Re: [PATCHv3 net-next 1/5] sctp: add SCTP_ADDR_POTENTIALLY_FAILED notification

[Xin Long <lucien.xin@gmail.com>]

On Fri, Oct 18, 2019 at 11:56 PM David Laight <David.Laight@aculab.com> wrote:
>
> I've found v3 :-)
ah okay. sorry.

> But it isn't that much better than v2.
>
> From: Xin Long
> > Sent: 14 October 2019 07:15
> > SCTP Quick failover draft section 5.1, point 5 has been removed
> > from rfc7829. Instead, "the sender SHOULD (i) notify the Upper
> > Layer Protocol (ULP) about this state transition", as said in
> > section 3.2, point 8.
> >
> > So this patch is to add SCTP_ADDR_POTENTIALLY_FAILED, defined
> > in section 7.1, "which is reported if the affected address
> > becomes PF". Also remove transport cwnd's update when moving
> > from PF back to ACTIVE , which is no longer in rfc7829 either.
> >
> > v1->v2:
> >   - no change
> > v2->v3:
> >   - define SCTP_ADDR_PF SCTP_ADDR_POTENTIALLY_FAILED
> >
> > Signed-off-by: Xin Long <lucien.xin@gmail.com>
> > ---
> >  include/uapi/linux/sctp.h |  2 ++
> >  net/sctp/associola.c      | 17 ++++-------------
> >  2 files changed, 6 insertions(+), 13 deletions(-)
> >
> > diff --git a/include/uapi/linux/sctp.h b/include/uapi/linux/sctp.h
> > index 6bce7f9..f4ab7bb 100644
> > --- a/include/uapi/linux/sctp.h
> > +++ b/include/uapi/linux/sctp.h
> > @@ -410,6 +410,8 @@ enum sctp_spc_state {
> >       SCTP_ADDR_ADDED,
> >       SCTP_ADDR_MADE_PRIM,
> >       SCTP_ADDR_CONFIRMED,
> > +     SCTP_ADDR_POTENTIALLY_FAILED,
> > +#define SCTP_ADDR_PF SCTP_ADDR_POTENTIALLY_FAILED
> >  };
> >
> >
> > diff --git a/net/sctp/associola.c b/net/sctp/associola.c
> > index 1ba893b..4f9efba 100644
> > --- a/net/sctp/associola.c
> > +++ b/net/sctp/associola.c
> > @@ -801,14 +801,6 @@ void sctp_assoc_control_transport(struct sctp_association *asoc,
> >                       spc_state = SCTP_ADDR_CONFIRMED;
> >               else
> >                       spc_state = SCTP_ADDR_AVAILABLE;
> > -             /* Don't inform ULP about transition from PF to
> > -              * active state and set cwnd to 1 MTU, see SCTP
> > -              * Quick failover draft section 5.1, point 5
> > -              */
> > -             if (transport->state == SCTP_PF) {
> > -                     ulp_notify = false;
> > -                     transport->cwnd = asoc->pathmtu;
> > -             }
>
> This is wrong.
> If the old state is PF and the application hasn't exposed PF the event should be
> ignored.
yeps, in Patch 2/5:
+               if (transport->state == SCTP_PF &&
+                   asoc->pf_expose != SCTP_PF_EXPOSE_ENABLE)
+                       ulp_notify = false;
+               else if (transport->state == SCTP_UNCONFIRMED &&
+                        error == SCTP_HEARTBEAT_SUCCESS)
                        spc_state = SCTP_ADDR_CONFIRMED;
                else
                        spc_state = SCTP_ADDR_AVAILABLE;

>
> >               transport->state = SCTP_ACTIVE;
> >               break;
> >
> > @@ -817,19 +809,18 @@ void sctp_assoc_control_transport(struct sctp_association *asoc,
> >                * to inactive state.  Also, release the cached route since
> >                * there may be a better route next time.
> >                */
> > -             if (transport->state != SCTP_UNCONFIRMED)
> > +             if (transport->state != SCTP_UNCONFIRMED) {
> >                       transport->state = SCTP_INACTIVE;
> > -             else {
> > +                     spc_state = SCTP_ADDR_UNREACHABLE;
> > +             } else {
> >                       sctp_transport_dst_release(transport);
> >                       ulp_notify = false;
> >               }
> > -
> > -             spc_state = SCTP_ADDR_UNREACHABLE;
> >               break;
> >
> >       case SCTP_TRANSPORT_PF:
> >               transport->state = SCTP_PF;
> > -             ulp_notify = false;
>
> Again the event should be supressed if PF isn't exposed.
it will be suppressed after Patch 2/5:
+               if (asoc->pf_expose != SCTP_PF_EXPOSE_ENABLE)
+                       ulp_notify = false;
+               else
+                       spc_state = SCTP_ADDR_POTENTIALLY_FAILED;
                break;

>
> > +             spc_state = SCTP_ADDR_POTENTIALLY_FAILED;
> >               break;
> >
> >       default:
> > --
> > 2.1.0
>
> I also haven't spotted where the test that the application has actually enabled
> state transition events is in the code.
all events will be created, but dropped in sctp_ulpq_tail_event() when trying
to deliver up:

        /* Check if the user wishes to receive this event.  */
        if (!sctp_ulpevent_is_enabled(event, ulpq->asoc->subscribe))
                goto out_free;

> I'd have thought it would be anything is built and allocated.
>
>         David
>
> -
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