OS::Neutron::Subnet constraint to validate allocation_pool cidr

[Dan Prince]

In TripleO we've got some templates which create OS::Neutron::Subnet resources that expose an allocation_pools parameter:

http://git.openstack.org/cgit/openstack/tripleo-heat-templates/tree/network/external.yaml#n50

We've discovered that it is quite easy for end users to specify a CIDR which does not match the parameter they specified for allocation_pools. If the CIDR and allocation_pool don't match Neutron will fail... but it would be really nice if Heat could also pre-check the same subnet parameters ahead of time and provide the end user a clear error message.

http://git.openstack.org/cgit/openstack/heat/tree/heat/engine/resources/openstack/neutron/subnet.py#n130

Do we have any other inter-parameter constraint validations like this in Heat? Or would it be better to accomplish this sort of validation via an external tool?

[Rabi Mishra (rabi)]

AFAIK, there is nothing atm for inter property validation contraints. Some cases we do that in resource validate method.
We can possibly add an validation to check this and raise something similar to OutOfBoundsAllocationPool error thrown by neutron if that helps?