Paper/patches/server/0512-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 1ff9dbde24d6e15076c4e90a73ce5801c47ef3f2..2675012b619705d7d55406aba10bdbd7c1ccf6cd 100644
--- a/src/main/java/com/destroystokyo/paper/PaperConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperConfig.java
@@ -446,4 +446,9 @@ public class PaperConfig {
         config.set("settings.unsupported-settings.allow-headless-pistons-readme", "This setting controls if players should be able to create headless pistons.");
         allowHeadlessPistons = getBoolean("settings.unsupported-settings.allow-headless-pistons", false);
     }
+
+    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 7607bf75968cc32d616e2b44e89901b3681b1131..d32b96a5f51d745869cfc40c01c54de58e1eb843 100644
--- a/src/main/java/net/minecraft/network/Connection.java
+++ b/src/main/java/net/minecraft/network/Connection.java
@@ -37,6 +37,7 @@ 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;
@@ -373,10 +374,22 @@ 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).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) {