[Kea-users] Missing features from dhcp-eval

[Darren Ankney]

Hi Vladimir,

You should be able to do something like this with the flex option
hook: https://kea.readthedocs.io/en/kea-2.4.0/arm/hooks.html#libdhcp-flex-option-so-flexible-option-actions-for-option-value-settings

Just need to find out what can be tested for.  Is the traffic relayed?
 Will there be a specific giaddr for the client in the subnet that you
want to set the custom options?  You can test for a specific relay
agent IP (giaddr) with pkt4.giaddr == 192.0.2.1, for example.  You can
test if a client is a member of the PXEClients class with
member('PXEClients').

Hope this helps!

Thank you,

Darren Ankney

On Sun, Oct 15, 2023 at 11:40 AM Vladimir Nikolic <vladimir at nikolic.si> wrote:
>
> Let's say I want to send custom next-server and filename to PXE clients,
> depending on subnet in which they are located.
>
> In dhcpd, I define a new option, e.g.:
> option something-new code 250 = string;
>
> Then I set its value in some of the subnets:
> subnet xyz {
>      option something-new "my-value";
> ...
>
> And within a class definition, I can set up options (e.g. next-server
> and filename) based on the value of something-new option (defined within
> subnets):
> class "PXEClients" {
>      match if substring(option vendor-class-identifier, 0, 9) =
> "PXEClient";
>      if config-option something-new = "my-value"
>          next-server my-new-server;
>          filename "my-new-filename";
>      } else {
>          next-server my-old-server;
>          filename "my-old-filename";
>      }
> ...
>
> So it's one class with different next-server/filename options, based on
> the subnet in which clients live.
>
>  From what I've seen so far, you can't do something similar in KEA.
> You have to define next-server and filename in every of those subnets,
> and that will apply to all the clients in that subnet (not just to those
> belonging to PXEClients class).
>
> Thanks
>
>
> On 2023-10-15 17:18, Darren Ankney wrote:
> > Hi,
> >
> > I'm not entirely sure what you are asking here.  Do you mean that you
> > need to add a client to a class based on what subnet was selected?
> >
> > Thank you,
> >
> > Darren Ankney
> >
> > On Fri, Oct 13, 2023 at 12:36 PM Vladimir Nikolic via Kea-users
> > <kea-users at lists.isc.org> wrote:
> >>
> >> Hi,
> >>
> >> We are struggling with the migration from DHCPD to KEA.
> >> Is there any easy alternative to this dhcp-eval feature:
> >>
> >> config-option option-name
> >>       The config-option operator returns the value for the specified
> >> option that the DHCP client or server has been configured to send.
> >>
> >> In DHCPD, we define an option, and then set it up on particular
> >> subnets.
> >> It can then be used during class evaluation, by config-option feature.
> >> In that way, different classes (with e.g. different next-server and/or
> >> filename defined) can be assigned to similar clients, just based on
> >> the
> >> option value set in a subnet definition.
> >>
> >>  From what we've seen so far, something like that is not possible with
> >> KEA.
> >> Looks like we'll have to find an alternative solution.
> >>
> >> Thanks
> >> --
> >> ISC funds the development of this software with paid support
> >> subscriptions. Contact us at https://www.isc.org/contact/ for more
> >> information.
> >>
> >> To unsubscribe visit https://lists.isc.org/mailman/listinfo/kea-users.
> >>
> >> Kea-users mailing list
> >> Kea-users at lists.isc.org
> >> https://lists.isc.org/mailman/listinfo/kea-users