Adjust mdns to support arbitrary number of fabrics.

[cecille]

Problem

Need to adjust mdns to support the number of fabrics the device actually supports.

see: https://github.com/CHIP-Specifications/connectedhomeip-spec/issues/2551

Proposed Solution

Template response sender, get setting from wherever that info comes into the SDK.

[cecille]

There was also a request to support arbitrary numbers of fabrics for the more capable devices - see PR #8610. In general, this is something we will need to tackle on a larger scale - what's CHIP's philosophy on static vs. dynamic allocation and do we support multiple configs of this?

[cecille]

Note: possible good solution would be to hook into the in-progress pool impl. #8299

[cecille]

@andy31415 - I had an issue opened for this. I think you've done this already? I know you were working on it. If so, would you mind closing this.

[bzbarsky-apple]

@cecille Is this issue about minimal mdns specifically, or mdns in general?

For minimal mdns we have:

using QueryResponderPtrPool = std::array<mdns::Minimal::QueryResponderBase *, CHIP_CONFIG_MAX_FABRICS + 2>;

which should have enough space for CHIP_CONFIG_MAX_FABRICS operational things, commissionable discovery, commissioner discovery.

For platform mdns I don't know where things stand on the various platforms.

[andy31415]

Maximum number of records returned is configurable - #16535 added that functionality.

[andy31415]

Marking as closed: combination of #16535 and #16181