code: func sysctlIface(iface string, af seesaw.AF, name, value string) error {
  	components := []string{
  		"net", strings.ToLower(af.String()), "conf", iface, name,
  	}
  	_, err := sysctlByComponents(components, value)
  	return err
  }
docs: // sysctlIface sets a sysctl for a given address family and network interface.