Add PROXY protocol support (#108)

proxy/build.gradle

@@ -29,6 +29,7 @@ dependencies {
     compile project(':velocity-native')
 
     compile "io.netty:netty-codec:${nettyVersion}"
+    compile "io.netty:netty-codec-haproxy:${nettyVersion}"
     compile "io.netty:netty-codec-http:${nettyVersion}"
     compile "io.netty:netty-handler:${nettyVersion}"
     compile "io.netty:netty-transport-native-epoll:${nettyVersion}"

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

@@ -280,6 +280,10 @@ public class VelocityConfiguration extends AnnotatedConfig implements ProxyConfi
         return advanced.getReadTimeout();
     }
 
+    public boolean isProxyProtocol() {
+        return advanced.isProxyProtocol();
+    }
+
     @Override
     public String toString() {
         return MoreObjects.toStringHelper(this)
@@ -433,6 +437,9 @@ public class VelocityConfiguration extends AnnotatedConfig implements ProxyConfi
         @Comment({"Specify a read timeout for connections here. The default is 30 seconds."})
         @ConfigKey("read-timeout")
         private int readTimeout = 30000;
+        @Comment("Enables compatibility with HAProxy.")
+        @ConfigKey("proxy-protocol")
+        private boolean proxyProtocol = false;
 
         private Advanced() {
         }
@@ -444,6 +451,7 @@ public class VelocityConfiguration extends AnnotatedConfig implements ProxyConfi
                 this.loginRatelimit = toml.getLong("login-ratelimit", 3000L).intValue();
                 this.connectionTimeout = toml.getLong("connection-timeout", 5000L).intValue();
                 this.readTimeout = toml.getLong("read-timeout", 30000L).intValue();
+                this.proxyProtocol = toml.getBoolean("proxy-protocol", false);
             }
         }
 
@@ -467,6 +475,10 @@ public class VelocityConfiguration extends AnnotatedConfig implements ProxyConfi
             return readTimeout;
         }
 
+        public boolean isProxyProtocol() {
+            return proxyProtocol;
+        }
+
         @Override
         public String toString() {
             return "Advanced{" +
@@ -475,6 +487,7 @@ public class VelocityConfiguration extends AnnotatedConfig implements ProxyConfi
                     ", loginRatelimit=" + loginRatelimit +
                     ", connectionTimeout=" + connectionTimeout +
                     ", readTimeout=" + readTimeout +
+                    ", proxyProtocol=" + proxyProtocol +
                     '}';
         }
     }

proxy/src/main/java/com/velocitypowered/proxy/connection/MinecraftConnection.java

@@ -12,12 +12,15 @@ import com.velocitypowered.proxy.protocol.StateRegistry;
 import com.velocitypowered.proxy.protocol.netty.*;
 import io.netty.buffer.ByteBuf;
 import io.netty.channel.*;
+import io.netty.handler.codec.haproxy.HAProxyMessage;
 import io.netty.util.ReferenceCountUtil;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
 import javax.crypto.SecretKey;
 import javax.crypto.spec.SecretKeySpec;
+import java.net.InetSocketAddress;
+import java.net.SocketAddress;
 import java.security.GeneralSecurityException;
 
 import static com.velocitypowered.proxy.network.Connections.*;
@@ -30,6 +33,7 @@ public class MinecraftConnection extends ChannelInboundHandlerAdapter {
     private static final Logger logger = LogManager.getLogger(MinecraftConnection.class);
 
     private final Channel channel;
+    private SocketAddress remoteAddress;
     private StateRegistry state;
     private MinecraftSessionHandler sessionHandler;
     private int protocolVersion;
@@ -40,6 +44,7 @@ public class MinecraftConnection extends ChannelInboundHandlerAdapter {
 
     public MinecraftConnection(Channel channel, VelocityServer server) {
         this.channel = channel;
+        this.remoteAddress = channel.remoteAddress();
         this.server = server;
         this.state = StateRegistry.HANDSHAKE;
     }
@@ -77,6 +82,13 @@ public class MinecraftConnection extends ChannelInboundHandlerAdapter {
             if (!pkt.handle(sessionHandler)) {
                 sessionHandler.handleGeneric((MinecraftPacket) msg);
             }
+        } else if (msg instanceof HAProxyMessage) {
+            if (sessionHandler.beforeHandle()) {
+                return;
+            }
+
+            HAProxyMessage proxyMessage = (HAProxyMessage) msg;
+            this.remoteAddress = new InetSocketAddress(proxyMessage.sourceAddress(), proxyMessage.sourcePort());
         } else if (msg instanceof ByteBuf) {
             try {
                 if (sessionHandler.beforeHandle()) {
@@ -153,6 +165,10 @@ public class MinecraftConnection extends ChannelInboundHandlerAdapter {
         return !channel.isActive();
     }
 
+    public SocketAddress getRemoteAddress() {
+        return remoteAddress;
+    }
+
     public StateRegistry getState() {
         return state;
     }

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

@@ -122,7 +122,7 @@ public class ConnectedPlayer implements MinecraftConnectionAssociation, Player {
 
     @Override
     public InetSocketAddress getRemoteAddress() {
-        return (InetSocketAddress) connection.getChannel().remoteAddress();
+        return (InetSocketAddress) connection.getRemoteAddress();
     }
 
     @Override

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

@@ -77,7 +77,7 @@ public class HandshakeSessionHandler implements MinecraftSessionHandler {
                     return true;
                 }
 
-                InetAddress address = ((InetSocketAddress) connection.getChannel().remoteAddress()).getAddress();
+                InetAddress address = ((InetSocketAddress) connection.getRemoteAddress()).getAddress();
                 if (!server.getIpAttemptLimiter().attempt(address)) {
                     connection.closeWith(Disconnect.create(TextComponent.of("You are logging in too fast, try again later.")));
                     return true;
@@ -129,7 +129,7 @@ public class HandshakeSessionHandler implements MinecraftSessionHandler {
 
         @Override
         public InetSocketAddress getRemoteAddress() {
-            return (InetSocketAddress) connection.getChannel().remoteAddress();
+            return (InetSocketAddress) connection.getRemoteAddress();
         }
 
         @Override

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

@@ -18,7 +18,7 @@ class InitialInboundConnection implements InboundConnection {
 
     @Override
     public InetSocketAddress getRemoteAddress() {
-        return (InetSocketAddress) connection.getChannel().remoteAddress();
+        return (InetSocketAddress) connection.getRemoteAddress();
     }
 
     @Override

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

@@ -101,7 +101,7 @@ public class LoginSessionHandler implements MinecraftSessionHandler {
             byte[] decryptedSharedSecret = EncryptionUtils.decryptRsa(serverKeyPair, packet.getSharedSecret());
             String serverId = EncryptionUtils.generateServerId(decryptedSharedSecret, serverKeyPair.getPublic());
 
-            String playerIp = ((InetSocketAddress) inbound.getChannel().remoteAddress()).getHostString();
+            String playerIp = ((InetSocketAddress) inbound.getRemoteAddress()).getHostString();
             server.getHttpClient()
                     .get(new URL(String.format(MOJANG_SERVER_AUTH_URL, login.getUsername(), serverId, playerIp)))
                     .thenAcceptAsync(profileResponse -> {

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

@@ -20,6 +20,7 @@ import io.netty.channel.socket.SocketChannel;
 import io.netty.channel.socket.nio.NioDatagramChannel;
 import io.netty.channel.socket.nio.NioServerSocketChannel;
 import io.netty.channel.socket.nio.NioSocketChannel;
+import io.netty.handler.codec.haproxy.HAProxyMessageDecoder;
 import io.netty.handler.timeout.ReadTimeoutHandler;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -77,6 +78,10 @@ public final class ConnectionManager {
                         connection.setState(StateRegistry.HANDSHAKE);
                         connection.setSessionHandler(new HandshakeSessionHandler(connection, server));
                         ch.pipeline().addLast(Connections.HANDLER, connection);
+                        
+                        if (server.getConfiguration().isProxyProtocol()) {
+                            ch.pipeline().addFirst(new HAProxyMessageDecoder());
+                        }
                     }
                 })
                 .childOption(ChannelOption.TCP_NODELAY, true)