code: func ifaceAddIPAddr(iface *net.Interface, ip net.IP, mask net.IPMask) error {
  	if ip.To4() != nil {
  		return ifaceAddIPv4Addr(iface, ip, mask)
  	}
  	return ifaceAddIPv6Addr(iface, ip, mask)
  }
docs: // ifaceAddIPAddr adds the given IP address to the network interface.