Paper/Spigot-Server-Patches/0560-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 faa1b775e45563b93ac1d5b904938b1f5ad8d80c..545948f20efd6c8dd42140b565af94cd6b52b661 100644
--- a/src/main/java/com/destroystokyo/paper/PaperConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperConfig.java
@@ -457,4 +457,9 @@ 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/server/NetworkManager.java b/src/main/java/net/minecraft/server/NetworkManager.java
index 06d8ad7f57aa629c3c6060545a45411343affc81..fc4ad72ffaed5e747cfecc71e9ac8ee2b556ce31 100644
--- a/src/main/java/net/minecraft/server/NetworkManager.java
+++ b/src/main/java/net/minecraft/server/NetworkManager.java
@@ -365,10 +365,22 @@ public class NetworkManager 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 a() {
         this.p();
+        // Paper start
+        if (currTick != MinecraftServer.currentTick) {
+            currTick = MinecraftServer.currentTick;
+            joinAttemptsThisTick = 0;
+        }
+        // Paper end
         if (this.packetListener instanceof LoginListener) {
+            if ( ((LoginListener) this.packetListener).getLoginState() != LoginListener.EnumProtocolState.READY_TO_ACCEPT // Paper
+                     || (joinAttemptsThisTick++ < MAX_PER_TICK)) { // Paper - limit the number of joins which can be processed each tick
             ((LoginListener) this.packetListener).tick();
+            } // Paper
         }
 
         if (this.packetListener instanceof PlayerConnection) {