In answer to your off topic comments:
The opennds package provides this.
Although support for radius would require development using the opennds fas api (I am aware of one or two implementations.)....
The question I pose though is "Why does anyone use radius these days?".
Sure, some large corporates have used radius for over 30 years but for new development, what does it give that can't be done easier in a variety of much less complicated ways?