[Xen-devel] Re: [PATCH] xen: netfront: Drop GSO SKBs which do not have csum_blank.

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 01/05/2011 05:23 AM, Ian Campbell wrote:
> The Linux network stack expects all GSO SKBs to have ip_summed ==
> CHECKSUM_PARTIAL (which implies that the frame contains a partial
> checksum) and the Xen network ring protocol similarly expects an SKB
> which has GSO set to also have NETRX_csum_blank (which also implies a
> partial checksum). Therefore drop such frames on receive otherwise
> they will trigger the warning in skb_gso_segment.
>
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> Cc: netdev@xxxxxxxxxxxxxxx
> ---
>  drivers/net/xen-netfront.c |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
> index cdbeec9..8b8c480 100644
> --- a/drivers/net/xen-netfront.c
> +++ b/drivers/net/xen-netfront.c
> @@ -836,6 +836,11 @@ static int handle_incoming_queue(struct net_device *dev,
>                               dev->stats.rx_errors++;
>                               continue;
>                       }
> +             } else if (skb_is_gso(skb)) {
> +                     kfree_skb(skb);
> +                     packets_dropped++;
> +                     dev->stats.rx_errors++;
> +                     continue;

This looks redundant; why not something like:

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 47e6a71..c1b8f64 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -852,13 +852,12 @@ static int handle_incoming_queue(struct net_device *dev,
                /* Ethernet work: Delayed to here as it peeks the header. */
                skb->protocol = eth_type_trans(skb, dev);
 
-               if (skb->ip_summed == CHECKSUM_PARTIAL) {
-                       if (skb_checksum_setup(skb)) {
-                               kfree_skb(skb);
-                               packets_dropped++;
-                               dev->stats.rx_errors++;
-                               continue;
-                       }
+               if (skb->ip_summed != CHECKSUM_PARTIAL ||
+                   skb_checksum_setup(skb)) {
+                       kfree_skb(skb);
+                       packets_dropped++;
+                       dev->stats.rx_errors++;
+                       continue;
                }
 
                dev->stats.rx_packets++;

Thanks,
        J



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