Remove most-times unnecessary client reconfiguration

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

@@ -37,6 +37,7 @@
 import com.velocitypowered.proxy.protocol.packet.LoginAcknowledgedPacket;
 import com.velocitypowered.proxy.protocol.packet.LoginPluginMessagePacket;
 import com.velocitypowered.proxy.protocol.packet.LoginPluginResponsePacket;
+import com.velocitypowered.proxy.protocol.packet.ObjectivePacket;
 import com.velocitypowered.proxy.protocol.packet.PingIdentifyPacket;
 import com.velocitypowered.proxy.protocol.packet.PluginMessagePacket;
 import com.velocitypowered.proxy.protocol.packet.RemovePlayerInfoPacket;
@@ -364,4 +365,8 @@ default boolean handle(ClientboundCustomReportDetailsPacket packet) {
   default boolean handle(ClientboundServerLinksPacket packet) {
     return false;
   }
+
+  default boolean handle(ObjectivePacket packet) {
+    return false;
+  }
 }

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

@@ -56,6 +56,7 @@
 import com.velocitypowered.proxy.protocol.packet.DisconnectPacket;
 import com.velocitypowered.proxy.protocol.packet.KeepAlivePacket;
 import com.velocitypowered.proxy.protocol.packet.LegacyPlayerListItemPacket;
+import com.velocitypowered.proxy.protocol.packet.ObjectivePacket;
 import com.velocitypowered.proxy.protocol.packet.PluginMessagePacket;
 import com.velocitypowered.proxy.protocol.packet.RemovePlayerInfoPacket;
 import com.velocitypowered.proxy.protocol.packet.RemoveResourcePackPacket;
@@ -183,6 +184,16 @@ public boolean handle(BossBarPacket packet) {
     return false; // forward
   }
 
+  @Override
+  public boolean handle(ObjectivePacket packet) {
+    if (packet.getAction() == ObjectivePacket.ADD) {
+      playerSessionHandler.getServerObjectives().add(packet.getName());
+    } else if (packet.getAction() == ObjectivePacket.REMOVE) {
+      playerSessionHandler.getServerObjectives().remove(packet.getName());
+    }
+    return false; // forward
+  }
+
   @Override
   public boolean handle(final ResourcePackRequestPacket packet) {
     final ResourcePackInfo.Builder builder = new VelocityResourcePackInfo.BuilderImpl(

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

@@ -36,6 +36,7 @@
 import com.velocitypowered.proxy.connection.util.ConnectionRequestResults;
 import com.velocitypowered.proxy.connection.util.ConnectionRequestResults.Impl;
 import com.velocitypowered.proxy.protocol.MinecraftPacket;
+import com.velocitypowered.proxy.protocol.ProtocolUtils;
 import com.velocitypowered.proxy.protocol.StateRegistry;
 import com.velocitypowered.proxy.protocol.netty.MinecraftDecoder;
 import com.velocitypowered.proxy.protocol.packet.ClientboundCookieRequestPacket;
@@ -50,13 +51,16 @@
 import com.velocitypowered.proxy.protocol.packet.config.ClientboundCustomReportDetailsPacket;
 import com.velocitypowered.proxy.protocol.packet.config.ClientboundServerLinksPacket;
 import com.velocitypowered.proxy.protocol.packet.config.FinishedUpdatePacket;
+import com.velocitypowered.proxy.protocol.packet.config.KnownPacksPacket;
 import com.velocitypowered.proxy.protocol.packet.config.RegistrySyncPacket;
 import com.velocitypowered.proxy.protocol.packet.config.StartUpdatePacket;
 import com.velocitypowered.proxy.protocol.packet.config.TagsUpdatePacket;
 import com.velocitypowered.proxy.protocol.util.PluginMessageUtil;
 import java.io.IOException;
 import java.net.InetSocketAddress;
 import java.util.concurrent.CompletableFuture;
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.Unpooled;
 import net.kyori.adventure.key.Key;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -226,24 +230,21 @@ public boolean handle(RemoveResourcePackPacket packet) {
   public boolean handle(FinishedUpdatePacket packet) {
     final MinecraftConnection smc = serverConn.ensureConnected();
     final ConnectedPlayer player = serverConn.getPlayer();
-    final ClientConfigSessionHandler configHandler = (ClientConfigSessionHandler) player.getConnection().getActiveSessionHandler();
 
     smc.getChannel().pipeline().get(MinecraftDecoder.class).setState(StateRegistry.PLAY);
-    //noinspection DataFlowIssue
-    configHandler.handleBackendFinishUpdate(serverConn).thenRunAsync(() -> {
-      smc.write(FinishedUpdatePacket.INSTANCE);
-      if (serverConn == player.getConnectedServer()) {
-        smc.setActiveSessionHandler(StateRegistry.PLAY);
-        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));
-      }
-      if (player.resourcePackHandler().getFirstAppliedPack() == null && resourcePackToApply != null) {
-        player.resourcePackHandler().queueResourcePack(resourcePackToApply);
+    if (player.getConnection().getActiveSessionHandler() instanceof ClientConfigSessionHandler configHandler) {
+      configHandler.handleBackendFinishUpdate(serverConn).thenRunAsync(this::finish, smc.eventLoop());
+    } else {
+      final String brand = serverConn.getPlayer().getClientBrand();
+      if (brand != null) {
+        final ByteBuf buf = Unpooled.buffer();
+        ProtocolUtils.writeString(buf, brand);
+        final PluginMessagePacket brandPacket = new PluginMessagePacket("minecraft:brand", buf);
+        smc.write(brandPacket);
       }
-    }, smc.eventLoop());
+
+      finish();
+    }
     return true;
   }
 
@@ -296,6 +297,17 @@ public boolean handle(TransferPacket packet) {
     return true;
   }
 
+  @Override
+  public boolean handle(KnownPacksPacket packet) {
+    // Server expects us to reply to this packet
+    if (serverConn.getPlayer().getConnection().getState() != StateRegistry.CONFIG) {
+      // TODO: just replay the first packet the user sent
+      serverConn.ensureConnected().write(packet);
+      return true;
+    }
+    return false; // forward
+  }
+
   @Override
   public boolean handle(ClientboundStoreCookiePacket packet) {
     server.getEventManager()
@@ -348,6 +360,24 @@ private void switchFailure(Throwable cause) {
     resultFuture.completeExceptionally(cause);
   }
 
+  private void finish() {
+    final MinecraftConnection smc = serverConn.ensureConnected();
+    final ConnectedPlayer player = serverConn.getPlayer();
+
+    smc.write(FinishedUpdatePacket.INSTANCE);
+    if (serverConn == player.getConnectedServer()) {
+      smc.setActiveSessionHandler(StateRegistry.PLAY);
+      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));
+    }
+    if (player.resourcePackHandler().getFirstAppliedPack() == null && resourcePackToApply != null) {
+      player.resourcePackHandler().queueResourcePack(resourcePackToApply);
+    }
+  }
+
   /**
    * Represents the state of the configuration stage.
    */

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

@@ -163,10 +163,7 @@ public boolean handle(ServerLoginSuccessPacket packet) {
       if (player.getClientSettingsPacket() != null) {
         smc.write(player.getClientSettingsPacket());
       }
-      if (player.getConnection().getActiveSessionHandler() instanceof ClientPlaySessionHandler clientPlaySessionHandler) {
-        smc.setAutoReading(false);
-        clientPlaySessionHandler.doSwitch().thenAcceptAsync((unused) -> smc.setAutoReading(true), smc.eventLoop());
-      } else {
+      if (!(player.getConnection().getActiveSessionHandler() instanceof ClientPlaySessionHandler)) {
         // 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/ClientConfigSessionHandler.java

@@ -125,8 +125,9 @@ public boolean handle(final PluginMessagePacket packet) {
       // but at this time the backend server may not be ready
     } else if (serverConn != null) {
       serverConn.ensureConnected().write(packet.retain());
+      return true;
     }
-    return true;
+    return false;
   }
 
   @Override
@@ -141,14 +142,11 @@ public boolean handle(PingIdentifyPacket packet) {
 
   @Override
   public boolean handle(KnownPacksPacket packet) {
-    callConfigurationEvent().thenRun(() -> {
-      player.getConnectionInFlightOrConnectedServer().ensureConnected().write(packet);
-    }).exceptionally(ex -> {
-      logger.error("Error forwarding known packs response to backend:", ex);
-      return null;
-    });
-
-    return true;
+    if (player.getConnectionInFlight() != null) {
+      player.getConnectionInFlight().ensureConnected().write(packet);
+      return true;
+    }
+    return false;
   }
 
   @Override

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

@@ -47,6 +47,7 @@
 import com.velocitypowered.proxy.protocol.packet.ClientSettingsPacket;
 import com.velocitypowered.proxy.protocol.packet.JoinGamePacket;
 import com.velocitypowered.proxy.protocol.packet.KeepAlivePacket;
+import com.velocitypowered.proxy.protocol.packet.ObjectivePacket;
 import com.velocitypowered.proxy.protocol.packet.PluginMessagePacket;
 import com.velocitypowered.proxy.protocol.packet.ResourcePackResponsePacket;
 import com.velocitypowered.proxy.protocol.packet.RespawnPacket;
@@ -81,8 +82,10 @@
 import java.time.Instant;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Queue;
+import java.util.Set;
 import java.util.UUID;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ConcurrentLinkedQueue;
@@ -104,6 +107,7 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
   private final ConnectedPlayer player;
   private boolean spawned = false;
   private final List<UUID> serverBossBars = new ArrayList<>();
+  private final Set<String> serverObjectives = new HashSet<>();
   private final Queue<PluginMessagePacket> loginPluginMessages = new ConcurrentLinkedQueue<>();
   private final VelocityServer server;
   private @Nullable TabCompleteRequestPacket outstandingTabComplete;
@@ -526,6 +530,7 @@ public CompletableFuture<Void> doSwitch() {
       // Config state clears everything in the client. No need to clear later.
       spawned = false;
       serverBossBars.clear();
+      serverObjectives.clear();
       player.clearPlayerListHeaderAndFooterSilent();
       player.getTabList().clearAllSilent();
     }
@@ -574,6 +579,13 @@ public void handleBackendJoinGame(JoinGamePacket joinGame, VelocityServerConnect
       player.getConnection().delayedWrite(deletePacket);
     }
     serverBossBars.clear();
+    for (String serverObjective : serverObjectives) {
+      ObjectivePacket deletePacket = new ObjectivePacket();
+      deletePacket.setName(serverObjective);
+      deletePacket.setAction(ObjectivePacket.REMOVE);
+      player.getConnection().delayedWrite(deletePacket);
+    }
+    serverObjectives.clear();
 
     // Tell the server about the proxy's plugin message channels.
     ProtocolVersion serverVersion = serverMc.getProtocolVersion();
@@ -645,6 +657,10 @@ public List<UUID> getServerBossBars() {
     return serverBossBars;
   }
 
+  public Set<String> getServerObjectives() {
+    return serverObjectives;
+  }
+
   private boolean handleCommandTabComplete(TabCompleteRequestPacket packet) {
     // In 1.13+, we need to do additional work for the richer suggestions available.
     String command = packet.getCommand().substring(1);

proxy/src/main/java/com/velocitypowered/proxy/protocol/StateRegistry.java

@@ -68,6 +68,7 @@
 import com.velocitypowered.proxy.protocol.packet.LoginAcknowledgedPacket;
 import com.velocitypowered.proxy.protocol.packet.LoginPluginMessagePacket;
 import com.velocitypowered.proxy.protocol.packet.LoginPluginResponsePacket;
+import com.velocitypowered.proxy.protocol.packet.ObjectivePacket;
 import com.velocitypowered.proxy.protocol.packet.PingIdentifyPacket;
 import com.velocitypowered.proxy.protocol.packet.PluginMessagePacket;
 import com.velocitypowered.proxy.protocol.packet.RemovePlayerInfoPacket;
@@ -706,6 +707,24 @@ public enum StateRegistry {
           ClientboundServerLinksPacket::new,
           map(0x7B, MINECRAFT_1_21, false),
           map(0x82, MINECRAFT_1_21_2, false));
+      clientbound.register(
+          ObjectivePacket.class,
+          ObjectivePacket::new,
+          map(0x3B, MINECRAFT_1_8, false),
+          map(0x3F, MINECRAFT_1_9, false),
+          map(0x41, MINECRAFT_1_12, false),
+          map(0x42, MINECRAFT_1_12_1, false),
+          map(0x45, MINECRAFT_1_13, false),
+          map(0x49, MINECRAFT_1_14, false),
+          map(0x4A, MINECRAFT_1_15, false),
+          map(0x53, MINECRAFT_1_17, false),
+          map(0x56, MINECRAFT_1_19_1, false),
+          map(0x54, MINECRAFT_1_19_3, false),
+          map(0x58, MINECRAFT_1_19_4, false),
+          map(0x5A, MINECRAFT_1_20_2, false),
+          map(0x5C, MINECRAFT_1_20_3, false),
+          map(0x5E, MINECRAFT_1_20_5, false),
+          map(0x64, MINECRAFT_1_21_2, false));
     }
   },
   LOGIN {