To get IPF filtering IPv6 on NBSD .1.5x, I had to use the patched 
netinet6/ip6_forward.c that Darren updated, and which was then removed
a few days later.  Look through the CVS history to see what happened
to that file.  Darren's changes got pulled.

This was on top of using IPF.recent, not the IPF.middleaged found in
the CVS tree.

It works fine, as far as I've been able to tell.

Carl