>	btw, freebsd changed the value from "off" to "on" between
>	4.x to 5.x to secure itself from the possible vulnerabilities.
>	http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/netinet6/in6_proto.c.diff?r1=1.17&r2=1.18
>	openbsd does not implement IPv4 mapped address behavior at all.
>	why netbsd has to make the backward change, i.e. secure behavior to
>	insecure behavior?  portable programs cope with the issue already
>	(since MS WinXP is basically "v6only=1").

	fwiw, kame will not change the behavior (v6only=1).

itojun