From 753e40b5abc1fde5f33910bd9b5a77898f44ea0d 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

---
 .../server/PacketPlayInKeepAlive.java         |  1 +
 .../minecraft/server/PlayerConnection.java    | 26 +++++++++++++++++++
 .../java/net/pl3x/purpur/PurpurConfig.java    |  5 ++++
 3 files changed, 32 insertions(+)

diff --git a/src/main/java/net/minecraft/server/PacketPlayInKeepAlive.java b/src/main/java/net/minecraft/server/PacketPlayInKeepAlive.java
index 8e93f1540..470f92c4f 100644
--- a/src/main/java/net/minecraft/server/PacketPlayInKeepAlive.java
+++ b/src/main/java/net/minecraft/server/PacketPlayInKeepAlive.java
@@ -22,6 +22,7 @@ public class PacketPlayInKeepAlive implements Packet<PacketListenerPlayIn> {
         packetdataserializer.writeLong(this.a);
     }
 
+    public long getId() { return b(); } // Purpur - OBFHELPER
     public long b() {
         return this.a;
     }
diff --git a/src/main/java/net/minecraft/server/PlayerConnection.java b/src/main/java/net/minecraft/server/PlayerConnection.java
index 85016aa76..d2d96eacc 100644
--- a/src/main/java/net/minecraft/server/PlayerConnection.java
+++ b/src/main/java/net/minecraft/server/PlayerConnection.java
@@ -75,6 +75,7 @@ public class PlayerConnection implements PacketListenerPlayIn {
     private long lastKeepAlive = SystemUtils.getMonotonicMillis(); private void setLastPing(long lastPing) { this.lastKeepAlive = lastPing;}; private long getLastPing() { return this.lastKeepAlive;}; // Paper - OBFHELPER
     private boolean awaitingKeepAlive; private void setPendingPing(boolean isPending) { this.awaitingKeepAlive = isPending;}; private boolean isPendingPing() { return this.awaitingKeepAlive;}; // Paper - OBFHELPER
     private long h; private void setKeepAliveID(long keepAliveID) { this.h = keepAliveID;}; private long getKeepAliveID() {return this.h; };  // Paper - OBFHELPER
+    private java.util.List<Long> keepAlives = new java.util.ArrayList<>(); // Purpur
     // CraftBukkit start - multithreaded fields
     private volatile int chatThrottle;
     private static final AtomicIntegerFieldUpdater chatSpamField = AtomicIntegerFieldUpdater.newUpdater(PlayerConnection.class, "chatThrottle");
@@ -201,6 +202,21 @@ public class PlayerConnection implements PacketListenerPlayIn {
         long currentTime = SystemUtils.getMonotonicMillis();
         long elapsedTime = currentTime - this.getLastPing();
 
+        // Purpur start
+        if (net.pl3x.purpur.PurpurConfig.useAlternateKeepAlive) {
+            if (elapsedTime >= 1000L) { // 1 second
+                if (!processedDisconnect && keepAlives.size() > KEEPALIVE_LIMIT) {
+                    PlayerConnection.LOGGER.warn("{} was kicked due to keepalive timeout!", player.getName());
+                    disconnect(new ChatMessage("disconnect.timeout"));
+                } else {
+                    setLastPing(currentTime); // hijack this field for 1 second intervals
+                    keepAlives.add(currentTime); // currentTime is ID
+                    sendPacket(new PacketPlayOutKeepAlive(currentTime));
+                }
+            }
+        } else
+        // Purpur end
+
         if (this.isPendingPing()) {
             if (!this.processedDisconnect && elapsedTime >= KEEPALIVE_LIMIT) { // check keepalive limit, don't fire if already disconnected
                 PlayerConnection.LOGGER.warn("{} was kicked due to keepalive timeout!", this.player.getName()); // more info
@@ -2704,6 +2720,16 @@ public class PlayerConnection implements PacketListenerPlayIn {
 
     @Override
     public void a(PacketPlayInKeepAlive packetplayinkeepalive) {
+        // Purpur start
+        if (net.pl3x.purpur.PurpurConfig.useAlternateKeepAlive) {
+            long id = packetplayinkeepalive.getId();
+            if (keepAlives.size() > 0 && keepAlives.contains(id)) {
+                int ping = (int) (SystemUtils.getMonotonicMillis() - id);
+                player.ping = (player.ping * 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.awaitingKeepAlive && packetplayinkeepalive.b() == this.h) {
             int i = (int) (SystemUtils.getMonotonicMillis() - this.lastKeepAlive);
diff --git a/src/main/java/net/pl3x/purpur/PurpurConfig.java b/src/main/java/net/pl3x/purpur/PurpurConfig.java
index d8b826f6b..571917ffa 100644
--- a/src/main/java/net/pl3x/purpur/PurpurConfig.java
+++ b/src/main/java/net/pl3x/purpur/PurpurConfig.java
@@ -152,6 +152,11 @@ 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 boolean barrelSixRows = false;
     public static boolean enderChestSixRows = false;
     public static boolean enderChestPermissionRows = false;
-- 
2.26.2