Paper/Spigot-Server-Patches/0557-Buffer-joins-to-world.patch

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/NetworkManager.java b/src/main/java/net/minecraft/network/NetworkManager.java
index ab70eeaeca222de7de7cab1b3db14b2c4761c3c3..878f879f8d410c428ad8a4c49e0c86c559bc47a9 100644
--- a/src/main/java/net/minecraft/network/NetworkManager.java
+++ b/src/main/java/net/minecraft/network/NetworkManager.java
@@ -33,6 +33,7 @@ import net.minecraft.network.protocol.game.PacketPlayOutTabComplete;
 import net.minecraft.network.protocol.game.PacketPlayOutTitle;
 import net.minecraft.server.CancelledPacketHandleException;
 import net.minecraft.server.MCUtil;
+import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.level.EntityPlayer;
 import net.minecraft.server.network.LoginListener;
 import net.minecraft.server.network.PlayerConnection;
@@ -382,10 +383,22 @@ public class NetworkManager 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 a() {
         this.p();
+        // Paper start
+        if (currTick != MinecraftServer.currentTick) {
+            currTick = MinecraftServer.currentTick;
+            joinAttemptsThisTick = 0;
+        }
+        // Paper end
         if (this.packetListener instanceof LoginListener) {
+            if ( ((LoginListener) this.packetListener).getLoginState() != LoginListener.EnumProtocolState.READY_TO_ACCEPT // Paper
+                     || (joinAttemptsThisTick++ < MAX_PER_TICK)) { // Paper - limit the number of joins which can be processed each tick
             ((LoginListener) this.packetListener).tick();
+            } // Paper
         }
 
         if (this.packetListener instanceof PlayerConnection) {
diff --git a/src/main/java/net/minecraft/server/network/LoginListener.java b/src/main/java/net/minecraft/server/network/LoginListener.java
index 06e2b48ed6d6d52d0eb17301254ed07fb69cb8af..e9fc38f69af815f021a08a94dd41b91171dbf2d6 100644
--- a/src/main/java/net/minecraft/server/network/LoginListener.java
+++ b/src/main/java/net/minecraft/server/network/LoginListener.java
@@ -417,7 +417,7 @@ public class LoginListener implements PacketLoginInListener {
         return new GameProfile(uuid, gameprofile.getName());
     }
 
-    static enum EnumProtocolState {
+    public enum EnumProtocolState { // Paper - package private -> public
 
         HELLO, KEY, AUTHENTICATING, NEGOTIATING, READY_TO_ACCEPT, DELAY_ACCEPT, ACCEPTED;