netdev - Re: [PATCH V4 net 2/2] net: fix tcp reset packet flowlabel for ipv6

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Date:   Mon, 31 Jul 2017 15:35:02 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Shaohua Li <shli@...nel.org>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>, Shaohua Li <shli@...com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Florent Fourcot <flo@...rcot.fr>
Subject: Re: [PATCH V4 net 2/2] net: fix tcp reset packet flowlabel for ipv6

On Mon, Jul 31, 2017 at 3:19 PM, Shaohua Li <shli@...nel.org> wrote:
>  static inline __be32 ip6_make_flowlabel(struct net *net, struct sk_buff *skb,
>                                         __be32 flowlabel, bool autolabel,
> -                                       struct flowi6 *fl6)
> +                                       struct flowi6 *fl6, u32 hash)
>  {
> -       u32 hash;
> -
>         /* @flowlabel may include more than a flow label, eg, the traffic class.
>          * Here we want only the flow label value.
>          */
> @@ -788,7 +786,8 @@ static inline __be32 ip6_make_flowlabel(struct net *net, struct sk_buff *skb,
>              net->ipv6.sysctl.auto_flowlabels != IP6_AUTO_FLOW_LABEL_FORCED))
>                 return flowlabel;
>
> -       hash = skb_get_hash_flowi6(skb, fl6);
> +       if (skb)
> +               hash = skb_get_hash_flowi6(skb, fl6);


Why not just move skb_get_hash_flowi6() to its caller?
This check is not necessary. If you don't want to touch
existing callers, you can just introduce a wrapper:


static inline __be32 ip6_make_flowlabel(struct net *net, struct sk_buff *skb,
                                        __be32 flowlabel, bool autolabel,
                                        struct flowi6 *fl6)
{
  u32 hash = skb_get_hash_flowi6(skb, fl6);
  return __ip6_make_flowlabel(net, flowlabel, autolabel, hash);
}

And your code can just call:

__ip6_make_flowlabel(net, flowlabel, autolabel, sk->sk_txhash);