new_unrhdr
sc->sc_unr = new_unrhdr(1, IWI_MAX_IBSSNODE-1, &sc->sc_mtx);
struct unrhdr *new_unrhdr(int low, int high, struct mtx *mutex);
ueunit = new_unrhdr(0, INT_MAX/16, NULL);
ueunit = new_unrhdr(0, INT_MAX, NULL);