Hardly surprising. Unless the net filter mob have changed their habits substantially they will have not have any userland documentation whatsoever. (If I am wrong some _please_ point to me the doco. I would love to be proven wrong.)
I've banged on about this subject before http://lwn.net/Articles/325243/ Patrick (kaber) made promises in a reply. As far as I can tell nothing has changed.
Copyright © 2017, Eklektix, Inc.
Comments and public postings are copyrighted by their creators.
Linux is a registered trademark of Linus Torvalds