Paper/Spigot-Server-Patches/0379-Allow-login-events-to-fire-only-after-the-server-plu.patch

From 0418b980eb03e413cbefe1533d029549047dff03 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Sun, 31 Mar 2019 22:02:24 -0700
Subject: [PATCH] Allow login events to fire only after the server plugins are
 enabled

Event threads will simply block until they're ready to accept.

diff --git a/src/main/java/net/minecraft/server/LoginListener.java b/src/main/java/net/minecraft/server/LoginListener.java
index 9e4bc24058..028c23dbe6 100644
--- a/src/main/java/net/minecraft/server/LoginListener.java
+++ b/src/main/java/net/minecraft/server/LoginListener.java
@@ -285,6 +285,36 @@ public class LoginListener implements PacketLoginInListener {
         }
     }
 
+    // Paper start - Delay async prelogin until plugins are ready
+    private static volatile Object blockingLogins = new Object();
+
+    public static void checkStartupAndBlock() {
+        final Object lock = LoginListener.blockingLogins;
+        if (lock != null) {
+            synchronized (lock) {
+                for (;;) {
+                    if (LoginListener.blockingLogins == null) {
+                        return;
+                    }
+                    try {
+                        lock.wait();
+                    } catch (final InterruptedException ignore) {// handled by the if statement above
+                        Thread.currentThread().interrupt();
+                    }
+                }
+            }
+        }
+    }
+
+    public static void allowLogins() {
+        final Object lock = LoginListener.blockingLogins;
+        synchronized (lock) {
+            LoginListener.blockingLogins = null;
+            lock.notifyAll();
+        }
+    }
+    // Paper end
+
     // Spigot start
     public class LoginHandler {
 
@@ -295,6 +325,7 @@ public class LoginListener implements PacketLoginInListener {
                                 return;
                             }
                             // Paper end
+                            LoginListener.checkStartupAndBlock(); // Paper - Delay async login events until plugins are ready
                             String playerName = i.getName();
                             java.net.InetAddress address = ((java.net.InetSocketAddress) networkManager.getSocketAddress()).getAddress();
                             java.util.UUID uniqueId = i.getId();
diff --git a/src/main/java/net/minecraft/server/MinecraftServer.java b/src/main/java/net/minecraft/server/MinecraftServer.java
index 6e77fa35b4..70f730996c 100644
--- a/src/main/java/net/minecraft/server/MinecraftServer.java
+++ b/src/main/java/net/minecraft/server/MinecraftServer.java
@@ -462,6 +462,7 @@ public abstract class MinecraftServer extends IAsyncTaskHandlerReentrant<TickTas
         // Paper end
 
         this.server.enablePlugins(org.bukkit.plugin.PluginLoadOrder.POSTWORLD);
+        LoginListener.allowLogins(); // Paper - Allow logins once postworld
         this.server.getPluginManager().callEvent(new ServerLoadEvent(ServerLoadEvent.LoadType.STARTUP));
         // CraftBukkit end
 
-- 
2.21.0