net: dns-sd: additional rfc6733 features

[cfriedt]

Is your enhancement proposal related to a problem? Please describe.
Currently, dns-sd does not support

1. domain enumeration (chapter 11)
2. sub-types (chapter 7.2)
3. service domains (chapter 7.2)

Items 2 and 3 deal with fully-qualified names (FQN's). Examples of FQN's that are unsupported are of the form:

<sub>._sub.<sn>._tcp.<servicedomain>.<parentdomain>.

or anything other than "local" for a <domain>, where

<domain> := <servicedomain>.<parentdomain>.

The struct dns_sd_rec actually has insufficient fields to represent all types of names.

Describe the solution you'd like

• 1 additional local "service domain", either configured from e.g. DHCP or via Kconfig
• remove the proto, service, and instance fields of struct dns_sd_rec
• use only a name field and name_size, domain field and domain_size, and text and text_size
• use accessor methods to extract the above values into callee-provided storage
• support domain enumeration via kconfig switch (ch 11)
• support all fully-qualified names described in ch 7.2
• an additional pass of helpful features from RFC 6763

Describe alternatives you've considered

Additional context
https://datatracker.ietf.org/doc/html/rfc6763

The driver seems to not initiate device-side announcements or probing at startup as described in section 8: https://datatracker.ietf.org/doc/html/rfc6762#section-8. This causes my device to remain undiscovered when the server has avahi-daemon running.

[cfriedt]

The driver seems to not initiate device-side announcements or probing at startup as described in section 8: https://datatracker.ietf.org/doc/html/rfc6762#section-8. This causes my device to remain undiscovered when the server has avahi-daemon running.

Thanks for finding this! I see that it's part of the greater mdns picture (rfc6762) so I might create a separate issue for general mdns improvements.

[cfriedt]

Pushing this back, as I have no actual dedicated hours to work on this at the moment (most of my upstream work is still unfortunately evenings and weekends).