rt_alloc
if ((rt = rt_alloc(rnh, dst, netmask)) == NULL) {
struct rtentry *rt_new = rt_alloc(rh_dst, rt_key(rt), rt_mask(rt));
if ((rt = rt_alloc(rnh, dst, netmask)) == NULL)
struct rtentry *rt_alloc(struct rib_head *rnh, const struct sockaddr *dst,