> ... I just  searched the source tree. The only user-level code I found
> that uses IP_HDRINCL is traceroute and mrouted, both of which pass
> in zero for ip_off, and pass in ip_len in native byte order.

This sounds like an ad-hoc result rather than a design decision.
IMHO, for consistency this interface should be the same as all other
IP network interfaces - that is, the data should be swapped by the
user, not by the kernel.

			       _MelloN_