Re: [PATCH mptcp-next v2 1/6] mptcp: add subflow unique id

[Paolo Abeni <pabeni@redhat.com>]

On Tue, 2023-05-23 at 17:20 +0200, Matthieu Baerts wrote:
> Hi Paolo,
> 
> On 22/05/2023 15:56, Paolo Abeni wrote:
> > The user-space need to preperly account the data received/sent by
> > individual subflows. When additional subflows are created and/or
> > closed during the MPTCP socket lifetime, the information currently
> > exposed via MPTCP_TCPINFO are not enough: subflows are identifed only
> > by the sequential position inside the info dumps, and that will change
> > with the above mentioned events.
> > 
> > To solve the above problem, this patch introduces a new subflow identifier
> > that is unique inside the given mptcp socket scope.
> > 
> > The initial subflow get the id 1 and the other subflows get incremental
> > values at join time.
> > 
> > Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> > ---
> > v1 -> v2:
> >  - properly set subflow_id for the first passive subflow and active subflows, too
> >  - drop the tcpi_fackets overload
> > ---
> 
> (...)
> 
> > @@ -3203,6 +3206,7 @@ struct sock *mptcp_sk_clone_init(const struct sock *sk,
> >  	msk->snd_nxt = msk->write_seq;
> >  	msk->snd_una = msk->write_seq;
> >  	msk->wnd_end = msk->snd_nxt + req->rsk_rcv_wnd;
> > +	msk->subflow_id++;
> 
> It is a bit confusing. Just to be sure, here it would be the same to do
> 
>   msk->subflow_id = 1;
> 
> because subflow_id from the listener will be 0, right?

You are right, my code above is confusing and even incorrect. I'll
replace it with the plain assignment.

Thanks!

/P