TUN-7545: Add support for full bidirectionally streaming with close signal propagation

stream/stream.go

@@ -15,6 +15,36 @@ import (
 	"github.com/cloudflare/cloudflared/cfio"
 )
 
+type Stream interface {
+	Reader
+	WriterCloser
+}
+
+type Reader interface {
+	io.Reader
+}
+
+type WriterCloser interface {
+	io.Writer
+	WriteCloser
+}
+
+type WriteCloser interface {
+	CloseWrite() error
+}
+
+type nopCloseWriterAdapter struct {
+	io.ReadWriter
+}
+
+func NopCloseWriterAdapter(stream io.ReadWriter) *nopCloseWriterAdapter {
+	return &nopCloseWriterAdapter{stream}
+}
+
+func (n *nopCloseWriterAdapter) CloseWrite() error {
+	return nil
+}
+
 type bidirectionalStreamStatus struct {
 	doneChan chan struct{}
 	anyDone  uint32
@@ -32,8 +62,24 @@ func (s *bidirectionalStreamStatus) markUniStreamDone() {
 	s.doneChan <- struct{}{}
 }
 
-func (s *bidirectionalStreamStatus) waitAnyDone() {
+func (s *bidirectionalStreamStatus) wait(maxWaitForSecondStream time.Duration) error {
 	<-s.doneChan
+
+	// Only wait for second stream to finish if maxWait is greater than zero
+	if maxWaitForSecondStream > 0 {
+
+		timer := time.NewTimer(maxWaitForSecondStream)
+		defer timer.Stop()
+
+		select {
+		case <-timer.C:
+			return fmt.Errorf("timeout waiting for second stream to finish")
+		case <-s.doneChan:
+			return nil
+		}
+	}
+
+	return nil
 }
 func (s *bidirectionalStreamStatus) isAnyDone() bool {
 	return atomic.LoadUint32(&s.anyDone) > 0
@@ -41,16 +87,28 @@ func (s *bidirectionalStreamStatus) isAnyDone() bool {
 
 // Pipe copies copy data to & from provided io.ReadWriters.
 func Pipe(tunnelConn, originConn io.ReadWriter, log *zerolog.Logger) {
-	status := newBiStreamStatus()
-
-	go unidirectionalStream(tunnelConn, originConn, "origin->tunnel", status, log)
-	go unidirectionalStream(originConn, tunnelConn, "tunnel->origin", status, log)
-
-	// If one side is done, we are done.
-	status.waitAnyDone()
+	PipeBidirectional(NopCloseWriterAdapter(tunnelConn), NopCloseWriterAdapter(originConn), 0, log)
 }
 
-func unidirectionalStream(dst io.Writer, src io.Reader, dir string, status *bidirectionalStreamStatus, log *zerolog.Logger) {
+// PipeBidirectional copies data two BidirectionStreams. It is a special case of Pipe where it receives a concept that allows for Read and Write side to be closed independently.
+// The main difference is that when piping data from a reader to a writer, if EOF is read, then this implementation propagates the EOF signal to the destination/writer by closing the write side of the
+// Bidirectional Stream.
+// Finally, depending on once EOF is ready from one of the provided streams, the other direction of streaming data will have a configured time period to also finish, otherwise,
+// the method will return immediately  with a timeout error. It is however, the responsability of the caller to close the associated streams in both ends in order to free all the resources/go-routines.
+func PipeBidirectional(downstream, upstream Stream, maxWaitForSecondStream time.Duration, log *zerolog.Logger) error {
+	status := newBiStreamStatus()
+
+	go unidirectionalStream(downstream, upstream, "upstream->downstream", status, log)
+	go unidirectionalStream(upstream, downstream, "downstream->upstream", status, log)
+
+	if err := status.wait(maxWaitForSecondStream); err != nil {
+		return errors.Wrap(err, "unable to wait for both streams while proxying")
+	}
+
+	return nil
+}
+
+func unidirectionalStream(dst WriterCloser, src Reader, dir string, status *bidirectionalStreamStatus, log *zerolog.Logger) {
 	defer func() {
 		// The bidirectional streaming spawns 2 goroutines to stream each direction.
 		// If any ends, the callstack returns, meaning the Tunnel request/stream (depending on http2 vs quic) will
@@ -71,6 +129,8 @@ func unidirectionalStream(dst io.Writer, src io.Reader, dir string, status *bidi
 		}
 	}()
 
+	defer dst.CloseWrite()
+
 	_, err := copyData(dst, src, dir)
 	if err != nil {
 		log.Debug().Msgf("%s copy: %v", dir, err)