From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: MrHua269 <wangxyper@163.com>
Date: Sun, 12 Jan 2025 11:43:15 +0800
Subject: [PATCH] Purpur: Use alternative keep alive

As part of: Purpur (https://github.com/PurpurMC/Purpur/blob/09f547de09fc5d886f18f6d99ff389289766ec9d/purpur-server/minecraft-patches/sources/net/minecraft/server/network/ServerCommonPacketListenerImpl.java.patch)
Licensed under: MIT (https://github.com/PurpurMC/Purpur/blob/09f547de09fc5d886f18f6d99ff389289766ec9d/LICENSE)

diff --git a/net/minecraft/server/network/ServerCommonPacketListenerImpl.java b/net/minecraft/server/network/ServerCommonPacketListenerImpl.java
index 62b00aae7d31b79356dec44ce89cf9f2ce9c9bc2..a483d3001e05649ea332f17359218b6e21d9c527 100644
--- a/net/minecraft/server/network/ServerCommonPacketListenerImpl.java
+++ b/net/minecraft/server/network/ServerCommonPacketListenerImpl.java
@@ -43,6 +43,7 @@ public abstract class ServerCommonPacketListenerImpl implements ServerCommonPack
     private long keepAliveChallenge;
     private long closedListenerTime;
     private boolean closed = false;
+    private it.unimi.dsi.fastutil.longs.LongList keepAlives = new it.unimi.dsi.fastutil.longs.LongArrayList(); // Purpur
     private int latency;
     private volatile boolean suspendFlushingOnServerThread = false;
     // CraftBukkit start
@@ -132,6 +133,16 @@ public abstract class ServerCommonPacketListenerImpl implements ServerCommonPack
 
     @Override
     public void handleKeepAlive(ServerboundKeepAlivePacket packet) {
+        // Purpur start
+        if (me.earthme.luminol.config.modules.optimizations.PurpurAlternativeKeepaliveConfig.useAlternateKeepAlive) {
+            if (this.keepAlivePending && !keepAlives.isEmpty() && keepAlives.contains(packet.getId())) {
+                int ping = (int) (Util.getMillis() - packet.getId());
+                this.latency = (this.latency * 3 + ping) / 4;
+                this.keepAlivePending = false;
+                keepAlives.clear(); // we got a valid response, lets roll with it and forget the rest
+            }
+        } else
+        // Purpur end
         if (this.keepAlivePending && packet.getId() == this.keepAliveChallenge) {
             int i = (int)(Util.getMillis() - this.keepAliveTime);
             this.latency = (this.latency * 3 + i) / 4;
@@ -262,6 +273,21 @@ public abstract class ServerCommonPacketListenerImpl implements ServerCommonPack
         // Paper start - give clients a longer time to respond to pings as per pre 1.12.2 timings
         // This should effectively place the keepalive handling back to "as it was" before 1.12.2
         final long elapsedTime = millis - this.keepAliveTime;
+        // Purpur start
+        if (me.earthme.luminol.config.modules.optimizations.PurpurAlternativeKeepaliveConfig.useAlternateKeepAlive) {
+            if (elapsedTime >= 1000L) { // 1 second
+                if (this.keepAlivePending && !this.processedDisconnect && keepAlives.size() * 1000L >= KEEPALIVE_LIMIT) {
+                    LOGGER.warn("{} was kicked due to keepalive timeout!", this.player.getScoreboardName());
+                    this.disconnect(ServerCommonPacketListenerImpl.TIMEOUT_DISCONNECTION_MESSAGE, org.bukkit.event.player.PlayerKickEvent.Cause.TIMEOUT);
+                } else if (this.checkIfClosed(millis)) {
+                    this.keepAlivePending = true;
+                    this.keepAliveTime = millis; // hijack this field for 1 second intervals
+                    this.keepAlives.add(millis); // currentTime is ID
+                    this.send(new ClientboundKeepAlivePacket(millis));
+                }
+            }
+        } else {
+
         if (!this.isSingleplayerOwner() && elapsedTime >= 15000L) { // use vanilla's 15000L between keep alive packets
             if (this.keepAlivePending) {
                 if (!this.processedDisconnect && elapsedTime >= KEEPALIVE_LIMIT) { // check keepalive limit, don't fire if already disconnected
@@ -275,6 +301,7 @@ public abstract class ServerCommonPacketListenerImpl implements ServerCommonPack
                 this.send(new ClientboundKeepAlivePacket(this.keepAliveChallenge));
             }
         }
+        } // Purpur end
 
         Profiler.get().pop();
     }