[net-next,0/2] net_sched: sch_sfq: reject limit of 1

Message

Octavian Purdila Dec. 4, 2024, 3:05 a.m. UTC

The implementation does not properly support limits of 1. Add an
in-kernel check, in addition to existing iproute2 check, since other
tools may be used for configuration.

This patch set also adds a selfcheck to test that a limit of 1 is
rejected.

An alternative (or in addition) we could fix the implementation by
setting q->tail to NULL in sfq_drop if this is the last slot we marked
empty, e.g.:

  --- a/net/sched/sch_sfq.c
  +++ b/net/sched/sch_sfq.c
  @@ -317,8 +317,11 @@ static unsigned int sfq_drop(struct Qdisc *sch, struct sk_buff **to_free)
                  /* It is difficult to believe, but ALL THE SLOTS HAVE LENGTH 1. */
                  x = q->tail->next;
                  slot = &q->slots[x];
  -               q->tail->next = slot->next;
                  q->ht[slot->hash] = SFQ_EMPTY_SLOT;
  +               if (x == slot->next)
  +                       q->tail = NULL; /* no more active slots */
  +               else
  +                       q->tail->next = slot->next;
                  goto drop;
          }

Octavian Purdila (2):
  net_sched: sch_sfq: don't allow 1 packet limit
  selftests/tc-testing: sfq: test that kernel rejects limit of 1

 net/sched/sch_sfq.c                           |  4 ++++
 .../tc-testing/scripts/sfq_rejects_limit_1.py | 21 +++++++++++++++++++
 .../tc-testing/tc-tests/qdiscs/sfq.json       | 20 ++++++++++++++++++
 3 files changed, 45 insertions(+)
 create mode 100755 tools/testing/selftests/tc-testing/scripts/sfq_rejects_limit_1.py