Re: [Xen-devel] [PATCH 6/6] xen-netback: don't disconnect frontend when seeing oversize frame

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Mon, Mar 25, 2013 at 11:08:22AM +0000, Wei Liu wrote:
> Some buggy frontends may generate frames larger than 64 KiB. We should
> aggresively consume all slots and drop the packet instead of disconnecting the
> frontend.
> 
> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>

CC stable@xxxxxxxxxxxxxxx ?

> ---
>  drivers/net/xen-netback/netback.c |   32 ++++++++++++++++++++++++++------
>  1 file changed, 26 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/xen-netback/netback.c 
> b/drivers/net/xen-netback/netback.c
> index a634dc5..1971623 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -924,10 +924,12 @@ static void netbk_fatal_tx_err(struct xenvif *vif)
>  static int netbk_count_requests(struct xenvif *vif,
>                               struct xen_netif_tx_request *first,
>                               struct xen_netif_tx_request *txp,
> -                             int work_to_do)
> +                             int work_to_do,
> +                             RING_IDX first_idx)
>  {
>       RING_IDX cons = vif->tx.req_cons;
>       int slots = 0;
> +     bool drop = false;
>  
>       if (!(first->flags & XEN_NETTXF_more_data))
>               return 0;
> @@ -947,10 +949,21 @@ static int netbk_count_requests(struct xenvif *vif,
>  
>               memcpy(txp, RING_GET_REQUEST(&vif->tx, cons + slots),
>                      sizeof(*txp));
> -             if (txp->size > first->size) {
> -                     netdev_err(vif->dev, "Packet is bigger than frame.\n");
> -                     netbk_fatal_tx_err(vif);
> -                     return -EIO;
> +
> +             /* If the guest submitted a frame >= 64 KiB then
> +              * first->size overflowed and following slots will
> +              * appear to be larger than the frame.
> +              *
> +              * This cannot be fatal error as there are buggy
> +              * frontends that do this.
> +              *
> +              * Consume all slots and drop the packet.
> +              */
> +             if (!drop && txp->size > first->size) {
> +                     if (net_ratelimit())
> +                             netdev_dbg(vif->dev,
> +                                        "Packet is bigger than frame.\n");
> +                     drop = true;
>               }
>  
>               first->size -= txp->size;
> @@ -963,6 +976,12 @@ static int netbk_count_requests(struct xenvif *vif,
>                       return -EINVAL;
>               }
>       } while ((txp++)->flags & XEN_NETTXF_more_data);
> +
> +     if (drop) {
> +             netbk_tx_err(vif, first, first_idx + slots);
> +             return -EIO;
> +     }
> +
>       return slots;
>  }
>  
> @@ -1429,7 +1448,8 @@ static unsigned xen_netbk_tx_build_gops(struct 
> xen_netbk *netbk)
>                               continue;
>               }
>  
> -             ret = netbk_count_requests(vif, &txreq, txfrags, work_to_do);
> +             ret = netbk_count_requests(vif, &txreq, txfrags,
> +                                        work_to_do, idx);
>               if (unlikely(ret < 0))
>                       continue;
>  
> -- 
> 1.7.10.4
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxx
> http://lists.xen.org/xen-devel
> 

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