Extend scope to support DNS-SD (RFC 6763)

[backkem]

Extend the current WebRTC-focused mDNS implementation to full RFC 6762/6763 compliance with service discovery and non-blocking APIs.

Current state: Partial RFC 6762 + WebRTC ICE draft. Monolithic Conn struct, limited to A/AAAA records, blocking queries, strict name filtering.

TODO

• Phase 1: Refactoring & Architecture
• Phase 2: DNS-SD Support (RFC 6763)
• Phase 3: Advanced mDNS Features (RFC 6762)
• Phase 4: API Polish & Non-blocking Operations

Original motivation

I am looking to use this library for backkem/matter which relies on full DNS-SD capabilities beyond the current Host Resolution (RFC 6762) implementation.

The library currently focuses on A/AAAA records. It explicitly filters out PTR, SRV, and TXT queries required for
Service Discovery.

I would like to contribute support for:

• Service Advertising (PTR responses).
• SRV and TXT record management (including updates).
• Service Subtypes (e.g., _custom._sub._service._udp).

[backkem]

Phase 1: Core Architecture Refactor

Modernize the codebase from a monolithic conn.go to a modular design without breaking external behavior.

Why

The current conn.go mixes socket management, packet parsing, querying, and responding in a single 800+ line struct. This makes adding DNS-SD, caching, and probing/tiebreaking difficult and error-prone.

A modular architecture unlocks:

• Testability — Mock networking layer independently
• Extensibility — Centralized engine enables record caching and zone management
• Clarity — Distinct Client/Server types signal API intent

Approach

Atomic PRs preserving API compatibility. Existing Server() remains functional; new NewClient/NewServer become the preferred path forward.

TODOs

I'll put a tracker in the OP.

[JoTurk]

@backkem I think we should use the options patterns for the new API. we have been moving all of our libraries, we're currently moving, sctp and dtls. and we moved ICE, RTP and many more in past releases.

examples:

• https://github.com/pion/ice/blob/f0c4479e20a4dca876813969bc0f9f94f761264d/agent.go#L184-L186
• https://github.com/pion/ice/blob/f0c4479e20a4dca876813969bc0f9f94f761264d/agent_options.go
• Add NewPacketizerWithOptions for configuration rtp#305
• Update this library to use options API sctp#446
• Config pattern dtls#765

[jwetzell]

AH, this seems like this stuff will add what I was missing last time I looked at this mdns library. The Query function really just being a A/AAAA querier was pretty much a deal breaker. If there is any place that I might be able to help out I'd be happy to try!

[JoTurk]

@jwetzell thank you for your interest in contribution we actually need some help with this library, with review, and implementing features, if you would like i can invite you to the org so you can review directly and make branches.

[jwetzell]

@JoTurk if that is easiest, that works for me. I was planning on checking out main and trying a couple of my use-cases again to see where things are at. I did also see the draft PR that mentions some things that might be related to this.

[backkem]

Would still love to help push this forward, just more time constrained at the moment.

[JoTurk]

@jwetzell I invited you, really excited to get this library active again :)