Paper/patches/unapplied/server/0154-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/ServerCommonPacketListenerImpl.java b/src/main/java/net/minecraft/server/network/ServerCommonPacketListenerImpl.java
index 5e5e669f564c6130d1dea004ae8810939954da98..9b1df397e1d2d8ca04b34012808be2110526f401 100644
--- a/src/main/java/net/minecraft/server/network/ServerCommonPacketListenerImpl.java
+++ b/src/main/java/net/minecraft/server/network/ServerCommonPacketListenerImpl.java
@@ -74,7 +74,7 @@ public abstract class ServerCommonPacketListenerImpl implements ServerCommonPack
     protected final MinecraftServer server;
     public final Connection connection; // Paper
     private final boolean transferred;
-    private long keepAliveTime;
+    private long keepAliveTime = Util.getMillis(); // Paper
     private boolean keepAlivePending;
     private long keepAliveChallenge;
     private long closedListenerTime;
@@ -82,6 +82,7 @@ public abstract class ServerCommonPacketListenerImpl implements ServerCommonPack
     private int latency;
     private volatile boolean suspendFlushingOnServerThread = false;
     public final java.util.Map<java.util.UUID, net.kyori.adventure.resource.ResourcePackCallback> packCallbacks = new java.util.concurrent.ConcurrentHashMap<>(); // Paper - adventure resource pack callbacks
+    private static final long KEEPALIVE_LIMIT = Long.getLong("paper.playerconnection.keepalive", 30) * 1000; // Paper - provide property to set keepalive limit
 
     public ServerCommonPacketListenerImpl(MinecraftServer minecraftserver, Connection networkmanager, CommonListenerCookie commonlistenercookie, ServerPlayer player) { // CraftBukkit
         this.server = minecraftserver;
@@ -232,18 +233,22 @@ public abstract class ServerCommonPacketListenerImpl implements ServerCommonPack
 
     protected void keepConnectionAlive() {
         this.server.getProfiler().push("keepAlive");
-        long i = Util.getMillis();
+        // 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.isSingleplayerOwner() && i - this.keepAliveTime >= 25000L) { // CraftBukkit
-            if (this.keepAlivePending) {
+        if (!this.isSingleplayerOwner() && elapsedTime >= 15000L) { // Paper - use vanilla's 15000L between keep alive packets
+            if (this.keepAlivePending && !this.processedDisconnect && elapsedTime >= KEEPALIVE_LIMIT) { // Paper - check keepalive limit, don't fire if already disconnected
                 this.disconnect(ServerCommonPacketListenerImpl.TIMEOUT_DISCONNECTION_MESSAGE);
-            } else if (this.checkIfClosed(i)) {
+            } else if (this.checkIfClosed(currentTime)) { // Paper
                 this.keepAlivePending = true;
-                this.keepAliveTime = i;
-                this.keepAliveChallenge = i;
+                this.keepAliveTime = currentTime;
+                this.keepAliveChallenge = currentTime;
                 this.send(new ClientboundKeepAlivePacket(this.keepAliveChallenge));
             }
         }
+        // Paper end - give clients a longer time to respond to pings as per pre 1.12.2 timings
 
         this.server.getProfiler().pop();
     }