Re: [PATCH mptcp-net] mptcp: sockopt: set timestamp flags on subflow socket, not msk

[gang.yan@linux.dev]

April 20, 2026 at 5:46 PM, "Matthieu Baerts" <matttbe@kernel.org mailto:matttbe@kernel.org?to=%22Matthieu%20Baerts%22%20%3Cmatttbe%40kernel.org%3E > wrote:


> 
> Hi Gang,
> 
> On 20/04/2026 11:33, Gang Yan wrote:
> 
> > 
> > From: Gang Yan <yangang@kylinos.cn>
> >  
> >  Both mptcp_setsockopt_sol_socket_tstamp() and
> >  mptcp_setsockopt_sol_socket_timestamping() iterate over subflows,
> >  acquire the subflow socket lock, but then erroneously pass the MPTCP
> >  msk socket to sock_set_timestamp() / sock_set_timestamping() instead
> >  of the subflow ssk. As a result, the timestamp flags are set on the
> >  wrong socket and have no effect on the actual subflows.
> >  
> >  Pass ssk instead of sk to both helpers.
> > 
> Good catch! How did you find the issue? It would be good to add a test
> for that, but not sure how.
> 

Hi Matt,

Sorry for the late feedback.

Thanks! I’ve been using AI assistance to study and understand this part of
the code recently, and that’s how I found the issue.

And I noticed the issue of sashiko mentioned. I’ll take time to look into it
recently, and I will post updates on this issue to the mailing list.

Thanks
Gang
> > 
> > Fixes: 3f4f958c3a3c ("mptcp: sockopt: propagate timestamp request to subflows")
> > 
> It looks like this commit doesn't exist in the 'export' or 'export-net'
> branches. I guess you meant to use 9061f24bf82e instead?
> 
> When you do a git blame, do not use branches from the TopGit tree. Use
> 'net', 'net-next', or the 'export' ones.
> 
> > 
> > Fixes: 6c9a0a0f2333 ("mptcp: setsockopt: convert to mptcp_setsockopt_sol_socket_timestamping()")
> >  Assisted-by: GLM-5.1
> > 
> Thank you for using this tag!
> 
> Apart from the above, it looks good to me:
> 
> Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
> 
> I will wait for the CI, but I can also fix the SHA (if correct) when
> applying the patch.
> 
> Cheers,
> Matt
> -- 
> Sponsored by the NGI0 Core fund.
>