in_ifaddr
#define ifatoia(ifa) ((struct in_ifaddr *)(ifa))
struct in_ifaddr *
ifa = (struct in_ifaddr *)ifp->in_ifaddr;
struct in_ifaddr *ifa;
if (ifp->in_ifaddr != NULL)
ifp->in_ifaddr = ifa;
struct in_ifaddr *ifa;
struct in_ifaddr *ia_next; /* next in list of internet addresses */
#define IA_SIN(ia) ((struct sockaddr_in *)(&((struct in_ifaddr *)ia)->ia_addr))