagramUnicastTest extends AbstractDatagramTest {
             }
             assertTrue(cc.isConnected());
 
+            assertNotNull(cc.localAddress());
+            assertNotNull(cc.remoteAddress());
+
             // Test what happens when we call disconnect()
             cc.disconnect().syncUninterruptibly();
             assertFalse(cc.isConnected());
+            assertNotNull(cc.localAddress());
+            assertNull(cc.remoteAddress());
 
             ChannelFuture future = cc.writeAndFlush(
                     buf.retain().duplicate()).awaitUninterruptibly();

transport-native-epoll/src/main/java/io/netty/channel/epoll/AbstractEpollChannel.java

@@ -191,6 +191,11 @@ abstract class AbstractEpollChannel extends AbstractChannel implements UnixChann
         }
     }
 
+    void resetCachedAddresses() {
+        local = socket.localAddress();
+        remote = socket.remoteAddress();
+    }
+
     @Override
     protected void doDisconnect() throws Exception {
         doClose();

transport-native-epoll/src/main/java/io/netty/channel/epoll/EpollDatagramChannel.java

@@ -453,6 +453,7 @@ public final class EpollDatagramChannel extends AbstractEpollChannel implements
     protected void doDisconnect() throws Exception {
         socket.disconnect();
         connected = active = false;
+        resetCachedAddresses();
     }
 
     @Override

transport-native-kqueue/src/main/java/io/netty/channel/kqueue/AbstractKQueueChannel.java

@@ -132,6 +132,11 @@ abstract class AbstractKQueueChannel extends AbstractChannel implements UnixChan
         doClose();
     }
 
+    void resetCachedAddresses() {
+        local = socket.localAddress();
+        remote = socket.remoteAddress();
+    }
+
     @Override
     protected boolean isCompatible(EventLoop loop) {
         return loop instanceof KQueueEventLoop;

transport-native-kqueue/src/main/java/io/netty/channel/kqueue/KQueueDatagramChannel.java

@@ -386,6 +386,7 @@ public final class KQueueDatagramChannel extends AbstractKQueueChannel implement
     protected void doDisconnect() throws Exception {
         socket.disconnect();
         connected = active = false;
+        resetCachedAddresses();
     }
 
     @Override

transport/src/main/java/io/netty/channel/AbstractChannel.java

@@ -578,6 +578,9 @@ public abstract class AbstractChannel extends DefaultAttributeMap implements Cha
             boolean wasActive = isActive();
             try {
                 doDisconnect();
+                // Reset remoteAddress and localAddress
+                remoteAddress = null;
+                localAddress = null;
             } catch (Throwable t) {
                 safeSetFailure(promise, t);
                 closeIfClosed();