Geyser/bootstrap/spigot/src/main/java/org/geysermc/geyser/platform/spigot/GeyserSpigotInjector.java

/*
 * Copyright (c) 2019-2022 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.geyser.platform.spigot;

import com.github.steveice10.mc.protocol.MinecraftProtocol;
import com.viaversion.viaversion.bukkit.handlers.BukkitChannelInitializer;
import io.netty.bootstrap.ServerBootstrap;
import io.netty.channel.*;
import io.netty.channel.local.LocalAddress;
import io.netty.util.concurrent.DefaultThreadFactory;
import org.bukkit.Bukkit;
import org.geysermc.geyser.GeyserBootstrap;
import org.geysermc.geyser.network.netty.GeyserInjector;
import org.geysermc.geyser.network.netty.LocalServerChannelWrapper;
import org.geysermc.geyser.network.netty.LocalSession;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.net.InetAddress;
import java.util.List;

public class GeyserSpigotInjector extends GeyserInjector {
    /**
     * Used to determine if ViaVersion is setup to a state where Geyser players will fail at joining if injection is enabled
     */
    private final boolean isViaVersion;
    /**
     * Used to uninject ourselves on shutdown.
     */
    private List<ChannelFuture> allServerChannels;

    public GeyserSpigotInjector(boolean isViaVersion) {
        this.isViaVersion = isViaVersion;
    }

    @Override
    @SuppressWarnings("unchecked")
    protected void initializeLocalChannel0(GeyserBootstrap bootstrap) throws Exception {
        Class<?> serverClazz;
        try {
            serverClazz = Class.forName("net.minecraft.server.MinecraftServer");
            // We're using 1.17+
        } catch (ClassNotFoundException e) {
            // We're using pre-1.17
            String prefix = Bukkit.getServer().getClass().getPackage().getName().replace("org.bukkit.craftbukkit", "net.minecraft.server");
            serverClazz = Class.forName(prefix + ".MinecraftServer");
        }
        Method getServer = serverClazz.getDeclaredMethod("getServer");
        Object server = getServer.invoke(null);
        Object connection = null;
        // Find the class that manages network IO
        for (Method m : serverClazz.getDeclaredMethods()) {
            if (m.getReturnType() != null) {
                // First is Spigot-mapped name, second is Mojang-mapped name which is implemented as future-proofing
                if (m.getReturnType().getSimpleName().equals("ServerConnection") || m.getReturnType().getSimpleName().equals("ServerConnectionListener")) {
                    if (m.getParameterTypes().length == 0) {
                        connection = m.invoke(server);
                    }
                }
            }
        }
        if (connection == null) {
            throw new RuntimeException("Unable to find ServerConnection class!");
        }

        // Find the channel that Minecraft uses to listen to connections
        ChannelFuture listeningChannel = null;
        for (Field field : connection.getClass().getDeclaredFields()) {
            if (field.getType() != List.class) {
                continue;
            }
            field.setAccessible(true);
            boolean rightList = ((ParameterizedType) field.getGenericType()).getActualTypeArguments()[0] == ChannelFuture.class;
            if (!rightList) continue;

            allServerChannels = (List<ChannelFuture>) field.get(connection);
            for (ChannelFuture o : allServerChannels) {
                listeningChannel = o;
                break;
            }
        }
        if (listeningChannel == null) {
            throw new RuntimeException("Unable to find listening channel!");
        }

        // Making this a function prevents childHandler from being treated as a non-final variable
        ChannelInitializer<Channel> childHandler = getChildHandler(bootstrap, listeningChannel);
        // This method is what initializes the connection in Java Edition, after Netty is all set.
        Method initChannel = childHandler.getClass().getDeclaredMethod("initChannel", Channel.class);
        initChannel.setAccessible(true);

        ChannelFuture channelFuture = (new ServerBootstrap()
                .channel(LocalServerChannelWrapper.class)
                .childHandler(new ChannelInitializer<Channel>() {
                    @Override
                    protected void initChannel(Channel ch) throws Exception {
                        initChannel.invoke(childHandler, ch);
                    }
                })
                // Set to MAX_PRIORITY as MultithreadEventLoopGroup#newDefaultThreadFactory which DefaultEventLoopGroup implements does by default
                .group(new DefaultEventLoopGroup(0, new DefaultThreadFactory("Geyser Spigot connection thread", Thread.MAX_PRIORITY)))
                .localAddress(LocalAddress.ANY))
                .bind()
                .syncUninterruptibly();
        // We don't need to add to the list, but plugins like ProtocolSupport and ProtocolLib that add to the main pipeline
        // will work when we add to the list.
        allServerChannels.add(channelFuture);
        this.localChannel = channelFuture;
        this.serverSocketAddress = channelFuture.channel().localAddress();

        workAroundWeirdBug(bootstrap);
    }

    @SuppressWarnings("unchecked")
    private ChannelInitializer<Channel> getChildHandler(GeyserBootstrap bootstrap, ChannelFuture listeningChannel) {
        List<String> names = listeningChannel.channel().pipeline().names();
        ChannelInitializer<Channel> childHandler = null;
        for (String name : names) {
            ChannelHandler handler = listeningChannel.channel().pipeline().get(name);
            try {
                Field childHandlerField = handler.getClass().getDeclaredField("childHandler");
                childHandlerField.setAccessible(true);
                childHandler = (ChannelInitializer<Channel>) childHandlerField.get(handler);
                // ViaVersion non-Paper-injector workaround so we aren't double-injecting
                if (isViaVersion && childHandler instanceof BukkitChannelInitializer) {
                    childHandler = ((BukkitChannelInitializer) childHandler).getOriginal();
                }
                break;
            } catch (Exception e) {
                if (bootstrap.getGeyserConfig().isDebugMode()) {
                    bootstrap.getGeyserLogger().debug("The handler " + name + " isn't a ChannelInitializer. THIS ERROR IS SAFE TO IGNORE!");
                    e.printStackTrace();
                }
            }
        }
        if (childHandler == null) {
            throw new RuntimeException();
        }
        return childHandler;
    }

    /**
     * Work around an odd bug where the first connection might not initialize all channel handlers on the main pipeline -
     * send a dummy status request down that acts as the first connection, then.
     * For the future, if someone wants to properly fix this - as of December 28, 2021, it happens on 1.16.5/1.17.1/1.18.1 EXCEPT Spigot 1.16.5
     */
    private void workAroundWeirdBug(GeyserBootstrap bootstrap) {
        LocalSession session = new LocalSession(bootstrap.getGeyserConfig().getRemote().getAddress(),
                bootstrap.getGeyserConfig().getRemote().getPort(), this.serverSocketAddress,
                InetAddress.getLoopbackAddress().getHostAddress(), new MinecraftProtocol());
        session.connect();
    }

    @Override
    public void shutdown() {
        if (this.allServerChannels != null) {
            this.allServerChannels.remove(this.localChannel);
            this.allServerChannels = null;
        }
        super.shutdown();
    }
}