Merge branch 'dev/1.1.0' into decode-multiple

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

@@ -1,5 +1,7 @@
 package com.velocitypowered.api.command;
 
+import java.util.concurrent.CompletableFuture;
+
 /**
  * Represents an interface to register a command executor with the proxy.
  */
@@ -34,11 +36,52 @@ public interface CommandManager {
   void unregister(String alias);
 
   /**
-   * Attempts to execute a command from the specified {@code cmdLine}.
+   * Calls CommandExecuteEvent and attempts to execute a command using the specified {@code cmdLine}
+   * in a blocking fashion.
    *
    * @param source the command's source
    * @param cmdLine the command to run
    * @return true if the command was found and executed, false if it was not
+   * 
+   * @deprecated This method will block current thread during event call and command execution.
+   *             Prefer {@link #executeAsync(CommandSource, String)} instead.
    */
+  @Deprecated
   boolean execute(CommandSource source, String cmdLine);
+
+  /**
+   * Attempts to execute a command using the specified {@code cmdLine} in a blocking fashion without
+   * calling CommandExecuteEvent.
+   *
+   * @param source the command's source
+   * @param cmdLine the command to run
+   * @return true if the command was found and executed, false if it was not
+   * 
+   * @deprecated This method will block current thread during event and command execution.
+   *             Prefer {@link #executeImmediatelyAsync(CommandSource, String)} instead.
+   */
+  @Deprecated
+  boolean executeImmediately(CommandSource source, String cmdLine);
+
+  /**
+   * Calls CommandExecuteEvent and attempts to execute a command from the specified {@code cmdLine}
+   * async.
+   *
+   * @param source the command's source
+   * @param cmdLine the command to run
+   * @return A future that will be completed with the result of the command execution.
+   *         Can be completed exceptionally if exception was thrown during execution.
+   */
+  CompletableFuture<Boolean> executeAsync(CommandSource source, String cmdLine);
+
+  /**
+   * Attempts to execute a command from the specified {@code cmdLine} async
+   * without calling CommandExecuteEvent.
+   *
+   * @param source the command's source
+   * @param cmdLine the command to run
+   * @return A future that will be completed with the result of the command execution.
+   *         Can be completed exceptionally if exception was thrown during execution.
+   */
+  CompletableFuture<Boolean> executeImmediatelyAsync(CommandSource source, String cmdLine);
 }

api/src/main/java/com/velocitypowered/api/event/command/CommandExecuteEvent.java

@@ -0,0 +1,143 @@
+package com.velocitypowered.api.event.command;
+
+import com.google.common.base.Preconditions;
+import com.velocitypowered.api.command.CommandSource;
+import com.velocitypowered.api.event.ResultedEvent;
+import com.velocitypowered.api.event.command.CommandExecuteEvent.CommandResult;
+import java.util.Optional;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+/**
+ * This event is fired when someone executing command.
+ */
+public final class CommandExecuteEvent implements ResultedEvent<CommandResult> {
+
+  private final CommandSource commandSource;
+  private final String command;
+  private CommandResult result;
+
+  /**
+   * Constructs a CommandExecuteEvent.
+   * @param commandSource the source executing the command
+   * @param command the command being executed without first slash
+   */
+  public CommandExecuteEvent(CommandSource commandSource, String command) {
+    this.commandSource = Preconditions.checkNotNull(commandSource, "commandSource");
+    this.command = Preconditions.checkNotNull(command, "command");
+    this.result = CommandResult.allowed();
+  }
+
+  public CommandSource getCommandSource() {
+    return commandSource;
+  }
+
+  /**
+   * Gets the original command being executed without first slash.
+   * @return the original command being executed
+   */
+  public String getCommand() {
+    return command;
+  }
+
+  @Override
+  public CommandResult getResult() {
+    return result;
+  }
+
+  @Override
+  public void setResult(CommandResult result) {
+    this.result = Preconditions.checkNotNull(result, "result");
+  }
+
+  @Override
+  public String toString() {
+    return "CommandExecuteEvent{"
+        + "commandSource=" + commandSource
+        + ", command=" + command
+        + ", result=" + result
+        + '}';
+  }
+
+  /**
+   * Represents the result of the {@link CommandExecuteEvent}.
+   */
+  public static final class CommandResult implements Result {
+
+    private static final CommandResult ALLOWED = new CommandResult(true, false,null);
+    private static final CommandResult DENIED = new CommandResult(false, false,null);
+    private static final CommandResult FORWARD_TO_SERVER = new CommandResult(false, true, null);
+
+    private @Nullable String command;
+    private final boolean status;
+    private final boolean forward;
+
+    private CommandResult(boolean status, boolean forward, @Nullable String command) {
+      this.status = status;
+      this.forward = forward;
+      this.command = command;
+    }
+
+    public Optional<String> getCommand() {
+      return Optional.ofNullable(command);
+    }
+
+    public boolean isForwardToServer() {
+      return forward;
+    }
+
+    @Override
+    public boolean isAllowed() {
+      return status;
+    }
+
+    @Override
+    public String toString() {
+      return status ? "allowed" : "denied";
+    }
+
+    /**
+     * Allows the command to be sent, without modification.
+     * @return the allowed result
+     */
+    public static CommandResult allowed() {
+      return ALLOWED;
+    }
+
+    /**
+     * Prevents the command from being executed.
+     * @return the denied result
+     */
+    public static CommandResult denied() {
+      return DENIED;
+    }
+
+    /**
+     * Prevents the command from being executed, but forward command to server.
+     * @return the forward result
+     */
+    public static CommandResult forwardToServer() {
+      return FORWARD_TO_SERVER;
+    }
+
+    /**
+     * Prevents the command from being executed on proxy, but forward command to server.
+     * @param newCommand the command without first slash to use instead
+     * @return a result with a new command being forwarded to server
+     */
+    public static CommandResult forwardToServer(@NonNull String newCommand) {
+      Preconditions.checkNotNull(newCommand, "newCommand");
+      return new CommandResult(false, true, newCommand);
+    }
+
+    /**
+     * Allows the command to be executed, but silently replaced old command with another.
+     * @param newCommand the command to use instead without first slash
+     * @return a result with a new command
+     */
+    public static CommandResult command(@NonNull String newCommand) {
+      Preconditions.checkNotNull(newCommand, "newCommand");
+      return new CommandResult(true, false, newCommand);
+    }
+  }
+}

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

@@ -60,13 +60,11 @@ public final class GameProfileRequestEvent {
   }
 
   /**
-   * Sets the game profile to use for this connection. It is invalid to use this method on an
-   * online-mode connection.
+   * Sets the game profile to use for this connection.
    *
    * @param gameProfile the profile for this connection, {@code null} uses the original profile
    */
   public void setGameProfile(@Nullable GameProfile gameProfile) {
-    Preconditions.checkState(!onlineMode, "Profiles can not be faked in online mode!");
     this.gameProfile = gameProfile;
   }
 

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

@@ -70,6 +70,10 @@ public final class PlayerChatEvent implements ResultedEvent<PlayerChatEvent.Chat
       this.message = message;
     }
 
+    public Optional<String> getMessage() {
+      return Optional.ofNullable(message);
+    }
+
     @Override
     public boolean isAllowed() {
       return status;
@@ -96,10 +100,6 @@ public final class PlayerChatEvent implements ResultedEvent<PlayerChatEvent.Chat
       return DENIED;
     }
 
-    public Optional<String> getMessage() {
-      return Optional.ofNullable(message);
-    }
-
     /**
      * Allows the message to be sent, but silently replaced with another.
      * @param message the message to use instead
@@ -110,6 +110,4 @@ public final class PlayerChatEvent implements ResultedEvent<PlayerChatEvent.Chat
       return new ChatResult(true, message);
     }
   }
-
-
 }

api/src/main/java/com/velocitypowered/api/proxy/config/ProxyConfig.java

@@ -62,6 +62,15 @@ public interface ProxyConfig {
    */
   boolean isOnlineMode();
 
+  /**
+   * If client's ISP/AS sent from this proxy is different from the one from Mojang's
+   * authentication server, the player is kicked. This disallows some VPN and proxy
+   * connections but is a weak form of protection.
+   *
+   * @return whether to prevent client proxy connections by checking the IP with Mojang servers
+   */
+  boolean shouldPreventClientProxyConnections();
+
   /**
    * Get a Map of all servers registered in <code>velocity.toml</code>. This method does
    * <strong>not</strong> return all the servers currently in memory, although in most cases it

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

@@ -44,6 +44,8 @@ import com.velocitypowered.proxy.util.bossbar.VelocityBossBar;
 import com.velocitypowered.proxy.util.ratelimit.Ratelimiter;
 import com.velocitypowered.proxy.util.ratelimit.Ratelimiters;
 import io.netty.bootstrap.Bootstrap;
+import io.netty.channel.Channel;
+import io.netty.channel.ChannelInitializer;
 import io.netty.channel.EventLoopGroup;
 import java.io.IOException;
 import java.net.InetSocketAddress;
@@ -93,7 +95,7 @@ public class VelocityServer implements ProxyServer {
   private @MonotonicNonNull VelocityConfiguration configuration;
   private @MonotonicNonNull KeyPair serverKeyPair;
   private final ServerMap servers;
-  private final VelocityCommandManager commandManager = new VelocityCommandManager();
+  private final VelocityCommandManager commandManager;
   private final AtomicBoolean shutdownInProgress = new AtomicBoolean(false);
   private boolean shutdown = false;
   private final VelocityPluginManager pluginManager;
@@ -109,6 +111,7 @@ public class VelocityServer implements ProxyServer {
   VelocityServer(final ProxyOptions options) {
     pluginManager = new VelocityPluginManager(this);
     eventManager = new VelocityEventManager(pluginManager);
+    commandManager = new VelocityCommandManager(eventManager);
     scheduler = new VelocityScheduler(pluginManager);
     console = new VelocityConsole(this);
     cm = new ConnectionManager(this);
@@ -268,6 +271,10 @@ public class VelocityServer implements ProxyServer {
     return this.cm.createWorker(group);
   }
 
+  public ChannelInitializer<Channel> getBackendChannelInitializer() {
+    return this.cm.backendChannelInitializer.get();
+  }
+
   public boolean isShutdown() {
     return shutdown;
   }

proxy/src/main/java/com/velocitypowered/proxy/command/ServerCommand.java

@@ -12,8 +12,6 @@ import com.velocitypowered.api.proxy.ProxyServer;
 import com.velocitypowered.api.proxy.ServerConnection;
 import com.velocitypowered.api.proxy.server.RegisteredServer;
 import com.velocitypowered.api.proxy.server.ServerInfo;
-import java.util.ArrayList;
-import java.util.Comparator;
 import java.util.List;
 import java.util.Optional;
 import java.util.stream.Collectors;
@@ -25,6 +23,7 @@ import org.checkerframework.checker.nullness.qual.NonNull;
 
 public class ServerCommand implements Command {
 
+  public static final int MAX_SERVERS_TO_LIST = 50;
   private final ProxyServer server;
 
   public ServerCommand(ProxyServer server) {
@@ -61,10 +60,16 @@ public class ServerCommand implements Command {
     executor.sendMessage(of("You are currently connected to " + currentServer + ".",
         TextColor.YELLOW));
 
+    List<RegisteredServer> servers = BuiltinCommandUtil.sortedServerList(server);
+    if (servers.size() > MAX_SERVERS_TO_LIST) {
+      executor.sendMessage(of("Too many servers to list. Tab-complete to show all servers.",
+          TextColor.RED));
+      return;
+    }
+
     // Assemble the list of servers as components
     TextComponent.Builder serverListBuilder = TextComponent.builder("Available servers: ")
         .color(TextColor.YELLOW);
-    List<RegisteredServer> servers = BuiltinCommandUtil.sortedServerList(server);
     for (int i = 0; i < servers.size(); i++) {
       RegisteredServer rs = servers.get(i);
       serverListBuilder.append(formatServerComponent(currentServer, rs));

proxy/src/main/java/com/velocitypowered/proxy/command/VelocityCommandManager.java

@@ -7,16 +7,26 @@ import com.velocitypowered.api.command.Command;
 import com.velocitypowered.api.command.CommandManager;
 import com.velocitypowered.api.command.CommandSource;
 import com.velocitypowered.api.command.RawCommand;
+import com.velocitypowered.api.event.command.CommandExecuteEvent;
+import com.velocitypowered.api.event.command.CommandExecuteEvent.CommandResult;
+import com.velocitypowered.proxy.plugin.VelocityEventManager;
+
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.CompletableFuture;
 
 public class VelocityCommandManager implements CommandManager {
 
   private final Map<String, RawCommand> commands = new HashMap<>();
+  private final VelocityEventManager eventManager;
+
+  public VelocityCommandManager(VelocityEventManager eventManager) {
+    this.eventManager = eventManager;
+  }
 
   @Override
   @Deprecated
@@ -47,9 +57,36 @@ public class VelocityCommandManager implements CommandManager {
     this.commands.remove(alias.toLowerCase(Locale.ENGLISH));
   }
 
+  /**
+   * Calls CommandExecuteEvent.
+   * @param source the command's source
+   * @param cmd the command
+   * @return CompletableFuture of event
+   */
+  public CompletableFuture<CommandExecuteEvent> callCommandEvent(CommandSource source, String cmd) {
+    Preconditions.checkNotNull(source, "source");
+    Preconditions.checkNotNull(cmd, "cmd");
+    return eventManager.fire(new CommandExecuteEvent(source, cmd));
+  }
+
   @Override
   public boolean execute(CommandSource source, String cmdLine) {
-    Preconditions.checkNotNull(source, "invoker");
+    Preconditions.checkNotNull(source, "source");
+    Preconditions.checkNotNull(cmdLine, "cmdLine");
+
+    CommandExecuteEvent event = callCommandEvent(source, cmdLine).join();
+    CommandResult commandResult = event.getResult();
+    if (commandResult.isForwardToServer() || !commandResult.isAllowed()) {
+      return false;
+    }
+    cmdLine = commandResult.getCommand().orElse(event.getCommand());
+
+    return executeImmediately(source, cmdLine);
+  }
+
+  @Override
+  public boolean executeImmediately(CommandSource source, String cmdLine) {
+    Preconditions.checkNotNull(source, "source");
     Preconditions.checkNotNull(cmdLine, "cmdLine");
 
     String alias = cmdLine;
@@ -75,6 +112,40 @@ public class VelocityCommandManager implements CommandManager {
     }
   }
 
+
+  @Override
+  public CompletableFuture<Boolean> executeAsync(CommandSource source, String cmdLine) {
+    CompletableFuture<Boolean> result = new CompletableFuture<>();
+    callCommandEvent(source, cmdLine).thenAccept(event -> {
+      CommandResult commandResult = event.getResult();
+      if (commandResult.isForwardToServer() || !commandResult.isAllowed()) {
+        result.complete(false);
+      }
+      String command = commandResult.getCommand().orElse(event.getCommand());
+      try {
+        result.complete(executeImmediately(source, command));
+      } catch (Exception e) {
+        result.completeExceptionally(e);
+      }
+    });
+    return result;
+  }
+
+  @Override
+  public CompletableFuture<Boolean> executeImmediatelyAsync(CommandSource source, String cmdLine) {
+    Preconditions.checkNotNull(source, "source");
+    Preconditions.checkNotNull(cmdLine, "cmdLine");
+    CompletableFuture<Boolean> result = new CompletableFuture<>();
+    eventManager.getService().execute(() -> {
+      try {
+        result.complete(executeImmediately(source, cmdLine));
+      } catch (Exception e) {
+        result.completeExceptionally(e);
+      }
+    });
+    return result;
+  }
+
   public boolean hasCommand(String command) {
     return commands.containsKey(command);
   }
@@ -167,7 +238,14 @@ public class VelocityCommandManager implements CommandManager {
       if (line.isEmpty()) {
         return new String[0];
       }
-      return line.trim().split(" ", -1);
+
+      String[] trimmed = line.trim().split(" ", -1);
+      if (line.endsWith(" ") && !line.trim().isEmpty()) {
+        // To work around a 1.13+ specific bug we have to inject a space at the end of the arguments
+        trimmed = Arrays.copyOf(trimmed, trimmed.length + 1);
+        trimmed[trimmed.length - 1] = "";
+      }
+      return trimmed;
     }
 
     @Override

proxy/src/main/java/com/velocitypowered/proxy/config/VelocityConfiguration.java

@@ -54,6 +54,14 @@ public class VelocityConfiguration extends AnnotatedConfig implements ProxyConfi
   @ConfigKey("online-mode")
   private boolean onlineMode = true;
 
+  @Comment({
+      "If client's ISP/AS sent from this proxy is different from the one from Mojang's",
+      "authentication server, the player is kicked. This disallows some VPN and proxy",
+      "connections but is a weak form of protection."
+  })
+  @ConfigKey("prevent-client-proxy-connections")
+  private boolean preventClientProxyConnections = false;
+
   @Comment({
       "Should we forward IP addresses and other data to backend servers?",
       "Available options:",
@@ -328,6 +336,11 @@ public class VelocityConfiguration extends AnnotatedConfig implements ProxyConfi
     return onlineMode;
   }
 
+  @Override
+  public boolean shouldPreventClientProxyConnections() {
+    return preventClientProxyConnections;
+  }
+
   public PlayerInfoForwarding getPlayerInfoForwardingMode() {
     return playerInfoForwardingMode;
   }
@@ -402,6 +415,10 @@ public class VelocityConfiguration extends AnnotatedConfig implements ProxyConfi
     return pingPassthrough;
   }
 
+  public boolean isBungeePluginChannelEnabled() {
+    return advanced.isBungeePluginMessageChannel();
+  }
+
   @Override
   public String toString() {
     return MoreObjects.toStringHelper(this)
@@ -654,6 +671,10 @@ public class VelocityConfiguration extends AnnotatedConfig implements ProxyConfi
     @ConfigKey("tcp-fast-open")
     private boolean tcpFastOpen = false;
 
+    @Comment("Enables BungeeCord plugin messaging channel support on Velocity.")
+    @ConfigKey("bungee-plugin-message-channel")
+    private boolean bungeePluginMessageChannel = true;
+
     private Advanced() {
     }
 
@@ -666,6 +687,7 @@ public class VelocityConfiguration extends AnnotatedConfig implements ProxyConfi
         this.readTimeout = toml.getLong("read-timeout", 30000L).intValue();
         this.proxyProtocol = toml.getBoolean("proxy-protocol", false);
         this.tcpFastOpen = toml.getBoolean("tcp-fast-open", false);
+        this.bungeePluginMessageChannel = toml.getBoolean("bungee-plugin-message-channel", true);
       }
     }
 
@@ -697,6 +719,10 @@ public class VelocityConfiguration extends AnnotatedConfig implements ProxyConfi
       return tcpFastOpen;
     }
 
+    public boolean isBungeePluginMessageChannel() {
+      return bungeePluginMessageChannel;
+    }
+
     @Override
     public String toString() {
       return "Advanced{"
@@ -707,6 +733,7 @@ public class VelocityConfiguration extends AnnotatedConfig implements ProxyConfi
           + ", readTimeout=" + readTimeout
           + ", proxyProtocol=" + proxyProtocol
           + ", tcpFastOpen=" + tcpFastOpen
+          + ", bungeePluginMessageChannel=" + bungeePluginMessageChannel
           + '}';
     }
   }

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

@@ -15,6 +15,7 @@ import com.velocitypowered.proxy.protocol.util.ByteBufDataOutput;
 import com.velocitypowered.proxy.server.VelocityRegisteredServer;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
+import java.util.Optional;
 import java.util.StringJoiner;
 import net.kyori.text.serializer.legacy.LegacyComponentSerializer;
 
@@ -43,8 +44,11 @@ class BungeeCordMessageResponder {
     String playerName = in.readUTF();
     String serverName = in.readUTF();
 
-    proxy.getPlayer(playerName).flatMap(player -> proxy.getServer(serverName))
-        .ifPresent(server -> player.createConnectionRequest(server).fireAndForget());
+    Optional<Player> referencedPlayer = proxy.getPlayer(playerName);
+    Optional<RegisteredServer> referencedServer = proxy.getServer(serverName);
+    if (referencedPlayer.isPresent() && referencedServer.isPresent()) {
+      referencedPlayer.get().createConnectionRequest(referencedServer.get()).fireAndForget();
+    }
   }
 
   private void processIp(ByteBufDataInput in) {
@@ -269,6 +273,10 @@ class BungeeCordMessageResponder {
   }
 
   boolean process(PluginMessage message) {
+    if (!proxy.getConfiguration().isBungeePluginChannelEnabled()) {
+      return false;
+    }
+
     if (!MODERN_CHANNEL.getId().equals(message.getChannel()) && !LEGACY_CHANNEL.getId()
         .equals(message.getChannel())) {
       return false;

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

@@ -80,22 +80,7 @@ public class VelocityServerConnection implements MinecraftConnectionAssociation,
     // Note: we use the event loop for the connection the player is on. This reduces context
     // switches.
     server.createBootstrap(proxyPlayer.getConnection().eventLoop())
-        .handler(new ChannelInitializer<Channel>() {
-          @Override
-          protected void initChannel(Channel ch) throws Exception {
-            ch.pipeline()
-                .addLast(READ_TIMEOUT,
-                    new ReadTimeoutHandler(server.getConfiguration().getReadTimeout(),
-                        TimeUnit.MILLISECONDS))
-                .addLast(FRAME_DECODER, new MinecraftVarintFrameDecoder())
-                .addLast(FRAME_ENCODER, MinecraftVarintLengthEncoder.INSTANCE)
-                .addLast(FLOW_HANDLER, new FlowControlHandler())
-                .addLast(MINECRAFT_DECODER,
-                    new MinecraftDecoder(ProtocolUtils.Direction.CLIENTBOUND))
-                .addLast(MINECRAFT_ENCODER,
-                    new MinecraftEncoder(ProtocolUtils.Direction.SERVERBOUND));
-          }
-        })
+        .handler(server.getBackendChannelInitializer())
         .connect(registeredServer.getServerInfo().getAddress())
         .addListener((ChannelFutureListener) future -> {
           if (future.isSuccess()) {

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

@@ -4,6 +4,7 @@ import static com.velocitypowered.api.network.ProtocolVersion.MINECRAFT_1_13;
 import static com.velocitypowered.api.network.ProtocolVersion.MINECRAFT_1_8;
 import static com.velocitypowered.proxy.protocol.util.PluginMessageUtil.constructChannelsPacket;
 
+import com.velocitypowered.api.event.command.CommandExecuteEvent;
 import com.velocitypowered.api.event.connection.PluginMessageEvent;
 import com.velocitypowered.api.event.player.PlayerChatEvent;
 import com.velocitypowered.api.event.player.PlayerResourcePackStatusEvent;
@@ -123,17 +124,30 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
 
     String msg = packet.getMessage();
     if (msg.startsWith("/")) {
-      try {
-        if (!server.getCommandManager().execute(player, msg.substring(1))) {
-          return false;
-        }
-      } catch (Exception e) {
-        logger.info("Exception occurred while running command for {}", player.getUsername(),
-                e);
-        player.sendMessage(
-            TextComponent.of("An error occurred while running this command.", TextColor.RED));
-        return true;
-      }
+
+      server.getCommandManager().callCommandEvent(player, msg.substring(1))
+          .thenAcceptAsync(event -> {
+            CommandExecuteEvent.CommandResult commandResult = event.getResult();
+            Optional<String> eventCommand = event.getResult().getCommand();
+            String command = eventCommand.orElse(event.getCommand());
+            if (commandResult.isForwardToServer()) {
+              smc.write(Chat.createServerbound("/" + command));
+              return;
+            }
+            if (commandResult.isAllowed()) {
+              try {
+                if (!server.getCommandManager().executeImmediately(player, command)) {
+                  smc.write(Chat.createServerbound("/" + command));
+                }
+              } catch (Exception e) {
+                logger.info("Exception occurred while running command for {}", player.getUsername(),
+                    e);
+                player.sendMessage(
+                    TextComponent.of("An error occurred while running this command.",
+                        TextColor.RED));
+              }
+            }
+          }, smc.eventLoop());
     } else {
       PlayerChatEvent event = new PlayerChatEvent(player, msg);
       server.getEventManager().fire(event)
@@ -371,12 +385,12 @@ public class ClientPlaySessionHandler implements MinecraftSessionHandler {
   private boolean handleCommandTabComplete(TabCompleteRequest packet) {
     // In 1.13+, we need to do additional work for the richer suggestions available.
     String command = packet.getCommand().substring(1);
-    int spacePos = command.indexOf(' ');
-    if (spacePos == -1) {
-      spacePos = command.length();
+    int commandEndPosition = command.indexOf(' ');
+    if (commandEndPosition == -1) {
+      commandEndPosition = command.length();
     }
 
-    String commandLabel = command.substring(0, spacePos);
+    String commandLabel = command.substring(0, commandEndPosition);
     if (!server.getCommandManager().hasCommand(commandLabel)) {
       if (player.getProtocolVersion().compareTo(MINECRAFT_1_13) < 0) {
         // Outstanding tab completes are recorded for use with 1.12 clients and below to provide

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

@@ -50,7 +50,7 @@ public class LoginSessionHandler implements MinecraftSessionHandler {
 
   private static final Logger logger = LogManager.getLogger(LoginSessionHandler.class);
   private static final String MOJANG_HASJOINED_URL =
-      "https://sessionserver.mojang.com/session/minecraft/hasJoined?username=%s&serverId=%s&ip=%s";
+      "https://sessionserver.mojang.com/session/minecraft/hasJoined?username=%s&serverId=%s";
 
   private final VelocityServer server;
   private final MinecraftConnection mcConnection;
@@ -96,8 +96,11 @@ public class LoginSessionHandler implements MinecraftSessionHandler {
 
       String playerIp = ((InetSocketAddress) mcConnection.getRemoteAddress()).getHostString();
       String url = String.format(MOJANG_HASJOINED_URL,
-          urlFormParameterEscaper().escape(login.getUsername()), serverId,
-          urlFormParameterEscaper().escape(playerIp));
+          urlFormParameterEscaper().escape(login.getUsername()), serverId);
+
+      if (server.getConfiguration().shouldPreventClientProxyConnections()) {
+        url += "&ip=" + urlFormParameterEscaper().escape(playerIp);
+      }
 
       ListenableFuture<Response> hasJoinedResponse = server.getAsyncHttpClient().prepareGet(url)
           .execute();

proxy/src/main/java/com/velocitypowered/proxy/console/VelocityConsole.java

@@ -8,6 +8,8 @@ import com.velocitypowered.api.permission.Tristate;
 import com.velocitypowered.api.proxy.ConsoleCommandSource;
 import com.velocitypowered.proxy.VelocityServer;
 import java.util.List;
+import java.util.concurrent.CompletableFuture;
+
 import net.kyori.text.Component;
 import net.kyori.text.TextComponent;
 import net.kyori.text.format.TextColor;

proxy/src/main/java/com/velocitypowered/proxy/network/BackendChannelInitializer.java

@@ -0,0 +1,45 @@
+package com.velocitypowered.proxy.network;
+
+import static com.velocitypowered.proxy.network.Connections.FLOW_HANDLER;
+import static com.velocitypowered.proxy.network.Connections.FRAME_DECODER;
+import static com.velocitypowered.proxy.network.Connections.FRAME_ENCODER;
+import static com.velocitypowered.proxy.network.Connections.MINECRAFT_DECODER;
+import static com.velocitypowered.proxy.network.Connections.MINECRAFT_ENCODER;
+import static com.velocitypowered.proxy.network.Connections.READ_TIMEOUT;
+
+import com.velocitypowered.proxy.VelocityServer;
+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 io.netty.channel.Channel;
+import io.netty.channel.ChannelInitializer;
+import io.netty.handler.flow.FlowControlHandler;
+import io.netty.handler.timeout.ReadTimeoutHandler;
+import java.util.concurrent.TimeUnit;
+
+@SuppressWarnings("WeakerAccess")
+public class BackendChannelInitializer extends ChannelInitializer<Channel> {
+
+  private final VelocityServer server;
+
+  public BackendChannelInitializer(VelocityServer server) {
+    this.server = server;
+  }
+
+  @Override
+  protected void initChannel(Channel ch) throws Exception {
+    ch.pipeline()
+        .addLast(READ_TIMEOUT,
+            new ReadTimeoutHandler(server.getConfiguration().getReadTimeout(),
+                TimeUnit.MILLISECONDS))
+        .addLast(FRAME_DECODER, new MinecraftVarintFrameDecoder())
+        .addLast(FRAME_ENCODER, MinecraftVarintLengthEncoder.INSTANCE)
+        .addLast(FLOW_HANDLER, new FlowControlHandler())
+        .addLast(MINECRAFT_DECODER,
+            new MinecraftDecoder(ProtocolUtils.Direction.CLIENTBOUND))
+        .addLast(MINECRAFT_ENCODER,
+            new MinecraftEncoder(ProtocolUtils.Direction.SERVERBOUND));
+  }
+}

proxy/src/main/java/com/velocitypowered/proxy/network/BackendChannelInitializerHolder.java

@@ -0,0 +1,35 @@
+package com.velocitypowered.proxy.network;
+
+import io.netty.channel.Channel;
+import io.netty.channel.ChannelInitializer;
+import java.util.function.Supplier;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+public class BackendChannelInitializerHolder implements Supplier<ChannelInitializer<Channel>> {
+
+  private static final Logger LOGGER = LogManager.getLogger(ConnectionManager.class);
+  private ChannelInitializer<Channel> initializer;
+
+  BackendChannelInitializerHolder(final ChannelInitializer<Channel> initializer) {
+    this.initializer = initializer;
+  }
+
+  @Override
+  public ChannelInitializer<Channel> get() {
+    return this.initializer;
+  }
+
+  /**
+   * Sets the channel initializer.
+   *
+   * @param initializer the new initializer to use
+   * @deprecated Internal implementation detail
+   */
+  @Deprecated
+  public void set(final ChannelInitializer<Channel> initializer) {
+    LOGGER.warn("The backend channel initializer has been replaced by {}",
+        Thread.currentThread().getStackTrace()[2]);
+    this.initializer = initializer;
+  }
+}

proxy/src/main/java/com/velocitypowered/proxy/network/ConnectionManager.java

@@ -42,10 +42,12 @@ public final class ConnectionManager {
   private final EventLoopGroup bossGroup;
   private final EventLoopGroup workerGroup;
   private final VelocityServer server;
-  // This is intentionally made public for plugins like ViaVersion, which inject their own
+  // These are intentionally made public for plugins like ViaVersion, which inject their own
   // protocol logic into the proxy.
   @SuppressWarnings("WeakerAccess")
   public final ServerChannelInitializerHolder serverChannelInitializer;
+  @SuppressWarnings("WeakerAccess")
+  public final BackendChannelInitializerHolder backendChannelInitializer;
 
   private final DnsAddressResolverGroup resolverGroup;
   private final AsyncHttpClient httpClient;
@@ -62,6 +64,8 @@ public final class ConnectionManager {
     this.workerGroup = this.transportType.createEventLoopGroup(TransportType.Type.WORKER);
     this.serverChannelInitializer = new ServerChannelInitializerHolder(
         new ServerChannelInitializer(this.server));
+    this.backendChannelInitializer = new BackendChannelInitializerHolder(
+        new BackendChannelInitializer(this.server));
     this.resolverGroup = new DnsAddressResolverGroup(new DnsNameResolverBuilder()
         .channelType(this.transportType.datagramChannelClass)
         .negativeTtl(15)
@@ -204,4 +208,8 @@ public final class ConnectionManager {
   public AsyncHttpClient getHttpClient() {
     return httpClient;
   }
+
+  public BackendChannelInitializerHolder getBackendChannelInitializer() {
+    return this.backendChannelInitializer;
+  }
 }

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

@@ -185,6 +185,10 @@ public class VelocityEventManager implements EventManager {
     fireEvent(new ProxyShutdownEvent());
   }
 
+  public ExecutorService getService() {
+    return service;
+  }
+
   private static class VelocityMethodScanner implements MethodScanner<Object> {
 
     @Override