code: func (ncc *SeesawNCC) ARPSendGratuitous(arp *ncctypes.ARPGratuitous, out *int) error {
  	iface, err := net.InterfaceByName(arp.IfaceName)
  	if err != nil {
  		return fmt.Errorf("failed to get interface %q: %v", arp.IfaceName, err)
  	}
  	log.V(2).Infof("Sending gratuitous ARP for %s (%s) via %s", arp.IP, iface.HardwareAddr, iface.Name)
  	m, err := gratuitousARPReply(arp.IP, iface.HardwareAddr)
  	if err != nil {
  		return err
  	}
  	return sendARP(iface, m)
  }
docs: // ARPSendGratuitous sends a gratuitous ARP message via the specified interface.