Facebook canvas app with rails3

I'm writing facebook canvas application with Rails3 using omniauth-facebook gem.
The few moments are not clear:

    Rdirect after sing in (in '/auth/facebook/callback' => 'session#create'):
    After successful sing_in if user is redirected to root_url it sometime
arrives to my canvas page URL (http://localhost:3000) outside of the frame. On
other hand, when redirecting him to my app url (http://apps.facebook.com/my_app)
it sometime stacks on blank page inside the frame. So how to handle this
redirect correctly?

    What is a proper way to link between pages inside my app? Currently I use
relative links and top.location url is always stay my app url
(http://apps.facebook.com/my_app). But I saw that many facebook apps redirect
the client top.location (http://apps.facebook.com/my_app/internal_link)… It
raises one more question:

    Now facebook always fetch my app into the iframe using POST method. How to
handle this behavior in RESTful rails application?

I'd very thankful for any advices...