papermc/Spigot-Server-Patches/0242-revert-serverside-behavior-of-keepalives.patch

From c0932b4bd2689009449872c10b1ef7e8689b5f3f Mon Sep 17 00:00:00 2001
From: Shane Freeder <theboyetronic@gmail.com>
Date: Sun, 15 Oct 2017 00:29:07 +0100
Subject: [PATCH] revert serverside behavior of keepalives

This patch intends to bump up the time that a client has to reply to the
server back to 30 seconds as per pre 1.12.2, which allowed clients
more than enough time to reply potentially allowing them to be less
tempermental due to lag spikes on the network thread, e.g. that caused
by plugins that are interacting with netty.

We also add a system property to allow people to tweak how long the server
will wait for a reply. There is a compromise here between lower and higher
values, lower values will mean that dead connections can be closed sooner,
whereas higher values will make this less sensitive to issues such as spikes
from networking or during connections flood of chunk packets on slower clients,
 at the cost of dead connections being kept open for longer.

diff --git a/src/main/java/net/minecraft/server/PlayerConnection.java b/src/main/java/net/minecraft/server/PlayerConnection.java
index 869a2b402..167e386c8 100644
--- a/src/main/java/net/minecraft/server/PlayerConnection.java
+++ b/src/main/java/net/minecraft/server/PlayerConnection.java
@@ -100,6 +100,7 @@ public class PlayerConnection implements PacketListenerPlayIn, ITickable {
     private int receivedMovePackets;
     private int processedMovePackets;
     private AutoRecipe H = new AutoRecipe();
+    private static final long KEEPALIVE_LIMIT = Long.getLong("paper.playerconnection.keepalive", 30) * 1000; // Paper - provide property to set keepalive limit
 
     public PlayerConnection(MinecraftServer minecraftserver, NetworkManager networkmanager, EntityPlayer entityplayer) {
         this.minecraftServer = minecraftserver;
@@ -179,18 +180,25 @@ public class PlayerConnection implements PacketListenerPlayIn, ITickable {
         }
 
         this.minecraftServer.methodProfiler.a("keepAlive");
-        long i = this.d();
-
-        if (i - this.f >= 25000L) { // CraftBukkit
-            if (this.g) {
-                this.disconnect(new ChatMessage("disconnect.timeout", new Object[0]));
-            } else {
-                this.g = true;
-                this.f = i;
-                this.h = i;
-                this.sendPacket(new PacketPlayOutKeepAlive(this.h));
+        // 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
+        long currentTime = this.getCurrentMillis();
+        long elapsedTime = currentTime - this.getLastPing();
+        if (this.isPendingPing()) {
+            // We're pending a ping from the client
+            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
+                this.disconnect(new ChatMessage("disconnect.timeout"));
+            }
+        } else {
+            if (elapsedTime >= 15000L) { // 15 seconds
+                this.setPendingPing(true);
+                this.setLastPing(currentTime);
+                this.setKeepAliveID(currentTime);
+                this.sendPacket(new PacketPlayOutKeepAlive(this.getKeepAliveID()));
             }
         }
+        // Paper end
 
         this.minecraftServer.methodProfiler.b();
         // CraftBukkit start
-- 
2.16.2