[net,0/3] net_sched: sch_sfq: reject a derived limit of 1

Message

Octavian Purdila March 28, 2025, 8:16 p.m. UTC

Because sfq parameters can influence each other there can be
situations where although the user sets a limit of 2 it can be lowered
to 1:

$ tc qdisc add dev dummy0 handle 1: root sfq limit 2 flows 1 depth 1
$ tc qdisc show dev dummy0
qdisc sfq 1: dev dummy0 root refcnt 2 limit 1p quantum 1514b depth 1 divisor 1024

$ tc qdisc add dev dummy0 handle 1: root sfq limit 2 flows 10 depth 1 divisor 1
$ tc qdisc show dev dummy0
qdisc sfq 2: root refcnt 2 limit 1p quantum 1514b depth 1 divisor 1

As a limit of 1 is invalid, this patch series moves the limit
validation to after all configuration changes have been done. To do
so, the configuration is done in a temporary work area then applied to
the internal state.

The patch series also adds new test cases.

Octavian Purdila (3):
  net_sched: sch_sfq: use a temporary work area for validating
    configuration
  net_sched: sch_sfq: move the limit validation
  selftests/tc-testing: sfq: check that a derived limit of 1 is rejected

 net/sched/sch_sfq.c                           | 70 ++++++++++++++-----
 .../tc-testing/tc-tests/qdiscs/sfq.json       | 36 ++++++++++
 2 files changed, 90 insertions(+), 16 deletions(-)