Paper/patches/server/0494-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 1fd89294fabcd2a390ba7f1502acbfeb9a2343d6..8111e5e1752d93f94b773e35f7ff3857144def63 100644
--- a/src/main/java/com/destroystokyo/paper/PaperConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperConfig.java
@@ -91,6 +91,11 @@ public class PaperConfig {
         }
     }
 
+    public static int maxJoinsPerTick;
+    private static void maxJoinsPerTick() {
+        maxJoinsPerTick = getInt("settings.max-joins-per-tick", 3);
+    }
+
     public static void registerCommands() {
         for (Map.Entry<String, Command> entry : commands.entrySet()) {
             MinecraftServer.getServer().server.getCommandMap().register(entry.getKey(), "Paper", entry.getValue());
diff --git a/src/main/java/net/minecraft/network/Connection.java b/src/main/java/net/minecraft/network/Connection.java
index fc33e1dd5db461d380cfcbb3dacea095dd55b757..93a75f66935b19475aa878ebb00b44f35b3e29d6 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) {