Getting rid of socat

Signed-off-by: abhi <[email protected]>

Author: abhi

pkg/server/sandbox_portforward.go

@@ -17,11 +17,10 @@ limitations under the License.
 package server
 
 import (
-	"bytes"
 	"fmt"
 	"io"
-	"os/exec"
-	"strings"
+	"net"
+	"sync"
 
 	"github.com/containernetworking/plugins/pkg/ns"
 	"github.com/pkg/errors"
@@ -58,46 +57,31 @@ func (c *criService) portForward(id string, port int32, stream io.ReadWriteClose
 		return errors.Errorf("failed to find network namespace fo sandbox %q in store", id)
 	}
 
-	socat, err := exec.LookPath("socat")
-	if err != nil {
-		return errors.Wrap(err, "failed to find socat")
-	}
-
-	// Check following links for meaning of the options:
-	// * socat: https://linux.die.net/man/1/socat
-	args := []string{"-", fmt.Sprintf("TCP4:localhost:%d", port)}
-	logrus.Infof("Executing port forwarding command: %s %s", socat, strings.Join(args, " "))
 	err = s.NetNS.GetNs().Do(func(_ ns.NetNS) error {
-		cmd := exec.Command(socat, args...)
-		cmd.Stdout = stream
-
-		stderr := new(bytes.Buffer)
-		cmd.Stderr = stderr
-
-		// If we use Stdin, command.Run() won't return until the goroutine that's copying
-		// from stream finishes. Unfortunately, if you have a client like telnet connected
-		// via port forwarding, as long as the user's telnet client is connected to the user's
-		// local listener that port forwarding sets up, the telnet session never exits. This
-		// means that even if socat has finished running, command.Run() won't ever return
-		// (because the client still has the connection and stream open).
-		//
-		// The work around is to use StdinPipe(), as Wait() (called by Run()) closes the pipe
-		// when the command (socat) exits.
-		in, err := cmd.StdinPipe()
+		var wg sync.WaitGroup
+		client, err := net.Dial("tcp4", fmt.Sprintf("localhost:%d", port))
 		if err != nil {
-			return errors.Wrap(err, "failed to create stdin pipe")
+			return errors.Wrap(err, "failed to dial")
 		}
+		defer client.Close()
+
+		wg.Add(1)
 		go func() {
-			if _, err := io.Copy(in, stream); err != nil {
-				logrus.WithError(err).Errorf("Failed to copy port forward input for %q port %d", id, port)
+			if _, err := io.Copy(client, stream); err != nil {
+				logrus.WithError(err).Errorf("Failed to copy port forward input from %q port %d", id, port)
 			}
-			in.Close()
-			logrus.Debugf("Finish copy port forward input for %q port %d: %v", id, port)
+			wg.Done()
 		}()
+		wg.Add(1)
+		go func() {
+			if _, err := io.Copy(stream, client); err != nil {
+				logrus.WithError(err).Errorf("Failed to copy port forward output for %q port %d", id, port)
+			}
+			wg.Done()
+		}()
+		wg.Wait()
+		logrus.Infof("Finish copy port forward input for %q port %d: %v", id, port)
 
-		if err := cmd.Run(); err != nil {
-			return errors.Wrapf(err, "socat command returns error, stderr: %q", stderr.String())
-		}
 		return nil
 	})
 	if err != nil {