Paper/patches/unapplied/server/0513-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 6b725dc2217e68255286caad6a0820bcccffb6da..6733e78ba6bf2993bb2adde4cf9f1f6ca366679c 100644
--- a/src/main/java/com/destroystokyo/paper/PaperConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperConfig.java
@@ -481,4 +481,9 @@ 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/Connection.java b/src/main/java/net/minecraft/network/Connection.java
index 3faf9bc694016f3f46576a549814ff8e6070598a..7f6405ac44fef423dc8b21f3dbeaae26a1005077 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).state != 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) {