From 3cfe0e4cd7612acdd852103fc878b098fa95eeea Mon Sep 17 00:00:00 2001
From: Shane Freeder <theboyetronic@gmail.com>
Date: Fri, 12 Oct 2018 14:28:52 +0100
Subject: [PATCH] Add Configuration to allow empty packets

This setting provides the ability to allow servers/clients
to send empty packets without kicking the player with an error.

This option is not encouraged or supported in any capacity, and is
provided as a last ditch effort for server owners to allow players
to connect in such a broken state as allowed by vanilla.

diff --git a/api/src/main/java/net/md_5/bungee/api/ProxyConfig.java b/api/src/main/java/net/md_5/bungee/api/ProxyConfig.java
index 8680fd9b..f792426e 100644
--- a/api/src/main/java/net/md_5/bungee/api/ProxyConfig.java
+++ b/api/src/main/java/net/md_5/bungee/api/ProxyConfig.java
@@ -191,4 +191,6 @@ public interface ProxyConfig
      * @return should we disable the tab completion limit for 1.13+ clients
      */
     boolean isDisableModernTabLimiter();
+
+    boolean isAllowEmptyPackets();
 }
diff --git a/protocol/src/main/java/net/md_5/bungee/protocol/Varint21FrameDecoder.java b/protocol/src/main/java/net/md_5/bungee/protocol/Varint21FrameDecoder.java
index 29e54dba..880a3dc7 100644
--- a/protocol/src/main/java/net/md_5/bungee/protocol/Varint21FrameDecoder.java
+++ b/protocol/src/main/java/net/md_5/bungee/protocol/Varint21FrameDecoder.java
@@ -12,6 +12,13 @@ public class Varint21FrameDecoder extends ByteToMessageDecoder
 {
 
     private static boolean DIRECT_WARNING;
+    // Waterfall start
+    private boolean allowEmptyPackets;
+
+    public Varint21FrameDecoder(boolean allowEmptyPackets) {
+        this.allowEmptyPackets = allowEmptyPackets;
+    }
+    // Waterfall end
 
     @Override
     protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception
@@ -31,7 +38,7 @@ public class Varint21FrameDecoder extends ByteToMessageDecoder
             if ( buf[i] >= 0 )
             {
                 int length = DefinedPacket.readVarInt( Unpooled.wrappedBuffer( buf ) );
-                if ( length == 0 )
+                if ( length == 0 && !allowEmptyPackets) // Waterfall
                 {
                     throw new CorruptedFrameException( "Empty Packet!" );
                 }
diff --git a/proxy/src/main/java/io/github/waterfallmc/waterfall/conf/WaterfallConfiguration.java b/proxy/src/main/java/io/github/waterfallmc/waterfall/conf/WaterfallConfiguration.java
index d343e9b8..ea06f3ba 100644
--- a/proxy/src/main/java/io/github/waterfallmc/waterfall/conf/WaterfallConfiguration.java
+++ b/proxy/src/main/java/io/github/waterfallmc/waterfall/conf/WaterfallConfiguration.java
@@ -49,6 +49,17 @@ public class WaterfallConfiguration extends Configuration {
     private int tabThrottle = 1000;
     private boolean disableModernTabLimiter = true;
 
+
+    /**
+     * This setting provides the ability to allow servers/clients
+     * to send empty packets without kicking the player with an error.
+     *
+     * This option is not encouraged or supported in any capacity, and is
+     * provided as a last ditch effort for server owners to allow players
+     * to connect in such a broken state as allowed by vanilla.
+     */
+    private boolean allowEmptyPackets = false;
+
     @Override
     public void load() {
         super.load();
@@ -61,6 +72,7 @@ public class WaterfallConfiguration extends Configuration {
         // Throttling options
         tabThrottle = config.getInt("throttling.tab_complete", tabThrottle);
         disableModernTabLimiter = config.getBoolean("disable_modern_tab_limiter", disableModernTabLimiter);
+        allowEmptyPackets = config.getBoolean("allow_empty_packets", allowEmptyPackets);
     }
 
     @Override
@@ -92,4 +104,9 @@ public class WaterfallConfiguration extends Configuration {
     public boolean isDisableModernTabLimiter() {
         return disableModernTabLimiter;
     }
+
+    @Override
+    public boolean isAllowEmptyPackets() {
+        return false;
+    }
 }
diff --git a/proxy/src/main/java/net/md_5/bungee/netty/PipelineUtils.java b/proxy/src/main/java/net/md_5/bungee/netty/PipelineUtils.java
index c26fc55b..3f082afb 100644
--- a/proxy/src/main/java/net/md_5/bungee/netty/PipelineUtils.java
+++ b/proxy/src/main/java/net/md_5/bungee/netty/PipelineUtils.java
@@ -139,7 +139,7 @@ public class PipelineUtils
             ch.config().setWriteBufferWaterMark( MARK );
 
             ch.pipeline().addLast( TIMEOUT_HANDLER, new ReadTimeoutHandler( BungeeCord.getInstance().config.getTimeout(), TimeUnit.MILLISECONDS ) );
-            ch.pipeline().addLast( FRAME_DECODER, new Varint21FrameDecoder() );
+            ch.pipeline().addLast( FRAME_DECODER, new Varint21FrameDecoder( BungeeCord.getInstance().getConfig().isAllowEmptyPackets()) ); // Waterfall
             ch.pipeline().addLast( FRAME_PREPENDER, framePrepender );
 
             ch.pipeline().addLast( BOSS_HANDLER, new HandlerBoss() );
-- 
2.19.1