From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Shane Freeder <theboyetronic@gmail.com>
Date: Wed, 19 Aug 2020 05:05:54 +0100
Subject: [PATCH] Buffer joins to world

This patch buffers the number of logins which will attempt to join
the world per tick, this attempts to reduce the impact that join floods
has on the server

diff --git a/src/main/java/com/destroystokyo/paper/PaperConfig.java b/src/main/java/com/destroystokyo/paper/PaperConfig.java
index ff855232e9b94d1b05d7abb8fd5ce243cc0cd324..503d0a15a39d70c26140987f076047e3835ce9fa 100644
--- a/src/main/java/com/destroystokyo/paper/PaperConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperConfig.java
@@ -91,6 +91,11 @@ public class PaperConfig {
         }
     }
 
+    public static int maxJoinsPerTick;
+    private static void maxJoinsPerTick() {
+        maxJoinsPerTick = getInt("settings.max-joins-per-tick", 3);
+    }
+
     public static void registerCommands() {
         for (Map.Entry<String, Command> entry : commands.entrySet()) {
             MinecraftServer.getServer().server.getCommandMap().register(entry.getKey(), "Paper", entry.getValue());
diff --git a/src/main/java/net/minecraft/network/Connection.java b/src/main/java/net/minecraft/network/Connection.java
index c469688c2b55b1c93435a2ac6e8e4494ab7e5229..1c63947958d202d00593e2b76d113c8b327706d7 100644
--- a/src/main/java/net/minecraft/network/Connection.java
+++ b/src/main/java/net/minecraft/network/Connection.java
@@ -40,6 +40,7 @@ import net.minecraft.network.protocol.Packet;
 import net.minecraft.network.protocol.PacketFlow;
 import net.minecraft.network.protocol.game.ClientboundDisconnectPacket;
 import net.minecraft.network.protocol.login.ClientboundLoginDisconnectPacket;
+import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.RunningOnDifferentThreadException;
 import net.minecraft.server.network.ServerGamePacketListenerImpl;
 import net.minecraft.server.network.ServerLoginPacketListenerImpl;
@@ -385,10 +386,22 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
     }
     // Paper end
 
+    private static final int MAX_PER_TICK = com.destroystokyo.paper.PaperConfig.maxJoinsPerTick; // Paper
+    private static int joinAttemptsThisTick; // Paper
+    private static int currTick; // Paper
     public void tick() {
         this.flushQueue();
+        // Paper start
+        if (currTick != MinecraftServer.currentTick) {
+            currTick = MinecraftServer.currentTick;
+            joinAttemptsThisTick = 0;
+        }
+        // Paper end
         if (this.packetListener instanceof ServerLoginPacketListenerImpl) {
+            if ( ((ServerLoginPacketListenerImpl) this.packetListener).state != ServerLoginPacketListenerImpl.State.READY_TO_ACCEPT // Paper
+                     || (joinAttemptsThisTick++ < MAX_PER_TICK)) { // Paper - limit the number of joins which can be processed each tick
             ((ServerLoginPacketListenerImpl) this.packetListener).tick();
+            } // Paper
         }
 
         if (this.packetListener instanceof ServerGamePacketListenerImpl) {
