Do you want to check it in then?

On Fri, Nov 22, 2013 at 04:53:09PM -0800, Andy Zhou wrote:
> Yes, this patch would eliminate code duplications.  The logic looks right
> to me.
> 
> 
> On Fri, Nov 22, 2013 at 3:57 PM, Ben Pfaff <[email protected]> wrote:
> 
> > On Thu, Nov 21, 2013 at 08:45:22PM -0800, Andy Zhou wrote:
> > > Noting updating slow path subfacet's time stamp can cause their datapath
> > > flows deleted periodically. For example, CFM datapath flow have usespace
> > > actions that are handled in dpif slow path. They are deleted and
> > > recreated periodically without the fix.
> > >
> > > This bug are not obvious during normal operation. Deleted CFM flow
> > > would cause CFM packets to be handled by flow miss handler which will
> > > reinstall the flow in the datapath. The only potentially observable
> > > behavior is that when the user space is overwhelmed with flow miss
> > packets,
> > > the periodic CFM miss packets may get stuck behind other miss packets,
> > > cause tunnel flapping.
> > >
> > > Reported-by: Guolin Yang <[email protected]>
> > > Signed-off-by: Andy Zhou <[email protected]>
> >
> > I agree that this fixes the problem.  However, it seems to duplicate
> > some logic.  What do you think about this alternative patch, which
> > instead refactors slightly to avoid code duplication?
> >
> > diff --git a/ofproto/ofproto-dpif.c b/ofproto/ofproto-dpif.c
> > index c1c206b..b56202c 100644
> > --- a/ofproto/ofproto-dpif.c
> > +++ b/ofproto/ofproto-dpif.c
> > @@ -213,7 +213,8 @@ struct subfacet {
> >
> >  #define SUBFACET_DESTROY_MAX_BATCH 50
> >
> > -static struct subfacet *subfacet_create(struct facet *, struct flow_miss
> > *);
> > +static struct subfacet *subfacet_create(struct facet *, struct flow_miss
> > *,
> > +                                        uint32_t key_hash);
> >  static struct subfacet *subfacet_find(struct dpif_backer *,
> >                                        const struct nlattr *key, size_t
> > key_len,
> >                                        uint32_t key_hash);
> > @@ -3222,13 +3223,32 @@ handle_flow_miss_with_facet(struct flow_miss
> > *miss, struct facet *facet,
> >  {
> >      enum subfacet_path want_path;
> >      struct subfacet *subfacet;
> > +    uint32_t key_hash;
> >
> > +    /* Update facet stats. */
> >      facet->packet_count += miss->stats.n_packets;
> >      facet->prev_packet_count += miss->stats.n_packets;
> >      facet->byte_count += miss->stats.n_bytes;
> >      facet->prev_byte_count += miss->stats.n_bytes;
> >
> > -    want_path = facet->xout.slow ? SF_SLOW_PATH : SF_FAST_PATH;
> > +    /* Look for an existing subfacet.  If we find one, update its used
> > time. */
> > +    key_hash = odp_flow_key_hash(miss->key, miss->key_len);
> > +    if (!list_is_empty(&facet->subfacets)) {
> > +        subfacet = subfacet_find(miss->ofproto->backer,
> > +                                 miss->key, miss->key_len, key_hash);
> > +        if (subfacet) {
> > +            if (subfacet->facet == facet) {
> > +                subfacet->used = MAX(subfacet->used, miss->stats.used);
> > +            } else {
> > +                /* This shouldn't happen. */
> > +                VLOG_ERR_RL(&rl, "subfacet with wrong facet");
> > +                subfacet_destroy(subfacet);
> > +                subfacet = NULL;
> > +            }
> > +        }
> > +    } else {
> > +        subfacet = NULL;
> > +    }
> >
> >      /* Don't install the flow if it's the result of the "userspace"
> >       * action for an already installed facet.  This can occur when a
> > @@ -3240,7 +3260,13 @@ handle_flow_miss_with_facet(struct flow_miss *miss,
> > struct facet *facet,
> >          return;
> >      }
> >
> > -    subfacet = subfacet_create(facet, miss);
> > +    /* Create a subfacet, if we don't already have one. */
> > +    if (!subfacet) {
> > +        subfacet = subfacet_create(facet, miss, key_hash);
> > +    }
> > +
> > +    /* Install the subfacet, if it's not already installed. */
> > +    want_path = facet->xout.slow ? SF_SLOW_PATH : SF_FAST_PATH;
> >      if (subfacet->path != want_path) {
> >          struct flow_miss_op *op = &ops[(*n_ops)++];
> >          struct dpif_flow_put *put = &op->dpif_op.u.flow_put;
> > @@ -4382,37 +4408,20 @@ subfacet_find(struct dpif_backer *backer, const
> > struct nlattr *key,
> >      return NULL;
> >  }
> >
> > -/* Searches 'facet' (within 'ofproto') for a subfacet with the specified
> > - * 'key_fitness', 'key', and 'key_len' members in 'miss'.  Returns the
> > - * existing subfacet if there is one, otherwise creates and returns a
> > - * new subfacet. */
> > +/* Creates and returns a new subfacet within 'facet' for the flow in
> > 'miss'.
> > + * 'key_hash' must be a hash over miss->key.  The caller must have already
> > + * ensured that no subfacet subfacet already exists. */
> >  static struct subfacet *
> > -subfacet_create(struct facet *facet, struct flow_miss *miss)
> > +subfacet_create(struct facet *facet, struct flow_miss *miss, uint32_t
> > key_hash)
> >  {
> >      struct dpif_backer *backer = miss->ofproto->backer;
> >      const struct nlattr *key = miss->key;
> >      size_t key_len = miss->key_len;
> > -    uint32_t key_hash;
> >      struct subfacet *subfacet;
> >
> > -    key_hash = odp_flow_key_hash(key, key_len);
> > -
> > -    if (list_is_empty(&facet->subfacets)) {
> > -        subfacet = &facet->one_subfacet;
> > -    } else {
> > -        subfacet = subfacet_find(backer, key, key_len, key_hash);
> > -        if (subfacet) {
> > -            if (subfacet->facet == facet) {
> > -                return subfacet;
> > -            }
> > -
> > -            /* This shouldn't happen. */
> > -            VLOG_ERR_RL(&rl, "subfacet with wrong facet");
> > -            subfacet_destroy(subfacet);
> > -        }
> > -
> > -        subfacet = xmalloc(sizeof *subfacet);
> > -    }
> > +    subfacet = (list_is_empty(&facet->subfacets)
> > +                ? &facet->one_subfacet
> > +                : xmalloc(sizeof *subfacet));
> >
> >      COVERAGE_INC(subfacet_create);
> >      hmap_insert(&backer->subfacets, &subfacet->hmap_node, key_hash);
> >
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