netdev - Re: veth regression with "don’t modify ip_summed; doing so treats packets with bad checksums as good."

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Date:	Thu, 24 Mar 2016 22:13:33 -0700
From:	Ben Greear <greearb@...delatech.com>
To:	Cong Wang <xiyou.wangcong@...il.com>
CC:	Vijay Pandurangan <vijayp@...ayp.ca>,
	netdev <netdev@...r.kernel.org>, Evan Jones <ej@...njones.ca>,
	Cong Wang <cwang@...pensource.com>
Subject: Re: veth regression with "don’t modify ip_summed; doing so treats packets with bad checksums as good."



On 03/24/2016 10:06 PM, Cong Wang wrote:
> On Thu, Mar 24, 2016 at 9:34 PM, Ben Greear <greearb@...delatech.com> wrote:
>>
>>
>> On 03/24/2016 06:44 PM, Vijay Pandurangan wrote:
>>>
>>> Oops, I think my last email didn't go through due to an inadvertent
>>> html attachment from my phone mail client.
>>>
>>> Can you send us a copy of a packet you're sending and/or confirm that
>>> the IP and UDP4 checksums are set correctly in the packet?
>>>
>>> If those are set right, I think we need to read through the networking
>>> code again to see why this is broken...
>>
>>
>> Wireshark decodes the packet as having no checksum errors.
>>
>> I think the contents of the packet is correct, but the 'ip_summed'
>> field is set incorrectly to 'NONE' when transmitting on a raw packet
>> socket.
>
> Yeah, these bugs are all due to the different interpretations of
> ip_summed on TX path and RX path. I think the following patch
> should work, if the comments don't mislead me. Could you give
> it a try?
>
> For the long term, we need to unify the meaning of ip_summed
> on TX path and RX path, or at least translate it in skb_scrub_packet().

I can test this tomorrow, but I think it will not work.  I'm not sending raw
IP frames, I'm sending full ethernet frames.  Socket is PF_PACKET, SOCK_RAW.

Your patch may still be useful for others though?

Thanks,
Ben

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