@normanm @trustin This hack appears to fix all my issues with writing ByteBufs directly to channels. new @lazertester.party(). Others, please note this still isn't even a beta quality build. Due to memory laziness this build will only accept one connection.

proxy/src/main/java/net/md_5/bungee/connection/DownstreamBridge.java

@@ -15,6 +15,7 @@ import net.md_5.bungee.api.config.ServerInfo;
 import net.md_5.bungee.api.connection.ProxiedPlayer;
 import net.md_5.bungee.api.event.ChatEvent;
 import net.md_5.bungee.api.event.PluginMessageEvent;
+import net.md_5.bungee.netty.Wrapper;
 import net.md_5.bungee.packet.Packet0KeepAlive;
 import net.md_5.bungee.packet.Packet3Chat;
 import net.md_5.bungee.packet.PacketC9PlayerListItem;
@@ -50,9 +51,9 @@ public class DownstreamBridge extends PacketHandler
     }
 
     @Override
-    public void handle(ByteBuf buf) throws Exception
+    public void handle(Wrapper buf) throws Exception
     {
-        EntityMap.rewrite( buf, con.serverEntityId, con.clientEntityId );
+        EntityMap.rewrite( buf.buf, con.serverEntityId, con.clientEntityId );
         con.ch.write( buf );
     }
 

proxy/src/main/java/net/md_5/bungee/connection/UpstreamBridge.java

@@ -10,6 +10,7 @@ import net.md_5.bungee.api.ProxyServer;
 import net.md_5.bungee.api.event.ChatEvent;
 import net.md_5.bungee.api.event.PlayerDisconnectEvent;
 import net.md_5.bungee.api.event.PluginMessageEvent;
+import net.md_5.bungee.netty.Wrapper;
 import net.md_5.bungee.packet.Packet0KeepAlive;
 import net.md_5.bungee.packet.Packet3Chat;
 import net.md_5.bungee.packet.PacketFAPluginMessage;
@@ -44,9 +45,9 @@ public class UpstreamBridge extends PacketHandler
     }
 
     @Override
-    public void handle(ByteBuf buf) throws Exception
+    public void handle(Wrapper buf) throws Exception
     {
-        EntityMap.rewrite( buf, con.clientEntityId, con.serverEntityId );
+        EntityMap.rewrite( buf.buf, con.clientEntityId, con.serverEntityId );
         if ( con.getServer() != null )
         {
             con.getServer().getCh().write( buf );

proxy/src/main/java/net/md_5/bungee/netty/HackEncoder.java

@@ -0,0 +1,17 @@
+package net.md_5.bungee.netty;
+
+import io.netty.buffer.ByteBuf;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.handler.codec.MessageToByteEncoder;
+
+public class HackEncoder extends MessageToByteEncoder<Wrapper>
+{
+
+    @Override
+    protected void encode(ChannelHandlerContext ctx, Wrapper msg, ByteBuf out) throws Exception
+    {
+        out.capacity( msg.buf.readableBytes() );
+        out.writeBytes( msg.buf );
+        msg.buf.release();
+    }
+}

proxy/src/main/java/net/md_5/bungee/netty/HandlerBoss.java

@@ -16,7 +16,7 @@ import net.md_5.bungee.packet.PacketHandler;
  * channels to maintain simple states, and only call the required, adapted
  * methods when the channel is connected.
  */
-public class HandlerBoss extends ChannelInboundMessageHandlerAdapter<ByteBuf>
+public class HandlerBoss extends ChannelInboundMessageHandlerAdapter<Wrapper>
 {
 
     private PacketHandler handler;
@@ -48,11 +48,11 @@ public class HandlerBoss extends ChannelInboundMessageHandlerAdapter<ByteBuf>
     }
 
     @Override
-    public void messageReceived(ChannelHandlerContext ctx, ByteBuf msg) throws Exception
+    public void messageReceived(ChannelHandlerContext ctx, Wrapper msg) throws Exception
     {
         if ( handler != null && ctx.channel().isActive() )
         {
-            DefinedPacket packet = DefinedPacket.packet( msg );
+            DefinedPacket packet = DefinedPacket.packet( msg.buf );
             boolean sendPacket = true;
             if ( packet != null )
             {

proxy/src/main/java/net/md_5/bungee/netty/PacketDecoder.java

@@ -17,7 +17,7 @@ import net.md_5.bungee.protocol.netty.PacketReader;
  * when all needed data is present.
  */
 @AllArgsConstructor
-public class PacketDecoder extends ReplayingDecoder<ByteBuf>
+public class PacketDecoder extends ReplayingDecoder<Void>
 {
 
     @Getter
@@ -25,10 +25,11 @@ public class PacketDecoder extends ReplayingDecoder<ByteBuf>
     private int protocol;
 
     @Override
-    protected ByteBuf decode(ChannelHandlerContext ctx, ByteBuf in) throws Exception
+    protected Wrapper decode(ChannelHandlerContext ctx, ByteBuf in) throws Exception
     {
         int startIndex = in.readerIndex();
         PacketReader.readPacket( in, protocol );
-        return in.copy( startIndex, in.readerIndex() - startIndex );
+        ByteBuf ret = in.copy( startIndex, in.readerIndex() - startIndex );
+        return new Wrapper( ret );
     }
 }

proxy/src/main/java/net/md_5/bungee/netty/PipelineUtils.java

@@ -58,6 +58,7 @@ public class PipelineUtils
             }
             ch.pipeline().addLast( "timer", new ReadTimeoutHandler( BungeeCord.getInstance().config.getTimeout(), TimeUnit.MILLISECONDS ) );
             ch.pipeline().addLast( "decoder", new PacketDecoder( PacketDefinitions.VANILLA_PROTOCOL ) );
+            ch.pipeline().addLast( "encoder", new HackEncoder() );
             ch.pipeline().addLast( "handler", new HandlerBoss() );
         }
     };

proxy/src/main/java/net/md_5/bungee/netty/Wrapper.java

@@ -0,0 +1,14 @@
+package net.md_5.bungee.netty;
+
+import io.netty.buffer.ByteBuf;
+import lombok.RequiredArgsConstructor;
+
+/**
+ * Hack for Netty.
+ */
+@RequiredArgsConstructor
+public class Wrapper
+{
+
+    public final ByteBuf buf;
+}

proxy/src/main/java/net/md_5/bungee/packet/PacketHandler.java

@@ -2,6 +2,7 @@ package net.md_5.bungee.packet;
 
 import io.netty.buffer.ByteBuf;
 import io.netty.channel.Channel;
+import net.md_5.bungee.netty.Wrapper;
 
 public abstract class PacketHandler
 {
@@ -21,7 +22,7 @@ public abstract class PacketHandler
     {
     }
 
-    public void handle(ByteBuf buf) throws Exception
+    public void handle(Wrapper buf) throws Exception
     {
     }