NETMAP_RING_MASK
u_int i = ringid & NETMAP_RING_MASK;
q &= NETMAP_RING_MASK;
r = (r < NETMAP_RING_MASK) ? (r | NETMAP_HW_RING) : 0;
d->req.nr_ringid |= (flags & ~NETMAP_RING_MASK);
d->req.nr_ringid & NETMAP_RING_MASK;