Function get_nhgrp

freebsd/net/route/nhgrp_ctl.c:431–500

* Creates or looks up an existing nexthop group based on @wn and @num_nhops. * * Returns referenced nhop group or NULL, passing error code in @perror. */

 * Returns referenced nhop group or NULL, passing error code in @perror.
 */
struct nhgrp_priv *
get_nhgrp(struct nh_control *ctl, struct weightened_nhop *wn, int num_nhops,
    int *perror)
{
	struct nhgrp_priv *key, *nhg_priv;

	if (num_nhops > RIB_MAX_MPATH_WIDTH) {
		*perror = E2BIG;
		return (NULL);
	}

	if (ctl->gr_head.hash_size == 0) {
		/* First multipath request. Bootstrap mpath datastructures. */
		if (nhgrp_ctl_alloc_default(ctl, M_NOWAIT) == 0) {
			*perror = ENOMEM;
			return (NULL);
		}
	}

	/* Sort nexthops & check there are no duplicates */
	sort_weightened_nhops(wn, num_nhops);
	uint32_t last_id = 0;
	for (int i = 0; i < num_nhops; i++) {
		if (wn[i].nh->nh_priv->nh_idx == last_id) {
			*perror = EEXIST;
			return (NULL);
		}
		last_id = wn[i].nh->nh_priv->nh_idx;
	}

	if ((key = alloc_nhgrp(wn, num_nhops)) == NULL) {
		*perror = ENOMEM;
		return (NULL);
	}

	nhg_priv = find_nhgrp(ctl, key);
	if (nhg_priv != NULL) {
		/*
		 * Free originally-created group. As it hasn't been linked
		 *  and the dependent nexhops haven't been referenced, just free
		 *  the group.
		 */
		destroy_nhgrp_int(key);
		*perror = 0;
		return (nhg_priv);
	} else {
		/* No existing group, try to link the new one */
		if (!ref_nhgrp_nhops(key)) {
			/*
			 * Some of the nexthops have been scheduled for deletion.
			 * As the group hasn't been linked / no nexhops have been
			 *  referenced, call the final destructor immediately.
			 */
			destroy_nhgrp_int(key);
			*perror = EAGAIN;
			return (NULL);
		}
		if (link_nhgrp(ctl, key) == 0) {