Function iflib_txq_drain

freebsd/net/iflib.c:3726–3832

}

static uint32_t
iflib_txq_drain(struct ifmp_ring *r, uint32_t cidx, uint32_t pidx)
{
	iflib_txq_t txq = r->cookie;
	if_ctx_t ctx = txq->ift_ctx;
	if_t ifp = ctx->ifc_ifp;
	struct mbuf *m, **mp;
	int avail, bytes_sent, skipped, count, err, i;
	int mcast_sent, pkt_sent, reclaimed;
	bool do_prefetch, rang, ring;

	if (__predict_false(!(if_getdrvflags(ifp) & IFF_DRV_RUNNING) ||
			    !LINK_ACTIVE(ctx))) {
		DBG_COUNTER_INC(txq_drain_notready);
		return (0);
	}
	reclaimed = iflib_completed_tx_reclaim(txq, RECLAIM_THRESH(ctx));
	rang = iflib_txd_db_check(txq, reclaimed && txq->ift_db_pending);
	avail = IDXDIFF(pidx, cidx, r->size);

	if (__predict_false(ctx->ifc_flags & IFC_QFLUSH)) {
		/*
		 * The driver is unloading so we need to free all pending packets.
		 */
		DBG_COUNTER_INC(txq_drain_flushing);
		for (i = 0; i < avail; i++) {
			if (__predict_true(r->items[(cidx + i) & (r->size-1)] != (void *)txq))
				m_freem(r->items[(cidx + i) & (r->size-1)]);
			r->items[(cidx + i) & (r->size-1)] = NULL;
		}
		return (avail);
	}

	if (__predict_false(if_getdrvflags(ctx->ifc_ifp) & IFF_DRV_OACTIVE)) {
		txq->ift_qstatus = IFLIB_QUEUE_IDLE;
		CALLOUT_LOCK(txq);
		callout_stop(&txq->ift_timer);
		CALLOUT_UNLOCK(txq);
		DBG_COUNTER_INC(txq_drain_oactive);
		return (0);
	}

	/*
	 * If we've reclaimed any packets this queue cannot be hung.
	 */
	if (reclaimed)
		txq->ift_qstatus = IFLIB_QUEUE_IDLE;
	skipped = mcast_sent = bytes_sent = pkt_sent = 0;
	count = MIN(avail, TX_BATCH_SIZE);
#ifdef INVARIANTS
	if (iflib_verbose_debug)
		printf("%s avail=%d ifc_flags=%x txq_avail=%d ", __FUNCTION__,
		       avail, ctx->ifc_flags, TXQ_AVAIL(txq));
#endif
	do_prefetch = (ctx->ifc_flags & IFC_PREFETCH);
	err = 0;
	for (i = 0; i < count && TXQ_AVAIL(txq) >= MAX_TX_DESC(ctx) + 2; i++) {
		int rem = do_prefetch ? count - i : 0;