Re: vmxnet3 driver - vlan offload is on end descriptor

[Stephen Hemminger <stephen@networkplumber.org>]

On Thu, 7 Apr 2016 17:11:19 +0000
John Guzik <john@shieldxnetworks.com> wrote:

> With the new jumbo frame patch a latent bug has appeared to have been uncovered: the VLAN offload is on the last rx descriptor, when rcd->eop is true, not the first rx descriptor, when rcd->sop is true and rcd->eop could be false.
> Most likely the reason this has not been seen before is that for non-jumbo frames rcd->eop has always been true when rcd->sop is true as well.
> 
> The following patch should fix the problem:
> 
> diff --git a/drivers/net/vmxnet3/vmxnet3_rxtx.c b/drivers/net/vmxnet3/vmxnet3_rxtx.c
> index 4ac0456..3d4a5eb 100644
> --- a/drivers/net/vmxnet3/vmxnet3_rxtx.c
> +++ b/drivers/net/vmxnet3/vmxnet3_rxtx.c
> @@ -587,12 +587,6 @@ vmxnet3_post_rx_bufs(vmxnet3_rx_queue_t *rxq, uint8_t ring_id)
> static void
> vmxnet3_rx_offload(const Vmxnet3_RxCompDesc *rcd, struct rte_mbuf *rxm)
> {
> -       /* Check for hardware stripped VLAN tag */
> -       if (rcd->ts) {
> -               rxm->ol_flags |= PKT_RX_VLAN_PKT;
> -               rxm->vlan_tci = rte_le_to_cpu_16((uint16_t)rcd->tci);
> -       }
> -
>         /* Check for RSS */
>         if (rcd->rssType != VMXNET3_RCD_RSS_TYPE_NONE) {
>                 rxm->ol_flags |= PKT_RX_RSS_HASH;
> @@ -737,7 +731,15 @@ vmxnet3_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts, uint16_t nb_pkts)
>                 rxq->last_seg = rxm;
> 
>                 if (rcd->eop) {
> -                       rx_pkts[nb_rx++] = rxq->start_seg;
> +                       struct rte_mbuf *start = rxq->start_seg;
> +
> +                       /* Check for hardware stripped VLAN tag */
> +                       if (rcd->ts) {
> +                               start->ol_flags |= PKT_RX_VLAN_PKT;
> +                               start->vlan_tci = rte_le_to_cpu_16((uint16_t)rcd->tci);
> +                       }
> +
> +                       rx_pkts[nb_rx++] = start;
>                         rxq->start_seg = NULL;
>                 }
> 
> 

Yes, your analysis and bug fix looks correct. The Linux driver checks for VLAN tag in the
last (eop) segment.

Acked-by: Stephen Hemminger <stephen@networkplumber.org>