From 51165fe4b5385c5b6710710b83548ae96e8cc153 Mon Sep 17 00:00:00 2001
From: Outfluencer <git@outfluencer.dev>
Date: Mon, 17 Feb 2025 18:54:36 +0100
Subject: [PATCH] Set autoread to false and clear tcp read buf, ensure only do
 it once

---
 .../bungee/protocol/Varint21FrameDecoder.java |  8 ++++-
 .../net/md_5/bungee/netty/ChannelWrapper.java | 34 ++++++++++++++-----
 .../net/md_5/bungee/netty/HandlerBoss.java    |  8 -----
 3 files changed, 33 insertions(+), 17 deletions(-)

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 277e70e8a2..e318a28e0f 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
@@ -6,12 +6,18 @@
 import io.netty.handler.codec.ByteToMessageDecoder;
 import io.netty.handler.codec.CorruptedFrameException;
 import java.util.List;
+import lombok.Setter;
 
 public class Varint21FrameDecoder extends ByteToMessageDecoder
 {
 
     private static boolean DIRECT_WARNING;
 
+    // discard will be set to true before we close a connection to ensure
+    // that no packets will be handled anymore
+    @Setter
+    private boolean discard;
+
     @Override
     protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) throws Exception
     {
@@ -19,7 +25,7 @@ protected void decode(ChannelHandlerContext ctx, ByteBuf in, List<Object> out) t
         // the Netty ByteToMessageDecoder will continue to frame more packets and potentially call fireChannelRead()
         // on them, likely with more invalid packets. Therefore, check if the connection is no longer active and if so
         // sliently discard the packet.
-        if ( !ctx.channel().isActive() )
+        if ( !ctx.channel().isActive() || discard )
         {
             in.skipBytes( in.readableBytes() );
             return;
diff --git a/proxy/src/main/java/net/md_5/bungee/netty/ChannelWrapper.java b/proxy/src/main/java/net/md_5/bungee/netty/ChannelWrapper.java
index fda4f54eb8..05111ec245 100644
--- a/proxy/src/main/java/net/md_5/bungee/netty/ChannelWrapper.java
+++ b/proxy/src/main/java/net/md_5/bungee/netty/ChannelWrapper.java
@@ -18,6 +18,7 @@
 import net.md_5.bungee.protocol.MinecraftEncoder;
 import net.md_5.bungee.protocol.PacketWrapper;
 import net.md_5.bungee.protocol.Protocol;
+import net.md_5.bungee.protocol.Varint21FrameDecoder;
 import net.md_5.bungee.protocol.packet.Kick;
 
 public class ChannelWrapper
@@ -130,6 +131,13 @@ public void close(Object packet)
     {
         if ( !closed )
         {
+            // do not do it twice
+            if ( !closing )
+            {
+                // clear tcp read buffer
+                discardInbound();
+            }
+
             closed = closing = true;
 
             // disable auto read so the pipeline doesn't read more traffic
@@ -152,21 +160,31 @@ public void delayedClose(final Kick kick)
         {
             closing = true;
 
+            // clear tcp read buffer
+            discardInbound();
+
             // disable auto read so the pipeline doesn't read more traffic
             ch.config().setAutoRead( false );
 
             // Minecraft client can take some time to switch protocols.
             // Sending the wrong disconnect packet whilst a protocol switch is in progress will crash it.
             // Delay 250ms to ensure that the protocol switch (if any) has definitely taken place.
-            ch.eventLoop().schedule( new Runnable()
-            {
+            ch.eventLoop().schedule( () -> close( kick ), 250, TimeUnit.MILLISECONDS );
+        }
+    }
 
-                @Override
-                public void run()
-                {
-                    close( kick );
-                }
-            }, 250, TimeUnit.MILLISECONDS );
+    /**
+     * Disable auto read so the pipeline doesn't read more traffic
+     * Also discard all inbound traffic to free the tcp read buffer
+     * This clears the tcp read buffer
+     */
+    private void discardInbound()
+    {
+        ch.config().setAutoRead( false );
+        Varint21FrameDecoder frameDecoder = ch.pipeline().get( Varint21FrameDecoder.class );
+        if ( frameDecoder != null )
+        {
+            frameDecoder.setDiscard( true );
         }
     }
 
diff --git a/proxy/src/main/java/net/md_5/bungee/netty/HandlerBoss.java b/proxy/src/main/java/net/md_5/bungee/netty/HandlerBoss.java
index 634968968e..a73a29c77d 100644
--- a/proxy/src/main/java/net/md_5/bungee/netty/HandlerBoss.java
+++ b/proxy/src/main/java/net/md_5/bungee/netty/HandlerBoss.java
@@ -128,14 +128,6 @@ public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception
                 {
                     handler, limiter.getCounter(), limiter.getDataCounter()
                 } );
-
-                // somehow sometimes if you spam big packets fast enough the channel will not be closed immediately
-                // it seems that this only happens on linux, the PacketLimiter will trigger a kick multiple times
-                // but the connection will still be active
-                if ( channel.getHandle().isActive() )
-                {
-                    ctx.close();
-                }
                 return;
             }