get_unit
extern struct ifnet *get_unit __P((char *, int, ipf_stack_t *));
ifp = get_unit(iface, IP_V(ip), ifs);
# define GETIFP(x, v, ifs) get_unit(x,v, ifs)
# define GETIFP(n, v, ifs) (void *)get_unit(n, v, ifs)
# define GETIFP(n, v, ifs) get_unit(n, v, ifs)
extern struct ifnet *get_unit __P((char *, int, ipf_stack_t *));
extern phy_if_t get_unit __P((char *, int, ipf_stack_t *));
static int get_unit(dev_info_t *dip, int *cntrl_num);
if (get_unit(dip, &cntlr_num) != DDI_SUCCESS)