netdev - Re: [PATCH] tcp: really ignore MSG_ZEROCOPY if no SO

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Date:   Thu, 6 Sep 2018 15:44:48 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     vincent.whitchurch@...s.com
Cc:     David Miller <davem@...emloft.net>,
        Network Development <netdev@...r.kernel.org>,
        Willem de Bruijn <willemb@...gle.com>, rabinv@...s.com
Subject: Re: [PATCH] tcp: really ignore MSG_ZEROCOPY if no SO_ZEROCOPY

On Thu, Sep 6, 2018 at 9:58 AM Vincent Whitchurch
<vincent.whitchurch@...s.com> wrote:
>
> According to the documentation in msg_zerocopy.rst, the SO_ZEROCOPY
> flag was introduced because send(2) ignores unknown message flags and
> any legacy application which was accidentally passing the equivalent of
> MSG_ZEROCOPY earlier should not see any new behaviour.
>
> Before commit f214f915e7db ("tcp: enable MSG_ZEROCOPY"), a send(2) call
> which passed the equivalent of MSG_ZEROCOPY without setting SO_ZEROCOPY
> would succeed.  However, after that commit, it fails with -ENOBUFS.  So
> it appears that the SO_ZEROCOPY flag fails to fulfill its intended
> purpose.  Fix it.
>
> Fixes: f214f915e7db ("tcp: enable MSG_ZEROCOPY")
>
> Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>

Acked-by: Willem de Bruijn <willemb@...gle.com>

Good catch, thanks for fixing this.

Please remember to mark patches with PATCH net