go-tunnel/control/control.go

package control

import (
	"context"
	"encoding/json"
	"net"
	"sync/atomic"
	"time"

	"github.com/pkg/errors"
	"github.com/xtaci/smux"
	"gitlab.com/wpetit/goweb/logger"
)

type Control struct {
	encoder    *json.Encoder
	decoder    *json.Decoder
	stream     *smux.Stream
	sess       *smux.Session
	proxyClock int64
}

func (c *Control) AuthRequest(credentials interface{}) (bool, error) {
	req := NewMessage(TypeAuthRequest, &AuthRequestPayload{
		Credentials: credentials,
	})

	res := NewMessage(TypeAuthResponse, nil)

	if err := c.reqRes(req, res); err != nil {
		return false, errors.WithStack(err)
	}

	authResPayload, ok := res.Payload.(*AuthResponsePayload)
	if !ok {
		return false, errors.WithStack(ErrUnexpectedMessage)
	}

	return authResPayload.Success, nil
}

func (c *Control) Proxy(ctx context.Context, network, address string) (net.Conn, error) {
	var (
		stream *smux.Stream
		err    error
	)

	requestID := atomic.AddInt64(&c.proxyClock, 1)

	req := NewMessage(TypeProxyRequest, &ProxyRequestPayload{
		RequestID: requestID,
		Network:   network,
		Address:   address,
	})

	ctx = logger.With(ctx, logger.F("network", network), logger.F("address", address))

	logger.Debug(ctx, "proxying")

	if err := c.Write(req); err != nil {
		return nil, errors.WithStack(err)
	}

	logger.Debug(ctx, "opening stream")

	stream, err = c.sess.AcceptStream()
	if err != nil {
		return nil, errors.WithStack(err)
	}

	go func() {
		<-ctx.Done()

		req := NewMessage(TypeCloseProxy, &CloseProxyPayload{
			RequestID: requestID,
		})

		if err := c.Write(req); err != nil {
			logger.Error(ctx, "error while closing proxy", logger.E(err))
		}

		logger.Debug(ctx, "closing proxy conn")
		stream.Close()
	}()

	return stream, nil
}

func (c *Control) Listen(ctx context.Context, handlers Handlers) error {
	for {
		logger.Debug(ctx, "reading next message")

		req, err := c.Read()
		if err != nil {
			return errors.WithStack(err)
		}

		go func() {
			subCtx := logger.With(ctx, logger.F("messageType", req.Type))

			handler, exists := handlers[req.Type]
			if !exists {
				logger.Error(subCtx, "no message handler registered")

				return
			}

			res, err := handler(subCtx, req)
			if err != nil {
				logger.Error(subCtx, "error while handling message", logger.E(err))

				return
			}

			if res == nil {
				return
			}

			if err := c.Write(res); err != nil {
				logger.Error(subCtx, "error while write message response", logger.E(err))

				return
			}
		}()
	}
}

func (c *Control) Read() (*Message, error) {
	message := &Message{}

	if err := c.read(message); err != nil {
		return nil, errors.WithStack(err)
	}

	return message, nil
}

func (c *Control) Write(m *Message) error {
	if err := c.write(m); err != nil {
		return errors.WithStack(err)
	}

	return nil
}

func (c *Control) reqRes(req *Message, res *Message) error {
	if err := c.write(req); err != nil {
		return errors.WithStack(err)
	}

	if err := c.read(res); err != nil {
		return errors.WithStack(err)
	}

	return nil
}

func (c *Control) read(m *Message) error {
	if err := c.decoder.Decode(m); err != nil {
		return errors.WithStack(err)
	}

	return nil
}

func (c *Control) write(m *Message) error {
	if err := c.stream.SetWriteDeadline(time.Now().Add(time.Second)); err != nil {
		return errors.WithStack(err)
	}

	if err := c.encoder.Encode(m); err != nil {
		return errors.WithStack(err)
	}

	return nil
}

func New(sess *smux.Session, controlStream *smux.Stream) *Control {
	return &Control{
		encoder: json.NewEncoder(controlStream),
		decoder: json.NewDecoder(controlStream),
		sess:    sess,
		stream:  controlStream,
	}
}