Fix a race condition where local channel's closeFuture is notified early

- Added AbstractChannel.doPreClose() to allow a transport to perform
  a task before closeFuture is notified

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

@@ -708,6 +708,10 @@ public abstract class AbstractChannel extends DefaultAttributeMap implements Cha
     protected abstract Runnable doRegister() throws Exception;
     protected abstract void doBind(SocketAddress localAddress) throws Exception;
     protected abstract void doDisconnect() throws Exception;
+    protected void doPreClose() throws Exception {
+        // NOOP by default
+    }
+
     protected abstract void doClose() throws Exception;
     protected abstract void doDeregister() throws Exception;
     protected void doFlushByteBuffer(ByteBuf buf) throws Exception {
@@ -799,7 +803,7 @@ public abstract class AbstractChannel extends DefaultAttributeMap implements Cha
         }
     }
 
-    private static final class CloseFuture extends DefaultChannelFuture implements ChannelFuture.Unsafe {
+    private final class CloseFuture extends DefaultChannelFuture implements ChannelFuture.Unsafe {
 
         CloseFuture(AbstractChannel ch) {
             super(ch, false);
@@ -816,6 +820,11 @@ public abstract class AbstractChannel extends DefaultAttributeMap implements Cha
         }
 
         boolean setClosed() {
+            try {
+                doPreClose();
+            } catch (Exception e) {
+                logger.warn("doPreClose() raised an exception.", e);
+            }
             return super.setSuccess();
         }
     }

transport/src/main/java/io/netty/channel/local/LocalChannel.java

@@ -17,10 +17,10 @@ package io.netty.channel.local;
 
 import io.netty.channel.AbstractChannel;
 import io.netty.channel.Channel;
+import io.netty.channel.ChannelBufferType;
 import io.netty.channel.ChannelConfig;
 import io.netty.channel.ChannelException;
 import io.netty.channel.ChannelFuture;
-import io.netty.channel.ChannelBufferType;
 import io.netty.channel.DefaultChannelConfig;
 import io.netty.channel.EventLoop;
 import io.netty.channel.SingleThreadEventLoop;
@@ -171,17 +171,22 @@ public class LocalChannel extends AbstractChannel {
     }
 
     @Override
-    protected void doClose() throws Exception {
+    protected void doPreClose() throws Exception {
         if (state > 2) {
             // Closed already
             return;
         }
 
+        // Update all internal state before the closeFuture is notified.
         if (parent() == null) {
             LocalChannelRegistry.unregister(localAddress);
         }
         localAddress = null;
         state = 3;
+    }
+
+    @Override
+    protected void doClose() throws Exception {
         if (peer.isActive()) {
             peer.unsafe().close(peer.unsafe().voidFuture());
             peer = null;

transport/src/main/java/io/netty/channel/local/LocalServerChannel.java

@@ -96,17 +96,23 @@ public class LocalServerChannel extends AbstractServerChannel {
     }
 
     @Override
-    protected void doClose() throws Exception {
+    protected void doPreClose() throws Exception {
         if (state > 1) {
             // Closed already.
             return;
         }
 
+        // Update all internal state before the closeFuture is notified.
         LocalChannelRegistry.unregister(localAddress);
         localAddress = null;
         state = 2;
     }
 
+    @Override
+    protected void doClose() throws Exception {
+        // All internal state was updated already at doPreClose().
+    }
+
     @Override
     protected void doDeregister() throws Exception {
         ((SingleThreadEventLoop) eventLoop()).removeShutdownHook(shutdownHook);