nm_ring_space
tot += nm_ring_space(NETMAP_RXRING(d->nifp, i));
tot += nm_ring_space(NETMAP_TXRING(d->nifp, i));
m = nm_ring_space(rxring);
m = nm_ring_space(txring);
n = nm_ring_space(ring);
txavail = nm_ring_space(txring);
n = nm_ring_space(ring);
space = nm_ring_space(ring);
limit = nm_ring_space(ring);