netdev - Re: [PATCH RFC v2 00/12] socket sendmsg MSG

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Message-ID: <1488321643.9415.272.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Tue, 28 Feb 2017 14:40:43 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        netdev <netdev@...r.kernel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Linux API <linux-api@...r.kernel.org>
Subject: Re: [PATCH RFC v2 00/12] socket sendmsg MSG_ZEROCOPY

On Tue, 2017-02-28 at 14:25 -0800, Andy Lutomirski wrote:
> On Tue, Feb 28, 2017 at 1:47 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> > On Tue, 2017-02-28 at 13:09 -0800, Andy Lutomirski wrote:
> >
> >> Does this mean that a user program that does a zerocopy send can cause
> >> a retransmitted segment to contain different data than the original
> >> segment?  If so, is that okay?
> >
> > Same remark applies to sendfile() already
> 
> True.
> 
> >, or other zero copy modes
> > (vmsplice() + splice() )
> 
> I hate vmsplice().  I thought I remembered it being essentially
> disabled at some point due to security problems.

Right, zero copy is hard ;)

vmsplice() is not disabled in current kernels, unless I missed
something.