It seems that if I open an ipv6 socket and send a packet to the ipv4
address (or to the ipv4 encapusated in an ipv6 address, with the ipv4
prefix) NetBSD doesn't send this out the wire as an IPV4 packet, but
instead I get "no route to host."

linux does this right, as do other ipv6 stacks I've dabbled in
recently.  Shouldn't we?

--Michael