FInding out which before_filters are already set in Rails 3

Question

I have a DSL for controller configuration. The underlying functionality relies on before_filters. To prevent setting the before_filter more than once, I really need to find out whether a before_filter is already set in a Rails 3 controller. Since before_filter work different from class variables (inheritance, class reloading), I cannot just set a class variable to check.

Digging through the new highly abstracted code for the AbstractController callbacks does not give any clue to me whether this is possible at all.

Do I really need to call skip_filter for every DSL call in the controller?