tun: linux: work out netpoll trick

tun/tun_linux.go

@@ -17,8 +17,8 @@ import (
 	"golang.zx2c4.com/wireguard/rwcancel"
 	"net"
 	"os"
-	"strconv"
 	"sync"
+	"syscall"
 	"time"
 	"unsafe"
 )
@@ -30,8 +30,6 @@ const (
 
 type NativeTun struct {
 	tunFile                 *os.File
-	fd                      uintptr
-	fdCancel                *rwcancel.RWCancel
 	index                   int32         // if index
 	name                    string        // name of interface
 	errors                  chan error    // async error handling
@@ -52,9 +50,17 @@ func (tun *NativeTun) routineHackListener() {
 	/* This is needed for the detection to work across network namespaces
 	 * If you are reading this and know a better method, please get in touch.
 	 */
-	fd := int(tun.fd)
 	for {
-		_, err := unix.Write(fd, nil)
+		sysconn, err := tun.tunFile.SyscallConn()
+		if err != nil {
+			return
+		}
+		err2 := sysconn.Control(func(fd uintptr) {
+			_, err = unix.Write(int(fd), nil)
+		})
+		if err2 != nil {
+			return
+		}
 		switch err {
 		case unix.EINVAL:
 			tun.events <- TUNEventUp
@@ -248,22 +254,32 @@ func (tun *NativeTun) MTU() (int, error) {
 		uintptr(unsafe.Pointer(&ifr[0])),
 	)
 	if errno != 0 {
-		return 0, errors.New("failed to get MTU of TUN device: " + strconv.FormatInt(int64(errno), 10))
+		return 0, errors.New("failed to get MTU of TUN device: " + errno.Error())
 	}
 
 	return int(*(*int32)(unsafe.Pointer(&ifr[unix.IFNAMSIZ]))), nil
 }
 
 func (tun *NativeTun) Name() (string, error) {
+	sysconn, err := tun.tunFile.SyscallConn()
+	if err != nil {
+		return "", err
+	}
 	var ifr [ifReqSize]byte
-	_, _, errno := unix.Syscall(
+	var errno syscall.Errno
+	err = sysconn.Control(func(fd uintptr) {
+		_, _, errno = unix.Syscall(
 			unix.SYS_IOCTL,
-		tun.fd,
+			fd,
 			uintptr(unix.TUNGETIFF),
 			uintptr(unsafe.Pointer(&ifr[0])),
 		)
+	})
+	if err != nil {
+		return "", errors.New("failed to get name of TUN device: " + err.Error())
+	}
 	if errno != 0 {
-		return "", errors.New("failed to get name of TUN device: " + strconv.FormatInt(int64(errno), 10))
+		return "", errors.New("failed to get name of TUN device: " + errno.Error())
 	}
 	nullStr := ifr[:]
 	i := bytes.IndexByte(nullStr, 0)
@@ -302,7 +318,7 @@ func (tun *NativeTun) Write(buff []byte, offset int) (int, error) {
 	return tun.tunFile.Write(buff)
 }
 
-func (tun *NativeTun) doRead(buff []byte, offset int) (int, error) {
+func (tun *NativeTun) Read(buff []byte, offset int) (int, error) {
 	select {
 	case err := <-tun.errors:
 		return 0, err
@@ -320,18 +336,6 @@ func (tun *NativeTun) doRead(buff []byte, offset int) (int, error) {
 	}
 }
 
-func (tun *NativeTun) Read(buff []byte, offset int) (int, error) {
-	for {
-		n, err := tun.doRead(buff, offset)
-		if err == nil || !rwcancel.RetryAfterError(err) {
-			return n, err
-		}
-		if !tun.fdCancel.ReadyRead() {
-			return 0, errors.New("tun device closed")
-		}
-	}
-}
-
 func (tun *NativeTun) Events() chan TUNEvent {
 	return tun.events
 }
@@ -347,15 +351,11 @@ func (tun *NativeTun) Close() error {
 		close(tun.events)
 	}
 	err2 := tun.tunFile.Close()
-	err3 := tun.fdCancel.Cancel()
 
 	if err1 != nil {
 		return err1
 	}
-	if err2 != nil {
 	return err2
-	}
-	return err3
 }
 
 func CreateTUN(name string, mtu int) (TUNDevice, error) {
@@ -364,13 +364,6 @@ func CreateTUN(name string, mtu int) (TUNDevice, error) {
 		return nil, err
 	}
 
-	fd := os.NewFile(uintptr(nfd), cloneDevicePath)
-	if err != nil {
-		return nil, err
-	}
-
-	// create new device
-
 	var ifr [ifReqSize]byte
 	var flags uint16 = unix.IFF_TUN // | unix.IFF_NO_PI (disabled for TUN status hack)
 	nameBytes := []byte(name)
@@ -382,13 +375,21 @@ func CreateTUN(name string, mtu int) (TUNDevice, error) {
 
 	_, _, errno := unix.Syscall(
 		unix.SYS_IOCTL,
-		fd.Fd(),
+		uintptr(nfd),
 		uintptr(unix.TUNSETIFF),
 		uintptr(unsafe.Pointer(&ifr[0])),
 	)
 	if errno != 0 {
 		return nil, errno
 	}
+	err = unix.SetNonblock(nfd, true)
+
+	// Note that the above -- open,ioctl,nonblock -- must happen prior to handing it to netpoll as below this line.
+
+	fd := os.NewFile(uintptr(nfd), cloneDevicePath)
+	if err != nil {
+		return nil, err
+	}
 
 	return CreateTUNFromFile(fd, mtu)
 }
@@ -396,7 +397,6 @@ func CreateTUN(name string, mtu int) (TUNDevice, error) {
 func CreateTUNFromFile(file *os.File, mtu int) (TUNDevice, error) {
 	tun := &NativeTun{
 		tunFile:                 file,
-		fd:                      file.Fd(),
 		events:                  make(chan TUNEvent, 5),
 		errors:                  make(chan error, 5),
 		statusListenersShutdown: make(chan struct{}),
@@ -404,11 +404,6 @@ func CreateTUNFromFile(file *os.File, mtu int) (TUNDevice, error) {
 	}
 	var err error
 
-	tun.fdCancel, err = rwcancel.NewRWCancel(int(tun.fd))
-	if err != nil {
-		return nil, err
-	}
-
 	_, err = tun.Name()
 	if err != nil {
 		return nil, err
@@ -444,23 +439,20 @@ func CreateTUNFromFile(file *os.File, mtu int) (TUNDevice, error) {
 	return tun, nil
 }
 
-func CreateUnmonitoredTUNFromFD(tunFd int) (TUNDevice, string, error) {
+func CreateUnmonitoredTUNFromFD(fd int) (TUNDevice, string, error) {
-	file := os.NewFile(uintptr(tunFd), "/dev/tun")
+	err := unix.SetNonblock(fd, true)
+	if err != nil {
+		return nil, "", err
+	}
+	file := os.NewFile(uintptr(fd), "/dev/tun")
 	tun := &NativeTun{
 		tunFile: file,
-		fd:      file.Fd(),
 		events:  make(chan TUNEvent, 5),
 		errors:  make(chan error, 5),
 		nopi:    true,
 	}
-	var err error
-	tun.fdCancel, err = rwcancel.NewRWCancel(int(tun.fd))
-	if err != nil {
-		return nil, "", err
-	}
 	name, err := tun.Name()
 	if err != nil {
-		tun.fdCancel.Cancel()
 		return nil, "", err
 	}
 	return tun, name, nil