netdev - Re: [PATCH 2/2] ipv6: don't deliver packets with zero length to raw sockets

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Message-ID: <CAOTh05BdKhTaWJ5OG=BE49TMha4jPjK4rgQ-Xad40W9A0D6HxA@mail.gmail.com>
Date:   Sat, 22 Apr 2017 22:10:31 +1000
From:   Jamie Bainbridge <jbainbri@...hat.com>
To:     David Miller <davem@...emloft.net>
Cc:     Sabrina Dubroca <sd@...asysnail.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        James Morris <jmorris@...ei.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>, netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] ipv6: don't deliver packets with zero length to raw sockets

On Sat, Apr 22, 2017 at 12:53 AM, David Miller <davem@...emloft.net> wrote:
> From: Jamie Bainbridge <jbainbri@...hat.com>
> Date: Fri, 21 Apr 2017 21:18:00 +1000
>
>> I cannot see the use in delivering a skb with zero bytes after the
>> network header to a raw socket.
>
> Then it cannot be used to look at zero length UDP packets, which are
> completely legal and used.
>
> So we must deliver it.

Understood, thank you both for the clarification.

That would mean the pattern of select/ioctl/recvfrom is the incorrect
way to code an IPv6 raw socket application. I will let our user know.

How about the other patch in this series? That actually is a valid bug
when skb are paged in a certain way. That patch does not change
behaviour, it just allows ioctl to return the correct result whether
data is linear or paged. Will I resubmit that patch on its own with a
revised commit message?

Jamie