Merge pull request #16 from github/jg/ignore-pf-errs

port forwarder: ignore conn errors

port_forwarder.go

@@ -84,9 +84,7 @@ func (fwd *PortForwarder) Forward(ctx context.Context, conn io.ReadWriteCloser)
 	// Create buffered channel so that send doesn't get stuck after context cancellation.
 	errc := make(chan error, 1)
 	go func() {
-		if err := fwd.handleConnection(ctx, id, conn); err != nil {
-			errc <- err
-		}
+		errc <- fwd.handleConnection(ctx, id, conn)
 	}()
 	return awaitError(ctx, errc)
 }
@@ -129,6 +127,7 @@ func (fwd *PortForwarder) handleConnection(ctx context.Context, id channelID, co
 		}
 	}()
 
+	// bi-directional copy of data.
 	errs := make(chan error, 2)
 	copyConn := func(w io.Writer, r io.Reader) {
 		_, err := io.Copy(w, r)
@@ -137,13 +136,20 @@ func (fwd *PortForwarder) handleConnection(ctx context.Context, id channelID, co
 	go copyConn(conn, channel)
 	go copyConn(channel, conn)
 
-	// await result
-	for i := 0; i < 2; i++ {
-		if err := <-errs; err != nil && err != io.EOF {
-			return fmt.Errorf("tunnel connection: %v", err)
+	// Wait until context is cancelled or both copies are done.
+	// Discard errors from io.Copy; they should not cause (e.g.) ForwardToListener to fail.
+	// TODO: how can we proxy errors from Copy so that each peer can distinguish an error from a short file?
+	for i := 0; ; {
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		case <-errs:
+			i++
+			if i == 2 {
+				return nil
+			}
 		}
 	}
-	return nil
 }
 
 // safeClose reports the error (to *err) from closing the stream only