Integrate BungeeQuack functionality into Velocity

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

@@ -31,6 +31,7 @@ public class BackendPlaySessionHandler implements MinecraftSessionHandler {
   private final VelocityServerConnection serverConn;
   private final ClientPlaySessionHandler playerSessionHandler;
   private final MinecraftConnection playerConnection;
+  private final BungeeCordMessageResponder bungeecordMessageResponder;
   private boolean exceptionTriggered = false;
 
   BackendPlaySessionHandler(VelocityServer server, VelocityServerConnection serverConn) {
@@ -44,6 +45,9 @@ public class BackendPlaySessionHandler implements MinecraftSessionHandler {
           "Initializing BackendPlaySessionHandler with no backing client play session handler!");
     }
     this.playerSessionHandler = (ClientPlaySessionHandler) psh;
+
+    this.bungeecordMessageResponder = new BungeeCordMessageResponder(server,
+        serverConn.getPlayer());
   }
 
   @Override
@@ -86,6 +90,10 @@ public class BackendPlaySessionHandler implements MinecraftSessionHandler {
 
   @Override
   public boolean handle(PluginMessage packet) {
+    if (bungeecordMessageResponder.process(packet)) {
+      return true;
+    }
+
     if (!serverConn.getPlayer().canForwardPluginMessage(serverConn.ensureConnected()
         .getProtocolVersion(), packet)) {
       return true;

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

@@ -0,0 +1,325 @@
+package com.velocitypowered.proxy.connection.backend;
+
+import com.velocitypowered.api.network.ProtocolVersion;
+import com.velocitypowered.api.proxy.Player;
+import com.velocitypowered.api.proxy.ServerConnection;
+import com.velocitypowered.api.proxy.messages.LegacyChannelIdentifier;
+import com.velocitypowered.api.proxy.messages.MinecraftChannelIdentifier;
+import com.velocitypowered.api.proxy.server.RegisteredServer;
+import com.velocitypowered.api.util.UuidUtils;
+import com.velocitypowered.proxy.VelocityServer;
+import com.velocitypowered.proxy.connection.MinecraftConnection;
+import com.velocitypowered.proxy.connection.client.ConnectedPlayer;
+import com.velocitypowered.proxy.protocol.packet.PluginMessage;
+import com.velocitypowered.proxy.protocol.util.ByteBufDataInput;
+import com.velocitypowered.proxy.protocol.util.ByteBufDataOutput;
+import com.velocitypowered.proxy.server.VelocityRegisteredServer;
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufUtil;
+import io.netty.buffer.Unpooled;
+import java.util.StringJoiner;
+import java.util.stream.Collectors;
+import net.kyori.text.serializer.legacy.LegacyComponentSerializer;
+
+class BungeeCordMessageResponder {
+
+  private static final MinecraftChannelIdentifier MODERN_CHANNEL = MinecraftChannelIdentifier
+      .create("bungeecord", "main");
+  private static final LegacyChannelIdentifier LEGACY_CHANNEL =
+      new LegacyChannelIdentifier("BungeeCord");
+
+  private final VelocityServer proxy;
+  private final ConnectedPlayer player;
+
+  BungeeCordMessageResponder(VelocityServer proxy, ConnectedPlayer player) {
+    this.proxy = proxy;
+    this.player = player;
+  }
+
+  private void processConnect(ByteBufDataInput in) {
+    String serverName = in.readUTF();
+    proxy.getServer(serverName).ifPresent(server -> player.createConnectionRequest(server)
+        .fireAndForget());
+  }
+
+  private void processConnectOther(ByteBufDataInput in) {
+    String playerName = in.readUTF();
+    String serverName = in.readUTF();
+
+    proxy.getPlayer(playerName).ifPresent(player -> {
+      proxy.getServer(serverName).ifPresent(server -> player.createConnectionRequest(server)
+          .fireAndForget());
+    });
+  }
+
+  private void processIp(ByteBufDataInput in) {
+    ByteBuf buf = Unpooled.buffer();
+    ByteBufDataOutput out = new ByteBufDataOutput(buf);
+    out.writeUTF("IP");
+    out.writeUTF(player.getRemoteAddress().getHostString());
+    out.writeInt(player.getRemoteAddress().getPort());
+    sendResponse(buf);
+  }
+
+  private void processPlayerCount(ByteBufDataInput in) {
+    ByteBuf buf = Unpooled.buffer();
+    ByteBufDataOutput out = new ByteBufDataOutput(buf);
+
+    String target = in.readUTF();
+    if (target.equals("ALL")) {
+      out.writeUTF("PlayerCount");
+      out.writeUTF("ALL");
+      out.writeInt(proxy.getPlayerCount());
+    } else {
+      proxy.getServer(target).ifPresent(rs -> {
+        int playersOnServer = rs.getPlayersConnected().size();
+        out.writeUTF("PlayerCount");
+        out.writeUTF(rs.getServerInfo().getName());
+        out.writeInt(playersOnServer);
+      });
+    }
+
+    if (buf.isReadable()) {
+      sendResponse(buf);
+    } else {
+      buf.release();
+    }
+  }
+
+  private void processPlayerList(ByteBufDataInput in) {
+    ByteBuf buf = Unpooled.buffer();
+    ByteBufDataOutput out = new ByteBufDataOutput(buf);
+
+    String target = in.readUTF();
+    if (target.equals("ALL")) {
+      out.writeUTF("PlayerList");
+      out.writeUTF("ALL");
+
+      StringJoiner joiner = new StringJoiner(", ");
+      for (Player online : proxy.getAllPlayers()) {
+        joiner.add(online.getUsername());
+      }
+      out.writeUTF(joiner.toString());
+    } else {
+      proxy.getServer(target).ifPresent(info -> {
+        out.writeUTF("PlayerList");
+        out.writeUTF(info.getServerInfo().getName());
+
+        StringJoiner joiner = new StringJoiner(", ");
+        for (Player online : info.getPlayersConnected()) {
+          joiner.add(online.getUsername());
+        }
+        out.writeUTF(joiner.toString());
+      });
+    }
+
+    if (buf.isReadable()) {
+      sendResponse(buf);
+    } else {
+      buf.release();
+    }
+  }
+
+  private void processGetServers(ByteBufDataInput in) {
+    StringJoiner joiner = new StringJoiner(", ");
+    for (RegisteredServer server : proxy.getAllServers()) {
+      joiner.add(server.getServerInfo().getName());
+    }
+
+    ByteBuf buf = Unpooled.buffer();
+    ByteBufDataOutput out = new ByteBufDataOutput(buf);
+    out.writeUTF("GetServers");
+    out.writeUTF(joiner.toString());
+
+    sendResponse(buf);
+  }
+
+  private void processMessage(ByteBufDataInput in) {
+    String target = in.readUTF();
+    String message = in.readUTF();
+    if (target.equals("ALL")) {
+      for (Player player : proxy.getAllPlayers()) {
+        player.sendMessage(LegacyComponentSerializer.INSTANCE.deserialize(message));
+      }
+    } else {
+      proxy.getPlayer(target).ifPresent(player -> {
+        player.sendMessage(LegacyComponentSerializer.INSTANCE.deserialize(message));
+      });
+    }
+  }
+
+  private void processGetServer(ByteBufDataInput in) {
+    ByteBuf buf = Unpooled.buffer();
+    ByteBufDataOutput out = new ByteBufDataOutput(buf);
+
+    out.writeUTF("GetServer");
+    out.writeUTF(player.ensureAndGetCurrentServer().getServerInfo().getName());
+
+    sendResponse(buf);
+  }
+
+  private void processUuid(ByteBufDataInput in) {
+    ByteBuf buf = Unpooled.buffer();
+    ByteBufDataOutput out = new ByteBufDataOutput(buf);
+
+    out.writeUTF("UUID");
+    out.writeUTF(UuidUtils.toUndashed(player.getUniqueId()));
+
+    sendResponse(buf);
+  }
+
+  private void processUuidOther(ByteBufDataInput in) {
+    proxy.getPlayer(in.readUTF()).ifPresent(player -> {
+      ByteBuf buf = Unpooled.buffer();
+      ByteBufDataOutput out = new ByteBufDataOutput(buf);
+
+      out.writeUTF("UUIDOther");
+      out.writeUTF(player.getUsername());
+      out.writeUTF(UuidUtils.toUndashed(player.getUniqueId()));
+
+      sendResponse(buf);
+    });
+  }
+
+  private void processServerIp(ByteBufDataInput in) {
+    proxy.getServer(in.readUTF()).ifPresent(info -> {
+      ByteBuf buf = Unpooled.buffer();
+      ByteBufDataOutput out = new ByteBufDataOutput(buf);
+
+      out.writeUTF("ServerIP");
+      out.writeUTF(info.getServerInfo().getName());
+      out.writeUTF(info.getServerInfo().getAddress().getHostString());
+      out.writeShort(info.getServerInfo().getAddress().getPort());
+
+      sendResponse(buf);
+    });
+  }
+
+  private void processKick(ByteBufDataInput in) {
+    proxy.getPlayer(in.readUTF()).ifPresent(player -> {
+      String kickReason = in.readUTF();
+      player.disconnect(LegacyComponentSerializer.INSTANCE.deserialize(kickReason));
+    });
+  }
+
+  private ByteBuf prepareForwardMessage(ByteBufDataInput in) {
+    String channel = in.readUTF();
+    short messageLength = in.readShort();
+
+    ByteBuf buf = Unpooled.buffer();
+    ByteBufDataOutput forwarded = new ByteBufDataOutput(buf);
+    forwarded.writeUTF(channel);
+    forwarded.writeShort(messageLength);
+    buf.writeBytes(in.unwrap().readSlice(messageLength));
+    return buf;
+  }
+
+  private void processForwardToPlayer(ByteBufDataInput in) {
+    proxy.getPlayer(in.readUTF())
+        .flatMap(Player::getCurrentServer)
+        .ifPresent(server -> sendResponse(player, prepareForwardMessage(in)));
+  }
+
+  private void processForwardToServer(ByteBufDataInput in) {
+    ByteBuf toForward = prepareForwardMessage(in);
+    String target = in.readUTF();
+    if (target.equals("ALL")) {
+      ByteBuf unreleasableForward = Unpooled.unreleasableBuffer(toForward);
+      try {
+        for (RegisteredServer rs : proxy.getAllServers()) {
+          ((VelocityRegisteredServer) rs).sendPluginMessage(LEGACY_CHANNEL, unreleasableForward);
+        }
+      } finally {
+        toForward.release();
+      }
+    } else {
+      proxy.getServer(target).ifPresent(rs -> ((VelocityRegisteredServer) rs)
+          .sendPluginMessage(LEGACY_CHANNEL, toForward));
+    }
+  }
+
+  // Note: this method will always release the buffer!
+  private void sendResponse(ByteBuf buf) {
+    sendResponse(this.player, buf);
+  }
+
+  // Note: this method will always release the buffer!
+  private static void sendResponse(ConnectedPlayer player, ByteBuf buf) {
+    MinecraftConnection serverConnection = player.ensureAndGetCurrentServer().ensureConnected();
+    String chan = serverConnection.getProtocolVersion().compareTo(ProtocolVersion.MINECRAFT_1_13)
+        >= 0 ? MODERN_CHANNEL.getId() : LEGACY_CHANNEL.getId();
+
+    PluginMessage msg = null;
+    boolean released = false;
+
+    try {
+      VelocityServerConnection vsc = player.getConnectedServer();
+      if (vsc == null) {
+        return;
+      }
+
+      MinecraftConnection serverConn = vsc.ensureConnected();
+      msg = new PluginMessage(chan, buf);
+      serverConn.write(msg);
+      released = true;
+    } finally {
+      if (!released && msg != null) {
+        msg.release();
+      }
+    }
+  }
+
+  public boolean process(PluginMessage message) {
+    if (!MODERN_CHANNEL.getId().equals(message.getChannel()) && !LEGACY_CHANNEL.getId()
+        .equals(message.getChannel())) {
+      return false;
+    }
+
+    ByteBufDataInput in = new ByteBufDataInput(message.content());
+    String subChannel = in.readUTF();
+    if (subChannel.equals("ForwardToPlayer")) {
+      this.processForwardToPlayer(in);
+    }
+    if (subChannel.equals("Forward")) {
+      this.processForwardToServer(in);
+    }
+    if (subChannel.equals("Connect")) {
+      this.processConnect(in);
+    }
+    if (subChannel.equals("ConnectOther")) {
+      this.processConnectOther(in);
+    }
+    if (subChannel.equals("IP")) {
+      this.processIp(in);
+    }
+    if (subChannel.equals("PlayerCount")) {
+      this.processPlayerCount(in);
+    }
+    if (subChannel.equals("PlayerList")) {
+      this.processPlayerList(in);
+    }
+    if (subChannel.equals("GetServers")) {
+      this.processGetServers(in);
+    }
+    if (subChannel.equals("Message")) {
+      this.processMessage(in);
+    }
+    if (subChannel.equals("GetServer")) {
+      this.processGetServer(in);
+    }
+    if (subChannel.equals("UUID")) {
+      this.processUuid(in);
+    }
+    if (subChannel.equals("UUIDOther")) {
+      this.processUuidOther(in);
+    }
+    if (subChannel.equals("ServerIP")) {
+      this.processServerIp(in);
+    }
+    if (subChannel.equals("KickPlayer")) {
+      this.processKick(in);
+    }
+
+    return true;
+  }
+}

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

@@ -34,6 +34,7 @@ import com.velocitypowered.proxy.protocol.packet.Handshake;
 import com.velocitypowered.proxy.protocol.packet.PluginMessage;
 import com.velocitypowered.proxy.protocol.packet.ServerLogin;
 import com.velocitypowered.proxy.server.VelocityRegisteredServer;
+import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelFutureListener;
@@ -210,12 +211,16 @@ public class VelocityServerConnection implements MinecraftConnectionAssociation,
 
   @Override
   public boolean sendPluginMessage(ChannelIdentifier identifier, byte[] data) {
+    return sendPluginMessage(identifier, Unpooled.wrappedBuffer(data));
+  }
+
+  public boolean sendPluginMessage(ChannelIdentifier identifier, ByteBuf data) {
     Preconditions.checkNotNull(identifier, "identifier");
     Preconditions.checkNotNull(data, "data");
 
     MinecraftConnection mc = ensureConnected();
 
-    PluginMessage message = new PluginMessage(identifier.getId(), Unpooled.wrappedBuffer(data));
+    PluginMessage message = new PluginMessage(identifier.getId(), data);
     mc.write(message);
     return true;
   }

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

@@ -135,6 +135,14 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player {
     return Optional.ofNullable(connectedServer);
   }
 
+  public VelocityServerConnection ensureAndGetCurrentServer() {
+    VelocityServerConnection con = this.connectedServer;
+    if (con == null) {
+      throw new IllegalStateException("Not connected to server!");
+    }
+    return con;
+  }
+
   @Override
   public GameProfile getGameProfile() {
     return profile;

proxy/src/main/java/com/velocitypowered/proxy/protocol/util/ByteBufDataInput.java

@@ -0,0 +1,110 @@
+package com.velocitypowered.proxy.protocol.util;
+
+import com.google.common.io.ByteArrayDataInput;
+import io.netty.buffer.ByteBuf;
+import java.io.DataInput;
+import java.io.DataInputStream;
+import java.io.IOException;
+
+/**
+ * A wrapper around {@link io.netty.buffer.ByteBuf} that implements the exception-free
+ * {@link ByteArrayDataInput} interface from Guava.
+ */
+public class ByteBufDataInput implements ByteArrayDataInput, DataInput {
+
+  private final ByteBuf in;
+
+  /**
+   * Creates a new ByteBufDataInput instance. The ByteBufDataInput simply "borrows" the ByteBuf
+   * while it is in use.
+   *
+   * @param buf the buffer to read from
+   */
+  public ByteBufDataInput(ByteBuf buf) {
+    this.in = buf;
+  }
+
+  public ByteBuf unwrap() {
+    return in;
+  }
+
+  @Override
+  public void readFully(byte[] b) {
+    in.readBytes(b);
+  }
+
+  @Override
+  public void readFully(byte[] b, int off, int len) {
+    in.readBytes(b, off, len);
+  }
+
+  @Override
+  public int skipBytes(int n) {
+    in.skipBytes(n);
+    return n;
+  }
+
+  @Override
+  public boolean readBoolean() {
+    return in.readBoolean();
+  }
+
+  @Override
+  public byte readByte() {
+    return in.readByte();
+  }
+
+  @Override
+  public int readUnsignedByte() {
+    return in.readUnsignedByte() & 0xFF;
+  }
+
+  @Override
+  public short readShort() {
+    return in.readShort();
+  }
+
+  @Override
+  public int readUnsignedShort() {
+    return in.readUnsignedShort();
+  }
+
+  @Override
+  public char readChar() {
+    return in.readChar();
+  }
+
+  @Override
+  public int readInt() {
+    return in.readInt();
+  }
+
+  @Override
+  public long readLong() {
+    return in.readLong();
+  }
+
+  @Override
+  public float readFloat() {
+    return in.readFloat();
+  }
+
+  @Override
+  public double readDouble() {
+    return in.readDouble();
+  }
+
+  @Override
+  public String readLine() {
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public String readUTF() {
+    try {
+      return DataInputStream.readUTF(this);
+    } catch (IOException e) {
+      throw new IllegalStateException(e);
+    }
+  }
+}

proxy/src/main/java/com/velocitypowered/proxy/protocol/util/ByteBufDataOutput.java

@@ -0,0 +1,105 @@
+package com.velocitypowered.proxy.protocol.util;
+
+import com.google.common.io.ByteArrayDataOutput;
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.ByteBufUtil;
+import java.io.DataOutput;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.nio.charset.StandardCharsets;
+
+/**
+ * A {@link DataOutput} equivalent to {@link ByteBufDataInput}.
+ */
+public class ByteBufDataOutput extends OutputStream implements DataOutput, ByteArrayDataOutput {
+
+  private final ByteBuf buf;
+  private final DataOutputStream utf8out;
+
+  public ByteBufDataOutput(ByteBuf buf) {
+    this.buf = buf;
+    this.utf8out = new DataOutputStream(this);
+  }
+
+  @Override
+  public byte[] toByteArray() {
+    return ByteBufUtil.getBytes(buf);
+  }
+
+  @Override
+  public void write(int b) {
+    buf.writeByte(b);
+  }
+
+  @Override
+  public void write(byte[] b) {
+    buf.writeBytes(b);
+  }
+
+  @Override
+  public void write(byte[] b, int off, int len) {
+    buf.writeBytes(b, off, len);
+  }
+
+  @Override
+  public void writeBoolean(boolean v) {
+    buf.writeBoolean(v);
+  }
+
+  @Override
+  public void writeByte(int v) {
+    buf.writeByte(v);
+  }
+
+  @Override
+  public void writeShort(int v) {
+    buf.writeShort(v);
+  }
+
+  @Override
+  public void writeChar(int v) {
+    buf.writeChar(v);
+  }
+
+  @Override
+  public void writeInt(int v) {
+    buf.writeInt(v);
+  }
+
+  @Override
+  public void writeLong(long v) {
+    buf.writeLong(v);
+  }
+
+  @Override
+  public void writeFloat(float v) {
+    buf.writeFloat(v);
+  }
+
+  @Override
+  public void writeDouble(double v) {
+    buf.writeDouble(v);
+  }
+
+  @Override
+  public void writeBytes(String s) {
+    buf.writeCharSequence(s, StandardCharsets.US_ASCII);
+  }
+
+  @Override
+  public void writeChars(String s) {
+    for (char c : s.toCharArray()) {
+      buf.writeChar(c);
+    }
+  }
+
+  @Override
+  public void writeUTF(String s) {
+    try {
+      this.utf8out.writeUTF(s);
+    } catch (IOException e) {
+      throw new IllegalStateException(e);
+    }
+  }
+}

proxy/src/main/java/com/velocitypowered/proxy/server/VelocityRegisteredServer.java

@@ -18,12 +18,16 @@ import com.velocitypowered.api.proxy.server.ServerInfo;
 import com.velocitypowered.api.proxy.server.ServerPing;
 import com.velocitypowered.proxy.VelocityServer;
 import com.velocitypowered.proxy.connection.MinecraftConnection;
+import com.velocitypowered.proxy.connection.backend.VelocityServerConnection;
 import com.velocitypowered.proxy.connection.client.ConnectedPlayer;
 import com.velocitypowered.proxy.protocol.ProtocolUtils;
 import com.velocitypowered.proxy.protocol.netty.MinecraftDecoder;
 import com.velocitypowered.proxy.protocol.netty.MinecraftEncoder;
 import com.velocitypowered.proxy.protocol.netty.MinecraftVarintFrameDecoder;
 import com.velocitypowered.proxy.protocol.netty.MinecraftVarintLengthEncoder;
+import com.velocitypowered.proxy.protocol.packet.PluginMessage;
+import io.netty.buffer.ByteBuf;
+import io.netty.buffer.Unpooled;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelFuture;
 import io.netty.channel.ChannelFutureListener;
@@ -119,8 +123,12 @@ public class VelocityRegisteredServer implements RegisteredServer {
 
   @Override
   public boolean sendPluginMessage(ChannelIdentifier identifier, byte[] data) {
+    return sendPluginMessage(identifier, Unpooled.wrappedBuffer(data));
+  }
+
+  public boolean sendPluginMessage(ChannelIdentifier identifier, ByteBuf data) {
     for (ConnectedPlayer player : players) {
-      ServerConnection connection = player.getConnectedServer();
+      VelocityServerConnection connection = player.getConnectedServer();
       if (connection != null && connection.getServerInfo().equals(serverInfo)) {
         return connection.sendPluginMessage(identifier, data);
       }