This adds stdio as a way to communicate between gvproxy and vm mainly…

… for use

with WSL2, although it should work for other cases as well.

When network connections between WSL2 and the Windows host are blocked, stdio
is the only reliable way to establish a channel between WSL2 and the Windows
host. Hyper-V socket for WSL2 is a possibility, but it requires undocumented
APIs and admin privileges.

Signed-off-by: Keiichi Shimamura <sakai135@users.noreply.github.com>

cmd/gvproxy/main.go

@@ -17,6 +17,7 @@ import (
 	"syscall"
 	"time"
 
+	"github.com/containers/gvisor-tap-vsock/pkg/net/stdio"
 	"github.com/containers/gvisor-tap-vsock/pkg/sshclient"
 	"github.com/containers/gvisor-tap-vsock/pkg/transport"
 	"github.com/containers/gvisor-tap-vsock/pkg/types"
@@ -34,6 +35,7 @@ var (
 	vpnkitSocket    string
 	qemuSocket      string
 	bessSocket      string
+	stdioSocket     string
 	forwardSocket   arrayFlags
 	forwardDest     arrayFlags
 	forwardUser     arrayFlags
@@ -56,12 +58,14 @@ func main() {
 	flag.StringVar(&vpnkitSocket, "listen-vpnkit", "", "VPNKit socket to be used by Hyperkit")
 	flag.StringVar(&qemuSocket, "listen-qemu", "", "Socket to be used by Qemu")
 	flag.StringVar(&bessSocket, "listen-bess", "", "unixpacket socket to be used by Bess-compatible applications")
+	flag.StringVar(&stdioSocket, "listen-stdio", "", "accept stdio pipe")
 	flag.Var(&forwardSocket, "forward-sock", "Forwards a unix socket to the guest virtual machine over SSH")
 	flag.Var(&forwardDest, "forward-dest", "Forwards a unix socket to the guest virtual machine over SSH")
 	flag.Var(&forwardUser, "forward-user", "SSH user to use for unix socket forward")
 	flag.Var(&forwardIdentify, "forward-identity", "Path to SSH identity key for forwarding")
 	flag.StringVar(&pidFile, "pid-file", "", "Generate a file with the PID in it")
 	flag.Parse()
+
 	ctx, cancel := context.WithCancel(context.Background())
 	// Make this the last defer statement in the stack
 	defer os.Exit(exitCode)
@@ -275,7 +279,7 @@ func run(ctx context.Context, g *errgroup.Group, configuration *types.Configurat
 			for {
 				select {
 				case <-time.After(5 * time.Second):
-					fmt.Printf("%v sent to the VM, %v received from the VM\n", humanize.Bytes(vn.BytesSent()), humanize.Bytes(vn.BytesReceived()))
+					log.Debugf("%v sent to the VM, %v received from the VM\n", humanize.Bytes(vn.BytesSent()), humanize.Bytes(vn.BytesReceived()))
 				case <-ctx.Done():
 					break debugLog
 				}
@@ -359,6 +363,13 @@ func run(ctx context.Context, g *errgroup.Group, configuration *types.Configurat
 		})
 	}
 
+	if stdioSocket != "" {
+		g.Go(func() error {
+			conn := stdio.GetStdioConn()
+			return vn.AcceptQemu(ctx, conn)
+		})
+	}
+
 	for i := 0; i < len(forwardSocket); i++ {
 		var (
 			src *url.URL

cmd/vm/main_linux.go

@@ -79,12 +79,14 @@ func run() error {
 	}
 	defer conn.Close()
 
-	req, err := http.NewRequest("POST", path, nil)
-	if err != nil {
-		return err
-	}
-	if err := req.Write(conn); err != nil {
-		return err
+	if path != "" {
+		req, err := http.NewRequest("POST", path, nil)
+		if err != nil {
+			return err
+		}
+		if err := req.Write(conn); err != nil {
+			return err
+		}
 	}
 
 	tap, err := water.New(water.Config{

pkg/net/stdio/dial.go

@@ -0,0 +1,51 @@
+package stdio
+
+import (
+	"net"
+	"os"
+	"os/exec"
+	"strconv"
+)
+
+func Dial(endpoint string, arg ...string) (net.Conn, error) {
+	cmd := exec.Command(endpoint, arg...)
+	cmd.Stderr = os.Stderr
+
+	stdin, err := cmd.StdinPipe()
+	if err != nil {
+		return nil, err
+	}
+
+	stdout, err := cmd.StdoutPipe()
+	if err != nil {
+		return nil, err
+	}
+
+	err = cmd.Start()
+	if err != nil {
+		return nil, err
+	}
+
+	local := IoAddr{path: strconv.Itoa(os.Getpid())}
+	remote := IoAddr{path: strconv.Itoa(cmd.Process.Pid)}
+	conn := IoConn{
+		reader: stdout,
+		writer: stdin,
+		local:  local,
+		remote: remote,
+		close:  cmd.Process.Kill,
+	}
+	return conn, nil
+}
+
+func GetStdioConn() net.Conn {
+	local := IoAddr{path: strconv.Itoa(os.Getpid())}
+	remote := IoAddr{path: "remote"}
+	conn := IoConn{
+		writer: os.Stdout,
+		reader: os.Stdin,
+		local:  local,
+		remote: remote,
+	}
+	return conn
+}

pkg/net/stdio/ioaddr.go

@@ -0,0 +1,12 @@
+package stdio
+
+type IoAddr struct {
+	path string
+}
+
+func (a IoAddr) Network() string {
+	return "stdio"
+}
+func (a IoAddr) String() string {
+	return a.path
+}

pkg/net/stdio/ioconn.go

@@ -0,0 +1,50 @@
+package stdio
+
+import (
+	"io"
+	"net"
+	"time"
+)
+
+type IoConn struct {
+	writer io.Writer
+	reader io.Reader
+	local  net.Addr
+	remote net.Addr
+	close  func() error
+}
+
+func (c IoConn) Read(b []byte) (n int, err error) {
+	return c.reader.Read(b)
+}
+
+func (c IoConn) Write(b []byte) (n int, err error) {
+	return c.writer.Write(b)
+}
+
+func (c IoConn) Close() error {
+	if c.close != nil {
+		return c.close()
+	}
+	return nil
+}
+
+func (c IoConn) LocalAddr() net.Addr {
+	return c.local
+}
+
+func (c IoConn) RemoteAddr() net.Addr {
+	return c.remote
+}
+
+func (c IoConn) SetDeadline(t time.Time) error {
+	return nil
+}
+
+func (c IoConn) SetReadDeadline(t time.Time) error {
+	return nil
+}
+
+func (c IoConn) SetWriteDeadline(t time.Time) error {
+	return nil
+}

pkg/transport/dial_linux.go

@@ -1,10 +1,12 @@
 package transport
 
 import (
+	"fmt"
 	"net"
 	"net/url"
 	"strconv"
 
+	"github.com/containers/gvisor-tap-vsock/pkg/net/stdio"
 	mdlayhervsock "github.com/mdlayher/vsock"
 	"github.com/pkg/errors"
 )
@@ -29,6 +31,15 @@ func Dial(endpoint string) (net.Conn, string, error) {
 	case "unix":
 		conn, err := net.Dial("unix", parsed.Path)
 		return conn, "/connect", err
+	case "stdio":
+		var values []string
+		for k, vs := range parsed.Query() {
+			for _, v := range vs {
+				values = append(values, fmt.Sprintf("-%s=%s", k, v))
+			}
+		}
+		conn, err := stdio.Dial(parsed.Path, values...)
+		return conn, "", err
 	default:
 		return nil, "", errors.New("unexpected scheme")
 	}

test/wsl.sh

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+
+set -x
+
+./bin/vm \
+    -url="stdio:$(pwd)/bin/gvproxy-windows.exe?listen-stdio=accept&debug=true" \
+    -iface="eth1" \
+    -stop-if-exist="" \
+    -debug