From sys/socket.h:

/* 
 * Address families.
 */   
#define AF_UNSPEC       0               /* unspecified */
#define AF_LOCAL        1               /* local to host (pipes, portals) */
#define AF_UNIX         AF_LOCAL        /* backward compatibility */ 
#define AF_INET         2               /* internetwork: UDP, TCP, etc. */
..
#define AF_NS           6               /* XEROX NS protocols */

etc. and from
ftp://ftp.isi.edu/in-notes/iana/assignments/address-family-numbers/

ADDRESS FAMILY NUMBERS

Several protocols deal with multiple address families.  The 16-bit
assignments are listed here.


Number    Description                                          Reference
------    ---------------------------------------------------- ---------
     0    Reserved
     1    IP (IP version 4)
     2    IP6 (IP version 6)
     3    NSAP
     4    HDLC (8-bit multidrop)
     5    BBN 1822
     6    802 (includes all 802 media plus Ethernet "canonical format")

Now presumably, these are two different things both called "address families".
Can someone enlighten me?

I was considering

                        tmp -> hw_address.htype = HTYPE_ETHER; /* XXX */

in src/usr.sbin/dhcp/common/dispatch.c - SIOCGIFCONF returns a sockaddr_dl
for an AF_LINK interface with sdl_type=6, but dhclient sets htype to 1. Is
this 6 "canonical format", and the 1 "IPv4"?

Cheers,

Patrick