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 511a480aa962fd2659e929bb274297db6baf437e..4ddd3a819648fe5418a19d4496a18dc20c4e086e 100644
--- a/src/main/java/net/minecraft/server/NetworkManager.java
+++ b/src/main/java/net/minecraft/server/NetworkManager.java
@@ -65,6 +65,10 @@ 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) {
@@ -88,6 +92,7 @@ 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");
@@ -158,19 +163,82 @@ public class NetworkManager extends SimpleChannelInboundHandler<Packet<?>> {
         Validate.notNull(packetlistener, "packetListener", new Object[0]);
         this.packetListener = packetlistener;
     }
+    // Paper start
+    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 ||
+                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.p();
-            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
@@ -184,51 +252,116 @@ 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.p(); } // Paper - OBFHELPER
-    private void p() {
-        if (this.channel != null && this.channel.isOpen()) {
-            Queue queue = this.packetQueue;
-
+    // Paper start - rewrite this to be safer if ran off main thread
+    private boolean sendPacketQueue() { return this.p(); } // OBFHELPER // void -> boolean
+    private boolean p() { // 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.p();
@@ -261,9 +394,21 @@ 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.
@@ -331,7 +476,7 @@ 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.k() != null) {
@@ -339,7 +484,7 @@ public class NetworkManager extends SimpleChannelInboundHandler<Packet<?>> {
                 } else if (this.j() != null) {
                     this.j().a(new ChatMessage("multiplayer.disconnect.generic"));
                 }
-                this.packetQueue.clear(); // Free up packet queue.
+                clearPacketQueue(); // Paper
                 // Paper start - Add PlayerConnectionCloseEvent
                 final PacketListener packetListener = this.j();
                 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 2d8e6a2f4a0c3c5d74a647d7164b0028781d3bf5..545dbe6ddcce1d172f465b4a7ab85654ee5fdbb4 100644
--- a/src/main/java/net/minecraft/server/Packet.java
+++ b/src/main/java/net/minecraft/server/Packet.java
@@ -1,5 +1,6 @@
 package net.minecraft.server;
 
+import io.netty.channel.ChannelFuture; // Paper
 import java.io.IOException;
 
 public interface Packet<T extends PacketListener> {
@@ -11,6 +12,20 @@ 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/ServerConnection.java b/src/main/java/net/minecraft/server/ServerConnection.java
index 8fcd8f4056620713d0c02fdd9b829053ba95e851..5f4dacf9c93c2495a07df2647fe0411f796da6af 100644
--- a/src/main/java/net/minecraft/server/ServerConnection.java
+++ b/src/main/java/net/minecraft/server/ServerConnection.java
@@ -16,6 +16,7 @@ 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;
@@ -41,10 +42,12 @@ 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
@@ -79,6 +82,7 @@ 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));
                     int j = ServerConnection.this.e.k();
                     Object object = j > 0 ? new NetworkManagerServer(j) : new NetworkManager(EnumProtocolDirection.SERVERBOUND);
