Prevent statistics update for certain requests

[Stefan Möding]

Hi!

We are using FreeRADIUS as service provider.  For certain realms we need
to forward the access request to customer specific radius servers while
the rest is authenticated on our radius.  This work in the following ways:

1) "user at example.net" wants access.
2) Our NAS tries to authenticate "example.net".
3) "example.net" is a realm that needs to be forwarded to a customer
   specific server so our radius sends a reply containing attributes (like
   the IP) that tells the NAS which specific radius server to use.  This
   is implemented by a local radius user named "example.net" with the
   specific set of reply attributes.
4) The NAS authenticates the user using the customer radius.

The other case is as follows:

1) "user at example.com" wants access.
2) Our NAS tries to authenticate "example.com".
3) "example.com" is a realm that should be authenticated locally so the
   radius server returns a reject.
4) The NAS then tries a second time using "user at example.com" and
   sucessfully authenticates the user.

As you can imagine the second case leads to a notably number of access
rejects in the statistics of the server.  Monitoring the rate of rejects
alone no longer is useful to monitor the health of the system as these
rejects are expected by design.

Now we are thinking about a solution and came up with the idea of
preventing a statistics update for these rejects.  A new internal
attribute (e.g. FreeRADIUS-Inhibit-Stats-Update) would be added to the
request and the statistics update function would ignore requests that have
this attribute set.  Setting that attribute in unlang would be easy as it
happens in a dedicated virtual server in our case.

Does this sound like a good solution for our problem?
Could that be useful for others as well (say: a pull-request on Github)?

Thanks!
--
Stefan