[ovs-dev] [PATCH v2] ofproto-dpif-xlate: Do not use zero-weight buckets in select groups.

[Ilya Maximets]

On 6/8/19 1:28 AM, Ben Pfaff wrote:
> The OpenFlow specification says that buckets in select groups with a weight
> of zero should not be selected, but the ofproto-dpif implementation could
> select them in corner cases.  This fixes the problem.
> 
> Reported-by: ychen <ychen103103 at 163.com>
> Reported-at: https://mail.openvswitch.org/pipermail/ovs-dev/2019-May/359349.html
> Signed-off-by: Ben Pfaff <blp at ovn.org>
> ---
> v1->v2: Simplify and fix figuring out whether a group is alive.

Hi, Ben.  I'm looking through old patches after the patchwork cleanup and this
one seems to be still valid.  It requires a minor rebase, but it's trivial.

Patch looks good to me in general and I could apply it.
What do you think?

It also looks like we will need to backport it.  Suggestions on how far it
should go are welcome.

Best regards, Ilya Maximets.

> 
>  ofproto/ofproto-dpif-xlate.c | 18 ++++++++++++------
>  1 file changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/ofproto/ofproto-dpif-xlate.c b/ofproto/ofproto-dpif-xlate.c
> index 04d69ed06c20..1ace92d22019 100644
> --- a/ofproto/ofproto-dpif-xlate.c
> +++ b/ofproto/ofproto-dpif-xlate.c
> @@ -1,4 +1,4 @@
> -/* Copyright (c) 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017 Nicira, Inc.
> +/* Copyright (c) 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2019 Nicira, Inc.
>   *
>   * Licensed under the Apache License, Version 2.0 (the "License");
>   * you may not use this file except in compliance with the License.
> @@ -1864,8 +1864,8 @@ group_is_alive(const struct xlate_ctx *ctx, uint32_t group_id, int depth)
>  #define MAX_LIVENESS_RECURSION 128 /* Arbitrary limit */
>  
>  static bool
> -bucket_is_alive(const struct xlate_ctx *ctx,
> -                struct ofputil_bucket *bucket, int depth)
> +bucket_is_alive(const struct xlate_ctx *ctx, const struct group_dpif *group,
> +                const struct ofputil_bucket *bucket, int depth)
>  {
>      if (depth >= MAX_LIVENESS_RECURSION) {
>          xlate_report_error(ctx, "bucket chaining exceeded %d links",
> @@ -1873,6 +1873,12 @@ bucket_is_alive(const struct xlate_ctx *ctx,
>          return false;
>      }
>  
> +    /* In "select" groups, buckets with weight 0 are not used.
> +     * In other kinds of groups, weight does not matter. */
> +    if (group->up.type == OFPGT11_SELECT && bucket->weight == 0) {
> +        return false;
> +    }
> +
>      return (!ofputil_bucket_has_liveness(bucket)
>              || (bucket->watch_port != OFPP_ANY
>                 && odp_port_is_alive(ctx, bucket->watch_port))
> @@ -1910,7 +1916,7 @@ group_first_live_bucket(const struct xlate_ctx *ctx,
>  {
>      struct ofputil_bucket *bucket;
>      LIST_FOR_EACH (bucket, list_node, &group->up.buckets) {
> -        if (bucket_is_alive(ctx, bucket, depth)) {
> +        if (bucket_is_alive(ctx, group, bucket, depth)) {
>              return bucket;
>          }
>          xlate_report_bucket_not_live(ctx, bucket);
> @@ -1929,7 +1935,7 @@ group_best_live_bucket(const struct xlate_ctx *ctx,
>  
>      struct ofputil_bucket *bucket;
>      LIST_FOR_EACH (bucket, list_node, &group->up.buckets) {
> -        if (bucket_is_alive(ctx, bucket, 0)) {
> +        if (bucket_is_alive(ctx, group, bucket, 0)) {
>              uint32_t score =
>                  (hash_int(bucket->bucket_id, basis) & 0xffff) * bucket->weight;
>              if (score >= best_score) {
> @@ -4535,7 +4541,7 @@ pick_dp_hash_select_group(struct xlate_ctx *ctx, struct group_dpif *group)
>          for (int i = 0; i <= hash_mask; i++) {
>              struct ofputil_bucket *b =
>                      group->hash_map[(dp_hash + i) & hash_mask];
> -            if (bucket_is_alive(ctx, b, 0)) {
> +            if (bucket_is_alive(ctx, group, b, 0)) {
>                  return b;
>              }
>          }
>