PaperMC/Remapped-Spigot-Server-Patches/0172-revert-serverside-behavior-of-keepalives.patch

From 0000000000000000000000000000000000000000 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/network/ServerGamePacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
index f0aab8639c7d8440e4d70dd096200313d7958780..525728268f56470fdc24c4fd2f19d66943447778 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -221,7 +221,7 @@ public class ServerGamePacketListenerImpl implements ServerGamePacketListener {
     private final MinecraftServer server;
     public ServerPlayer player;
     private int tickCount;
-    private long keepAliveTime; private void setLastPing(long lastPing) { this.keepAliveTime = lastPing;}; private long getLastPing() { return this.keepAliveTime;}; // Paper - OBFHELPER
+    private long keepAliveTime = Util.getMillis(); private void setLastPing(long lastPing) { this.keepAliveTime = lastPing;}; private long getLastPing() { return this.keepAliveTime;}; // Paper - OBFHELPER
     private boolean keepAlivePending; private void setPendingPing(boolean isPending) { this.keepAlivePending = isPending;}; private boolean isPendingPing() { return this.keepAlivePending;}; // Paper - OBFHELPER
     private long keepAliveChallenge; private void setKeepAliveID(long keepAliveID) { this.keepAliveChallenge = keepAliveID;}; private long getKeepAliveID() {return this.keepAliveChallenge; };  // Paper - OBFHELPER
     // CraftBukkit start - multithreaded fields
@@ -252,6 +252,7 @@ public class ServerGamePacketListenerImpl implements ServerGamePacketListener {
     private int aboveGroundVehicleTickCount;
     private int receivedMovePacketCount;
     private int knownMovePacketCount;
+    private static final long KEEPALIVE_LIMIT = Long.getLong("paper.playerconnection.keepalive", 30) * 1000; // Paper - provide property to set keepalive limit
 
     public ServerGamePacketListenerImpl(MinecraftServer server, Connection connection, ServerPlayer player) {
         this.server = server;
@@ -338,18 +339,25 @@ public class ServerGamePacketListenerImpl implements ServerGamePacketListener {
         }
 
         this.server.getProfiler().push("keepAlive");
-        long i = Util.getMillis();
-
-        if (i - this.keepAliveTime >= 25000L) { // CraftBukkit
-            if (this.keepAlivePending) {
-                this.disconnect(new TranslatableComponent("disconnect.timeout"));
-            } else {
-                this.keepAlivePending = true;
-                this.keepAliveTime = i;
-                this.keepAliveChallenge = i;
-                this.send(new ClientboundKeepAlivePacket(this.keepAliveChallenge));
+        // 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 = Util.getMillis();
+        long elapsedTime = currentTime - this.getLastPing();
+
+        if (this.isPendingPing()) {
+            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
+                this.disconnect(new TranslatableComponent("disconnect.timeout", new Object[0]));
+            }
+        } else {
+            if (elapsedTime >= 15000L) { // 15 seconds
+                this.setPendingPing(true);
+                this.setLastPing(currentTime);
+                this.setKeepAliveID(currentTime);
+                this.send(new ClientboundKeepAlivePacket(this.getKeepAliveID()));
             }
         }
+        // Paper end
 
         this.server.getProfiler().pop();
         // CraftBukkit start