PaperMC/patches/server/0940-Handle-Large-Packets-disconnecting-client.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Tue, 27 Nov 2018 21:18:06 -0500
Subject: [PATCH] Handle Large Packets disconnecting client

If a players inventory is too big to send in a single packet,
split the inventory set into multiple packets instead.

diff --git a/src/main/java/net/minecraft/network/Connection.java b/src/main/java/net/minecraft/network/Connection.java
index c12335bc83d31ec65fe2d7cbe0b084748e670010..b0413be1d8565df1c746102a6900806fe3d12373 100644
--- a/src/main/java/net/minecraft/network/Connection.java
+++ b/src/main/java/net/minecraft/network/Connection.java
@@ -176,6 +176,21 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
     }
 
     public void exceptionCaught(ChannelHandlerContext channelhandlercontext, Throwable throwable) {
+        // Paper start - Handle large packets disconnecting client
+        if (throwable instanceof io.netty.handler.codec.EncoderException && throwable.getCause() instanceof PacketEncoder.PacketTooLargeException packetTooLargeException) {
+            final Packet<?> packet = packetTooLargeException.getPacket();
+            if (packet.packetTooLarge(this)) {
+                ProtocolSwapHandler.handleOutboundTerminalPacket(channelhandlercontext, packet);
+                return;
+            } else if (packet.isSkippable()) {
+                Connection.LOGGER.debug("Skipping packet due to errors", throwable.getCause());
+                ProtocolSwapHandler.handleOutboundTerminalPacket(channelhandlercontext, packet);
+                return;
+            } else {
+                throwable = throwable.getCause();
+            }
+        }
+        // Paper end - Handle large packets disconnecting client
         if (throwable instanceof SkipPacketException) {
             Connection.LOGGER.debug("Skipping packet due to errors", throwable.getCause());
         } else {
diff --git a/src/main/java/net/minecraft/network/PacketEncoder.java b/src/main/java/net/minecraft/network/PacketEncoder.java
index 046bfc212b640de174b300e7a05cc30bb3cac93e..af3ec112e142a2c91c46882dad6180b18f39eec2 100644
--- a/src/main/java/net/minecraft/network/PacketEncoder.java
+++ b/src/main/java/net/minecraft/network/PacketEncoder.java
@@ -40,7 +40,33 @@ public class PacketEncoder<T extends PacketListener> extends MessageToByteEncode
 
             throw var9;
         } finally {
+            // Paper start - Handle large packets disconnecting client
+            int packetLength = byteBuf.readableBytes();
+            if (packetLength > MAX_PACKET_SIZE || (packetLength > MAX_FINAL_PACKET_SIZE && packet.hasLargePacketFallback())) {
+                throw new PacketTooLargeException(packet, packetLength);
+            }
+            // Paper end - Handle large packets disconnecting client
             ProtocolSwapHandler.handleOutboundTerminalPacket(channelHandlerContext, packet);
         }
     }
+
+    // Paper start
+    // packet size is encoded into 3-byte varint
+    private static final int MAX_FINAL_PACKET_SIZE = (1 << 21) - 1;
+    // Vanilla Max size for the encoder (before compression)
+    private static final int MAX_PACKET_SIZE = 8388608;
+
+    public static class PacketTooLargeException extends RuntimeException {
+        private final Packet<?> packet;
+
+        PacketTooLargeException(Packet<?> packet, int packetLength) {
+            super("PacketTooLarge - " + packet.getClass().getSimpleName() + " is " + packetLength + ". Max is " + MAX_PACKET_SIZE);
+            this.packet = packet;
+        }
+
+        public Packet<?> getPacket() {
+            return this.packet;
+        }
+    }
+    // Paper end
 }
diff --git a/src/main/java/net/minecraft/network/protocol/Packet.java b/src/main/java/net/minecraft/network/protocol/Packet.java
index 4c776c591dd0a7b36945a6487fdfe86d1187b4af..82fc12ffbd1585b4a8d09a025914830af77b0f8d 100644
--- a/src/main/java/net/minecraft/network/protocol/Packet.java
+++ b/src/main/java/net/minecraft/network/protocol/Packet.java
@@ -11,6 +11,19 @@ public interface Packet<T extends PacketListener> {
 
     void handle(T listener);
 
+    // Paper start
+    default boolean hasLargePacketFallback() {
+        return false;
+    }
+
+    /**
+     * override {@link #hasLargePacketFallback()} to return true when overriding in subclasses
+     */
+    default boolean packetTooLarge(net.minecraft.network.Connection manager) {
+        return false;
+    }
+    // Paper end
+
     default boolean isSkippable() {
         return false;
     }
diff --git a/src/main/java/net/minecraft/network/protocol/game/ClientboundContainerSetContentPacket.java b/src/main/java/net/minecraft/network/protocol/game/ClientboundContainerSetContentPacket.java
index f53c74fb1863a2d1268a4ddf8cf69d1fda32d73f..8d5939e03a065197af125d95a10134abbccd07ec 100644
--- a/src/main/java/net/minecraft/network/protocol/game/ClientboundContainerSetContentPacket.java
+++ b/src/main/java/net/minecraft/network/protocol/game/ClientboundContainerSetContentPacket.java
@@ -36,6 +36,21 @@ public class ClientboundContainerSetContentPacket implements Packet<ClientGamePa
         this.carriedItem = ItemStack.OPTIONAL_STREAM_CODEC.decode(buf);
     }
 
+    // Paper start - Handle large packets disconnecting client
+    @Override
+    public boolean hasLargePacketFallback() {
+        return true;
+    }
+
+    @Override
+    public boolean packetTooLarge(net.minecraft.network.Connection manager) {
+        for (int i = 0 ; i < this.items.size() ; i++) {
+            manager.send(new ClientboundContainerSetSlotPacket(this.containerId, this.stateId, i, this.items.get(i)));
+        }
+        return true;
+    }
+    // Paper end - Handle large packets disconnecting client
+
     private void write(RegistryFriendlyByteBuf buf) {
         buf.writeContainerId(this.containerId);
         buf.writeVarInt(this.stateId);
diff --git a/src/main/java/net/minecraft/network/protocol/game/ClientboundLevelChunkPacketData.java b/src/main/java/net/minecraft/network/protocol/game/ClientboundLevelChunkPacketData.java
index ec1cb034d840633240f2b379b09f7d2f1c8971a5..cf8fd671490863e126c059157e1ca234e6509d9f 100644
--- a/src/main/java/net/minecraft/network/protocol/game/ClientboundLevelChunkPacketData.java
+++ b/src/main/java/net/minecraft/network/protocol/game/ClientboundLevelChunkPacketData.java
@@ -52,7 +52,7 @@ public class ClientboundLevelChunkPacketData {
             throw new RuntimeException("Can't read heightmap in packet for [" + x + ", " + z + "]");
         } else {
             int i = buf.readVarInt();
-            if (i > 2097152) {
+            if (i > 2097152) { // Paper - diff on change - if this changes, update PacketEncoder
                 throw new RuntimeException("Chunk Packet trying to allocate too much memory on read.");
             } else {
                 this.buffer = new byte[i];