netdev - Re: [PATCH net v3 1/3] net/sched: act_csum: pull all VLAN headers before checksumming

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Message-ID: <CAM_iQpW68XR3Y6gyb0zyd3qooCwPHBM1Fm+THcS=migSNsHMzA@mail.gmail.com>
Date:   Fri, 31 May 2019 11:38:41 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Davide Caratti <dcaratti@...hat.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        "David S . Miller" <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Shuang Li <shuali@...hat.com>,
        Eli Britstein <elibr@...lanox.com>,
        Stephen Hemminger <stephen@...workplumber.org>
Subject: Re: [PATCH net v3 1/3] net/sched: act_csum: pull all VLAN headers
 before checksumming

On Fri, May 31, 2019 at 10:26 AM Davide Caratti <dcaratti@...hat.com> wrote:
> diff --git a/net/sched/act_csum.c b/net/sched/act_csum.c
> index 14bb525e355e..e8308ddcae9d 100644
> --- a/net/sched/act_csum.c
> +++ b/net/sched/act_csum.c
> @@ -574,7 +574,6 @@ static int tcf_csum_act(struct sk_buff *skb, const struct tc_action *a,
>                         struct tcf_result *res)
>  {
>         struct tcf_csum *p = to_tcf_csum(a);
> -       bool orig_vlan_tag_present = false;
>         unsigned int vlan_hdr_count = 0;
>         struct tcf_csum_params *params;
>         u32 update_flags;
> @@ -604,17 +603,8 @@ static int tcf_csum_act(struct sk_buff *skb, const struct tc_action *a,
>                 break;
>         case cpu_to_be16(ETH_P_8021AD): /* fall through */
>         case cpu_to_be16(ETH_P_8021Q):
> -               if (skb_vlan_tag_present(skb) && !orig_vlan_tag_present) {
> -                       protocol = skb->protocol;
> -                       orig_vlan_tag_present = true;
> -               } else {
> -                       struct vlan_hdr *vlan = (struct vlan_hdr *)skb->data;
> -
> -                       protocol = vlan->h_vlan_encapsulated_proto;
> -                       skb_pull(skb, VLAN_HLEN);
> -                       skb_reset_network_header(skb);
> -                       vlan_hdr_count++;
> -               }
> +               if (tc_skb_pull_vlans(skb, &vlan_hdr_count, &protocol))
> +                       goto drop;
>                 goto again;

Why do you still need to loop here? tc_skb_pull_vlans() already
contains a loop to pop all vlan tags?



>         }
>
> diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
> index d4699156974a..382ee69fb1a5 100644
> --- a/net/sched/cls_api.c
> +++ b/net/sched/cls_api.c
> @@ -3300,6 +3300,28 @@ unsigned int tcf_exts_num_actions(struct tcf_exts *exts)
>  }
>  EXPORT_SYMBOL(tcf_exts_num_actions);
>
> +int tc_skb_pull_vlans(struct sk_buff *skb, unsigned int *hdr_count,
> +                     __be16 *proto)


It looks like this function fits better in net/core/skbuff.c, because
I don't see anything TC specific.


> +{
> +       if (skb_vlan_tag_present(skb))
> +               *proto = skb->protocol;
> +
> +       while (eth_type_vlan(*proto)) {
> +               struct vlan_hdr *vlan;
> +
> +               if (unlikely(!pskb_may_pull(skb, VLAN_HLEN)))
> +                       return -ENOMEM;
> +
> +               vlan = (struct vlan_hdr *)skb->data;
> +               *proto = vlan->h_vlan_encapsulated_proto;
> +               skb_pull(skb, VLAN_HLEN);
> +               skb_reset_network_header(skb);

Any reason not to call __skb_vlan_pop() directly?


> +               (*hdr_count)++;
> +       }
> +       return 0;
> +}


Thanks.