On 11/16/2018 12:15 PM, Cong Wang wrote:
> On Thu, Nov 15, 2018 at 8:52 PM Eric Dumazet <eric.duma...@gmail.com> wrote:
>>
>> It is very possible NIC provides an incorrect CHECKSUM_COMPLETE, in the
>> case non zero trailer bytes were added by a buggy switch (or host)
>>
>> Saeed can comment/confirm, but the theory is that the NIC does header
>> analysis and
>> computes a checksum only on the bytes of the IP frame, not including the
>> tail bytes
>> that were added by a switch.
>
>
> This theory seems can't explain why Pawel saw this warning so often,
> which is beyond the probability of a buggy switch. I don't know.
Well the bug here would be the receiver NIC, not really respecting
CHECKSUM_COMPLETE premise
(provide a checksum over all the bytes, regardless of how smart header parsing
can be on the NIC)
'Buggy switch' would add random bytes after IP frames, but as I mentioned, any
AF_PACKET user
can cook arbitrary padding after a valid IP (or IPv6) frame.
>
> I will try it.
>
> Thanks.
>
