Function change_route_conditional

freebsd/net/route/route_ctl.c:1152–1207

* Conditionally update route nhop/weight IFF data in @nhd_orig is * consistent with the current route data. * Nexthop in @nhd_new is consumed. */

 * Nexthop in @nhd_new is consumed.
 */
int
change_route_conditional(struct rib_head *rnh, struct rtentry *rt,
    struct rt_addrinfo *info, struct route_nhop_data *rnd_orig,
    struct route_nhop_data *rnd_new, struct rib_cmd_info *rc)
{
	struct rtentry *rt_new;
	int error = 0;

	RIB_WLOCK(rnh);

	rt_new = (struct rtentry *)rnh->rnh_lookup(info->rti_info[RTAX_DST],
	    info->rti_info[RTAX_NETMASK], &rnh->head);

	if (rt_new == NULL) {
		if (rnd_orig->rnd_nhop == NULL)
			error = add_route_nhop(rnh, rt, info, rnd_new, rc);
		else {
			/*
			 * Prefix does not exist, which was not our assumption.
			 * Update @rnd_orig with the new data and return
			 */
			rnd_orig->rnd_nhop = NULL;
			rnd_orig->rnd_weight = 0;
			error = EAGAIN;
		}
	} else {
		/* Prefix exists, try to update */
		if (rnd_orig->rnd_nhop == rt_new->rt_nhop) {
			/*
			 * Nhop/mpath group hasn't changed. Flip
			 * to the new precalculated one and return
			 */
			error = change_route_nhop(rnh, rt_new, info, rnd_new, rc);
		} else {
			/* Update and retry */
			rnd_orig->rnd_nhop = rt_new->rt_nhop;
			rnd_orig->rnd_weight = rt_new->rt_weight;
			error = EAGAIN;
		}
	}

	RIB_WUNLOCK(rnh);

	if (error == 0) {
		rib_notify(rnh, RIB_NOTIFY_DELAYED, rc);

		if (rnd_orig->rnd_nhop != NULL)
			nhop_free_any(rnd_orig->rnd_nhop);

	} else {
		if (rnd_new->rnd_nhop != NULL)
			nhop_free_any(rnd_new->rnd_nhop);
	}

	return (error);
}

/*