Implementation of RFC-6763 mDNS and RFC 6763 DNS-SD

[tmcgilchrist]

Is there interest in restoring RFC-6763 mDNS and adding RFC-6763 DNS-SD to this project? I have been working on a Mirage implementation since January that is coming together, but I would appreciate some patient code review and suggestions. I haven't done a large contribution to this library before and thought I should ask before dropping a large feature PR.

Previously the support was removed in #159, it's unclear what the motivation was for the removal.

My motivation is to have an OCaml replacement for https://avahi.org that I can combine with other Mirage components.

[reynir]

Hi! Out of curiosity I found that mDNS was removed when uDNS was merged into this repository: https://discuss.ocaml.org/t/psa-dns-2-0-a-new-udns-era-dawns/3781 (there's an still-open issue to document the removal ha #160)

I don't know either RFC much and as such don't have an opinion on that at the moment.

[hannesm]

Such a contribution is welcome. The 2.0.0 area of OCaml-DNS was a complete rewrite, with a focus on (a) server and (b) resolver. For this, lots of things changed, and nobody really had energy and motivation to support mDNS and DNS-SD.

When it comes to reviewing time, I can't promise anything. I usually try to review PRs as quick as I can.

What you can do to help reviewing PRs is avoid unnecessary changes (formatting etc.), avoid force-pushes. Providing tests is usually a good path forward as well.

If you have orthogonal changes (refactoring/...), it is best to split them into separate PRs.

[tmcgilchrist]

Noted, thanks @hannesm

I'm working on the implementation so the git history isn't suitable for reviewing and I'm finding silly bugs in my implementation. There will be a small ~50 line change required to dns.mli/ml which I'll submit first.

[hannesm]

4 months later, is there anything we can do to get this integrated?

[tmcgilchrist]

Thanks for the prompt @hannesm I stopped working on this for a few months and have recently picked it back up. The unfiltered changes are on https://github.com/tmcgilchrist/ocaml-dns/tree/mdns, warning the git history isn't clean at all.

For getting this upstreamed there is an API change in 6411a5b to remodel Ptr as a Ptr_set, that could be discussed on a PR. I won't ask for a review on the rest of the code as I'm debugging the implementation against Avahi and Bonjour (macOS), then fixing my mistakes. So I expect the code to change.

Adjacent to mDNS support it would be useful to have Multicast Listening on Unikernel and mirage/mirage-tcpip#498. At the moment I'm using Lwt_unix.socket and setting things up myself with a native socket.

[tmcgilchrist]

mirage/mirage-tcpip#540 adds the minimal multicast options needed for mDNS/DNS-SD