linux-kernel - Re: [PATCH 3.2 085/115] veth: don’t modify ip_summed; doing so treats packets with bad checksums as good.

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Date:	Sat, 30 Apr 2016 12:40:07 -0700
From:	Ben Greear <greearb@...delatech.com>
To:	Ben Hutchings <ben@...adent.org.uk>,
	Sabrina Dubroca <sd@...asysnail.net>
CC:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	akpm@...ux-foundation.org, "David S. Miller" <davem@...emloft.net>,
	Vijay Pandurangan <vijayp@...ayp.ca>,
	Cong Wang <cwang@...pensource.com>, netdev@...r.kernel.org,
	Evan Jones <ej@...njones.ca>,
	Nicolas Dichtel <nicolas.dichtel@...nd.com>,
	Phil Sutter <phil@....cc>,
	Toshiaki Makita <makita.toshiaki@....ntt.co.jp>,
	xiyou.wangcong@...il.com
Subject: Re: [PATCH 3.2 085/115] veth: don’t modify ip_summed; doing so treats packets with bad checksums as good.



On 04/30/2016 11:33 AM, Ben Hutchings wrote:
> On Thu, 2016-04-28 at 12:29 +0200, Sabrina Dubroca wrote:
>> Hello,

>>> http://dmz2.candelatech.com/?p=linux-4.4.dev.y/.git;a=commitdiff;h=8153e983c0e5eba1aafe1fc296248ed2a553f1ac;hp=454b07405d694dad52e7f41af5816eed0190da8a
>> Actually, no, this is not really a regression.
> [...]
>
> It really is.  Even though the old behaviour was a bug (raw packets
> should not be changed), if there are real applications that depend on
> that then we have to keep those applications working somehow.

To be honest, I fail to see why the old behaviour is a bug when sending
raw packets from user-space.  If raw packets should not be changed, then
we need some way to specify what the checksum setting is to begin with,
otherwise, user-space has not enough control.

A socket option for new programs, and sysctl configurable defaults for raw sockets
for old binary programs would be sufficient I think.

Thanks,
Ben

-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com