static int
mlx5e_xmit_locked(if_t ifp, struct mlx5e_sq *sq, struct mbuf *mb)
{
        struct mbufq *mq;
        struct mbuf *m;
        int err = 0;

        if (unlikely((if_getdrvflags(ifp) & IFF_DRV_RUNNING) == 0 ||
            READ_ONCE(sq->running) == 0)) {
                m_freem(mb);
                return (ENETDOWN);
        }

        /* Do transmit */
        if (mb->m_pkthdr.csum_flags & CSUM_EXTX) {
                mq = mb->m_pkthdr.ex_txq;
                mb->m_pkthdr.ex_txq = NULL;
                mb->m_pkthdr.csum_flags &= ~CSUM_EXTX;
                while (err == 0 && (m = mbufq_dequeue(mq)) != NULL) {
                        err = mlx5e_sq_xmit(sq, &m);
                        if (err != 0) {
                                m_freem(m);
                                err = ENOBUFS;
                        }
                }
        } else {
                err = mlx5e_sq_xmit(sq, &mb);
                if (err != 0) {
                        /* NOTE: m_freem() is NULL safe */
                        m_freem(mb);
                        err = ENOBUFS;
                }
        }

        /* Write the doorbell record, if any. */
        mlx5e_tx_notify_hw(sq, false);