returning user and primary group (or any other ldap attribute) with radius response

Hi! After searching for long with google, or in the manuals, i was not able to find any cookbook recipe to advice freeradius to respond with username and primary group for an authenticated user. The access-point needs this to sort out users into guest or internal networks. So how can I set up freeradius to return username and primary group (or any other ldap attribute) with the OK-response? -- Thomas