Re: [PATCH mptcp-next v2] mptcp: fix checksum byte order

[Mat Martineau <mathew.j.martineau@linux.intel.com>]

On Wed, 11 May 2022, Paolo Abeni wrote:

> On Tue, 2022-05-10 at 16:10 -0700, Mat Martineau wrote:
>> On Tue, 10 May 2022, Paolo Abeni wrote:
>>
>>> The MPTCP code typecasts the checksum value to u16 and
>>> then convert it to big endian while storing the value into
>>> the MPTCP option.
>>>
>>> As a result, the wire encoding for little endian host is
>>> wrong, and that causes interoperabilty interoperability
>>> issues with other implementation or host with different endianess.
>>>
>>> Address the issue writing in the packet the unmodified __sum16 value.
>>>
>>> MPTCP checksum is disabled by default, interoperating with systems
>>> with bad mptcp-level csum encodying should cause fallback to TCP.
>>>
>>> Fixes: c5b39e26d003 ("mptcp: send out checksum for DSS")
>>> Fixes: 390b95a5fb84 ("mptcp: receive checksum for DSS")
>>> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
>>> ---
>>> v1 -> v2:
>>> - move the typecast inside put_len_csum (Mat)
>>> - updated the commit message (Mat)
>>> - fix a few sparse issues
>>
>> Hi Paolo, thanks for the v2:
>>
>> Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
>>
>> (for export-net)
>>
>> Still ok with you to apply this to export-net? There are a couple of minor
>> conflicts when rebasing to export-net, and it also creates a merge
>> conflict with net-next. But I think it's worth it to be able to say "every
>> 5.18 and later kernel has the checksum fix".
>
> Agreed.
>
>> Have you tried backporting this commit to 5.17-stable or 5.15-stable?
>
> No, that is likely worthy, but I really have my hands full :( I think I
> can have a look not earlier than next week.

No problem - I can handle the backporting and sending to the stable trees.

--
Mat Martineau
Intel