It's getting close to the time to actually needing filtering support for
IPv6 (if not past it).  Matthew and I discussed a number of alternatives
and eventually seemed content with the idea of adding a single pfil struct
to "struct protosw".  The contents of that struct would be private to pfil
but would likely include (at least) list heads for input and output
processing functions for packets in that protocol family.  The various pfil
support functions would need to be changed to accomodate a protocol value
as being a qualifier to the flag (which is either IN or OUT), along with
the current calling.

This provides us with a mechanism which supports the addition of filtering
functions for any of the defined protocols which use 'struct protosw' -
appletalk is another non-IP one which comes to mind.

With this done, the final step is to add pfil support to the IPv6 input
and output functions. 

These changes to pfil are independant of anything which might use them and
continues to provide a good framework for other code to use in implementing
a filtering mechanism.

Thoughts ?

Darren