netdev - Re: [PATCH V2 net] net: fix tcp reset packet flowlabel for ipv6

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Date:   Tue, 25 Jul 2017 14:32:15 -0700
From:   Shaohua Li <shli@...nel.org>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        kernel-team <Kernel-team@...com>, Shaohua Li <shli@...com>,
        Eric Dumazet <eric.dumazet@...il.com>, flo@...rcot.fr
Subject: Re: [PATCH V2 net] net: fix tcp reset packet flowlabel for ipv6

On Mon, Jul 24, 2017 at 04:12:53PM -0700, Cong Wang wrote:
> On Mon, Jul 24, 2017 at 1:34 PM, David Miller <davem@...emloft.net> wrote:
> > From: Shaohua Li <shli@...nel.org>
> > Date: Tue, 18 Jul 2017 12:03:37 -0700
> >
> >> +     /* Since this is being sent on the wire obfuscate hash a bit
> >> +      * to minimize possbility that any useful information to an
> >> +      * attacker is leaked. Only lower 20 bits are relevant.
> >> +      */
> >> +     rol32(hash, 16);
> >
> > This doesn't help anything at all.
> 
> I believe the above code is copy-n-pasted from ip6_make_flowlabel()
> (with few adjustments). Don't know why we can't refactor that function
> for reuse.

There are just several lines of code, I really don't want to add adhoc if-else
for fast path.

Thanks,
Shaohua