Duplicate Disconnect Prevention. In 1.7 mojang removed the this.disconnected flag. We add it back to prevent users from forcibly disconnecting themselves in a short amount of time.

CraftBukkit-Patches/0072-Duplicate-Disconnect-Prevention.patch

@@ -0,0 +1,42 @@
+From 61c2328ff2a651da8acb3c932e6b063e42071006 Mon Sep 17 00:00:00 2001
+From: md_5 <md_5@live.com.au>
+Date: Thu, 5 Dec 2013 16:33:16 +1100
+Subject: [PATCH] Duplicate Disconnect Prevention
+
+
+diff --git a/src/main/java/net/minecraft/server/PlayerConnection.java b/src/main/java/net/minecraft/server/PlayerConnection.java
+index 5534bc3..35c66c6 100644
+--- a/src/main/java/net/minecraft/server/PlayerConnection.java
++++ b/src/main/java/net/minecraft/server/PlayerConnection.java
+@@ -77,6 +77,7 @@ public class PlayerConnection implements PacketPlayInListener {
+     private double z;
+     private double q;
+     public boolean checkMovement = true; // CraftBukkit - private -> public
++    private boolean disconnected; // Spigot
+ 
+     public PlayerConnection(MinecraftServer minecraftserver, NetworkManager networkmanager, EntityPlayer entityplayer) {
+         this.minecraftServer = minecraftserver;
+@@ -149,6 +150,12 @@ public class PlayerConnection implements PacketPlayInListener {
+     }
+ 
+     public void disconnect(String s) {
++        // Spigot Start
++        if ( disconnected )
++        {
++            return;
++        }
++        // Spigot End
+         // CraftBukkit start
+         String leaveMessage = EnumChatFormat.YELLOW + this.player.getName() + " left the game.";
+ 
+@@ -170,6 +177,7 @@ public class PlayerConnection implements PacketPlayInListener {
+         this.networkManager.handle(new PacketPlayOutKickDisconnect(chatcomponenttext), new GenericFutureListener[] { new PlayerConnectionFuture(this, chatcomponenttext)});
+         this.a(chatcomponenttext); // CraftBukkit - Process quit immediately
+         this.networkManager.g();
++        disconnected = true; // Spigot
+     }
+ 
+     public void a(PacketPlayInSteerVehicle packetplayinsteervehicle) {
+-- 
+1.8.3.2
+