Re: [dnssd] SRP Update: which A/AAAA records to include?

[Esko Dijk <[e-mail]>]

Yes, I think the RFC 8766 section 5.5.2 is like the long version of my text proposal! (Hence the ‘SHOULD’: publish all your addresses except the ones that make no sense to your target audience.)
We don’t have to repeat a long list in the SRP draft, but I think including a sentence with the short version would be useful. It could also make reference to RFC 8766.

Thanks
Esko

From: Ted Lemon <[e-mail]>
Sent: Wednesday, May 18, 2022 16:05
To: Esko Dijk <[e-mail]>
Cc: [e-mail]
Subject: Re: [dnssd] SRP Update: which A/AAAA records to include?

I think the advice in RFC 8766 section 5.5.2 is relevant here. So any address that would only be reachable on the same link as the client probably shouldn’t be sent. But I think this is somewhat domain-specific. E.g., thread has a mesh-local prefix. Maybe we want to allow mesh-local addresses for stability when mesh clients are discovering each other?  At present I think ADK just sends off-mesh-reachable addresses. Dunno about OpenThread.

On Wed, May 18, 2022 at 09:59 Esko Dijk <[e-mail]<mailto:[e-mail]>> wrote:
Hello,

Here a question about draft-ietf-dnssd-srp-13: Section 2.2.1 defines what to publish in an SRP Update. It also refers to RFC 6763 for more details.
But, I cannot find what A / AAAA records a client should publish with an SRP Update, from the following text:

*  The Host Description records for a service are a KEY RR, used to
      claim exclusive ownership of the service registration, and one or
      more RRs of type A or AAAA, giving the IPv4 or IPv6 address(es) of
      the host where the service resides.

Is it all addresses? Or would a subset be okay also? RFC 6763 also does not mention more on this A / AAAA selection.
I found it more clear for mDNS RFC 6762:


When a Multicast DNS responder sends a Multicast DNS response message

   containing its own address records, it MUST include all addresses

   that are valid on the interface on which it is sending the message,

But the case of SRP is different. We could add  for SRP in 2.2.1:

“The Host Description records SHOULD include A and AAAA records for all IP addresses via which the service can be reached by all hosts that might query the DNS.”

This formulation borrows from 2.3.1.3, but now applied to the perspective of the SRP client.  E.g. link-local address is excluded due to this formulation. Also particular (ULA) addresses can be excluded if the client knows they have very limited scope of routing.

Regards
Esko

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