From 57f98e2c510b576b4d3c94b12384b1bc4b6b5e33 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sat, 2 Mar 2019 14:55:01 -0500
Subject: [PATCH] Handle Excessive Signs in Chunks creating large packets

Also adds a limit to stop sending Sign and other data to client after
a significant amount have been sent.

Use -DPaper.excessiveTELimit=750 to configure that limit, or -1
to disable the limit and let your players be abused.

With further contributions from

Co-Authored-by: Spottedleaf <spottedleaf@spottedleaf.dev>

diff --git a/src/main/java/net/minecraft/server/NetworkManager.java b/src/main/java/net/minecraft/server/NetworkManager.java
index b1dededc15..e966b6edcc 100644
--- a/src/main/java/net/minecraft/server/NetworkManager.java
+++ b/src/main/java/net/minecraft/server/NetworkManager.java
@@ -158,19 +158,55 @@ public class NetworkManager extends SimpleChannelInboundHandler<Packet<?>> {
         NetworkManager.LOGGER.debug("Set listener of {} to {}", this, packetlistener);
         this.packetListener = packetlistener;
     }
+    // Paper start
+    private static class InnerUtil { // Attempt to hide these methods from ProtocolLib so it doesn't accidently pick them up.
+        private static java.util.List<Packet> buildExtraPackets(Packet packet) {
+            java.util.List<Packet> extra = packet.getExtraPackets();
+            if (extra == null || extra.isEmpty()) {
+                return null;
+            }
+            java.util.List<Packet> ret = new java.util.ArrayList<>(1 + extra.size());
+            buildExtraPackets0(extra, ret);
+            return ret;
+        }
+
+        private static void buildExtraPackets0(java.util.List<Packet> extraPackets, java.util.List<Packet> into) {
+            for (Packet extra : extraPackets) {
+                into.add(extra);
+                java.util.List<Packet> extraExtra = extra.getExtraPackets();
+                if (extraExtra != null && !extraExtra.isEmpty()) {
+                    buildExtraPackets0(extraExtra, into);
+                }
+            }
+        }
+    }
+    // Paper end
 
     public void sendPacket(Packet<?> packet) {
         this.sendPacket(packet, (GenericFutureListener) null);
     }
 
     public void sendPacket(Packet<?> packet, @Nullable GenericFutureListener<? extends Future<? super Void>> genericfuturelistener) {
-        if (this.isConnected()) {
-            this.o();
-            this.b(packet, genericfuturelistener);
-        } else {
+        // Paper start - handle oversized packets better
+        // write the packets to the queue, then flush - antixray hooks there already
+        java.util.List<Packet> extraPackets = InnerUtil.buildExtraPackets(packet);
+        boolean hasExtraPackets = extraPackets != null && !extraPackets.isEmpty();
+        if (!hasExtraPackets) {
             this.packetQueue.add(new NetworkManager.QueuedPacket(packet, genericfuturelistener));
-        }
+        } else {
+            java.util.List<NetworkManager.QueuedPacket> packets = new java.util.ArrayList<>(1 + extraPackets.size());
+            packets.add(new NetworkManager.QueuedPacket(packet, null)); // delay the future listener until the end of the extra packets
 
+            for (int i = 0, len = extraPackets.size(); i < len;) {
+                Packet extra = extraPackets.get(i);
+                boolean end = ++i == len;
+                packets.add(new NetworkManager.QueuedPacket(extra, end ? genericfuturelistener : null)); // append listener to the end
+            }
+
+            this.packetQueue.addAll(packets); // atomic
+        }
+        this.sendPacketQueue(); // ensure only one flush call is made
+        // Paper end
     }
 
     private void dispatchPacket(Packet<?> packet, @Nullable GenericFutureListener<? extends Future<? super Void>> genericFutureListener) { this.b(packet, genericFutureListener); } // Paper - OBFHELPER
diff --git a/src/main/java/net/minecraft/server/Packet.java b/src/main/java/net/minecraft/server/Packet.java
index 2d8e6a2f4a..8d0965a053 100644
--- a/src/main/java/net/minecraft/server/Packet.java
+++ b/src/main/java/net/minecraft/server/Packet.java
@@ -11,6 +11,7 @@ public interface Packet<T extends PacketListener> {
     void a(T t0);
 
     // Paper start
+    default java.util.List<Packet> getExtraPackets() { return null; }
     default boolean packetTooLarge(NetworkManager manager) {
         return false;
     }
diff --git a/src/main/java/net/minecraft/server/PacketPlayOutMapChunk.java b/src/main/java/net/minecraft/server/PacketPlayOutMapChunk.java
index a0b87f89df..23223f3f45 100644
--- a/src/main/java/net/minecraft/server/PacketPlayOutMapChunk.java
+++ b/src/main/java/net/minecraft/server/PacketPlayOutMapChunk.java
@@ -23,6 +23,15 @@ public class PacketPlayOutMapChunk implements Packet<PacketListenerPlayOut> {
 
     public PacketPlayOutMapChunk() {}
 
+    // Paper start
+    private final java.util.List<Packet> extraPackets = new java.util.ArrayList<>();
+    private static final int TE_LIMIT = Integer.getInteger("Paper.excessiveTELimit", 750);
+
+    @Override
+    public java.util.List<Packet> getExtraPackets() {
+        return extraPackets;
+    }
+    // Paper end
     public PacketPlayOutMapChunk(Chunk chunk, int i) {
         ChunkCoordIntPair chunkcoordintpair = chunk.getPos();
 
@@ -49,6 +58,7 @@ public class PacketPlayOutMapChunk implements Packet<PacketListenerPlayOut> {
         this.c = this.a(new PacketDataSerializer(this.j()), chunk, i);
         this.g = Lists.newArrayList();
         iterator = chunk.getTileEntities().entrySet().iterator();
+        int totalTileEntities = 0; // Paper
 
         while (iterator.hasNext()) {
             entry = (Entry) iterator.next();
@@ -57,6 +67,15 @@ public class PacketPlayOutMapChunk implements Packet<PacketListenerPlayOut> {
             int j = blockposition.getY() >> 4;
 
             if (this.f() || (i & 1 << j) != 0) {
+                // Paper start - improve oversized chunk data packet handling
+                if (++totalTileEntities > TE_LIMIT) {
+                    PacketPlayOutTileEntityData updatePacket = tileentity.getUpdatePacket();
+                    if (updatePacket != null) {
+                        this.extraPackets.add(updatePacket);
+                        continue;
+                    }
+                }
+                // Paper end
                 NBTTagCompound nbttagcompound = tileentity.b();
                 if (tileentity instanceof TileEntitySkull) { TileEntitySkull.sanitizeTileEntityUUID(nbttagcompound); } // Paper
 
-- 
2.26.2