netdev - Re: [PATCH net] net: Handle negative checksum offset in skb-checksum-help

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Message-ID: <CALnjE+r+He=cyPnJO9qqqKyu0K9awrEgNeBefumqp1wDN=JbWw@mail.gmail.com>
Date:	Mon, 21 Sep 2015 19:49:17 -0700
From:	Pravin Shelar <pshelar@...ira.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Tom Herbert <tom@...bertland.com>
Subject: Re: [PATCH net] net: Handle negative checksum offset in skb-checksum-help

On Mon, Sep 21, 2015 at 7:14 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Mon, 2015-09-21 at 18:04 -0700, Pravin Shelar wrote:
>> On Mon, Sep 21, 2015 at 5:14 PM, David Miller <davem@...emloft.net> wrote:
>> > From: Pravin B Shelar <pshelar@...ira.com>
>> > Date: Sun, 20 Sep 2015 23:53:17 -0700
>> >
>> >> VXLAN device can receive skb with checksum partial. But the checksum
>> >> offset could be in outer header which is pulled on receive.
>> >
>> > Such a scenerio is a bug.
>> >
>> > Anything that pulls off a header should use a utility function such
>> > as skb_pull_rcsum() or skb_postpull_rcsum() to make sure this gets
>> > fixed up properly.
>>
>> skb_postpull_rcsum() does not change checksum-offset. vxlan receive
>> already calls this function.
>
> Then the bug is here.
>
> Otherwise we might have to 'fix' other places.
>
I posted a patch to fix skb_postpull_rcsum() to handle this case. But
that was not accepted.
https://patchwork.ozlabs.org/patch/512625/

And specific solution for skb_checksum_help() was suggested.

http://marc.info/?l=linux-netdev&m=144108078931774&w=2
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