In message <199610202116.OAA12953@skank.jnx.com> you write:
>Maybe the sockaddr could be pruned at four or eight bytes?

I'm uncomfortable with creating a 4-byte sockaddr_dl; I'd be afraid of
"generic" sockaddr_dl-handling code in a user program that assumes that
all of the sub-lengths are valid without checking the sockaddr length.
I'm happier with 8 bytes, but am not really sure how to come up with
the number 8.  Perhaps <net/if_dl.h> needs

#define	SDL_MINLEN	8		/* Minimum length sockaddr_dl */

since I don't think I'd want to use (sdl.sdl_data - (char *)&sdl) .

  Bill