Paper/patches/server/0471-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 bbedcdb71a326b3286805d0081e71c54a4312622..22e2e314a4bb1b22758130d4e9065f9b87b0116e 100644
--- a/src/main/java/net/minecraft/network/Connection.java
+++ b/src/main/java/net/minecraft/network/Connection.java
@@ -426,8 +426,23 @@ 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) {