From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: William Blake Galbreath <blake.galbreath@gmail.com>
Date: Fri, 11 Oct 2019 00:17:39 -0500
Subject: [PATCH] Alternative Keepalive Handling


diff --git a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
index efc2204bd712449a93e132a19d31ae99b702972d..aa05998ef190e8ee9c3c1bfcb61d0daef81dee3b 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -244,6 +244,7 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Ser
     private long keepAliveTime = Util.getMillis();
     private boolean keepAlivePending;
     private long keepAliveChallenge;
+    private java.util.List<Long> keepAlives = new java.util.ArrayList<>(); // Purpur
     // CraftBukkit start - multithreaded fields
     private final AtomicInteger chatSpamTickCount = new AtomicInteger();
     private final java.util.concurrent.atomic.AtomicInteger tabSpamLimiter = new java.util.concurrent.atomic.AtomicInteger(); // Paper - configurable tab spam limits
@@ -395,6 +396,21 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Ser
         long currentTime = Util.getMillis();
         long elapsedTime = currentTime - this.keepAliveTime;
 
+        // Purpur start
+        if (org.purpurmc.purpur.PurpurConfig.useAlternateKeepAlive) {
+            if (elapsedTime >= 1000L) { // 1 second
+                if (!processedDisconnect && keepAlives.size() > KEEPALIVE_LIMIT) {
+                    LOGGER.warn("{} was kicked due to keepalive timeout!", player.getName());
+                    disconnect(Component.translatable("disconnect.timeout"));
+                } else {
+                    keepAliveTime = currentTime; // hijack this field for 1 second intervals
+                    keepAlives.add(currentTime); // currentTime is ID
+                    send(new ClientboundKeepAlivePacket(currentTime));
+                }
+            }
+        } else
+        // Purpur end
+
         if (this.keepAlivePending) {
             if (!this.processedDisconnect && elapsedTime >= KEEPALIVE_LIMIT) { // check keepalive limit, don't fire if already disconnected
                 ServerGamePacketListenerImpl.LOGGER.warn("{} was kicked due to keepalive timeout!", this.player.getScoreboardName()); // more info
@@ -3351,6 +3367,16 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Ser
 
     @Override
     public void handleKeepAlive(ServerboundKeepAlivePacket packet) {
+        // Purpur start
+        if (org.purpurmc.purpur.PurpurConfig.useAlternateKeepAlive) {
+            long id = packet.getId();
+            if (keepAlives.size() > 0 && keepAlives.contains(id)) {
+                int ping = (int) (Util.getMillis() - id);
+                player.latency = (player.latency * 3 + ping) / 4;
+                keepAlives.clear(); // we got a valid response, lets roll with it and forget the rest
+            }
+        } else
+        // Purpur end
         //PlayerConnectionUtils.ensureMainThread(packetplayinkeepalive, this, this.player.getWorldServer()); // CraftBukkit // Paper - This shouldn't be on the main thread
         if (this.keepAlivePending && packet.getId() == this.keepAliveChallenge) {
             int i = (int) (Util.getMillis() - this.keepAliveTime);
diff --git a/src/main/java/org/purpurmc/purpur/PurpurConfig.java b/src/main/java/org/purpurmc/purpur/PurpurConfig.java
index 3b417ecebe7bb621aee76d5155d97695c826f4a6..8124b27f043beb763d70881593a883e06ea59f6e 100644
--- a/src/main/java/org/purpurmc/purpur/PurpurConfig.java
+++ b/src/main/java/org/purpurmc/purpur/PurpurConfig.java
@@ -191,6 +191,11 @@ public class PurpurConfig {
         laggingThreshold = getDouble("settings.lagging-threshold", laggingThreshold);
     }
 
+    public static boolean useAlternateKeepAlive = false;
+    private static void useAlternateKeepAlive() {
+        useAlternateKeepAlive = getBoolean("settings.use-alternate-keepalive", useAlternateKeepAlive);
+    }
+
     public static int barrelRows = 3;
     public static boolean enderChestSixRows = false;
     public static boolean enderChestPermissionRows = false;