From ea3c26b65e2b927e4ee386f35bc8fa93f24c97d7 Mon Sep 17 00:00:00 2001
From: Matthias Einwag <matthias.einwag@live.com>
Date: Fri, 26 Sep 2014 22:47:27 +0200
Subject: [PATCH] Send a websocket close frame with status code when receiving
 invalid frames

Motivation:

According to the websocket specification peers may send a close frame when
they detect a protocol violation (with status code 1002). The current
implementation simply closes the connection. This update should add this
functionality. The functionality is optional - but it might help other
implementations with debugging when they receive such a frame.

Modification:

When a protocol violation in the decoder is detected and a close was not
already initiated by the remote peer a close frame is
sent.

Result:

Remotes which will send an invalid frame will now get a close frame that
indicates the protocol violation instead of only seeing a closed
connection.
---
 .../codec/http/websocketx/WebSocket08FrameDecoder.java | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocket08FrameDecoder.java b/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocket08FrameDecoder.java
index c4a4cce17d..7f23028d8d 100644
--- a/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocket08FrameDecoder.java
+++ b/codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocket08FrameDecoder.java
@@ -314,8 +314,8 @@ public class WebSocket08FrameDecoder extends ReplayingDecoder<WebSocket08FrameDe
                         return;
                     }
                     if (frameOpcode == OPCODE_CLOSE) {
-                        checkCloseFrameBody(ctx, framePayload);
                         receivedClosingHandshake = true;
+                        checkCloseFrameBody(ctx, framePayload);
                         out.add(new CloseWebSocketFrame(frameFinalFlag, frameRsv, framePayload));
                         framePayload = null;
                         return;
@@ -414,7 +414,13 @@ public class WebSocket08FrameDecoder extends ReplayingDecoder<WebSocket08FrameDe
     private void protocolViolation(ChannelHandlerContext ctx, CorruptedFrameException ex) {
         checkpoint(State.CORRUPT);
         if (ctx.channel().isActive()) {
-            ctx.writeAndFlush(Unpooled.EMPTY_BUFFER).addListener(ChannelFutureListener.CLOSE);
+            Object closeMessage;
+            if (receivedClosingHandshake) {
+                closeMessage = Unpooled.EMPTY_BUFFER;
+            } else {
+                closeMessage = new CloseWebSocketFrame(1002, null);
+            }
+            ctx.writeAndFlush(closeMessage).addListener(ChannelFutureListener.CLOSE);
         }
         throw ex;
     }