Expose ChannelInitializerHolder in protocol module

protocol/src/main/java/net/md_5/bungee/protocol/channel/BungeeChannelInitializer.java

@@ -0,0 +1,84 @@
+package net.md_5.bungee.protocol.channel;
+
+import com.google.common.base.Preconditions;
+import io.netty.channel.Channel;
+import io.netty.channel.ChannelInitializer;
+import lombok.AccessLevel;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+/*
+ * This class holds all minecraft related channel initializers. BungeeCord will set these values
+ * on startup, and they can be used by third party plugins to modify the channel pipeline.
+ *
+ * Please note that this API is unsafe and doesn't provide any guarantees about the stability of the
+ * channel pipeline. Use at your own risk.
+ */
+@NoArgsConstructor(access = AccessLevel.PRIVATE)
+public abstract class BungeeChannelInitializer
+{
+    /**
+     * Holds the channel initializer for incoming connections
+     */
+    @Getter
+    private static BungeeChannelInitializer frontendHolder;
+    /**
+     * Holds the channel initializer for the connection to the backend server
+     */
+    @Getter
+    private static BungeeChannelInitializer backendHolder;
+    /**
+     * Holds the channel initializer for server info requests to the backend server
+     */
+    @Getter
+    private static BungeeChannelInitializer serverInfoHolder;
+
+    public abstract ChannelAcceptor getChannelAcceptor();
+    public abstract ChannelInitializer<Channel> getChannelInitializer();
+
+    /**
+     * Creates a new instance of BungeeChannelInitializer
+     *
+     * @param acceptor the {@link ChannelAcceptor} that will accept the channel and initializer the pipeline
+     * @return {@link BungeeChannelInitializer} containing a cached {@link ChannelInitializer} that will call the acceptor
+     */
+    public static BungeeChannelInitializer create(ChannelAcceptor acceptor)
+    {
+        return new BungeeChannelInitializer()
+        {
+            @Getter
+            private final ChannelAcceptor channelAcceptor = acceptor;
+
+            @Getter // cache the ChannelInitializer
+            private final ChannelInitializer<Channel> channelInitializer = new ChannelInitializer<Channel>()
+            {
+                @Override
+                protected void initChannel(Channel channel) throws Exception
+                {
+                    if ( !getChannelAcceptor().accept( channel ) )
+                    {
+                        channel.close();
+                    }
+                }
+            };
+        };
+    }
+
+    public static void setFrontendHolder(BungeeChannelInitializer channelInitializer)
+    {
+        Preconditions.checkNotNull( channelInitializer, "channelInitializer" );
+        frontendHolder = channelInitializer;
+    }
+
+    public static void setBackendHolder(BungeeChannelInitializer channelInitializer)
+    {
+        Preconditions.checkNotNull( channelInitializer, "channelInitializer" );
+        backendHolder = channelInitializer;
+    }
+
+    public static void setServerInfoHolder(BungeeChannelInitializer channelInitializer)
+    {
+        Preconditions.checkNotNull( channelInitializer, "channelInitializer" );
+        serverInfoHolder = channelInitializer;
+    }
+}

protocol/src/main/java/net/md_5/bungee/protocol/channel/ChannelAcceptor.java

@@ -0,0 +1,15 @@
+package net.md_5.bungee.protocol.channel;
+
+import io.netty.channel.Channel;
+
+@FunctionalInterface
+public interface ChannelAcceptor
+{
+    /**
+     * Inside this method the pipeline should be initialized.
+     *
+     * @param channel the channel to be accepted and initialized
+     * @return if the channel was accepted
+     */
+    boolean accept(Channel channel);
+}

proxy/src/main/java/net/md_5/bungee/BungeeCord.java

@@ -95,6 +95,7 @@
 import net.md_5.bungee.netty.PipelineUtils;
 import net.md_5.bungee.protocol.DefinedPacket;
 import net.md_5.bungee.protocol.ProtocolConstants;
+import net.md_5.bungee.protocol.channel.BungeeChannelInitializer;
 import net.md_5.bungee.protocol.packet.PluginMessage;
 import net.md_5.bungee.query.RemoteQuery;
 import net.md_5.bungee.scheduler.BungeeScheduler;
@@ -360,7 +361,7 @@ public void operationComplete(ChannelFuture future) throws Exception
                     .channel( PipelineUtils.getServerChannel( info.getSocketAddress() ) )
                     .option( ChannelOption.SO_REUSEADDR, true ) // TODO: Move this elsewhere!
                     .childAttr( PipelineUtils.LISTENER, info )
-                    .childHandler( PipelineUtils.SERVER_CHILD )
+                    .childHandler( BungeeChannelInitializer.getFrontendHolder().getChannelInitializer() )
                     .group( eventLoops )
                     .localAddress( info.getSocketAddress() )
                     .bind().addListener( listener );

proxy/src/main/java/net/md_5/bungee/BungeeServerInfo.java

@@ -29,6 +29,7 @@
 import net.md_5.bungee.netty.HandlerBoss;
 import net.md_5.bungee.netty.PipelineUtils;
 import net.md_5.bungee.protocol.DefinedPacket;
+import net.md_5.bungee.protocol.channel.BungeeChannelInitializer;
 import net.md_5.bungee.protocol.packet.PluginMessage;
 
 // CHECKSTYLE:OFF
@@ -186,7 +187,7 @@ public void operationComplete(ChannelFuture future) throws Exception
         new Bootstrap()
                 .channel( PipelineUtils.getChannel( socketAddress ) )
                 .group( BungeeCord.getInstance().eventLoops )
-                .handler( PipelineUtils.BASE_SERVERSIDE )
+                .handler( BungeeChannelInitializer.getServerInfoHolder().getChannelInitializer() )
                 .option( ChannelOption.CONNECT_TIMEOUT_MILLIS, BungeeCord.getInstance().getConfig().getRemotePingTimeout() )
                 .remoteAddress( socketAddress )
                 .connect()

proxy/src/main/java/net/md_5/bungee/ServerConnector.java

@@ -104,6 +104,7 @@ public void exception(Throwable t) throws Exception
     @Override
     public void connected(ChannelWrapper channel) throws Exception
     {
+        channel.setVersion( user.getPendingConnection().getVersion() );
         this.ch = channel;
 
         this.handshakeHandler = new ForgeServerHandler( user, ch, target );

proxy/src/main/java/net/md_5/bungee/UserConnection.java

@@ -3,10 +3,8 @@
 import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableMap;
 import io.netty.bootstrap.Bootstrap;
-import io.netty.channel.Channel;
 import io.netty.channel.ChannelFuture;
 import io.netty.channel.ChannelFutureListener;
-import io.netty.channel.ChannelInitializer;
 import io.netty.channel.ChannelOption;
 import io.netty.util.internal.PlatformDependent;
 import java.net.InetSocketAddress;
@@ -50,11 +48,10 @@
 import net.md_5.bungee.netty.HandlerBoss;
 import net.md_5.bungee.netty.PipelineUtils;
 import net.md_5.bungee.protocol.DefinedPacket;
-import net.md_5.bungee.protocol.MinecraftDecoder;
-import net.md_5.bungee.protocol.MinecraftEncoder;
 import net.md_5.bungee.protocol.PacketWrapper;
 import net.md_5.bungee.protocol.Protocol;
 import net.md_5.bungee.protocol.ProtocolConstants;
+import net.md_5.bungee.protocol.channel.BungeeChannelInitializer;
 import net.md_5.bungee.protocol.packet.Chat;
 import net.md_5.bungee.protocol.packet.ClientSettings;
 import net.md_5.bungee.protocol.packet.Kick;
@@ -362,17 +359,6 @@ private void connect0(final ServerConnectRequest request)
 
         pendingConnects.add( target );
 
-        ChannelInitializer initializer = new ChannelInitializer()
-        {
-            @Override
-            protected void initChannel(Channel ch) throws Exception
-            {
-                PipelineUtils.BASE_SERVERSIDE.initChannel( ch );
-                ch.pipeline().addAfter( PipelineUtils.FRAME_DECODER, PipelineUtils.PACKET_DECODER, new MinecraftDecoder( Protocol.HANDSHAKE, false, getPendingConnection().getVersion() ) );
-                ch.pipeline().addAfter( PipelineUtils.FRAME_PREPENDER, PipelineUtils.PACKET_ENCODER, new MinecraftEncoder( Protocol.HANDSHAKE, false, getPendingConnection().getVersion() ) );
-                ch.pipeline().get( HandlerBoss.class ).setHandler( new ServerConnector( bungee, UserConnection.this, target ) );
-            }
-        };
         ChannelFutureListener listener = new ChannelFutureListener()
         {
             @Override
@@ -401,13 +387,16 @@ public void operationComplete(ChannelFuture future) throws Exception
                     {
                         sendMessage( bungee.getTranslation( "fallback_kick", connectionFailMessage( future.cause() ) ) );
                     }
+                } else
+                {
+                    future.channel().pipeline().get( HandlerBoss.class ).setHandler( new ServerConnector( bungee, UserConnection.this, target ) );
                 }
             }
         };
         Bootstrap b = new Bootstrap()
                 .channel( PipelineUtils.getChannel( target.getAddress() ) )
                 .group( ch.getHandle().eventLoop() )
-                .handler( initializer )
+                .handler( BungeeChannelInitializer.getBackendHolder().getChannelInitializer() )
                 .option( ChannelOption.CONNECT_TIMEOUT_MILLIS, request.getConnectTimeout() )
                 .remoteAddress( target.getAddress() );
         // Windows is bugged, multi homed users will just have to live with random connecting IPs

proxy/src/main/java/net/md_5/bungee/netty/PipelineUtils.java

@@ -4,7 +4,6 @@
 import io.netty.buffer.PooledByteBufAllocator;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelException;
-import io.netty.channel.ChannelInitializer;
 import io.netty.channel.ChannelOption;
 import io.netty.channel.EventLoopGroup;
 import io.netty.channel.ServerChannel;
@@ -51,33 +50,33 @@
 import net.md_5.bungee.protocol.Varint21FrameDecoder;
 import net.md_5.bungee.protocol.Varint21LengthFieldExtraBufPrepender;
 import net.md_5.bungee.protocol.Varint21LengthFieldPrepender;
+import net.md_5.bungee.protocol.channel.BungeeChannelInitializer;
+import net.md_5.bungee.protocol.channel.ChannelAcceptor;
 
 public class PipelineUtils
 {
 
     public static final AttributeKey<ListenerInfo> LISTENER = AttributeKey.valueOf( "ListerInfo" );
-    public static final ChannelInitializer<Channel> SERVER_CHILD = new ChannelInitializer<Channel>()
+
+    private static void setChannelInitializerHolders()
     {
-        @Override
-        protected void initChannel(Channel ch) throws Exception
+        BungeeChannelInitializer.setFrontendHolder( BungeeChannelInitializer.create( ch ->
         {
             SocketAddress remoteAddress = ( ch.remoteAddress() == null ) ? ch.parent().localAddress() : ch.remoteAddress();
 
             if ( BungeeCord.getInstance().getConnectionThrottle() != null && BungeeCord.getInstance().getConnectionThrottle().throttle( remoteAddress ) )
             {
-                ch.close();
-                return;
+                return false;
             }
 
             ListenerInfo listener = ch.attr( LISTENER ).get();
 
             if ( BungeeCord.getInstance().getPluginManager().callEvent( new ClientConnectEvent( remoteAddress, listener ) ).isCancelled() )
             {
-                ch.close();
-                return;
+                return false;
             }
 
-            BASE.initChannel( ch );
+            BASE.accept( ch );
             ch.pipeline().addBefore( FRAME_DECODER, LEGACY_DECODER, new LegacyDecoder() );
             ch.pipeline().addAfter( FRAME_DECODER, PACKET_DECODER, new MinecraftDecoder( Protocol.HANDSHAKE, true, ProxyServer.getInstance().getProtocolVersion() ) );
             ch.pipeline().addAfter( FRAME_PREPENDER, PACKET_ENCODER, new MinecraftEncoder( Protocol.HANDSHAKE, true, ProxyServer.getInstance().getProtocolVersion() ) );
@@ -88,10 +87,22 @@ protected void initChannel(Channel ch) throws Exception
             {
                 ch.pipeline().addFirst( new HAProxyMessageDecoder() );
             }
-        }
-    };
-    public static final Base BASE = new Base( false );
-    public static final Base BASE_SERVERSIDE = new Base( true );
+            return true;
+        } ) );
+
+        BungeeChannelInitializer.setBackendHolder( BungeeChannelInitializer.create( ch ->
+        {
+            PipelineUtils.BASE_SERVERSIDE.accept( ch );
+            ch.pipeline().addAfter( PipelineUtils.FRAME_DECODER, PipelineUtils.PACKET_DECODER, new MinecraftDecoder( Protocol.HANDSHAKE, false, ProxyServer.getInstance().getProtocolVersion() ) );
+            ch.pipeline().addAfter( PipelineUtils.FRAME_PREPENDER, PipelineUtils.PACKET_ENCODER, new MinecraftEncoder( Protocol.HANDSHAKE, false, ProxyServer.getInstance().getProtocolVersion() ) );
+            return true;
+        } ) );
+
+        BungeeChannelInitializer.setServerInfoHolder( BungeeChannelInitializer.create( BASE_SERVERSIDE ) );
+    }
+
+    private static final ChannelAcceptor BASE = new Base( false );
+    private static final ChannelAcceptor BASE_SERVERSIDE = new Base( true );
     private static final KickStringWriter legacyKicker = new KickStringWriter();
     private static final Varint21LengthFieldExtraBufPrepender serverFramePrepender = new Varint21LengthFieldExtraBufPrepender();
     public static final String TIMEOUT_HANDLER = "timeout";
@@ -137,6 +148,8 @@ protected void initChannel(Channel ch) throws Exception
                 }
             }
         }
+
+        setChannelInitializerHolders();
     }
 
     public static EventLoopGroup newEventLoopGroup(int threads, ThreadFactory factory)
@@ -179,13 +192,13 @@ public static Class<? extends DatagramChannel> getDatagramChannel()
 
     @NoArgsConstructor // for backwards compatibility
     @AllArgsConstructor
-    public static final class Base extends ChannelInitializer<Channel>
+    public static final class Base implements ChannelAcceptor
     {
 
         private boolean toServer = false;
 
         @Override
-        public void initChannel(Channel ch) throws Exception
+        public boolean accept(Channel ch)
         {
             try
             {
@@ -204,6 +217,7 @@ public void initChannel(Channel ch) throws Exception
             ch.pipeline().addLast( FRAME_PREPENDER, ( toServer ) ? serverFramePrepender : new Varint21LengthFieldPrepender() );
 
             ch.pipeline().addLast( BOSS_HANDLER, new HandlerBoss() );
+            return true;
         }
     }
 }