NETTY-426 Prevent a user from reusing an upstream MessageEvent to write

something

Modified the pipeline implementations so that it rejects the attempt to
send an UpstreamMessageEvent to downstream

Author: trustin

src/main/java/org/jboss/netty/channel/DefaultChannelPipeline.java

@@ -590,6 +590,10 @@ public void sendDownstream(ChannelEvent e) {
     }
 
     void sendDownstream(DefaultChannelHandlerContext ctx, ChannelEvent e) {
+        if (e instanceof UpstreamMessageEvent) {
+            throw new IllegalArgumentException("cannot send an upstream event to downstream");
+        }
+        
         try {
             ((ChannelDownstreamHandler) ctx.getHandler()).handleDownstream(ctx, e);
         } catch (Throwable t) {

src/main/java/org/jboss/netty/channel/StaticChannelPipeline.java

@@ -407,6 +407,10 @@ public void sendDownstream(ChannelEvent e) {
     }
 
     void sendDownstream(StaticChannelHandlerContext ctx, ChannelEvent e) {
+        if (e instanceof UpstreamMessageEvent) {
+            throw new IllegalArgumentException("cannot send an upstream event to downstream");
+        }
+
         try {
             ((ChannelDownstreamHandler) ctx.getHandler()).handleDownstream(ctx, e);
         } catch (Throwable t) {