KKASSERT
KKASSERT(rxst_ring->rsr_index < ET_RX_NSTAT);
KKASSERT(rx_ring->rr_index < ET_RX_NDESC);
KKASSERT(tx_ring->tr_ready_index < ET_TX_NDESC);
KKASSERT(tx_ring->tr_ready_index < ET_TX_NDESC);
KKASSERT(last_idx >= 0);
KKASSERT(tbd->tbd_used <= ET_TX_NDESC);
KKASSERT(tbd->tbd_start_index < ET_TX_NDESC);
KKASSERT(tbd->tbd_used > 0);
KKASSERT(buf_idx < ET_RX_NDESC);