func setHairpinMode(nlh *netlink.Handle, link netlink.Link, enable bool) error {
err := nlh.LinkSetHairpin(link, enable)
if err != nil && err != syscall.EINVAL {
// If error is not EINVAL something else went wrong, bail out right away
return fmt.Errorf("unable to set hairpin mode on %s via netlink: %v",
link.Attrs().Name, err)
}
// Hairpin mode successfully set up
if err == nil {
return nil
}
// The netlink method failed with EINVAL which is probably because of an older
// kernel. Try one more time via the sysfs method.
path := filepath.Join("/sys/class/net", link.Attrs().Name, "brport/hairpin_mode")
var val []byte
if enable {
val = []byte{'1', '\n'}
} else {
val = []byte{'0', '\n'}
}
if err := ioutil.WriteFile(path, val, 0644); err != nil {
return fmt.Errorf("unable to set hairpin mode on %s via sysfs: %v", link.Attrs().Name, err)
}
return nil
}
