Paper/patches/server/0468-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/net/minecraft/network/Connection.java b/src/main/java/net/minecraft/network/Connection.java
index dca0c978b30962d4216dc443d7d105e54a29ae1b..3ae55dd6441b2dfdb67eb2f24ecf885bab89e7a6 100644
--- a/src/main/java/net/minecraft/network/Connection.java
+++ b/src/main/java/net/minecraft/network/Connection.java
@@ -434,8 +434,23 @@ public class Connection extends SimpleChannelInboundHandler<Packet<?>> {
     }
     // Paper end
 
+    private static final int MAX_PER_TICK = io.papermc.paper.configuration.GlobalConfiguration.get().misc.maxJoinsPerTick; // Paper
+    private static int joinAttemptsThisTick; // Paper
+    private static int currTick; // Paper
     public void tick() {
         this.flushQueue();
+        // Paper start
+        if (currTick != net.minecraft.server.MinecraftServer.currentTick) {
+            currTick = net.minecraft.server.MinecraftServer.currentTick;
+            joinAttemptsThisTick = 0;
+        }
+        // Paper end
+        if (this.packetListener instanceof net.minecraft.server.network.ServerLoginPacketListenerImpl) {
+            if ( ((net.minecraft.server.network.ServerLoginPacketListenerImpl) this.packetListener).state != net.minecraft.server.network.ServerLoginPacketListenerImpl.State.READY_TO_ACCEPT // Paper
+                || (joinAttemptsThisTick++ < MAX_PER_TICK)) { // Paper - limit the number of joins which can be processed each tick
+                ((net.minecraft.server.network.ServerLoginPacketListenerImpl) this.packetListener).tick();
+            } // Paper
+        }
         PacketListener packetlistener = this.packetListener;
 
         if (packetlistener instanceof TickablePacketListener) {