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

[Vladimir Nikolic]

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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