Paper/patches/server/0472-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 b8e35f493458ba9e072953dffe6b2429f1d821ec..c1a59f54f537395bebf6d78459beef3013ea67d9 100644
--- a/src/main/java/net/minecraft/network/Connection.java
+++ b/src/main/java/net/minecraft/network/Connection.java
@@ -425,8 +425,23 @@ 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) {