Re: [PATCH] sky2: don't do GRO on second port

Jarek Poplawski
2010-09-02T11:02:21Z

On Thu, Sep 02, 2010 at 12:41:45PM +0200, Eric Dumazet wrote:
> Le jeudi 02 septembre 2010 ?? 09:55 +0000, Jarek Poplawski a écrit :
>
> >
> > Exactly, but there is no "a single napi --> device mapping". And sky2
> > uses the same model. So, there is only a question of cost of this test,
> > and a question of probability of gro errors on collisions without such
> > a test in normal use. (And if gro can never do such errors for other
> > reasons?)
>
> Two vlans might carry packets in different domains, with a clash of IP
> space and TCP flows. Even with a probability of 0.000000001%, we cannot
> ever merge two packets of different domains. Really !

Hmm... But there is only a question of sky2 and this test in
__napi_gro_receive().

>
> napi->dev is not used in GRO path, as mentioned earlier,
> but in napi_get_frags(), while not needed.
>
> To make this very clear, I suggest following patch :

But where this skb gets its skb->dev now?

Jarek P.

>
> [PATCH net-next-2.6] gro: remove use of napi->dev
>
> Only use of napi->dev in GRO stack is the one found in napi_get_frags()
>
> We can remove it and use a plain dev_alloc_skb() call.
>
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> ---
> net/core/dev.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index d8c43e7..607057a 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -3248,9 +3248,11 @@ struct sk_buff *napi_get_frags(struct napi_struct *napi)
> struct sk_buff *skb = napi->skb;
>
> if (!skb) {
> - skb = netdev_alloc_skb_ip_align(napi->dev, GRO_MAX_HEAD);
> - if (skb)
> + skb = dev_alloc_skb(GRO_MAX_HEAD + NET_IP_ALIGN);
> + if (skb) {
> + skb_reserve(skb, NET_IP_ALIGN);
> napi->skb = skb;
> + }
> }
> return skb;
> }
>
>