Connect Geyser players directly to the server for plugin versions (#2413)

- Faster loading times and improved latency; Geyser no longer creates a physical TCP connection to join the server
- Less configuration: remote address and port are now irrelevant
- Accurate IP addresses without needing Floodgate.

Co-authored-by: Redned <redned235@gmail.com>

bootstrap/velocity/src/main/java/org/geysermc/platform/velocity/GeyserVelocityInjector.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2019-2021 GeyserMC. http://geysermc.org
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ * @author GeyserMC
+ * @link https://github.com/GeyserMC/Geyser
+ */
+
+package org.geysermc.platform.velocity;
+
+import com.github.steveice10.packetlib.io.local.LocalServerChannelWrapper;
+import com.velocitypowered.api.proxy.ProxyServer;
+import io.netty.bootstrap.ServerBootstrap;
+import io.netty.channel.*;
+import io.netty.channel.local.LocalAddress;
+import org.geysermc.connector.bootstrap.GeyserBootstrap;
+import org.geysermc.connector.common.GeyserInjector;
+
+import java.lang.reflect.Field;
+import java.util.function.Supplier;
+
+public class GeyserVelocityInjector extends GeyserInjector {
+    private final ProxyServer proxy;
+
+    public GeyserVelocityInjector(ProxyServer proxy) {
+        this.proxy = proxy;
+    }
+
+    @Override
+    @SuppressWarnings("unchecked")
+    protected void initializeLocalChannel0(GeyserBootstrap bootstrap) throws Exception {
+        Field cm = proxy.getClass().getDeclaredField("cm");
+        cm.setAccessible(true);
+        Object connectionManager = cm.get(proxy);
+        Class<?> connectionManagerClass = connectionManager.getClass();
+
+        Supplier<ChannelInitializer<Channel>> serverChannelInitializerHolder = (Supplier<ChannelInitializer<Channel>>) connectionManagerClass
+                .getMethod("getServerChannelInitializer")
+                .invoke(connectionManager);
+        ChannelInitializer<Channel> channelInitializer = serverChannelInitializerHolder.get();
+
+        // Is set on Velocity's end for listening to Java connections - required on ours or else the initial world load process won't finish sometimes
+        Field serverWriteMarkField = connectionManagerClass.getDeclaredField("SERVER_WRITE_MARK");
+        serverWriteMarkField.setAccessible(true);
+        WriteBufferWaterMark serverWriteMark = (WriteBufferWaterMark) serverWriteMarkField.get(null);
+
+        EventLoopGroup bossGroup = (EventLoopGroup) connectionManagerClass.getMethod("getBossGroup").invoke(connectionManager);
+
+        Field workerGroupField = connectionManagerClass.getDeclaredField("workerGroup");
+        workerGroupField.setAccessible(true);
+        EventLoopGroup workerGroup = (EventLoopGroup) workerGroupField.get(connectionManager);
+
+        ChannelFuture channelFuture = (new ServerBootstrap()
+                .channel(LocalServerChannelWrapper.class)
+                .childHandler(channelInitializer)
+                .group(bossGroup, workerGroup) // Cannot be DefaultEventLoopGroup
+                .childOption(ChannelOption.WRITE_BUFFER_WATER_MARK, serverWriteMark) // Required or else rare network freezes can occur
+                .localAddress(LocalAddress.ANY))
+                .bind()
+                .syncUninterruptibly();
+
+        this.localChannel = channelFuture;
+        this.serverSocketAddress = channelFuture.channel().localAddress();
+    }
+}

bootstrap/velocity/src/main/java/org/geysermc/platform/velocity/GeyserVelocityPlugin.java

@@ -28,6 +28,7 @@ package org.geysermc.platform.velocity;
 import com.google.inject.Inject;
 import com.velocitypowered.api.command.CommandManager;
 import com.velocitypowered.api.event.Subscribe;
+import com.velocitypowered.api.event.proxy.ListenerBoundEvent;
 import com.velocitypowered.api.event.proxy.ProxyInitializeEvent;
 import com.velocitypowered.api.event.proxy.ProxyShutdownEvent;
 import com.velocitypowered.api.plugin.Plugin;
@@ -45,11 +46,13 @@ import org.geysermc.connector.utils.FileUtils;
 import org.geysermc.connector.utils.LanguageUtils;
 import org.geysermc.platform.velocity.command.GeyserVelocityCommandExecutor;
 import org.geysermc.platform.velocity.command.GeyserVelocityCommandManager;
+import org.jetbrains.annotations.Nullable;
 import org.slf4j.Logger;
 
 import java.io.File;
 import java.io.IOException;
 import java.net.InetSocketAddress;
+import java.net.SocketAddress;
 import java.nio.file.Path;
 import java.nio.file.Paths;
 import java.util.UUID;
@@ -68,6 +71,7 @@ public class GeyserVelocityPlugin implements GeyserBootstrap {
 
     private GeyserVelocityCommandManager geyserCommandManager;
     private GeyserVelocityConfiguration geyserConfig;
+    private GeyserVelocityInjector geyserInjector;
     private GeyserVelocityLogger geyserLogger;
     private IGeyserPingPassthrough geyserPingPassthrough;
 
@@ -130,6 +134,9 @@ public class GeyserVelocityPlugin implements GeyserBootstrap {
 
         this.connector = GeyserConnector.start(PlatformType.VELOCITY, this);
 
+        this.geyserInjector = new GeyserVelocityInjector(proxyServer);
+        // Will be initialized after the proxy has been bound
+
         this.geyserCommandManager = new GeyserVelocityCommandManager(connector);
         this.commandManager.register("geyser", new GeyserVelocityCommandExecutor(connector));
         if (geyserConfig.isLegacyPingPassthrough()) {
@@ -141,7 +148,12 @@ public class GeyserVelocityPlugin implements GeyserBootstrap {
 
     @Override
     public void onDisable() {
-        connector.shutdown();
+        if (connector != null) {
+            connector.shutdown();
+        }
+        if (geyserInjector != null) {
+            geyserInjector.shutdown();
+        }
     }
 
     @Override
@@ -174,8 +186,20 @@ public class GeyserVelocityPlugin implements GeyserBootstrap {
         onDisable();
     }
 
+    @Subscribe
+    public void onProxyBound(ListenerBoundEvent event) {
+        // After this bound, we know that the channel initializer cannot change without it being ineffective for Velocity, too
+        geyserInjector.initializeLocalChannel(this);
+    }
+
     @Override
     public BootstrapDumpInfo getDumpInfo() {
         return new GeyserVelocityDumpInfo(proxyServer);
     }
+
+    @Nullable
+    @Override
+    public SocketAddress getSocketAddress() {
+        return this.geyserInjector.getServerSocketAddress();
+    }
 }