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

[Paolo Abeni <pabeni@redhat.com>]

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.

/P