From: Eric Dumazet <eric.dumazet@gmail.com>
To: Cong Wang <xiyou.wangcong@gmail.com>,
Eric Dumazet <eric.dumazet@gmail.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>,
Linux Kernel Network Developers <netdev@vger.kernel.org>,
Tom Herbert <tom@herbertland.com>,
Eric Dumazet <edumazet@google.com>,
Saeed Mahameed <saeedm@mellanox.com>
Subject: Re: [Patch net] net: invert the check of detecting hardware RX checksum fault
Date: Fri, 16 Nov 2018 13:33:35 -0800 [thread overview]
Message-ID: <5af4ca88-62f5-e54e-78b3-704405722925@gmail.com> (raw)
In-Reply-To: <CAM_iQpX8jpfq1CtavmsOvcfTW=ecPeUn5gJFNG1Z4NU+_urv6Q@mail.gmail.com>
On 11/16/2018 12:15 PM, Cong Wang wrote:
> On Thu, Nov 15, 2018 at 8:52 PM Eric Dumazet <eric.dumazet@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.
>
next prev parent reply other threads:[~2018-11-17 7:47 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-15 23:16 [Patch net] net: invert the check of detecting hardware RX checksum fault Cong Wang
2018-11-16 1:52 ` Herbert Xu
2018-11-16 2:23 ` Cong Wang
2018-11-16 4:50 ` Herbert Xu
2018-11-16 20:06 ` Cong Wang
2018-11-16 21:32 ` Cong Wang
2018-11-19 4:01 ` Herbert Xu
2018-11-19 19:25 ` Cong Wang
2018-11-20 3:09 ` Herbert Xu
2018-11-22 1:25 ` Paweł Staszewski
2018-11-16 4:52 ` Eric Dumazet
2018-11-16 4:59 ` Herbert Xu
2018-11-16 20:10 ` Cong Wang
2018-11-16 20:15 ` Cong Wang
2018-11-16 21:33 ` Eric Dumazet [this message]
2018-11-20 1:42 ` Cong Wang
2018-11-20 1:47 ` Eric Dumazet
2018-11-20 18:13 ` David Miller
2018-11-20 18:18 ` Eric Dumazet
2018-11-21 3:35 ` Herbert Xu
2018-11-18 0:40 ` David Miller
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