nm_bound_var
u_int nm_bound_var(u_int *v, u_int dflt, u_int lo, u_int hi, const char *msg);
nm_bound_var(&tmp_na.num_tx_rings, 1, 1, NM_BDG_MAXRINGS, NULL);
nm_bound_var(&tmp_na.num_rx_rings, 1, 1, NM_BDG_MAXRINGS, NULL);
nm_bound_var(&nmr->nr_tx_slots, NM_BRIDGE_RINGSIZE,
nm_bound_var(&nmr->nr_rx_slots, NM_BRIDGE_RINGSIZE,