PaperMC/patches/server/0159-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 04bff597b77e37ee90abecc2dabf8919c1ef4082..e206753e5b34b6ab7bd241a77a67e0cdcfa662d1 100644
--- a/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerGamePacketListenerImpl.java
@@ -259,7 +259,7 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
     public ServerPlayer player;
     private int tickCount;
     private int ackBlockChangesUpTo = -1;
-    private long keepAliveTime;
+    private long keepAliveTime = Util.getMillis();
     private boolean keepAlivePending;
     private long keepAliveChallenge;
     // CraftBukkit start - multithreaded fields
@@ -297,6 +297,7 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
     private final LastSeenMessagesValidator lastSeenMessages;
     private final MessageSignatureCache messageSignatureCache;
     private final FutureChain chatMessageChain;
+    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.lastChatTimeStamp = new AtomicReference(Instant.EPOCH);
@@ -388,18 +389,25 @@ public class ServerGamePacketListenerImpl implements ServerPlayerConnection, Tic
         }
 
         this.server.getProfiler().push("keepAlive");
-        long i = Util.getMillis();
-
-        if (i - this.keepAliveTime >= 25000L) { // CraftBukkit
-            if (this.keepAlivePending) {
-                this.disconnect(Component.translatable("disconnect.timeout"));
-            } else {
+        // 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.keepAliveTime;
+
+        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
+                this.disconnect(Component.translatable("disconnect.timeout", new Object[0]));
+            }
+        } else {
+            if (elapsedTime >= 15000L) { // 15 seconds
                 this.keepAlivePending = true;
-                this.keepAliveTime = i;
-                this.keepAliveChallenge = i;
+                this.keepAliveTime = currentTime;
+                this.keepAliveChallenge = currentTime;
                 this.send(new ClientboundKeepAlivePacket(this.keepAliveChallenge));
             }
         }
+        // Paper end
 
         this.server.getProfiler().pop();
         // CraftBukkit start