Re: [dpdk-dev] [PATCH] net/virtio: fix wrong TX pkt length stats

[Maxime Coquelin]

Hi Zhiyong,

On 10/11/2017 06:39 AM, Zhiyong Yang wrote:

In the function virtqueue_enqueue_xmit(), when can_push == 1 is true,
vtnet_hdr_size is added to pkt_len by calling rte_pktmbuf_prepend.
So, virtio header len should be subtracted before calling stats
function.

Fixes: 58169a9c8153 ("net/virtio: support Tx checksum offload")

Signed-off-by: Zhiyong Yang <zhiyong.y...@intel.com>
---
  drivers/net/virtio/virtio_rxtx.c | 6 ++++++
  1 file changed, 6 insertions(+)

diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
index 609b4138a..bf14f9a99 100644
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -1079,6 +1079,12 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf 
**tx_pkts, uint16_t nb_pkts)
                /* Enqueue Packet buffers */
                virtqueue_enqueue_xmit(txvq, txm, slots, use_indirect, 
can_push);

+ /* In function virtqueue_enqueue_xmit(), when can_push == 1

+                * is true, vtnet_hdr_size is added to pkt_len of mbuf. So, it
+                * should be subtracted before calling stats function.
+                */
+               if (can_push == 1)
+                       txm->pkt_len -= txvq->vq->hw->vtnet_hdr_size;
                txvq->stats.bytes += txm->pkt_len;

I acknowledge the problem, but I don't like modifying pkt_len.
This is not the case currently, but in case we want to do something
with the mbuf later in virtio_xmit_cleanup(), it could be good to have
the real length there.

What about:

if (can_push == 1)
    txvq->stats.bytes += txm->pkt_len - txvq->vq->hw->vtnet_hdr_size;
else
    txvq->stats.bytes += txm->pkt_len;

Thanks,
Maxime

                virtio_update_packet_stats(&txvq->stats, txm);
        }