TX_SKIP
sc->tx.cur = TX_SKIP(sc->tx.cur, nsegs);
#define TX_NEXT(n) TX_SKIP(n, 1)
index = TX_SKIP(index, nsegs);
sc->sc_tx.cur = TX_SKIP(sc->sc_tx.cur, nsegs);
#define TX_NEXT(n) TX_SKIP(n, 1)