[Kea-users] DDNS limitations - ddns-qualifying-suffix vs domain-name

[Darren Ankney]

Hi Vladimir,

I don't know for sure.  It might make an assumption that "myhost" is
not an FQDN while assuming that "myhost.SomeOtherLabel" is an FQDN.
Or it might look to see if the value from ddns-qualifying-suffix is
part of the host already and not append if it is...  Perhaps someone
else who knows for sure will be along to answer.

Thank you,

Darren Ankney

On Thu, Jan 4, 2024 at 1:41 PM Vladimir Nikolic <vladimir at nikolic.si> wrote:
>
> Hi Darren,
>
> Could DDNS Tuning hook help here?
> It says here
> https://kea.readthedocs.io/en/latest/arm/hooks.html#dhcpv4-host-name-generation:
>
> 4. If there is a ddns-tuning in-scope host-name expression (either
> global or subnet), calculate the host name using the expression. If the
> calculated value is not a fully qualified name and there is an in-scope
> ddns-qualifying-suffix, append the suffix.
>
> I wonder who does it determine if the calculated value is not a fully
> qualified name?
>
> Regards,
> Vladimir
>
>
> On 2023-10-22 19:44, Darren Ankney wrote:
> > Hi Vladimir,
> >
> > I thought about that, but that wouldn't necessarily work.  Without
> > looking up the provided hostname, Kea wouldn't understand if it should
> > add the suffix or not (i.e., is it a complete name?)  For example:
> >
> > - suffix could be 'example.org'
> > - 'example.org' might have sub domains such as 'office.example.org'
> > and 'warehouse.example.org'
> > - so there may be hostnames like 'laptop1.office' and
> > 'laptop2.warehouse' that would need example.org appended to them.
> >
> > Kea couldn't know this isn't the case without some other flag or some
> > very complex (very slow) lookup logic to try to figure out what the
> > administrator intends to happen.
> >
> > Thank you,
> >
> > Darren Ankney
> >
> > On Sun, Oct 22, 2023 at 10:33 AM Vladimir Nikolic <vladimir at nikolic.si>
> > wrote:
> >>
> >> Hi Darren,
> >>
> >> > There would have to be some way to flag hostnames that you wanted to
> >> > ignore a ddns-qualifying-suffix setting somehow to have it
> >> > simultaneously set to some value and not apply to all hostnames in
> >> > that block.
> >>
> >> Yeah, like if you end "hostname" parameter (within a host reservation)
> >> with a ".", then KEA should treat it as a FQDN, and not append
> >> "ddns-qualifying-suffix" from the subnet definition.
> >>
> >> Regards,
> >> Vladimir
> >>
> >> On 2023-10-21 18:54, Darren Ankney wrote:
> >> > Hi Vladimir,
> >> >
> >> > You can set it "ddns-qualifying-suffix": "", which resets it to empty
> >> > in the block in which you do that.  You could also only specify inside
> >> > subnets where you need it specified and not specify at global level.
> >> > There would have to be some way to flag hostnames that you wanted to
> >> > ignore a ddns-qualifying-suffix setting somehow to have it
> >> > simultaneously set to some value and not apply to all hostnames in
> >> > that block.
> >> >
> >> > Thank you,
> >> >
> >> > Darren Ankney
> >> >
> >> > On Tue, Oct 17, 2023 at 2:50 AM Vladimir Nikolić <vladimir at nikolic.si>
> >> > wrote:
> >> >>
> >> >> Thanks Darren.
> >> >>
> >> >> If ‘ddns-qualifying-subnet’ is being set on any level, it’s then
> >> >> appended to the ‘hostname’ value from the host reservation. ‘hostname’
> >> >> is the FQDN, only if ‘ddns-qualifying-subnet’ is empty.
> >> >> So it’s either one or another.
> >> >> Which is really inflexible.
> >> >>
> >> >> Regards
> >> >>
> >> >>
> >> >> > On 17 Oct 2023, at 12:26 am, Darren Ankney <darren.ankney at gmail.com> wrote:
> >> >> >
> >> >> > Hi Vladimir,
> >> >> >
> >> >> > The DHCPv4 domain-name option (15) isn't meant for use with ddns.  It
> >> >> > is a search domain that the client should use when performing name
> >> >> > resolution.  See: https://www.rfc-editor.org/rfc/rfc2132#section-3.17
> >> >> >
> >> >> > You can set ddns-qualifying-suffix at the global, shared-network and
> >> >> > subnet level.  In a host reservation, you can use the "hostname"
> >> >> > parameter to specify a FQDN to send to the client and for use in DDNS.
> >> >> > See here: https://kea.readthedocs.io/en/kea-2.4.0/arm/dhcp4-srv.html#reserving-a-hostname
> >> >> >
> >> >> >> On Mon, Oct 16, 2023 at 3:23 PM Vladimir Nikolic via Kea-users
> >> >> >> <kea-users at lists.isc.org> wrote:
> >> >> >>
> >> >> >> Hi,
> >> >> >>
> >> >> >> While trying to migrate DHCP service from ISC DHCP to ISC KEA, we are
> >> >> >> hitting following KEA limitations:
> >> >> >>
> >> >> >> - option domain-name has no part in DDNS names construction, it's only
> >> >> >> ddns-qualifying-suffix that's being honoured
> >> >> >> - ddns-qualifying-suffix can't be specified in the class definition (we
> >> >> >> have dedicated zone for our OOB devices)
> >> >> >> - there can be only one DDNS zone for all the clients in a subnet
> >> >> >> (ddns-qualifying-suffix), with ISC DHCP you can have one default
> >> >> >> domain-name for a subnet and every single host reservation with a
> >> >> >> different domain-name (DDNS zone)
> >> >> >>
> >> >> >> Regards,
> >> >> >> Vladimir
> >> >> >> --
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