From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Wed, 6 May 2020 04:53:35 -0400
Subject: [PATCH] Optimize Network Manager and add advanced packet support

Adds ability for 1 packet to bundle other packets to follow it
Adds ability for a packet to delay sending more packets until a state is ready.

Removes synchronization from sending packets
Removes processing packet queue off of main thread
  - for the few cases where it is allowed, order is not necessary nor
    should it even be happening concurrently in first place (handshaking/login/status)

Ensures packets sent asynchronously are dispatched on main thread

This helps ensure safety for ProtocolLib as packet listeners
are commonly accessing world state. This will allow you to schedule
a packet to be sent async, but itll be dispatched sync for packet
listeners to process.

This should solve some deadlock risks

Also adds Netty Channel Flush Consolidation to reduce the amount of flushing

Also avoids spamming closed channel exception by rechecking closed state in dispatch
and then catch exceptions and close if they fire.

Part of this commit was authored by: Spottedleaf

diff --git a/src/main/java/net/minecraft/server/NetworkManager.java b/src/main/java/net/minecraft/server/NetworkManager.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/NetworkManager.java
+++ b/src/main/java/net/minecraft/server/NetworkManager.java
@@ -0,0 +0,0 @@ public class NetworkManager extends SimpleChannelInboundHandler<Packet<?>> {
     public int protocolVersion;
     public java.net.InetSocketAddress virtualHost;
     private static boolean enableExplicitFlush = Boolean.getBoolean("paper.explicit-flush");
+    // Optimize network
+    boolean isPending = true;
+    boolean queueImmunity = false;
+    EnumProtocol protocol;
     // Paper end
 
     public NetworkManager(EnumProtocolDirection enumprotocoldirection) {
@@ -0,0 +0,0 @@ public class NetworkManager extends SimpleChannelInboundHandler<Packet<?>> {
     }
 
     public void setProtocol(EnumProtocol enumprotocol) {
+        protocol = enumprotocol; // Paper
         this.channel.attr(NetworkManager.c).set(enumprotocol);
         this.channel.config().setAutoRead(true);
         NetworkManager.LOGGER.debug("Enabled auto read");
@@ -0,0 +0,0 @@ public class NetworkManager extends SimpleChannelInboundHandler<Packet<?>> {
         Validate.notNull(packetlistener, "packetListener", new Object[0]);
         this.packetListener = packetlistener;
     }
+    // Paper start
+    private EntityPlayer getPlayer() {
+        if (packetListener instanceof PlayerConnection) {
+            return ((PlayerConnection) packetListener).player;
+        } else {
+            return null;
+        }
+    }
+    private static class InnerUtil { // Attempt to hide these methods from ProtocolLib so it doesn't accidently pick them up.
+        private static java.util.List<Packet> buildExtraPackets(Packet packet) {
+            java.util.List<Packet> extra = packet.getExtraPackets();
+            if (extra == null || extra.isEmpty()) {
+                return null;
+            }
+            java.util.List<Packet> ret = new java.util.ArrayList<>(1 + extra.size());
+            buildExtraPackets0(extra, ret);
+            return ret;
+        }
+
+        private static void buildExtraPackets0(java.util.List<Packet> extraPackets, java.util.List<Packet> into) {
+            for (Packet extra : extraPackets) {
+                into.add(extra);
+                java.util.List<Packet> extraExtra = extra.getExtraPackets();
+                if (extraExtra != null && !extraExtra.isEmpty()) {
+                    buildExtraPackets0(extraExtra, into);
+                }
+            }
+        }
+        // Paper start
+        private static boolean canSendImmediate(NetworkManager networkManager, Packet<?> packet) {
+            return networkManager.isPending || networkManager.protocol != EnumProtocol.PLAY || networkManager.queueImmunity ||
+                packet instanceof PacketPlayOutKeepAlive ||
+                packet instanceof PacketPlayOutChat ||
+                packet instanceof PacketPlayOutTabComplete;
+        }
+        // Paper end
+    }
+    // Paper end
 
     public void sendPacket(Packet<?> packet) {
         this.sendPacket(packet, (GenericFutureListener) null);
     }
 
     public void sendPacket(Packet<?> packet, @Nullable GenericFutureListener<? extends Future<? super Void>> genericfuturelistener) {
-        if (this.isConnected()) {
-            this.o();
-            this.b(packet, genericfuturelistener);
-        } else {
-            this.packetQueue.add(new NetworkManager.QueuedPacket(packet, genericfuturelistener));
+        // Paper start - handle oversized packets better
+        boolean connected = this.isConnected();
+        if (!connected && !preparing) {
+            return; // Do nothing
+        }
+        packet.onPacketDispatch(getPlayer());
+        if (connected && (InnerUtil.canSendImmediate(this, packet) || (
+            MCUtil.isMainThread() && packet.isReady() && this.packetQueue.isEmpty() &&
+            (packet.getExtraPackets() == null || packet.getExtraPackets().isEmpty())
+        ))) {
+            this.dispatchPacket(packet, genericfuturelistener);
+            return;
         }
+        // write the packets to the queue, then flush - antixray hooks there already
+        java.util.List<Packet> extraPackets = InnerUtil.buildExtraPackets(packet);
+        boolean hasExtraPackets = extraPackets != null && !extraPackets.isEmpty();
+        if (!hasExtraPackets) {
+            this.packetQueue.add(new NetworkManager.QueuedPacket(packet, genericfuturelistener));
+        } else {
+            java.util.List<NetworkManager.QueuedPacket> packets = new java.util.ArrayList<>(1 + extraPackets.size());
+            packets.add(new NetworkManager.QueuedPacket(packet, null)); // delay the future listener until the end of the extra packets
+
+            for (int i = 0, len = extraPackets.size(); i < len;) {
+                Packet extra = extraPackets.get(i);
+                boolean end = ++i == len;
+                packets.add(new NetworkManager.QueuedPacket(extra, end ? genericfuturelistener : null)); // append listener to the end
+            }
 
+            this.packetQueue.addAll(packets); // atomic
+        }
+        this.sendPacketQueue();
+        // Paper end
     }
 
     private void dispatchPacket(Packet<?> packet, @Nullable GenericFutureListener<? extends Future<? super Void>> genericFutureListener) { this.b(packet, genericFutureListener); } // Paper - OBFHELPER
@@ -0,0 +0,0 @@ public class NetworkManager extends SimpleChannelInboundHandler<Packet<?>> {
             this.channel.config().setAutoRead(false);
         }
 
+        EntityPlayer player = getPlayer(); // Paper
         if (this.channel.eventLoop().inEventLoop()) {
             if (enumprotocol != enumprotocol1) {
                 this.setProtocol(enumprotocol);
             }
+            // Paper start
+            if (!isConnected()) {
+                packet.onPacketDispatchFinish(player, null);
+                return;
+            }
+            try {
+                // Paper end
 
             ChannelFuture channelfuture = this.channel.writeAndFlush(packet);
 
             if (genericfuturelistener != null) {
                 channelfuture.addListener(genericfuturelistener);
             }
+            // Paper start
+            if (packet.hasFinishListener()) {
+                channelfuture.addListener((ChannelFutureListener) channelFuture -> packet.onPacketDispatchFinish(player, channelFuture));
+            }
+            // Paper end
 
             channelfuture.addListener(ChannelFutureListener.FIRE_EXCEPTION_ON_FAILURE);
+            // Paper start
+            } catch (Exception e) {
+                LOGGER.error("NetworkException: " + player, e);
+                close(new ChatMessage("disconnect.genericReason", "Internal Exception: " + e.getMessage()));;
+                packet.onPacketDispatchFinish(player, null);
+            }
+            // Paper end
         } else {
             this.channel.eventLoop().execute(() -> {
                 if (enumprotocol != enumprotocol1) {
                     this.setProtocol(enumprotocol);
                 }
 
+                // Paper start
+                if (!isConnected()) {
+                    packet.onPacketDispatchFinish(player, null);
+                    return;
+                }
+                try {
+                    // Paper end
                 ChannelFuture channelfuture1 = this.channel.writeAndFlush(packet);
 
+
                 if (genericfuturelistener != null) {
                     channelfuture1.addListener(genericfuturelistener);
                 }
+                // Paper start
+                if (packet.hasFinishListener()) {
+                    channelfuture1.addListener((ChannelFutureListener) channelFuture -> packet.onPacketDispatchFinish(player, channelFuture));
+                }
+                // Paper end
 
                 channelfuture1.addListener(ChannelFutureListener.FIRE_EXCEPTION_ON_FAILURE);
+                // Paper start
+                } catch (Exception e) {
+                    LOGGER.error("NetworkException: " + player, e);
+                    close(new ChatMessage("disconnect.genericReason", "Internal Exception: " + e.getMessage()));;
+                    packet.onPacketDispatchFinish(player, null);
+                }
+                // Paper end
             });
         }
 
     }
 
-    private void sendPacketQueue() { this.o(); } // Paper - OBFHELPER
-    private void o() {
-        if (this.channel != null && this.channel.isOpen()) {
-            Queue queue = this.packetQueue;
-
+    // Paper start - rewrite this to be safer on
+    private boolean sendPacketQueue() { return this.o(); } // OBFHELPER // void -> boolean
+    private boolean o() { // void -> boolean
+        if (!isConnected()) {
+            return true;
+        }
+        if (MCUtil.isMainThread()) {
+            return processQueue();
+        } else if (isPending) {
+            // Should only happen during login/status stages
             synchronized (this.packetQueue) {
-                NetworkManager.QueuedPacket networkmanager_queuedpacket;
-
-                while ((networkmanager_queuedpacket = (NetworkManager.QueuedPacket) this.packetQueue.poll()) != null) {
-                    this.b(networkmanager_queuedpacket.a, networkmanager_queuedpacket.b);
-                }
+                return this.processQueue();
+            }
+        }
+        return false;
+    }
+    private boolean processQueue() {
+        if (this.packetQueue.isEmpty()) return true;
+        // If we are on main, we are safe here in that nothing else should be processing queue off main anymore
+        // But if we are not on main due to login/status, the parent is synchronized on packetQueue
+        java.util.Iterator<QueuedPacket> iterator = this.packetQueue.iterator();
+        while (iterator.hasNext()) {
+            NetworkManager.QueuedPacket queued = iterator.next(); // poll -> peek
+
+            // Fix NPE (Spigot bug caused by handleDisconnection())
+            if (queued == null) {
+                return true;
+            }
 
+            Packet<?> packet = queued.getPacket();
+            if (!packet.isReady()) {
+                return false;
+            } else {
+                iterator.remove();
+                this.dispatchPacket(packet, queued.getGenericFutureListener());
             }
         }
+        return true;
     }
+    // Paper end
 
     public void a() {
         this.o();
@@ -0,0 +0,0 @@ public class NetworkManager extends SimpleChannelInboundHandler<Packet<?>> {
         return this.socketAddress;
     }
 
+    // Paper start
+    public void clearPacketQueue() {
+        EntityPlayer player = getPlayer();
+        packetQueue.forEach(queuedPacket -> {
+            Packet<?> packet = queuedPacket.getPacket();
+            if (packet.hasFinishListener()) {
+                packet.onPacketDispatchFinish(player, null);
+            }
+        });
+        packetQueue.clear();
+    } // Paper end
     public void close(IChatBaseComponent ichatbasecomponent) {
         // Spigot Start
         this.preparing = false;
+        clearPacketQueue(); // Paper
         // Spigot End
         if (this.channel.isOpen()) {
             this.channel.close(); // We can't wait as this may be called from an event loop.
@@ -0,0 +0,0 @@ public class NetworkManager extends SimpleChannelInboundHandler<Packet<?>> {
     public void handleDisconnection() {
         if (this.channel != null && !this.channel.isOpen()) {
             if (this.o) {
-                NetworkManager.LOGGER.warn("handleDisconnection() called twice");
+                //NetworkManager.LOGGER.warn("handleDisconnection() called twice"); // Paper - Do not log useless message
             } else {
                 this.o = true;
                 if (this.j() != null) {
@@ -0,0 +0,0 @@ public class NetworkManager extends SimpleChannelInboundHandler<Packet<?>> {
                 } else if (this.i() != null) {
                     this.i().a(new ChatMessage("multiplayer.disconnect.generic"));
                 }
-                this.packetQueue.clear(); // Free up packet queue.
+                clearPacketQueue(); // Paper
                 // Paper start - Add PlayerConnectionCloseEvent
                 final PacketListener packetListener = this.i();
                 if (packetListener instanceof PlayerConnection) {
diff --git a/src/main/java/net/minecraft/server/Packet.java b/src/main/java/net/minecraft/server/Packet.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/Packet.java
+++ b/src/main/java/net/minecraft/server/Packet.java
@@ -0,0 +0,0 @@
 package net.minecraft.server;
 
+import io.netty.channel.ChannelFuture; // Paper
 import java.io.IOException;
 
 public interface Packet<T extends PacketListener> {
@@ -0,0 +0,0 @@ public interface Packet<T extends PacketListener> {
     void a(T t0);
 
     // Paper start
+
+    /**
+     * @param player Null if not at PLAY stage yet
+     */
+    default void onPacketDispatch(@javax.annotation.Nullable EntityPlayer player) {}
+
+    /**
+     * @param player Null if not at PLAY stage yet
+     * @param future Can be null if packet was cancelled
+     */
+    default void onPacketDispatchFinish(@javax.annotation.Nullable EntityPlayer player, @javax.annotation.Nullable ChannelFuture future) {}
+    default boolean hasFinishListener() { return false; }
+    default boolean isReady() { return true; }
+    default java.util.List<Packet> getExtraPackets() { return null; }
     default boolean packetTooLarge(NetworkManager manager) {
         return false;
     }
diff --git a/src/main/java/net/minecraft/server/PlayerList.java b/src/main/java/net/minecraft/server/PlayerList.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/PlayerList.java
+++ b/src/main/java/net/minecraft/server/PlayerList.java
@@ -0,0 +0,0 @@ public abstract class PlayerList {
         boolean flag1 = gamerules.getBoolean(GameRules.REDUCED_DEBUG_INFO);
 
         // Spigot - view distance
+        networkmanager.queueImmunity = true; // Paper
         playerconnection.sendPacket(new PacketPlayOutLogin(entityplayer.getId(), entityplayer.playerInteractManager.getGameMode(), entityplayer.playerInteractManager.c(), BiomeManager.a(worldserver1.getSeed()), worlddata.isHardcore(), this.server.E(), this.s, worldserver1.getTypeKey(), worldserver1.getDimensionKey(), this.getMaxPlayers(), worldserver.spigotConfig.viewDistance, flag1, !flag, worldserver1.isDebugWorld(), worldserver1.isFlatWorld()));
         entityplayer.getBukkitEntity().sendSupportedChannels(); // CraftBukkit
         playerconnection.sendPacket(new PacketPlayOutCustomPayload(PacketPlayOutCustomPayload.a, (new PacketDataSerializer(Unpooled.buffer())).a(this.getServer().getServerModName())));
@@ -0,0 +0,0 @@ public abstract class PlayerList {
         playerconnection.sendPacket(new PacketPlayOutRecipeUpdate(this.server.getCraftingManager().b()));
         playerconnection.sendPacket(new PacketPlayOutTags(this.server.getTagRegistry()));
         playerconnection.sendPacket(new PacketPlayOutEntityStatus(entityplayer, (byte) (worldserver.getGameRules().getBoolean(GameRules.REDUCED_DEBUG_INFO) ? 22 : 23))); // Paper - fix this rule not being initialized on the client
+        networkmanager.queueImmunity = false; // Paper
         this.d(entityplayer);
         entityplayer.getStatisticManager().c();
         entityplayer.B().a(entityplayer);
diff --git a/src/main/java/net/minecraft/server/ServerConnection.java b/src/main/java/net/minecraft/server/ServerConnection.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/ServerConnection.java
+++ b/src/main/java/net/minecraft/server/ServerConnection.java
@@ -0,0 +0,0 @@ import io.netty.channel.epoll.EpollServerSocketChannel;
 import io.netty.channel.nio.NioEventLoopGroup;
 import io.netty.channel.socket.ServerSocketChannel;
 import io.netty.channel.socket.nio.NioServerSocketChannel;
+import io.netty.handler.flush.FlushConsolidationHandler; // Paper
 import io.netty.handler.timeout.ReadTimeoutHandler;
 import java.io.IOException;
 import java.net.InetAddress;
@@ -0,0 +0,0 @@ public class ServerConnection {
     private final List<NetworkManager> connectedChannels = Collections.synchronizedList(Lists.newArrayList());
     // Paper start - prevent blocking on adding a new network manager while the server is ticking
     private final java.util.Queue<NetworkManager> pending = new java.util.concurrent.ConcurrentLinkedQueue<>();
+    private static final boolean disableFlushConsolidation = Boolean.getBoolean("Paper.disableFlushConsolidate"); // Paper
     private void addPending() {
         NetworkManager manager = null;
         while ((manager = pending.poll()) != null) {
             connectedChannels.add(manager);
+            manager.isPending = false;
         }
     }
     // Paper end
@@ -0,0 +0,0 @@ public class ServerConnection {
                         ;
                     }
 
+                    if (!disableFlushConsolidation) channel.pipeline().addFirst(new FlushConsolidationHandler()); // Paper
                     channel.pipeline().addLast("timeout", new ReadTimeoutHandler(30)).addLast("legacy_query", new LegacyPingHandler(ServerConnection.this)).addLast("splitter", new PacketSplitter()).addLast("decoder", new PacketDecoder(EnumProtocolDirection.SERVERBOUND)).addLast("prepender", new PacketPrepender()).addLast("encoder", new PacketEncoder(EnumProtocolDirection.CLIENTBOUND));
                     NetworkManager networkmanager = new NetworkManager(EnumProtocolDirection.SERVERBOUND);
 
