[ovs-dev] [PATCH ovn v5 4/9] ofctrl_check_and_add_flow: Replace the actions of an existing flow if actions have changed.

[Numan Siddique]

On Wed, May 13, 2020 at 7:24 PM Dumitru Ceara <dceara at redhat.com> wrote:

> On 5/11/20 11:46 AM, numans at ovn.org wrote:
> > From: Numan Siddique <numans at ovn.org>
> >
> > If ofctrl_check_and_add_flow(F') is called where flow F' has
> match-actions (M, A2)
> > and if there already exists a flow F with match-actions (M, A1) in the
> desired flow
> > table, then this function  doesn't update the existing flow F with new
> actions
> > actions A2.
> >
> > This patch is required for the upcoming patch in this series which
> > adds incremental processing for OVS interface in the flow output stage.
> > Since we will be not be clearing the flow output data if these changes
> > are handled incrementally, some of the existing flows will be updated
> > with new actions. One such example would be flows in physical
> > table OFTABLE_LOCAL_OUTPUT (table 33). And this patch is required to
> > update such flows. Otherwise we will have incomplete actions installed.
> >
> > Signed-off-by: Numan Siddique <numans at ovn.org>
>
> Hi Numan,
>
> I think the title of the commit should be "ofctrl: Replace the actions
> of an existing flow if actions have changed."
>
> > ---
> >  controller/ofctrl.c | 23 ++++++++++++++++-------
> >  1 file changed, 16 insertions(+), 7 deletions(-)
> >
> > diff --git a/controller/ofctrl.c b/controller/ofctrl.c
> > index 4b51cd86e..8f2f13767 100644
> > --- a/controller/ofctrl.c
> > +++ b/controller/ofctrl.c
> > @@ -667,14 +667,23 @@ ofctrl_check_and_add_flow(struct
> ovn_desired_flow_table *flow_table,
> >
> >      ovn_flow_log(f, "ofctrl_add_flow");
> >
> > -    if (ovn_flow_lookup(&flow_table->match_flow_table, f, true)) {
> > -        if (log_duplicate_flow) {
> > -            static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5,
> 5);
> > -            if (!VLOG_DROP_DBG(&rl)) {
> > -                char *s = ovn_flow_to_string(f);
> > -                VLOG_DBG("dropping duplicate flow: %s", s);
> > -                free(s);
> > +    struct ovn_flow *existing_f =
> > +        ovn_flow_lookup(&flow_table->match_flow_table, f, true);
> > +    if (existing_f) {
> > +        if (ofpacts_equal(f->ofpacts, f->ofpacts_len,
> > +                          existing_f->ofpacts,
> existing_f->ofpacts_len)) {
> > +            if (log_duplicate_flow) {
> > +                static struct vlog_rate_limit rl =
> VLOG_RATE_LIMIT_INIT(5, 5);
> > +                if (!VLOG_DROP_DBG(&rl)) {
> > +                    char *s = ovn_flow_to_string(f);
> > +                    VLOG_DBG("dropping duplicate flow: %s", s);
> > +                    free(s);
> > +                }
> >              }
> > +        } else {
> > +            free(existing_f->ofpacts);
> > +            existing_f->ofpacts = xmemdup(f->ofpacts, f->ofpacts_len);
> > +            existing_f->ofpacts_len = f->ofpacts_len;
>
> We could avoid the free(existing_f->ofpacts) followed by xmemdup by
> swapping f->ofpacts with existing_f->ofpacts (same for ofpacts_len).
> We'd probably need a function for that and we'd have to call it in
> ofctrl_add_or_append_flow() too.
>
>
Good idea. I'll do as suggested. But I don't think we can do the same for
ofctrl_add_or_append_flow() as it appends the actions.

Thanks
Numan



> I'm not sure if that makes the code harder to read though. What do you
> think?
>
> Thanks,
> Dumitru
>
> >          }
> >          ovn_flow_destroy(f);
> >          return;
> >
>
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