tun: use IoctlCtlInfo from golang.org/x/sys/unix on macOS

Direct syscalls using unix.Syscall(unix.SYS_*, ...) are discouraged on
macOS and might not be supported in future versions. Switch to use
unix.IoctlCtlInfo to get the kernel control info.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

diff --git a/tun/tun_darwin.go b/tun/tun_darwin.go
index f04ace2e77871e91735b4af8294364022aa96fb1..c30e733720102e99e2590348db4cbb1f72f6e7ad 100644 (file)
--- a/tun/tun_darwin.go
+++ b/tun/tun_darwin.go
@@ -20,9 +20,6 @@ import (
 
 const utunControlName = "com.apple.net.utun_control"
 
-// _CTLIOCGINFO value derived from /usr/include/sys/{kern_control,ioccom}.h
-const _CTLIOCGINFO = (0x40000000 | 0x80000000) | ((100 & 0x1fff) << 16) | uint32(byte('N'))<<8 | 3
-
 // sockaddr_ctl specifeid in /usr/include/sys/kern_control.h
 type sockaddrCtl struct {
        scLen      uint8
@@ -130,29 +127,18 @@ func CreateTUN(name string, mtu int) (Device, error) {
                return nil, err
        }
 
-       var ctlInfo = &struct {
-               ctlID   uint32
-               ctlName [96]byte
-       }{}
-
-       copy(ctlInfo.ctlName[:], []byte(utunControlName))
-
-       _, _, errno := unix.Syscall(
-               unix.SYS_IOCTL,
-               uintptr(fd),
-               uintptr(_CTLIOCGINFO),
-               uintptr(unsafe.Pointer(ctlInfo)),
-       )
-
-       if errno != 0 {
-               return nil, fmt.Errorf("_CTLIOCGINFO: %v", errno)
+       ctlInfo := &unix.CtlInfo{}
+       copy(ctlInfo.Name[:], []byte(utunControlName))
+       err = unix.IoctlCtlInfo(fd, ctlInfo)
+       if err != nil {
+               return nil, fmt.Errorf("IoctlGetCtlInfo: %w", err)
        }
 
        sc := sockaddrCtl{
                scLen:     uint8(sockaddrCtlSize),
                scFamily:  unix.AF_SYSTEM,
                ssSysaddr: 2,
-               scID:      ctlInfo.ctlID,
+               scID:      ctlInfo.Id,
                scUnit:    uint32(ifIndex) + 1,
        }