From dd2af3af4926e0c273f5554ac74970ad9df08c2b Mon Sep 17 00:00:00 2001
From: Techcable <Techcable@techcable.net>
Date: Thu, 19 May 2016 17:09:22 -0600
Subject: [PATCH] Allow invalid packet ids for forge servers

Some forge mods (COFH) use negative packet ids instead of plugin channels for 'reasons'.
Vanilla servers still error on negative/invalid packets.

Original issue: https://github.com/WaterfallMC/Waterfall-Old/issues/11

diff --git a/protocol/src/main/java/net/md_5/bungee/protocol/MinecraftDecoder.java b/protocol/src/main/java/net/md_5/bungee/protocol/MinecraftDecoder.java
index ea44573d..5b32effe 100644
--- a/protocol/src/main/java/net/md_5/bungee/protocol/MinecraftDecoder.java
+++ b/protocol/src/main/java/net/md_5/bungee/protocol/MinecraftDecoder.java
@@ -16,6 +16,14 @@ public class MinecraftDecoder extends MessageToMessageDecoder<ByteBuf>
     private final boolean server;
     @Setter
     private int protocolVersion;
+    @Setter
+    private boolean supportsForge = false;
+
+    public MinecraftDecoder(Protocol protocol, boolean server, int protocolVersion) {
+        this.protocol = protocol;
+        this.server = server;
+        this.protocolVersion = protocolVersion;
+    }
 
     @Override
     protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception
@@ -27,7 +35,7 @@ public class MinecraftDecoder extends MessageToMessageDecoder<ByteBuf>
         {
             int packetId = DefinedPacket.readVarInt( in );
 
-            DefinedPacket packet = prot.createPacket( packetId, protocolVersion );
+            DefinedPacket packet = prot.createPacket( packetId, protocolVersion, supportsForge );
             if ( packet != null )
             {
                 packet.read( in, prot.getDirection(), protocolVersion );
diff --git a/protocol/src/main/java/net/md_5/bungee/protocol/Protocol.java b/protocol/src/main/java/net/md_5/bungee/protocol/Protocol.java
index 76c2bea0..96d3c99e 100644
--- a/protocol/src/main/java/net/md_5/bungee/protocol/Protocol.java
+++ b/protocol/src/main/java/net/md_5/bungee/protocol/Protocol.java
@@ -397,14 +397,23 @@ public enum Protocol
             return protocol;
         }
 
+        public boolean hasPacket(int i, boolean supportsForge) {
+            return supportsForge || i >= 0 && i <= MAX_PACKET_ID;
+        }
+
         public final DefinedPacket createPacket(int id, int version)
+        {
+            return createPacket(id, version, true);
+        }
+
+        public final DefinedPacket createPacket(int id, int version, boolean supportsForge)
         {
             ProtocolData protocolData = getProtocolData( version );
             if ( protocolData == null )
             {
                 throw new BadPacketException( "Unsupported protocol version" );
             }
-            if ( id > MAX_PACKET_ID )
+            if ( !hasPacket(id, supportsForge) )
             {
                 throw new BadPacketException( "Packet with id " + id + " outside of range " );
             }
diff --git a/proxy/src/main/java/net/md_5/bungee/ServerConnector.java b/proxy/src/main/java/net/md_5/bungee/ServerConnector.java
index ee8cdff2..44821171 100644
--- a/proxy/src/main/java/net/md_5/bungee/ServerConnector.java
+++ b/proxy/src/main/java/net/md_5/bungee/ServerConnector.java
@@ -31,7 +31,9 @@ import net.md_5.bungee.forge.ForgeUtils;
 import net.md_5.bungee.netty.ChannelWrapper;
 import net.md_5.bungee.netty.HandlerBoss;
 import net.md_5.bungee.netty.PacketHandler;
+import net.md_5.bungee.netty.PipelineUtils;
 import net.md_5.bungee.protocol.DefinedPacket;
+import net.md_5.bungee.protocol.MinecraftDecoder;
 import net.md_5.bungee.protocol.PacketWrapper;
 import net.md_5.bungee.protocol.Protocol;
 import net.md_5.bungee.protocol.ProtocolConstants;
@@ -198,6 +200,12 @@ public class ServerConnector extends PacketHandler
 
         ServerConnection server = new ServerConnection( ch, target );
         ServerConnectedEvent event = new ServerConnectedEvent( user, server );
+
+        if (server.isForgeServer() && user.isForgeUser()) {
+            ((MinecraftDecoder) server.getCh().getHandle().pipeline().get(PipelineUtils.PACKET_DECODER)).setSupportsForge(true);
+            ((MinecraftDecoder) user.getCh().getHandle().pipeline().get(PipelineUtils.PACKET_DECODER)).setSupportsForge(true);
+        }
+
         bungee.getPluginManager().callEvent( event );
 
         ch.write( BungeeCord.getInstance().registerChannels( user.getPendingConnection().getVersion() ) );
diff --git a/proxy/src/main/java/net/md_5/bungee/UserConnection.java b/proxy/src/main/java/net/md_5/bungee/UserConnection.java
index bc1227a5..61502ea8 100644
--- a/proxy/src/main/java/net/md_5/bungee/UserConnection.java
+++ b/proxy/src/main/java/net/md_5/bungee/UserConnection.java
@@ -71,6 +71,7 @@ public final class UserConnection implements ProxiedPlayer
     @NonNull
     private final ProxyServer bungee;
     @NonNull
+    @Getter
     private final ChannelWrapper ch;
     @Getter
     @NonNull
diff --git a/proxy/src/main/java/net/md_5/bungee/entitymap/EntityMap.java b/proxy/src/main/java/net/md_5/bungee/entitymap/EntityMap.java
index cae566f5..bad9773b 100644
--- a/proxy/src/main/java/net/md_5/bungee/entitymap/EntityMap.java
+++ b/proxy/src/main/java/net/md_5/bungee/entitymap/EntityMap.java
@@ -264,6 +264,12 @@ public abstract class EntityMap
         int packetId = DefinedPacket.readVarInt( packet );
         int packetIdLength = packet.readerIndex() - readerIndex;
 
+        if (packetId < 0 || packetId > ints.length || packetId > varints.length) { // Invalid packet id
+            // Ignore these invalid packets for compatibility reasons
+            packet.readerIndex( readerIndex );
+            return;
+        }
+
         if ( ints[packetId] )
         {
             rewriteInt( packet, oldId, newId, readerIndex + packetIdLength );
-- 
2.18.0