code: func delVlanLink(linkName string) error {
  	if strings.Contains(linkName, ".") {
  		_, _, err := parseVlan(linkName)
  		if err != nil {
  			return err
  		}
  		// delete the vlan subinterface
  		vlanLink, err := ns.NlHandle().LinkByName(linkName)
  		if err != nil {
  			return fmt.Errorf("failed to find interface %s on the Docker host : %v", linkName, err)
  		}
  		// verify a parent interface isn't being deleted
  		if vlanLink.Attrs().ParentIndex == 0 {
  			return fmt.Errorf("interface %s does not appear to be a slave device: %v", linkName, err)
  		}
  		// delete the macvlan slave device
  		if err := ns.NlHandle().LinkDel(vlanLink); err != nil {
  			return fmt.Errorf("failed to delete  %s link: %v", linkName, err)
  		}
  		logrus.Debugf("Deleted a vlan tagged netlink subinterface: %s", linkName)
  	}
  	// if the subinterface doesn't parse to iface.vlan_id leave the interface in
  	// place since it could be a user specified name not created by the driver.
  	return nil
  }
docs: // delVlanLink verifies only sub-interfaces with a vlan id get deleted