package dns

Multicast DNS (RFC 6762) Responder.

This is roughly the mDNS equivalent of Dns_server, in that it accepts mDNS query packets and responds with the matching records from a zone file.

The simplest usage is with shared resource records only, which requires the following steps:

1. Create a module from a zone buffer using the "Make" functor.
2. Call the module's "announce" function to announce the records.
3. After announcement completes, call the "process" function for each received packet.

The use of unique resource records requires alternative steps:

1. Create a module from a zone buffer using the "Make" functor.
2. Call "add_unique_hostname" to add the a unique "A" record.
3. Call the module's "first_probe" function to probe for uniqueness of the hostname. The name will be changed to something unique in the event of a conflict.
4. After probing completes, call the module's "announce" function.
5. After announcement completes, call the "process" function for each received packet.

As per RFC 6762 section 9, if at any time the responder observes a response that conflicts with a record that was previously already confirmed as unique, it restarts the probing sequence. Therefore, it is necessary to invoke the "stop_probe" function to shut down the responder.