Revise the ng_ppp(4) node, so that code flow is more clear. All non-link hooks get their per hook rcvdata methods, and all functions are organized corresponding to protocol stack model.
Revise the ng_ppp(4) node, so that code flow is more clear. All non-link
hooks get their per hook rcvdata methods, and all functions are organized
corresponding to protocol stack model.

Submitted by:	Alexander Motin <mav alkar.net>
Reviewed by:	archie, julian

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