netdev - Re: [PATCH net-next 2/2] net: optimize skb_postpull

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Message-ID: <CANn89i+sANhK4m_JptWgnjXf5VRuSYw6MkLKfS3ut5SbUbrmoQ@mail.gmail.com>
Date:   Fri, 3 Dec 2021 08:58:49 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     David Laight <David.Laight@...lab.com>,
        David Lebrun <dlebrun@...gle.com>
Cc:     Vladimir Oltean <olteanv@...il.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 2/2] net: optimize skb_postpull_rcsum()

On Fri, Dec 3, 2021 at 8:47 AM David Laight <David.Laight@...lab.com> wrote:
>
> > > Eric, could you please send a patch with this change?
> >
> > Sure, I will do this today, after more testing.
>
> I've just done a quick grep and found two ~csum_partial() in
> include/net/seg6.h.

This is what I already mentioned in this email thread, and the reason
I have CCed David Lebrun.

https://marc.info/?l=linux-netdev&m=163845851801840&w=2

David, can you comment on this ?


> Both are wrong (and completely horrid).
>
> There are also 40 csum_partial(buf, len, 0).
> If all the buffer is zero they'll return zero - invalid.
> They ought to be changed to csum_partial(buf, len, 0xffff).
>

Please point where all zero buffers can be valid in the first place.