rt_setgate
rt_setgate(rt, gateway) != 0) {
error = rt_setgate(rt, info->rti_info[RTAX_GATEWAY]);
error = rt_setgate(rt, gateway);
int rt_setgate(struct rtentry *, const struct sockaddr *);
rt_setgate(rt, &u.sa);
rt_setgate(rt, &u.sa);