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Use SyscallConn() instead of Fd() to persist TUN/TAP interface #674

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merged 1 commit into from
Sep 24, 2021
+22 −2
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Use SyscallConn() instead of Fd() to persist TUN/TAP interface #674

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24 changes: 22 additions & 2 deletions link_linux.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1260,9 +1260,26 @@ func (h *Handle) linkModify(link Link, flags int) error {

}

control := func(file *os.File, f func(fd uintptr)) error {
name := file.Name()
conn, err := file.SyscallConn()
if err != nil {
return fmt.Errorf("SyscallConn() failed on %s: %v", name, err)
}
if err := conn.Control(f); err != nil {
return fmt.Errorf("Failed to get file descriptor for %s: %v", name, err)
}
return nil
}

// only persist interface if NonPersist is NOT set
if !tuntap.NonPersist {
_, _, errno := unix.Syscall(unix.SYS_IOCTL, fds[0].Fd(), uintptr(unix.TUNSETPERSIST), 1)
var errno syscall.Errno
if err := control(fds[0], func(fd uintptr) {
_, _, errno = unix.Syscall(unix.SYS_IOCTL, fd, uintptr(unix.TUNSETPERSIST), 1)
}); err != nil {
return err
}
if errno != 0 {
cleanupFds(fds)
return fmt.Errorf("Tuntap IOCTL TUNSETPERSIST failed, errno %v", errno)
Expand All @@ -1279,7 +1296,10 @@ func (h *Handle) linkModify(link Link, flags int) error {
// un-persist (e.g. allow the interface to be removed) the tuntap
// should not hurt if not set prior, condition might be not needed
if !tuntap.NonPersist {
_, _, _ = unix.Syscall(unix.SYS_IOCTL, fds[0].Fd(), uintptr(unix.TUNSETPERSIST), 0)
// ignore error
_ = control(fds[0], func(fd uintptr) {
_, _, _ = unix.Syscall(unix.SYS_IOCTL, fd, uintptr(unix.TUNSETPERSIST), 0)
})
}
cleanupFds(fds)
return err
Expand Down