Merge branch 'dev/3.0.0' into forwarding-mode

# Conflicts:
#	proxy/src/main/java/com/velocitypowered/proxy/connection/backend/LoginSessionHandler.java

api/build.gradle.kts

@@ -67,7 +67,7 @@ tasks {
             "https://google.github.io/guice/api-docs/${libs.guice.get().version}/javadoc/",
             "https://docs.oracle.com/en/java/javase/17/docs/api/",
             "https://jd.advntr.dev/api/${libs.adventure.bom.get().version}/",
-            "https://javadoc.io/doc/com.github.ben-manes.caffeine/caffeine"
+            "https://javadoc.io/doc/com.github.ben-manes.caffeine/caffeine/${libs.caffeine.get().version}/"
         )
 
         o.tags(

api/src/main/java/com/velocitypowered/api/command/CommandManager.java

@@ -44,7 +44,7 @@ public interface CommandManager {
    * @param otherAliases additional aliases
    * @throws IllegalArgumentException if one of the given aliases is already registered, or
    *         the given command does not implement a registrable {@link Command} subinterface
-   * @see Command for a list of registrable {@link Command} subinterfaces
+   * @see Command for a list of registrable Command subinterfaces
    */
   default void register(String alias, Command command, String... otherAliases) {
     register(metaBuilder(alias).aliases(otherAliases).build(), command);
@@ -65,7 +65,7 @@ public interface CommandManager {
    * @param command the command to register
    * @throws IllegalArgumentException if one of the given aliases is already registered, or
    *         the given command does not implement a registrable {@link Command} subinterface
-   * @see Command for a list of registrable {@link Command} subinterfaces
+   * @see Command for a list of registrable Command subinterfaces
    */
   void register(CommandMeta meta, Command command);
 

api/src/main/java/com/velocitypowered/api/event/player/ServerResourcePackRemoveEvent.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright (C) 2018-2023 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;
+
+import com.google.common.base.Preconditions;
+import com.velocitypowered.api.event.ResultedEvent;
+import com.velocitypowered.api.event.annotation.AwaitingEvent;
+import com.velocitypowered.api.proxy.ServerConnection;
+import java.util.UUID;
+import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+/**
+ * This event is fired when the downstream server tries to remove a resource pack from player
+ * or clear all of them. The proxy will wait on this event to finish before forwarding the
+ * action to the user. If this event is denied, no resource packs will be removed from player.
+ */
+@AwaitingEvent
+public class ServerResourcePackRemoveEvent implements ResultedEvent<ResultedEvent.GenericResult> {
+
+  private GenericResult result;
+  private final @MonotonicNonNull UUID packId;
+  private final ServerConnection serverConnection;
+
+  /**
+   * Instantiates this event.
+   */
+  public ServerResourcePackRemoveEvent(UUID packId, ServerConnection serverConnection) {
+    this.result = ResultedEvent.GenericResult.allowed();
+    this.packId = packId;
+    this.serverConnection = serverConnection;
+  }
+
+  /**
+   * Returns the id of the resource pack, if it's null all the resource packs
+   * from player will be cleared.
+   *
+   * @return the id
+   */
+  @Nullable
+  public UUID getPackId() {
+    return packId;
+  }
+
+  /**
+   * Returns the server that tries to remove a resource pack from player or clear all of them.
+   *
+   * @return the server connection
+   */
+  public ServerConnection getServerConnection() {
+    return serverConnection;
+  }
+
+  @Override
+  public GenericResult getResult() {
+    return this.result;
+  }
+
+  @Override
+  public void setResult(GenericResult result) {
+    this.result = Preconditions.checkNotNull(result, "result");
+  }
+}

api/src/main/java/com/velocitypowered/api/event/player/configuration/PlayerConfigurationEvent.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 a player entered the configuration state and can be configured by Velocity.
+ * <p>Velocity will wait for this event before continuing/ending the configuration state.</p>
+ *
+ * @param player The player who can be configured.
+ * @param server The server that is currently configuring the player.
+ * @since 3.3.0
+ * @sinceMinecraft 1.20.2
+ */
+@AwaitingEvent
+public record PlayerConfigurationEvent(@NotNull Player player, ServerConnection server) {
+}

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

@@ -7,21 +7,23 @@
 
 package com.velocitypowered.api.event.player.configuration;
 
-import com.velocitypowered.api.network.ProtocolState;
+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 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>
+ * This event is executed when a player is about to enter the configuration state.
+ * It is <b>not</b> called for the initial configuration of a player after login.
+ * <p>Velocity will wait for this event before asking the client to enter configuration state.
+ * However due to backend server being unable to keep the connection alive during state changes,
+ * Velocity will only wait for a maximum of 5 seconds.</p>
  *
- * @param player The player that has entered the configuration phase.
- * @param server The server that will now (re-)configure the player.
+ * @param player The player who is about to enter configuration state.
+ * @param server The server that wants to reconfigure the player.
  * @since 3.3.0
  * @sinceMinecraft 1.20.2
  */
+@AwaitingEvent
 public record PlayerEnterConfigurationEvent(@NotNull Player player, ServerConnection server) {
 }

api/src/main/java/com/velocitypowered/api/event/player/configuration/PlayerEnteredConfigurationEvent.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 has entered the configuration state.
+ * <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 who has entered the configuration state.
+ * @param server The server that will now (re-)configure the player.
+ * @since 3.3.0
+ * @sinceMinecraft 1.20.2
+ */
+public record PlayerEnteredConfigurationEvent(@NotNull Player player, ServerConnection server) {
+}

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

@@ -13,11 +13,14 @@ 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>
+ * This event is executed when a player is about to finish the configuration state.
+ * <p>Velocity will wait for this event before asking the client to finish the configuration state.
+ * However due to backend server being unable to keep the connection alive during state changes,
+ * Velocity will only wait for a maximum of 5 seconds. If you need to hold a player in configuration
+ * state, use the {@link PlayerConfigurationEvent}.</p>
  *
- * @param player The player who is about to complete the configuration phase.
- * @param server The server that is currently (re-)configuring the player.
+ * @param player The player who is about to finish the configuration phase.
+ * @param server The server that has (re-)configured the player.
  * @since 3.3.0
  * @sinceMinecraft 1.20.2
  */

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

@@ -13,11 +13,11 @@ 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.
+ * This event is executed when a player has finished 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 player The player who has finished the configuration state.
  * @param server The server that has (re-)configured the player.
  * @since 3.3.0
  * @sinceMinecraft 1.20.2

gradle/libs.versions.toml

@@ -11,7 +11,7 @@ shadow = "io.github.goooler.shadow:8.1.5"
 spotless = "com.diffplug.spotless:6.25.0"
 
 [libraries]
-adventure-bom = "net.kyori:adventure-bom:4.16.0"
+adventure-bom = "net.kyori:adventure-bom:4.17.0"
 adventure-facet = "net.kyori:adventure-platform-facet:4.3.2"
 asm = "org.ow2.asm:asm:9.6"
 auto-service = "com.google.auto.service:auto-service:1.0.1"

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

@@ -29,6 +29,7 @@ import com.velocitypowered.api.event.connection.PreTransferEvent;
 import com.velocitypowered.api.event.player.CookieRequestEvent;
 import com.velocitypowered.api.event.player.CookieStoreEvent;
 import com.velocitypowered.api.event.player.PlayerResourcePackStatusEvent;
+import com.velocitypowered.api.event.player.ServerResourcePackRemoveEvent;
 import com.velocitypowered.api.event.player.ServerResourcePackSendEvent;
 import com.velocitypowered.api.event.proxy.ProxyPingEvent;
 import com.velocitypowered.api.network.ProtocolVersion;
@@ -258,14 +259,26 @@ public class BackendPlaySessionHandler implements MinecraftSessionHandler {
 
   @Override
   public boolean handle(RemoveResourcePackPacket packet) {
-    final ConnectedPlayer player = serverConn.getPlayer();
-    final ResourcePackHandler handler = player.resourcePackHandler();
-    if (packet.getId() != null) {
-      handler.remove(packet.getId());
-    } else {
-      handler.clearAppliedResourcePacks();
-    }
-    playerConnection.write(packet);
+    final ServerResourcePackRemoveEvent event = new ServerResourcePackRemoveEvent(
+            packet.getId(), this.serverConn);
+    server.getEventManager().fire(event).thenAcceptAsync(serverResourcePackRemoveEvent -> {
+      if (playerConnection.isClosed()) {
+        return;
+      }
+      if (serverResourcePackRemoveEvent.getResult().isAllowed()) {
+        final ConnectedPlayer player = serverConn.getPlayer();
+        final ResourcePackHandler handler = player.resourcePackHandler();
+        if (packet.getId() != null) {
+          handler.remove(packet.getId());
+        } else {
+          handler.clearAppliedResourcePacks();
+        }
+        playerConnection.write(packet);
+      }
+    }, playerConnection.eventLoop()).exceptionally((ex) -> {
+      logger.error("Exception while handling resource pack remove for {}", playerConnection, ex);
+      return null;
+    });
     return true;
   }
 

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

@@ -260,6 +260,13 @@ public class BungeeCordMessageResponder {
     });
   }
 
+  private void processKickRaw(ByteBufDataInput in) {
+    proxy.getPlayer(in.readUTF()).ifPresent(player -> {
+      String kickReason = in.readUTF();
+      player.disconnect(GsonComponentSerializer.gson().deserialize(kickReason));
+    });
+  }
+
   private void processForwardToPlayer(ByteBufDataInput in) {
     Optional<Player> player = proxy.getPlayer(in.readUTF());
     if (player.isPresent()) {
@@ -372,6 +379,9 @@ public class BungeeCordMessageResponder {
       case "KickPlayer":
         this.processKick(in);
         break;
+      case "KickPlayerRaw":
+        this.processKickRaw(in);
+        break;
       default:
         // Do nothing, unknown command
         break;

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

@@ -21,6 +21,7 @@ import com.velocitypowered.api.event.connection.PreTransferEvent;
 import com.velocitypowered.api.event.player.CookieRequestEvent;
 import com.velocitypowered.api.event.player.CookieStoreEvent;
 import com.velocitypowered.api.event.player.PlayerResourcePackStatusEvent;
+import com.velocitypowered.api.event.player.ServerResourcePackRemoveEvent;
 import com.velocitypowered.api.event.player.ServerResourcePackSendEvent;
 import com.velocitypowered.api.network.ProtocolVersion;
 import com.velocitypowered.api.proxy.player.ResourcePackInfo;
@@ -30,6 +31,7 @@ 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.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;
 import com.velocitypowered.proxy.connection.util.ConnectionRequestResults.Impl;
@@ -41,6 +43,7 @@ import com.velocitypowered.proxy.protocol.packet.ClientboundStoreCookiePacket;
 import com.velocitypowered.proxy.protocol.packet.DisconnectPacket;
 import com.velocitypowered.proxy.protocol.packet.KeepAlivePacket;
 import com.velocitypowered.proxy.protocol.packet.PluginMessagePacket;
+import com.velocitypowered.proxy.protocol.packet.RemoveResourcePackPacket;
 import com.velocitypowered.proxy.protocol.packet.ResourcePackRequestPacket;
 import com.velocitypowered.proxy.protocol.packet.ResourcePackResponsePacket;
 import com.velocitypowered.proxy.protocol.packet.TransferPacket;
@@ -192,6 +195,33 @@ public class ConfigSessionHandler implements MinecraftSessionHandler {
     return true;
   }
 
+  @Override
+  public boolean handle(RemoveResourcePackPacket packet) {
+    final MinecraftConnection playerConnection = this.serverConn.getPlayer().getConnection();
+
+    final ServerResourcePackRemoveEvent event = new ServerResourcePackRemoveEvent(
+            packet.getId(), this.serverConn);
+    server.getEventManager().fire(event).thenAcceptAsync(serverResourcePackRemoveEvent -> {
+      if (playerConnection.isClosed()) {
+        return;
+      }
+      if (serverResourcePackRemoveEvent.getResult().isAllowed()) {
+        final ConnectedPlayer player = serverConn.getPlayer();
+        final ResourcePackHandler handler = player.resourcePackHandler();
+        if (packet.getId() != null) {
+          handler.remove(packet.getId());
+        } else {
+          handler.clearAppliedResourcePacks();
+        }
+        playerConnection.write(packet);
+      }
+    }, playerConnection.eventLoop()).exceptionally((ex) -> {
+      logger.error("Exception while handling resource pack remove for {}", playerConnection, ex);
+      return null;
+    });
+    return true;
+  }
+
   @Override
   public boolean handle(FinishedUpdatePacket packet) {
     final MinecraftConnection smc = serverConn.ensureConnected();

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

@@ -19,6 +19,7 @@ package com.velocitypowered.proxy.connection.backend;
 
 import com.velocitypowered.api.event.player.CookieRequestEvent;
 import com.velocitypowered.api.event.player.ServerLoginPluginMessageEvent;
+import com.velocitypowered.api.event.player.configuration.PlayerEnteredConfigurationEvent;
 import com.velocitypowered.api.network.ProtocolVersion;
 import com.velocitypowered.api.proxy.messages.MinecraftChannelIdentifier;
 import com.velocitypowered.proxy.VelocityServer;
@@ -144,8 +145,7 @@ public class LoginSessionHandler implements MinecraftSessionHandler {
   public boolean handle(ServerLoginSuccessPacket packet) {
     if (server.getConfiguration().getServerPlayerInfoForwardingMode(serverConn.getServerInfo().getName()) == PlayerInfoForwarding.MODERN
         && !informationForwarded) {
-      resultFuture.complete(ConnectionRequestResults.forDisconnect(MODERN_IP_FORWARDING_FAILURE,
-          serverConn.getServer()));
+      resultFuture.complete(ConnectionRequestResults.forDisconnect(MODERN_IP_FORWARDING_FAILURE, serverConn.getServer()));
       serverConn.disconnect();
       return true;
     }
@@ -156,12 +156,10 @@ public class LoginSessionHandler implements MinecraftSessionHandler {
     // Move into the PLAY phase.
     MinecraftConnection smc = serverConn.ensureConnected();
     if (smc.getProtocolVersion().lessThan(ProtocolVersion.MINECRAFT_1_20_2)) {
-      smc.setActiveSessionHandler(StateRegistry.PLAY,
-          new TransitionSessionHandler(server, serverConn, resultFuture));
+      smc.setActiveSessionHandler(StateRegistry.PLAY, new TransitionSessionHandler(server, serverConn, resultFuture));
     } else {
       smc.write(new LoginAcknowledgedPacket());
-      smc.setActiveSessionHandler(StateRegistry.CONFIG,
-          new ConfigSessionHandler(server, serverConn, resultFuture));
+      smc.setActiveSessionHandler(StateRegistry.CONFIG, new ConfigSessionHandler(server, serverConn, resultFuture));
       ConnectedPlayer player = serverConn.getPlayer();
       if (player.getClientSettingsPacket() != null) {
         smc.write(player.getClientSettingsPacket());
@@ -169,6 +167,9 @@ public class LoginSessionHandler implements MinecraftSessionHandler {
       if (player.getConnection().getActiveSessionHandler() instanceof ClientPlaySessionHandler clientPlaySessionHandler) {
         smc.setAutoReading(false);
         clientPlaySessionHandler.doSwitch().thenAcceptAsync((unused) -> smc.setAutoReading(true), smc.eventLoop());
+      } else {
+        // Initial login - the player is already in configuration state.
+        server.getEventManager().fireAndForget(new PlayerEnteredConfigurationEvent(player, serverConn));
       }
     }
 

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

@@ -178,14 +178,14 @@ public class AuthSessionHandler implements MinecraftSessionHandler {
       inbound.disconnect(Component.translatable("multiplayer.disconnect.invalid_player_data"));
     } else {
       loginState = State.ACKNOWLEDGED;
-      mcConnection.setActiveSessionHandler(StateRegistry.CONFIG,
-          new ClientConfigSessionHandler(server, connectedPlayer));
+      mcConnection.setActiveSessionHandler(StateRegistry.CONFIG, new ClientConfigSessionHandler(server, connectedPlayer));
 
-      server.getEventManager().fire(new PostLoginEvent(connectedPlayer))
-          .thenCompose((ignored) -> connectToInitialServer(connectedPlayer)).exceptionally((ex) -> {
-            logger.error("Exception while connecting {} to initial server", connectedPlayer, ex);
-            return null;
-          });
+      server.getEventManager().fire(new PostLoginEvent(connectedPlayer)).thenCompose(ignored -> {
+        return connectToInitialServer(connectedPlayer);
+      }).exceptionally((ex) -> {
+        logger.error("Exception while connecting {} to initial server", connectedPlayer, ex);
+        return null;
+      });
     }
     return true;
   }
@@ -224,8 +224,7 @@ public class AuthSessionHandler implements MinecraftSessionHandler {
         player.disconnect0(reason.get(), true);
       } else {
         if (!server.registerConnection(player)) {
-          player.disconnect0(Component.translatable("velocity.error.already-connected-proxy"),
-              true);
+          player.disconnect0(Component.translatable("velocity.error.already-connected-proxy"), true);
           return;
         }
 
@@ -238,13 +237,13 @@ public class AuthSessionHandler implements MinecraftSessionHandler {
         loginState = State.SUCCESS_SENT;
         if (inbound.getProtocolVersion().lessThan(ProtocolVersion.MINECRAFT_1_20_2)) {
           loginState = State.ACKNOWLEDGED;
-          mcConnection.setActiveSessionHandler(StateRegistry.PLAY,
-              new InitialConnectSessionHandler(player, server));
-          server.getEventManager().fire(new PostLoginEvent(player))
-              .thenCompose((ignored) -> connectToInitialServer(player)).exceptionally((ex) -> {
-                logger.error("Exception while connecting {} to initial server", player, ex);
-                return null;
-              });
+          mcConnection.setActiveSessionHandler(StateRegistry.PLAY, new InitialConnectSessionHandler(player, server));
+          server.getEventManager().fire(new PostLoginEvent(player)).thenCompose((ignored) -> {
+            return connectToInitialServer(player);
+          }).exceptionally((ex) -> {
+            logger.error("Exception while connecting {} to initial server", player, ex);
+            return null;
+          });
         }
       }
     }, mcConnection.eventLoop()).exceptionally((ex) -> {

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

@@ -19,6 +19,7 @@ package com.velocitypowered.proxy.connection.client;
 
 import com.velocitypowered.api.event.player.CookieReceiveEvent;
 import com.velocitypowered.api.event.player.PlayerClientBrandEvent;
+import com.velocitypowered.api.event.player.configuration.PlayerConfigurationEvent;
 import com.velocitypowered.api.event.player.configuration.PlayerFinishConfigurationEvent;
 import com.velocitypowered.api.event.player.configuration.PlayerFinishedConfigurationEvent;
 import com.velocitypowered.proxy.VelocityServer;
@@ -48,8 +49,6 @@ import net.kyori.adventure.text.Component;
 import net.kyori.adventure.text.format.NamedTextColor;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
-import org.jetbrains.annotations.NotNull;
-import org.jetbrains.annotations.Nullable;
 
 /**
  * Handles the client config stage.
@@ -61,6 +60,7 @@ public class ClientConfigSessionHandler implements MinecraftSessionHandler {
   private final ConnectedPlayer player;
   private String brandChannel = null;
 
+  private CompletableFuture<?> configurationFuture;
   private CompletableFuture<Void> configSwitchFuture;
 
   /**
@@ -81,11 +81,7 @@ public class ClientConfigSessionHandler implements MinecraftSessionHandler {
 
   @Override
   public boolean handle(final KeepAlivePacket packet) {
-    final VelocityServerConnection serverConnection = player.getConnectedServer();
-    if (!this.sendKeepAliveToBackend(serverConnection, packet)) {
-      final VelocityServerConnection connectionInFlight = player.getConnectionInFlight();
-      this.sendKeepAliveToBackend(connectionInFlight, packet);
-    }
+    player.forwardKeepAlive(packet);
     return true;
   }
 
@@ -106,8 +102,7 @@ public class ClientConfigSessionHandler implements MinecraftSessionHandler {
 
   @Override
   public boolean handle(FinishedUpdatePacket packet) {
-    player.getConnection()
-        .setActiveSessionHandler(StateRegistry.PLAY, new ClientPlaySessionHandler(server, player));
+    player.getConnection().setActiveSessionHandler(StateRegistry.PLAY, new ClientPlaySessionHandler(server, player));
 
     configSwitchFuture.complete(null);
     return true;
@@ -141,12 +136,14 @@ public class ClientConfigSessionHandler implements MinecraftSessionHandler {
 
   @Override
   public boolean handle(KnownPacksPacket packet) {
-    if (player.getConnectionInFlight() != null) {
-      player.getConnectionInFlight().ensureConnected().write(packet);
-      return true;
-    }
+    callConfigurationEvent().thenRun(() -> {
+      player.getConnectionInFlightOrConnectedServer().ensureConnected().write(packet);
+    }).exceptionally(ex -> {
+      logger.error("Error forwarding known packs response to backend:", ex);
+      return null;
+    });
 
-    return false;
+    return true;
   }
 
   @Override
@@ -209,26 +206,25 @@ public class ClientConfigSessionHandler implements MinecraftSessionHandler {
 
   @Override
   public void exception(Throwable throwable) {
-    player.disconnect(
-        Component.translatable("velocity.error.player-connection-error", NamedTextColor.RED));
+    player.disconnect(Component.translatable("velocity.error.player-connection-error", NamedTextColor.RED));
   }
 
-  private boolean sendKeepAliveToBackend(
-          final @Nullable VelocityServerConnection serverConnection,
-          final @NotNull KeepAlivePacket packet
-  ) {
-    if (serverConnection != null) {
-      final Long sentTime = serverConnection.getPendingPings().remove(packet.getRandomId());
-      if (sentTime != null) {
-        final MinecraftConnection smc = serverConnection.getConnection();
-        if (smc != null) {
-          player.setPing(TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - sentTime));
-          smc.write(packet);
-          return true;
-        }
-      }
+  /**
+   * Calls the {@link PlayerConfigurationEvent}.
+   * For 1.20.5+ backends this is done when the client responds to
+   * the known packs request. The response is delayed until the event
+   * has been called.
+   * For 1.20.2-1.20.4 servers this is done when the client acknowledges
+   * the end of the configuration.
+   * This is handled differently because for 1.20.5+ servers can't keep
+   * their connection alive between states and older servers don't have
+   * the known packs transaction.
+   */
+  private CompletableFuture<?> callConfigurationEvent() {
+    if (configurationFuture != null) {
+      return configurationFuture;
     }
-    return false;
+    return configurationFuture = server.getEventManager().fire(new PlayerConfigurationEvent(player, player.getConnectionInFlightOrConnectedServer()));
   }
 
   /**
@@ -248,11 +244,17 @@ public class ClientConfigSessionHandler implements MinecraftSessionHandler {
       smc.write(brandPacket);
     }
 
-    server.getEventManager().fire(new PlayerFinishConfigurationEvent(player, serverConn)).thenAcceptAsync(event -> {
+    callConfigurationEvent().thenCompose(v -> {
+      return server.getEventManager().fire(new PlayerFinishConfigurationEvent(player, serverConn))
+          .completeOnTimeout(null, 5, TimeUnit.SECONDS);
+    }).thenRunAsync(() -> {
       player.getConnection().write(FinishedUpdatePacket.INSTANCE);
       player.getConnection().getChannel().pipeline().get(MinecraftEncoder.class).setState(StateRegistry.PLAY);
       server.getEventManager().fireAndForget(new PlayerFinishedConfigurationEvent(player, serverConn));
-    }, player.getConnection().eventLoop());
+    }, player.getConnection().eventLoop()).exceptionally(ex -> {
+      logger.error("Error finishing configuration state:", ex);
+      return null;
+    });
 
     return configSwitchFuture;
   }

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

@@ -27,7 +27,7 @@ import com.velocitypowered.api.event.player.CookieReceiveEvent;
 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.event.player.configuration.PlayerEnteredConfigurationEvent;
 import com.velocitypowered.api.network.ProtocolVersion;
 import com.velocitypowered.api.proxy.messages.ChannelIdentifier;
 import com.velocitypowered.api.proxy.messages.LegacyChannelIdentifier;
@@ -86,7 +86,6 @@ import java.util.Queue;
 import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ConcurrentLinkedQueue;
-import java.util.concurrent.TimeUnit;
 import net.kyori.adventure.key.Key;
 import net.kyori.adventure.text.Component;
 import net.kyori.adventure.text.format.NamedTextColor;
@@ -178,17 +177,7 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
 
   @Override
   public boolean handle(KeepAlivePacket packet) {
-    final VelocityServerConnection serverConnection = player.getConnectedServer();
-    if (serverConnection != null) {
-      final Long sentTime = serverConnection.getPendingPings().remove(packet.getRandomId());
-      if (sentTime != null) {
-        final MinecraftConnection smc = serverConnection.getConnection();
-        if (smc != null) {
-          player.setPing(TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - sentTime));
-          smc.write(packet);
-        }
-      }
-    }
+    player.forwardKeepAlive(packet);
     return true;
   }
 
@@ -408,7 +397,7 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
     // Complete client switch
     player.getConnection().setActiveSessionHandler(StateRegistry.CONFIG);
     VelocityServerConnection serverConnection = player.getConnectedServer();
-    server.getEventManager().fireAndForget(new PlayerEnterConfigurationEvent(player, serverConnection));
+    server.getEventManager().fireAndForget(new PlayerEnteredConfigurationEvent(player, serverConnection));
     if (serverConnection != null) {
       MinecraftConnection smc = serverConnection.ensureConnected();
       CompletableFuture.runAsync(() -> {

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

@@ -111,6 +111,7 @@ import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionException;
 import java.util.concurrent.ThreadLocalRandom;
+import java.util.concurrent.TimeUnit;
 import net.kyori.adventure.audience.MessageType;
 import net.kyori.adventure.bossbar.BossBar;
 import net.kyori.adventure.identity.Identity;
@@ -634,6 +635,10 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
     return connectionInFlight;
   }
 
+  public VelocityServerConnection getConnectionInFlightOrConnectedServer() {
+    return connectionInFlight != null ? connectionInFlight : connectedServer;
+  }
+
   public void resetInFlightConnection() {
     connectionInFlight = null;
   }
@@ -1239,21 +1244,46 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player,
     }
   }
 
+  /**
+   * Forwards the keep alive packet to the backend server it belongs to.
+   * This is either the connection in flight or the connected server.
+   */
+  public boolean forwardKeepAlive(final KeepAlivePacket packet) {
+    if (!this.sendKeepAliveToBackend(connectedServer, packet)) {
+      return this.sendKeepAliveToBackend(connectionInFlight, packet);
+    }
+    return false;
+  }
+
+  private boolean sendKeepAliveToBackend(final @Nullable VelocityServerConnection serverConnection, final @NotNull KeepAlivePacket packet) {
+    if (serverConnection != null) {
+      final Long sentTime = serverConnection.getPendingPings().remove(packet.getRandomId());
+      if (sentTime != null) {
+        final MinecraftConnection smc = serverConnection.getConnection();
+        if (smc != null) {
+          setPing(TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - sentTime));
+          smc.write(packet);
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+
   /**
    * Switches the connection to the client into config state.
    */
   public void switchToConfigState() {
-    CompletableFuture.runAsync(() -> {
-      connection.write(StartUpdatePacket.INSTANCE);
-      connection.getChannel().pipeline()
-              .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);
-      return null;
-    });
+    server.getEventManager().fire(new PlayerEnterConfigurationEvent(this, getConnectionInFlightOrConnectedServer()))
+        .completeOnTimeout(null, 5, TimeUnit.SECONDS).thenRunAsync(() -> {
+          connection.write(StartUpdatePacket.INSTANCE);
+          connection.getChannel().pipeline().get(MinecraftEncoder.class).setState(StateRegistry.CONFIG);
+          // Make sure we don't send any play packets to the player after update start
+          connection.addPlayPacketQueueHandler();
+        }, connection.eventLoop()).exceptionally((ex) -> {
+          logger.error("Error switching player connection to config state", ex);
+          return null;
+        });
   }
 
   /**

proxy/src/main/java/com/velocitypowered/proxy/plugin/VelocityPluginManager.java

@@ -43,13 +43,13 @@ import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.HashSet;
+import java.util.HashMap;
 import java.util.IdentityHashMap;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Optional;
-import java.util.Set;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
@@ -86,35 +86,48 @@ public class VelocityPluginManager implements PluginManager {
     checkNotNull(directory, "directory");
     checkArgument(directory.toFile().isDirectory(), "provided path isn't a directory");
 
-    List<PluginDescription> found = new ArrayList<>();
+    Map<String, PluginDescription> foundCandidates = new LinkedHashMap<>();
     JavaPluginLoader loader = new JavaPluginLoader(server, directory);
 
     try (DirectoryStream<Path> stream = Files.newDirectoryStream(directory,
         p -> p.toFile().isFile() && p.toString().endsWith(".jar"))) {
       for (Path path : stream) {
         try {
-          found.add(loader.loadCandidate(path));
+          PluginDescription candidate = loader.loadCandidate(path);
+
+          // If we found a duplicate candidate (with the same ID), don't load it.
+          PluginDescription maybeExistingCandidate = foundCandidates.putIfAbsent(
+              candidate.getId(), candidate);
+
+          if (maybeExistingCandidate != null) {
+            logger.error("Refusing to load plugin at path {} since we already "
+                    + "loaded a plugin with the same ID {} from {}",
+                candidate.getSource().map(Objects::toString).orElse("<UNKNOWN>"),
+                candidate.getId(),
+                maybeExistingCandidate.getSource().map(Objects::toString).orElse("<UNKNOWN>"));
+          }
         } catch (Throwable e) {
           logger.error("Unable to load plugin {}", path, e);
         }
       }
     }
 
-    if (found.isEmpty()) {
+    if (foundCandidates.isEmpty()) {
       // No plugins found
       return;
     }
 
-    List<PluginDescription> sortedPlugins = PluginDependencyUtils.sortCandidates(found);
+    List<PluginDescription> sortedPlugins = PluginDependencyUtils.sortCandidates(
+        new ArrayList<>(foundCandidates.values()));
 
-    Set<String> loadedPluginsById = new HashSet<>();
+    Map<String, PluginDescription> loadedCandidates = new HashMap<>();
     Map<PluginContainer, Module> pluginContainers = new LinkedHashMap<>();
     // Now load the plugins
     pluginLoad:
     for (PluginDescription candidate : sortedPlugins) {
       // Verify dependencies
       for (PluginDependency dependency : candidate.getDependencies()) {
-        if (!dependency.isOptional() && !loadedPluginsById.contains(dependency.getId())) {
+        if (!dependency.isOptional() && !loadedCandidates.containsKey(dependency.getId())) {
           logger.error("Can't load plugin {} due to missing dependency {}", candidate.getId(),
               dependency.getId());
           continue pluginLoad;
@@ -125,7 +138,7 @@ public class VelocityPluginManager implements PluginManager {
         PluginDescription realPlugin = loader.createPluginFromCandidate(candidate);
         VelocityPluginContainer container = new VelocityPluginContainer(realPlugin);
         pluginContainers.put(container, loader.createModule(container));
-        loadedPluginsById.add(realPlugin.getId());
+        loadedCandidates.put(realPlugin.getId(), realPlugin);
       } catch (Throwable e) {
         logger.error("Can't create module for plugin {}", candidate.getId(), e);
       }

proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/PlayPacketQueueInboundHandler.java

@@ -24,7 +24,7 @@ import com.velocitypowered.proxy.protocol.StateRegistry;
 import io.netty.channel.ChannelDuplexHandler;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.util.ReferenceCountUtil;
-import io.netty.util.internal.PlatformDependent;
+import java.util.ArrayDeque;
 import java.util.Queue;
 import org.jetbrains.annotations.NotNull;
 
@@ -42,7 +42,7 @@ import org.jetbrains.annotations.NotNull;
 public class PlayPacketQueueInboundHandler extends ChannelDuplexHandler {
 
   private final StateRegistry.PacketRegistry.ProtocolRegistry registry;
-  private final Queue<Object> queue = PlatformDependent.newMpscQueue();
+  private final Queue<Object> queue = new ArrayDeque<>();
 
   /**
    * Provides registries for client &amp; server bound packets.

proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/PlayPacketQueueOutboundHandler.java

@@ -25,7 +25,7 @@ import io.netty.channel.ChannelDuplexHandler;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.channel.ChannelPromise;
 import io.netty.util.ReferenceCountUtil;
-import io.netty.util.internal.PlatformDependent;
+import java.util.ArrayDeque;
 import java.util.Queue;
 import org.jetbrains.annotations.NotNull;
 
@@ -43,7 +43,7 @@ import org.jetbrains.annotations.NotNull;
 public class PlayPacketQueueOutboundHandler extends ChannelDuplexHandler {
 
   private final StateRegistry.PacketRegistry.ProtocolRegistry registry;
-  private final Queue<MinecraftPacket> queue = PlatformDependent.newMpscQueue();
+  private final Queue<MinecraftPacket> queue = new ArrayDeque<>();
 
   /**
    * Provides registries for client &amp; server bound packets.