Re: [dnssd] SRP: how to remove all published services?

The intention was certainly that the update deleting all records associated
with a host should only include the host instruction.

On Fri, Sep 15, 2023 at 12:29 PM Esko Dijk <esko.dijk@iotconsultancy.nl>
wrote:

> Thanks, I didn’t yet consider this paragraph because it said “when a host
> is removed” and my use case in mind was removing all the services but not
> the host.
>
> But, I see now that the Host Description Instruction is mandatory in the
> SRP Update, so that sending any valid SRP Update with a LEASE time of 0
> will always delete all services!
>
> That’s because the host gets deleted by this update and there’s no way to
> not include it.
>
>
>
> So there is no strict requirement to “retransmit its most recent update”
> at all, then. The requestor could just send a single Host instruction with
> lease time 0.
>
> Or include any one or more of its registered services; the effect should
> be the same.   It could even include a non-existing service in its SRP
> Update: even that should work.
>
>
>
> Why not make the SRP Update message as short as possible by not including
> any services – only the host instruction with lease time 0? On 6lowpan mesh
> networks that definitely is helpful.
>
> I tried the OpenThread implementation and it includes all registered
> services in the “delete all” SRP Update which shouldn’t be needed.
>
> Hope I’m not misunderstanding this here – still puzzled by the “most
> recent update” requirement :)
>
>
>
> Esko
>
>
>
> *From:* Ted Lemon <mellon@fugue.com>
> *Sent:* Friday, September 15, 2023 16:41
> *To:* Jonathan Hui <jonhui=40google.com@dmarc.ietf.org>
> *Cc:* Esko Dijk <esko.dijk@iotconsultancy.nl>; dnssd@ietf.org
> *Subject:* Re: [dnssd] SRP: how to remove all published services?
>
>
>
> Oh, except the text you quoted says precisely that, so I think we're okay.
> Thanks, Jonathan. :)
>
>
>
> On Fri, Sep 15, 2023 at 10:40 AM Ted Lemon <mellon@fugue.com> wrote:
>
> Was the question more "what if the requestor sends a partial remove (host
> plus not all services) with lease time zero?" I think the answer is that it
> removes all the services, because the other services are pointing to the
> host, and the host has to be removed; this means that any remaining
> services pointing to that host are simply invalid. We could certainly add a
> note clarifying this point, although it's a bit late in the process for
> that.
>
>
>
> On Fri, Sep 15, 2023 at 10:31 AM Jonathan Hui <jonhui=
> 40google.com@dmarc.ietf.org> wrote:
>
> Hi Esko,
>
>
>
> I believe this is addressed by the immediately following paragraphs in the
> same section? Specifically:
>
>
>
>    To support this, when removing services based on the lease time being
>    zero, an SRP registrar MUST remove all service instances pointing to
>    a host when a host is removed, even if the SRP requestor doesn't list
>    them explicitly.  If the key lease time is nonzero, the SRP registrar
>
>    MUST NOT delete the KEY records for these SRP requestors.
>
>
>
> So there is no need to list all the services that were previously
> registered.
>
>
>
> --
>
> Jonathan Hui
>
>
>
>
>
>
>
> On Fri, Sep 15, 2023 at 7:17 AM Esko Dijk <esko.dijk@iotconsultancy.nl>
> wrote:
>
> A question - in 3.2.5.5.1., Removing all published services, we have:
>
>
>
>    To remove all the services registered to a particular host, the SRP
> requestor retransmits its most recent update with an Update Lease option
> that has a LEASE value of zero.
>
>
>
> I wonder how this exactly works in the following case. If I’ve registered
> service A, and 10 minutes later registered service B in addition (without
> mentioning A in the second SRP Update), then both services A and B are
> actively registered.  Now I send the “most recent SRP Update” which has
> only service B to the SRP registrar, with a LEASE value of zero.
>
> Wouldn’t it be that only service B is removed (lease set to 0) while
> service A stays active?
>
>
>
> If so, we may need to clarify this text I think. Because it’s not always
> the “most recent SRP Update” then.
>
> (If not so, I’m having trouble understanding how the LEASE value in the
> SRP Update does apply to all currently registered services….)
>
>
>
> Esko
>
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