nlddcd is a Dynamic DNS client. It monitors network interfaces for address changes. When a change is detected for an interface specified in the configuration file, the new address is sent to the Dynamic DNS service configured for that interface, using an HTTP or HTTPS request.
nlddcd does not rely on periodic requests to an external service in order to detect address changes, but uses the Netlink interface to be notified of changes. Consequently, nlddcd does not work behind a NAT and must instead run directly on the router that contains the interface carrying the "external" IP address(es).
nlddcd supports IPv4 and IPv6 addresses and will automatically send updates containing both address types of a configured interface (however, only global, non-temporary IPv6 addresses will be considered).