That`s simple: Add another SQL module, that You would use in accounting section. The query on accounting stop would update the Session-Timeout appropriately. Comment out other queries in this added module. All info is in sql.conf - copy that file, modify queries, and include in radiusd.conf that modified file.
I haven`t tried it - maybe You don`t need to add another module, just add another query after semicolon. Greetings Marcin Mańk - List info/subscribe/unsubscribe? See http://www.freeradius.org/list/users.html
