nhgrp_get_group
error = nhgrp_get_group(rnh, wn_new, num_nhops, 0, &rnd_new.rnd_nhgrp);
int nhgrp_get_group(struct rib_head *rh, struct weightened_nhop *wn, int num_nhops,
error = nhgrp_get_group(rh, wn_new, num_nhops, unhop->un_idx, &nhg);