__can_use_af
ipv6_present = __can_use_af(AF_INET6);
ipv6_present = __can_use_af(AF_INET6);
ipv6_present = __can_use_af(AF_INET6);
extern int __can_use_af(sa_family_t af);
if (__can_use_af((strcmp(nc->nc_protofmly, NC_INET6) == 0) ?
extern int __can_use_af(sa_family_t);
if (__can_use_af(AF_INET6)) {