Add Configuration State API (PaperMC#1261)

* Implement Configuration State events

* Implement PlayerFinishedConfigurationEvent

* Fixed PlayerFinishConfigurationEvent execution

* Apply suggestions

* Fix keep alive when blocking PlayerFinishConfigurationEvent

* Add ServerConnection to configuration events

* Separate PlayPacketQueueHandler to fix AutoReadHolderHandler

---------

Co-authored-by: Gero <[email protected]>

api/src/main/java/com/velocitypowered/api/event/player/configuration/PlayerEnterConfigurationEvent.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) 2024 Velocity Contributors
+ *
+ * The Velocity API is licensed under the terms of the MIT License. For more details,
+ * reference the LICENSE file in the api top-level directory.
+ */
+
+package com.velocitypowered.api.event.player.configuration;
+
+import com.velocitypowered.api.network.ProtocolState;
+import com.velocitypowered.api.proxy.Player;
+import com.velocitypowered.api.proxy.ServerConnection;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * This event is executed when a player with version 1.20.2 or higher enters the configuration phase.
+ * <p>From this moment on, until the {@link PlayerFinishedConfigurationEvent} is executed,
+ * the {@linkplain Player#getProtocolState()} method is guaranteed
+ * to return {@link ProtocolState#CONFIGURATION}.</p>
+ *
+ * @param player The player that has entered the configuration phase.
+ * @param server The server that will now (re-)configure the player.
+ * @since 3.3.0
+ * @sinceMinecraft 1.20.2
+ */
+public record PlayerEnterConfigurationEvent(@NotNull Player player, ServerConnection server) {
+}

api/src/main/java/com/velocitypowered/api/event/player/configuration/PlayerFinishConfigurationEvent.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2024 Velocity Contributors
+ *
+ * The Velocity API is licensed under the terms of the MIT License. For more details,
+ * reference the LICENSE file in the api top-level directory.
+ */
+
+package com.velocitypowered.api.event.player.configuration;
+
+import com.velocitypowered.api.event.annotation.AwaitingEvent;
+import com.velocitypowered.api.proxy.Player;
+import com.velocitypowered.api.proxy.ServerConnection;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * This event is executed when the player is about to finish the Configuration state.
+ * <p>Velocity will wait for this event to finish the configuration phase on the client.</p>
+ *
+ * @param player The player who is about to complete the configuration phase.
+ * @param server The server that is currently (re-)configuring the player.
+ * @since 3.3.0
+ * @sinceMinecraft 1.20.2
+ */
+@AwaitingEvent
+public record PlayerFinishConfigurationEvent(@NotNull Player player, @NotNull ServerConnection server) {
+}

api/src/main/java/com/velocitypowered/api/event/player/configuration/PlayerFinishedConfigurationEvent.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2024 Velocity Contributors
+ *
+ * The Velocity API is licensed under the terms of the MIT License. For more details,
+ * reference the LICENSE file in the api top-level directory.
+ */
+
+package com.velocitypowered.api.event.player.configuration;
+
+import com.velocitypowered.api.network.ProtocolState;
+import com.velocitypowered.api.proxy.Player;
+import com.velocitypowered.api.proxy.ServerConnection;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Event executed when a player of version 1.20.2 or higher finishes the Configuration state.
+ * <p>From this moment on, the {@link Player#getProtocolState()} method
+ * will return {@link ProtocolState#PLAY}.</p>
+ *
+ * @param player The player who has completed the Configuration state
+ * @param server The server that has (re-)configured the player.
+ * @since 3.3.0
+ * @sinceMinecraft 1.20.2
+ */
+public record PlayerFinishedConfigurationEvent(@NotNull Player player, @NotNull ServerConnection server) {
+}

proxy/src/main/java/com/velocitypowered/proxy/VelocityServer.java

@@ -45,7 +45,7 @@
 import com.velocitypowered.proxy.command.builtin.VelocityCommand;
 import com.velocitypowered.proxy.config.VelocityConfiguration;
 import com.velocitypowered.proxy.connection.client.ConnectedPlayer;
-import com.velocitypowered.proxy.connection.player.VelocityResourcePackInfo;
+import com.velocitypowered.proxy.connection.player.resourcepack.VelocityResourcePackInfo;
 import com.velocitypowered.proxy.connection.util.ServerListPingHandler;
 import com.velocitypowered.proxy.console.VelocityConsole;
 import com.velocitypowered.proxy.crypto.EncryptionUtils;

proxy/src/main/java/com/velocitypowered/proxy/connection/MinecraftConnection.java

@@ -47,7 +47,8 @@
 import com.velocitypowered.proxy.protocol.netty.MinecraftDecoder;
 import com.velocitypowered.proxy.protocol.netty.MinecraftEncoder;
 import com.velocitypowered.proxy.protocol.netty.MinecraftVarintLengthEncoder;
-import com.velocitypowered.proxy.protocol.netty.PlayPacketQueueHandler;
+import com.velocitypowered.proxy.protocol.netty.PlayPacketQueueInboundHandler;
+import com.velocitypowered.proxy.protocol.netty.PlayPacketQueueOutboundHandler;
 import com.velocitypowered.proxy.protocol.packet.SetCompressionPacket;
 import com.velocitypowered.proxy.util.except.QuietDecoderException;
 import io.netty.buffer.ByteBuf;
@@ -148,13 +149,11 @@ public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception
         return;
       }
 
-      if (msg instanceof MinecraftPacket) {
-        MinecraftPacket pkt = (MinecraftPacket) msg;
+      if (msg instanceof MinecraftPacket pkt) {
         if (!pkt.handle(activeSessionHandler)) {
           activeSessionHandler.handleGeneric((MinecraftPacket) msg);
         }
-      } else if (msg instanceof HAProxyMessage) {
-        HAProxyMessage proxyMessage = (HAProxyMessage) msg;
+      } else if (msg instanceof HAProxyMessage proxyMessage) {
         this.remoteAddress = new InetSocketAddress(proxyMessage.sourceAddress(),
             proxyMessage.sourcePort());
       } else if (msg instanceof ByteBuf) {
@@ -383,20 +382,28 @@ public void setState(StateRegistry state) {
     if (state == StateRegistry.CONFIG) {
       // Activate the play packet queue
       addPlayPacketQueueHandler();
-    } else if (this.channel.pipeline().get(Connections.PLAY_PACKET_QUEUE) != null) {
+    } else {
       // Remove the queue
-      this.channel.pipeline().remove(Connections.PLAY_PACKET_QUEUE);
+      if (this.channel.pipeline().get(Connections.PLAY_PACKET_QUEUE_OUTBOUND) != null) {
+        this.channel.pipeline().remove(Connections.PLAY_PACKET_QUEUE_OUTBOUND);
+      }
+      if (this.channel.pipeline().get(Connections.PLAY_PACKET_QUEUE_INBOUND) != null) {
+        this.channel.pipeline().remove(Connections.PLAY_PACKET_QUEUE_INBOUND);
+      }
     }
   }
 
   /**
    * Adds the play packet queue handler.
    */
   public void addPlayPacketQueueHandler() {
-    if (this.channel.pipeline().get(Connections.PLAY_PACKET_QUEUE) == null) {
-      this.channel.pipeline().addAfter(Connections.MINECRAFT_ENCODER, Connections.PLAY_PACKET_QUEUE,
-          new PlayPacketQueueHandler(this.protocolVersion,
-              channel.pipeline().get(MinecraftEncoder.class).getDirection()));
+    if (this.channel.pipeline().get(Connections.PLAY_PACKET_QUEUE_OUTBOUND) == null) {
+      this.channel.pipeline().addAfter(Connections.MINECRAFT_ENCODER, Connections.PLAY_PACKET_QUEUE_OUTBOUND,
+           new PlayPacketQueueOutboundHandler(this.protocolVersion, channel.pipeline().get(MinecraftEncoder.class).getDirection()));
+    }
+    if (this.channel.pipeline().get(Connections.PLAY_PACKET_QUEUE_INBOUND) == null) {
+      this.channel.pipeline().addAfter(Connections.MINECRAFT_DECODER, Connections.PLAY_PACKET_QUEUE_INBOUND,
+           new PlayPacketQueueInboundHandler(this.protocolVersion, channel.pipeline().get(MinecraftDecoder.class).getDirection()));
     }
   }
 

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/BackendPlaySessionHandler.java

@@ -40,8 +40,8 @@
 import com.velocitypowered.proxy.connection.MinecraftSessionHandler;
 import com.velocitypowered.proxy.connection.client.ClientPlaySessionHandler;
 import com.velocitypowered.proxy.connection.client.ConnectedPlayer;
-import com.velocitypowered.proxy.connection.player.VelocityResourcePackInfo;
-import com.velocitypowered.proxy.connection.player.resourcepack.ResourcePackHandler;
+import com.velocitypowered.proxy.connection.player.resourcepack.VelocityResourcePackInfo;
+import com.velocitypowered.proxy.connection.player.resourcepack.handler.ResourcePackHandler;
 import com.velocitypowered.proxy.connection.util.ConnectionMessages;
 import com.velocitypowered.proxy.protocol.MinecraftPacket;
 import com.velocitypowered.proxy.protocol.StateRegistry;

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/BungeeCordMessageResponder.java

@@ -37,7 +37,6 @@
 import io.netty.buffer.Unpooled;
 import java.util.Optional;
 import java.util.StringJoiner;
-import net.kyori.adventure.identity.Identity;
 import net.kyori.adventure.text.Component;
 import net.kyori.adventure.text.serializer.ComponentSerializer;
 import net.kyori.adventure.text.serializer.gson.GsonComponentSerializer;
@@ -143,7 +142,7 @@ private void processPlayerList(ByteBufDataInput in) {
         out.writeUTF("PlayerList");
         out.writeUTF(info.getServerInfo().getName());
 
-        StringJoiner joiner = new StringJoiner(", ");
+        final StringJoiner joiner = new StringJoiner(", ");
         for (Player online : info.getPlayersConnected()) {
           joiner.add(online.getUsername());
         }
@@ -187,10 +186,9 @@ private void processMessage0(ByteBufDataInput in,
 
     Component messageComponent = serializer.deserialize(message);
     if (target.equals("ALL")) {
-      proxy.sendMessage(Identity.nil(), messageComponent);
+      proxy.sendMessage(messageComponent);
     } else {
-      proxy.getPlayer(target).ifPresent(player -> player.sendMessage(Identity.nil(),
-          messageComponent));
+      proxy.getPlayer(target).ifPresent(player -> player.sendMessage(messageComponent));
     }
   }
 

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/ConfigSessionHandler.java

@@ -29,7 +29,7 @@
 import com.velocitypowered.proxy.connection.MinecraftSessionHandler;
 import com.velocitypowered.proxy.connection.client.ClientConfigSessionHandler;
 import com.velocitypowered.proxy.connection.client.ConnectedPlayer;
-import com.velocitypowered.proxy.connection.player.VelocityResourcePackInfo;
+import com.velocitypowered.proxy.connection.player.resourcepack.VelocityResourcePackInfo;
 import com.velocitypowered.proxy.connection.util.ConnectionMessages;
 import com.velocitypowered.proxy.connection.util.ConnectionRequestResults;
 import com.velocitypowered.proxy.connection.util.ConnectionRequestResults.Impl;
@@ -132,7 +132,8 @@ public boolean handle(ClientboundServerLinksPacket packet) {
 
   @Override
   public boolean handle(KeepAlivePacket packet) {
-    serverConn.ensureConnected().write(packet);
+    serverConn.getPendingPings().put(packet.getRandomId(), System.nanoTime());
+    serverConn.getPlayer().getConnection().write(packet);
     return true;
   }
 
@@ -193,30 +194,25 @@ public boolean handle(final ResourcePackRequestPacket packet) {
 
   @Override
   public boolean handle(FinishedUpdatePacket packet) {
-    MinecraftConnection smc = serverConn.ensureConnected();
-    ConnectedPlayer player = serverConn.getPlayer();
-    ClientConfigSessionHandler configHandler =
-        (ClientConfigSessionHandler) player.getConnection().getActiveSessionHandler();
+    final MinecraftConnection smc = serverConn.ensureConnected();
+    final ConnectedPlayer player = serverConn.getPlayer();
+    final ClientConfigSessionHandler configHandler = (ClientConfigSessionHandler) player.getConnection().getActiveSessionHandler();
 
-    smc.setAutoReading(false);
-    // Even when not auto reading messages are still decoded. Decode them with the correct state
     smc.getChannel().pipeline().get(MinecraftDecoder.class).setState(StateRegistry.PLAY);
-    configHandler.handleBackendFinishUpdate(serverConn).thenAcceptAsync((unused) -> {
+    //noinspection DataFlowIssue
+    configHandler.handleBackendFinishUpdate(serverConn).thenRunAsync(() -> {
+      smc.write(FinishedUpdatePacket.INSTANCE);
       if (serverConn == player.getConnectedServer()) {
         smc.setActiveSessionHandler(StateRegistry.PLAY);
-        player.sendPlayerListHeaderAndFooter(
-            player.getPlayerListHeader(), player.getPlayerListFooter());
+        player.sendPlayerListHeaderAndFooter(player.getPlayerListHeader(), player.getPlayerListFooter());
         // The client cleared the tab list. TODO: Restore changes done via TabList API
         player.getTabList().clearAllSilent();
       } else {
-        smc.setActiveSessionHandler(StateRegistry.PLAY,
-            new TransitionSessionHandler(server, serverConn, resultFuture));
+        smc.setActiveSessionHandler(StateRegistry.PLAY, new TransitionSessionHandler(server, serverConn, resultFuture));
       }
-      if (player.resourcePackHandler().getFirstAppliedPack() == null
-              && resourcePackToApply != null) {
+      if (player.resourcePackHandler().getFirstAppliedPack() == null && resourcePackToApply != null) {
         player.resourcePackHandler().queueResourcePack(resourcePackToApply);
       }
-      smc.setAutoReading(true);
     }, smc.eventLoop());
     return true;
   }

proxy/src/main/java/com/velocitypowered/proxy/connection/backend/LoginSessionHandler.java

@@ -166,12 +166,9 @@ public boolean handle(ServerLoginSuccessPacket packet) {
       if (player.getClientSettingsPacket() != null) {
         smc.write(player.getClientSettingsPacket());
       }
-      if (player.getConnection().getActiveSessionHandler() instanceof ClientPlaySessionHandler) {
+      if (player.getConnection().getActiveSessionHandler() instanceof ClientPlaySessionHandler clientPlaySessionHandler) {
         smc.setAutoReading(false);
-        ((ClientPlaySessionHandler) player.getConnection()
-            .getActiveSessionHandler()).doSwitch().thenAcceptAsync((unused) -> {
-              smc.setAutoReading(true);
-            }, smc.eventLoop());
+        clientPlaySessionHandler.doSwitch().thenAcceptAsync((unused) -> smc.setAutoReading(true), smc.eventLoop());
       }
     }
 

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ClientConfigSessionHandler.java

@@ -19,6 +19,8 @@
 
 import com.velocitypowered.api.event.player.CookieReceiveEvent;
 import com.velocitypowered.api.event.player.PlayerClientBrandEvent;
+import com.velocitypowered.api.event.player.configuration.PlayerFinishConfigurationEvent;
+import com.velocitypowered.api.event.player.configuration.PlayerFinishedConfigurationEvent;
 import com.velocitypowered.proxy.VelocityServer;
 import com.velocitypowered.proxy.connection.MinecraftConnection;
 import com.velocitypowered.proxy.connection.MinecraftSessionHandler;
@@ -246,13 +248,11 @@ public CompletableFuture<Void> handleBackendFinishUpdate(VelocityServerConnectio
       smc.write(brandPacket);
     }
 
-    player.getConnection().eventLoop().execute(() -> {
+    server.getEventManager().fire(new PlayerFinishConfigurationEvent(player, serverConn)).thenAcceptAsync(event -> {
       player.getConnection().write(FinishedUpdatePacket.INSTANCE);
       player.getConnection().getChannel().pipeline().get(MinecraftEncoder.class).setState(StateRegistry.PLAY);
-    });
-
-    smc.write(FinishedUpdatePacket.INSTANCE);
-    smc.getChannel().pipeline().get(MinecraftEncoder.class).setState(StateRegistry.PLAY);
+      server.getEventManager().fireAndForget(new PlayerFinishedConfigurationEvent(player, serverConn));
+    }, player.getConnection().eventLoop());
 
     return configSwitchFuture;
   }

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ClientPlaySessionHandler.java

@@ -27,6 +27,7 @@
 import com.velocitypowered.api.event.player.PlayerChannelRegisterEvent;
 import com.velocitypowered.api.event.player.PlayerClientBrandEvent;
 import com.velocitypowered.api.event.player.TabCompleteEvent;
+import com.velocitypowered.api.event.player.configuration.PlayerEnterConfigurationEvent;
 import com.velocitypowered.api.network.ProtocolVersion;
 import com.velocitypowered.api.proxy.messages.ChannelIdentifier;
 import com.velocitypowered.api.proxy.messages.LegacyChannelIdentifier;
@@ -406,6 +407,7 @@ public boolean handle(FinishedUpdatePacket packet) {
     // Complete client switch
     player.getConnection().setActiveSessionHandler(StateRegistry.CONFIG);
     VelocityServerConnection serverConnection = player.getConnectedServer();
+    server.getEventManager().fireAndForget(new PlayerEnterConfigurationEvent(player, serverConnection));
     if (serverConnection != null) {
       MinecraftConnection smc = serverConnection.ensureConnected();
       CompletableFuture.runAsync(() -> {
@@ -512,7 +514,7 @@ public void writabilityChanged() {
    * @return a future that completes when the switch is complete
    */
   public CompletableFuture<Void> doSwitch() {
-    VelocityServerConnection existingConnection = player.getConnectedServer();
+    final VelocityServerConnection existingConnection = player.getConnectedServer();
 
     if (existingConnection != null) {
       // Shut down the existing server connection.

proxy/src/main/java/com/velocitypowered/proxy/connection/client/ConnectedPlayer.java

@@ -37,6 +37,7 @@
 import com.velocitypowered.api.event.player.PlayerModInfoEvent;
 import com.velocitypowered.api.event.player.PlayerSettingsChangedEvent;
 import com.velocitypowered.api.event.player.ServerPreConnectEvent;
+import com.velocitypowered.api.event.player.configuration.PlayerEnterConfigurationEvent;
 import com.velocitypowered.api.network.ProtocolState;
 import com.velocitypowered.api.network.ProtocolVersion;
 import com.velocitypowered.api.permission.PermissionFunction;
@@ -59,8 +60,9 @@
 import com.velocitypowered.proxy.connection.MinecraftConnection;
 import com.velocitypowered.proxy.connection.MinecraftConnectionAssociation;
 import com.velocitypowered.proxy.connection.backend.VelocityServerConnection;
-import com.velocitypowered.proxy.connection.player.VelocityResourcePackInfo;
-import com.velocitypowered.proxy.connection.player.resourcepack.ResourcePackHandler;
+import com.velocitypowered.proxy.connection.player.bundle.BundleDelimiterHandler;
+import com.velocitypowered.proxy.connection.player.resourcepack.VelocityResourcePackInfo;
+import com.velocitypowered.proxy.connection.player.resourcepack.handler.ResourcePackHandler;
 import com.velocitypowered.proxy.connection.util.ConnectionMessages;
 import com.velocitypowered.proxy.connection.util.ConnectionRequestResults.Impl;
 import com.velocitypowered.proxy.connection.util.VelocityInboundConnection;
@@ -806,7 +808,7 @@ private void handleKickEvent(KickedFromServerEvent originalEvent, Component frie
             }, connection.eventLoop());
       } else if (event.getResult() instanceof final Notify res) {
         if (event.kickedDuringServerConnect() && previousConnection != null) {
-          sendMessage(Identity.nil(), res.getMessageComponent());
+          sendMessage(res.getMessageComponent());
         } else {
           disconnect(res.getMessageComponent());
         }
@@ -1224,11 +1226,12 @@ public void switchToConfigState() {
     CompletableFuture.runAsync(() -> {
       connection.write(StartUpdatePacket.INSTANCE);
       connection.getChannel().pipeline()
-          .get(MinecraftEncoder.class).setState(StateRegistry.CONFIG);
+              .get(MinecraftEncoder.class).setState(StateRegistry.CONFIG);
       // Make sure we don't send any play packets to the player after update start
       connection.addPlayPacketQueueHandler();
+      server.getEventManager().fireAndForget(new PlayerEnterConfigurationEvent(this, connectionInFlight));
     }, connection.eventLoop()).exceptionally((ex) -> {
-      logger.error("Error switching player connection to config state:", ex);
+      logger.error("Error switching player connection to config state", ex);
       return null;
     });
   }
@@ -1363,24 +1366,20 @@ public CompletableFuture<Boolean> connectWithIndication() {
         }
 
         switch (status.getStatus()) {
-          case ALREADY_CONNECTED:
-            sendMessage(Identity.nil(), ConnectionMessages.ALREADY_CONNECTED);
-            break;
-          case CONNECTION_IN_PROGRESS:
-            sendMessage(Identity.nil(), ConnectionMessages.IN_PROGRESS);
-            break;
-          case CONNECTION_CANCELLED:
+          case ALREADY_CONNECTED -> sendMessage(ConnectionMessages.ALREADY_CONNECTED);
+          case CONNECTION_IN_PROGRESS -> sendMessage(ConnectionMessages.IN_PROGRESS);
+          case CONNECTION_CANCELLED -> {
             // Ignored; the plugin probably already handled this.
-            break;
-          case SERVER_DISCONNECTED:
-            Component reason = status.getReasonComponent()
-                .orElse(ConnectionMessages.INTERNAL_SERVER_CONNECTION_ERROR);
+          }
+          case SERVER_DISCONNECTED -> {
+            final Component reason = status.getReasonComponent()
+                    .orElse(ConnectionMessages.INTERNAL_SERVER_CONNECTION_ERROR);
             handleConnectionException(toConnect,
-                DisconnectPacket.create(reason, getProtocolVersion(), connection.getState()), status.isSafe());
-            break;
-          default:
+                    DisconnectPacket.create(reason, getProtocolVersion(), connection.getState()), status.isSafe());
+          }
+          default -> {
             // The only remaining value is successful (no need to do anything!)
-            break;
+          }
         }
       }, connection.eventLoop()).thenApply(Result::isSuccessful);
     }