Support mDNS

[Caligatio]

I would like to use c-ares in my Python asynchronous mDNS library but I need the ability for the underlying DNS logic to join a multicast group. I wasn't familiar at all with this process but, at a minimum it requires setting the socket option IP_ADD_MEMBERSHIP with the desired multicast group for the listening socket.

I think the rest of the multicast specific functionality can be hacked in using the existing functions (e.g. setting the destination "server" to be the multicast address).

[daviddrysdale]

Would setting the socket creation callback or the socket configuration callback do what you need? You could have a callback that set the multicast option you needed.

[jblachly]

I think the issue title is misleading as really what he is asking for (and what brought me here) is "Multicast DNS", not "multicast IP addresses".

https://en.wikipedia.org/wiki/Multicast_DNS (also called 'mDNS')

These take the form of hostname.local on your LAN and are provided on linux by avahi-daemon, by default on MacOS, and optionally by systemd on linux.