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 faa1b775e45563b93ac1d5b904938b1f5ad8d80c..545948f20efd6c8dd42140b565af94cd6b52b661 100644
--- a/src/main/java/com/destroystokyo/paper/PaperConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperConfig.java
@@ -457,4 +457,9 @@ public class PaperConfig {
             maxPlayerAutoSavePerTick = (playerAutoSaveRate == -1 || playerAutoSaveRate > 100) ? 10 : 20;
         }
     }
+
+    public static int maxJoinsPerTick;
+    private static void maxJoinsPerTick() {
+        maxJoinsPerTick = getInt("settings.max-joins-per-tick", 3);
+    }
 }
diff --git a/src/main/java/net/minecraft/network/Connection.java b/src/main/java/net/minecraft/network/Connection.java
index fc63df21aecd4721efdb45d4744666ed0b562c1b..6f7cbce5a049d87d4a0ed7cc4517cb4e8694efb5 100644
--- a/src/main/java/net/minecraft/network/Connection.java
+++ b/src/main/java/net/minecraft/network/Connection.java
@@ -32,6 +32,7 @@ import net.minecraft.network.protocol.game.ClientboundDisconnectPacket;
 import net.minecraft.network.protocol.game.ClientboundKeepAlivePacket;
 import net.minecraft.network.protocol.game.ClientboundSetTitlesPacket;
 import net.minecraft.server.MCUtil;
+import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.RunningOnDifferentThreadException;
 import net.minecraft.server.level.ServerPlayer;
 import net.minecraft.server.network.ServerGamePacketListenerImpl;
@@ -382,10 +383,22 @@ 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.p();
+        // Paper start
+        if (currTick != MinecraftServer.currentTick) {
+            currTick = MinecraftServer.currentTick;
+            joinAttemptsThisTick = 0;
+        }
+        // Paper end
         if (this.packetListener instanceof ServerLoginPacketListenerImpl) {
+            if ( ((ServerLoginPacketListenerImpl) this.packetListener).getLoginState() != 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) {
diff --git a/src/main/java/net/minecraft/server/network/ServerLoginPacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerLoginPacketListenerImpl.java
index e229c7735ba88be3d8721440104958408a2a075e..659bf14cf3c949b896d0333f893a3d5e16ab9c92 100644
--- a/src/main/java/net/minecraft/server/network/ServerLoginPacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerLoginPacketListenerImpl.java
@@ -420,7 +420,7 @@ public class ServerLoginPacketListenerImpl implements ServerLoginPacketListener
         return new GameProfile(uuid, profile.getName());
     }
 
-    static enum State {
+    public enum State { // Paper - package private -> public
 
         HELLO, KEY, AUTHENTICATING, NEGOTIATING, READY_TO_ACCEPT, DELAY_ACCEPT, ACCEPTED;