Fix a bunch of small issues, so that the proxy can establish a connection

This is still broken and has performance/bandwidth problems, which I will
fix very soon. For a first try, it's good enough.

src/main/java/io/minimum/minecraft/velocity/protocol/ProtocolUtils.java

@@ -9,33 +9,27 @@ public enum ProtocolUtils { ;
     private static final int DEFAULT_MAX_STRING_SIZE = 65536; // 64KiB
 
     public static int readVarInt(ByteBuf buf) {
-        int numRead = 0;
-        int result = 0;
-        byte read;
-        do {
-            read = buf.readByte();
-            int value = (read & 0b01111111);
-            result |= (value << (7 * numRead));
-
-            numRead++;
-            if (numRead > 5) {
-                throw new RuntimeException("VarInt is too big");
+        int i = 0;
+        int j = 0;
+        while (true) {
+            int k = buf.readByte();
+            i |= (k & 0x7F) << j++ * 7;
+            if (j > 5) throw new RuntimeException("VarInt too big");
+            if ((k & 0x80) != 128) break;
         }
-        } while ((read & 0b10000000) != 0);
-
-        return result;
+        return i;
     }
 
     public static void writeVarInt(ByteBuf buf, int value) {
-        do {
-            byte temp = (byte)(value & 0b01111111);
-            // Note: >>> means that the sign bit is shifted with the rest of the number rather than being left alone
-            value >>>= 7;
-            if (value != 0) {
-                temp |= 0b10000000;
+        while (true) {
+            if ((value & 0xFFFFFF80) == 0) {
+                buf.writeByte(value);
+                return;
+            }
+
+            buf.writeByte(value & 0x7F | 0x80);
+            value >>>= 7;
         }
-            buf.writeByte(temp);
-        } while (value != 0);
     }
 
     public static String readString(ByteBuf buf) {
@@ -44,7 +38,7 @@ public enum ProtocolUtils { ;
 
     public static String readString(ByteBuf buf, int cap) {
         int length = readVarInt(buf);
-        Preconditions.checkArgument(length < cap, "Bad string size (got %s, maximum is %s)", length, cap);
+        Preconditions.checkArgument(length <= cap, "Bad string size (got %s, maximum is %s)", length, cap);
         byte[] str = new byte[length];
         buf.readBytes(str);
         return new String(str, StandardCharsets.UTF_8);

src/main/java/io/minimum/minecraft/velocity/protocol/StateRegistry.java

@@ -32,7 +32,7 @@ public enum StateRegistry {
 
             TO_CLIENT.register(0x00, Disconnect.class, Disconnect::new);
             // Encryption Success will follow once Mojang auth/encryption is done
-            TO_CLIENT.register(0x02, ServerLoginSuccess.class, ServerLogin::new);
+            TO_CLIENT.register(0x02, ServerLoginSuccess.class, ServerLoginSuccess::new);
         }
     };
 

src/main/java/io/minimum/minecraft/velocity/protocol/netty/MinecraftDecoder.java

@@ -5,6 +5,7 @@ import io.minimum.minecraft.velocity.protocol.*;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufUtil;
 import io.netty.channel.ChannelHandlerContext;
+import io.netty.handler.codec.CorruptedFrameException;
 import io.netty.handler.codec.MessageToMessageDecoder;
 
 import java.util.List;
@@ -35,7 +36,12 @@ public class MinecraftDecoder extends MessageToMessageDecoder<ByteBuf> {
             msg.skipBytes(msg.readableBytes());
             out.add(new PacketWrapper(null, slice));
         } else {
+            try {
                 packet.decode(msg, direction, protocolVersion);
+            } catch (Exception e) {
+                throw new CorruptedFrameException("Error decoding " + packet.getClass() + " Direction " + direction
+                        + " Protocol " + protocolVersion + " State " + state + " ID " + Integer.toHexString(packetId), e);
+            }
             out.add(new PacketWrapper(packet, slice));
         }
     }

src/main/java/io/minimum/minecraft/velocity/protocol/packets/Handshake.java

@@ -55,17 +55,17 @@ public class Handshake implements MinecraftPacket {
 
     @Override
     public void decode(ByteBuf buf, ProtocolConstants.Direction direction, int protocolVersion) {
-        protocolVersion = ProtocolUtils.readVarInt(buf);
-        serverAddress = ProtocolUtils.readString(buf, 255);
-        port = buf.readUnsignedShort();
-        nextStatus = ProtocolUtils.readVarInt(buf);
+        this.protocolVersion = ProtocolUtils.readVarInt(buf);
+        this.serverAddress = ProtocolUtils.readString(buf, 255);
+        this.port = buf.readUnsignedShort();
+        this.nextStatus = ProtocolUtils.readVarInt(buf);
     }
 
     @Override
     public void encode(ByteBuf buf, ProtocolConstants.Direction direction, int protocolVersion) {
-        ProtocolUtils.writeVarInt(buf, protocolVersion);
-        ProtocolUtils.writeString(buf, serverAddress);
-        buf.writeShort(port);
-        ProtocolUtils.writeVarInt(buf, nextStatus);
+        ProtocolUtils.writeVarInt(buf, this.protocolVersion);
+        ProtocolUtils.writeString(buf, this.serverAddress);
+        buf.writeShort(this.port);
+        ProtocolUtils.writeVarInt(buf, this.nextStatus);
     }
 }

src/main/java/io/minimum/minecraft/velocity/proxy/ConnectedPlayer.java

@@ -37,11 +37,14 @@ public class ConnectedPlayer {
 
     public void handleConnectionException(Throwable throwable) {
         String error = "Exception: " + throwable.getClass().getName() + ": " + throwable.getMessage();
-
-        if (connectedServer == null) {
-            // The player isn't yet connected to a server - we should disconnect them.
         Disconnect disconnect = new Disconnect();
         disconnect.setReason(ComponentSerializers.JSON.serialize(TextComponent.of(error, TextColor.RED)));
+        handleConnectionException(disconnect);
+    }
+
+    public void handleConnectionException(Disconnect disconnect) {
+        if (connectedServer == null) {
+            // The player isn't yet connected to a server - we should disconnect them.
             connection.closeWith(disconnect);
         } else {
             // TODO

src/main/java/io/minimum/minecraft/velocity/proxy/InboundMinecraftConnection.java

@@ -1,10 +1,13 @@
 package io.minimum.minecraft.velocity.proxy;
 
 import com.google.common.base.Preconditions;
+import io.minimum.minecraft.velocity.data.ServerInfo;
+import io.minimum.minecraft.velocity.protocol.ProtocolConstants;
 import io.minimum.minecraft.velocity.protocol.StateRegistry;
 import io.minimum.minecraft.velocity.protocol.netty.MinecraftDecoder;
 import io.minimum.minecraft.velocity.protocol.netty.MinecraftEncoder;
 import io.minimum.minecraft.velocity.protocol.packets.Handshake;
+import io.minimum.minecraft.velocity.protocol.packets.ServerLoginSuccess;
 import io.minimum.minecraft.velocity.proxy.handler.HandshakeSessionHandler;
 import io.minimum.minecraft.velocity.proxy.handler.LoginSessionHandler;
 import io.minimum.minecraft.velocity.proxy.handler.StatusSessionHandler;
@@ -13,6 +16,7 @@ import io.netty.channel.ChannelFuture;
 import io.netty.channel.ChannelFutureListener;
 import io.netty.util.AttributeKey;
 
+import java.net.InetSocketAddress;
 import java.util.Optional;
 
 public class InboundMinecraftConnection {
@@ -82,7 +86,7 @@ public class InboundMinecraftConnection {
         Preconditions.checkState(!closed, "Connection is closed.");
     }
 
-    public void setStatus(StateRegistry state) {
+    private void setStatus(StateRegistry state) {
         Preconditions.checkNotNull(state, "state");
         this.state = state;
         channel.pipeline().get(MinecraftEncoder.class).setState(state);
@@ -100,4 +104,16 @@ public class InboundMinecraftConnection {
     public Optional<ConnectedPlayer> getConnectedPlayer() {
         return Optional.ofNullable(connectedPlayer);
     }
+
+    public int getProtocolVersion() {
+        return handshake == null ? ProtocolConstants.MINECRAFT_1_12 : handshake.getProtocolVersion();
+    }
+
+    public void initiatePlay(ServerLoginSuccess success) {
+        setStatus(StateRegistry.PLAY);
+        ConnectedPlayer player = new ConnectedPlayer(success.getUsername(), success.getUuid(), this);
+        ServerInfo info = new ServerInfo("test", new InetSocketAddress("127.0.0.1", 25565));
+        ServerConnection connection = new ServerConnection(info, player, VelocityServer.getServer());
+        connection.connect();
+    }
 }

src/main/java/io/minimum/minecraft/velocity/proxy/ServerConnection.java

@@ -2,7 +2,6 @@ package io.minimum.minecraft.velocity.proxy;
 
 import io.minimum.minecraft.velocity.protocol.MinecraftPacket;
 import io.minimum.minecraft.velocity.protocol.PacketWrapper;
-import io.minimum.minecraft.velocity.protocol.ProtocolConstants;
 import io.minimum.minecraft.velocity.protocol.StateRegistry;
 import io.minimum.minecraft.velocity.data.ServerInfo;
 import io.minimum.minecraft.velocity.protocol.netty.MinecraftDecoder;
@@ -13,9 +12,6 @@ import io.minimum.minecraft.velocity.protocol.packets.Handshake;
 import io.minimum.minecraft.velocity.protocol.packets.ServerLogin;
 import io.minimum.minecraft.velocity.protocol.packets.ServerLoginSuccess;
 import io.netty.channel.*;
-import net.kyori.text.serializer.ComponentSerializers;
-
-import java.io.IOException;
 
 public class ServerConnection {
     private Channel channel;
@@ -55,7 +51,7 @@ public class ServerConnection {
             // Initiate a handshake.
             Handshake handshake = new Handshake();
             handshake.setNextStatus(2); // login
-            handshake.setProtocolVersion(ProtocolConstants.MINECRAFT_1_12); // TODO: Expose client version
+            handshake.setProtocolVersion(proxyPlayer.getConnection().getProtocolVersion()); // TODO: Expose client version
             handshake.setServerAddress(info.getAddress().getHostString());
             handshake.setPort(info.getAddress().getPort());
             ctx.writeAndFlush(handshake, ctx.voidPromise());
@@ -77,6 +73,9 @@ public class ServerConnection {
                         case LOGIN:
                             onLogin(ctx, pw);
                             break;
+                        case PLAY:
+                            onPlay(ctx, pw);
+                            break;
                         default:
                             throw new UnsupportedOperationException("Unsupported state " + registry);
                     }
@@ -86,16 +85,23 @@ public class ServerConnection {
             }
         }
 
+        private void onPlay(ChannelHandlerContext ctx, PacketWrapper pw) {
+            proxyPlayer.getConnection().write(pw.getBuffer().retain());
+        }
+
         private void onLogin(ChannelHandlerContext ctx, PacketWrapper wrapper) {
+            //System.out.println("FROM PROXIED SERVER -> " + wrapper.getPacket() + " / " + ByteBufUtil.hexDump(wrapper.getBuffer()));
             MinecraftPacket packet = wrapper.getPacket();
             if (packet instanceof Disconnect) {
                 Disconnect disconnect = (Disconnect) packet;
                 ctx.close();
-                proxyPlayer.handleConnectionException(new IOException("Disconnected from target: " + jsonToPlain(disconnect.getReason())));
+                proxyPlayer.handleConnectionException(disconnect);
             }
 
             if (packet instanceof ServerLoginSuccess) {
-                System.out.println("got it");
+                // the player has been logged on.
+                System.out.println("Player connected to remote server");
+                setRegistry(StateRegistry.PLAY);
             }
         }
     }
@@ -105,10 +111,4 @@ public class ServerConnection {
         this.channel.pipeline().get(MinecraftEncoder.class).setState(registry);
         this.channel.pipeline().get(MinecraftDecoder.class).setState(registry);
     }
-
-    private static String jsonToPlain(String j) {
-        return ComponentSerializers.LEGACY.serialize(
-                ComponentSerializers.JSON.deserialize(j)
-        ).replaceAll("\\u00A7[a-z0-9]", "");
-    }
 }

src/main/java/io/minimum/minecraft/velocity/proxy/handler/LoginSessionHandler.java

@@ -3,7 +3,6 @@ package io.minimum.minecraft.velocity.proxy.handler;
 import com.google.common.base.Preconditions;
 import io.minimum.minecraft.velocity.data.ServerInfo;
 import io.minimum.minecraft.velocity.protocol.MinecraftPacket;
-import io.minimum.minecraft.velocity.protocol.StateRegistry;
 import io.minimum.minecraft.velocity.protocol.packets.ServerLogin;
 import io.minimum.minecraft.velocity.protocol.packets.ServerLoginSuccess;
 import io.minimum.minecraft.velocity.proxy.*;
@@ -30,13 +29,7 @@ public class LoginSessionHandler implements MinecraftSessionHandler {
         success.setUuid(generateOfflinePlayerUuid(username));
         connection.write(success);
 
-        connection.setStatus(StateRegistry.PLAY);
-
-        ConnectedPlayer player = new ConnectedPlayer(username, generateOfflinePlayerUuid(username), connection);
-
-        ServerInfo info = new ServerInfo("test", new InetSocketAddress("127.0.0.1", 25565));
-        ServerConnection connection = new ServerConnection(info, player, VelocityServer.getServer());
-        connection.connect();
+        connection.initiatePlay(success);
     }
 
     private static UUID generateOfflinePlayerUuid(String username) {