In some email I received from itojun@iijlab.net, sie wrote:
> 
> >	sys/netinet6 uses very different model from normal *BSD on
> >	onion-peeling, that is the reason for the difference in type.
> >	(sys/netinet6/IMPLEMENTATION, 1.8 or somewhere near 1.8)
> >	i prefer to leave them separate.
> 
> 	i'm not objecting to add pfil hook, just would like to remind you
> 	to add to *both*.

Yup, I understand this and your reasons now.  I'll be sure to modify both.

Thanks,
Darren