[PATCH net 0/3] Replace direct dequeue call with qdisc_dequeue_peeked

[Jamal Hadi Salim <jhs@mojatatu.com>]

When sfb and red qdiscs have children (eg qfq qdisc) whose peek() callback is
qdisc_peek_dequeued(), we could get a kernel panic. When the parent of such
qdiscs (eg illustrated in patch #3 as tbf) wants to retrieve an skb from
its child (red/sfb in this case), it will do the following:
 1a. do a peek() - and when sensing there's an skb the child can offer, then
     - the child in this case(red/sfb) calls its child's (qfq) peek.
        qfq does the right thing and will return the gso_skb queue packet.
        Note: if there wasnt a gso_skb entry then qfq will store it there.
 1b. invoke a dequeue() on the child (red/sfb). And herein lies the problem.
     - red/sfb will call the child's dequeue() which will essentially just
       try to grab something of qfq's queue.

The right thing to do in #1b is to grab the skb off gso_skb queue.
This patchset fixes that issue by changing #1b to use qdisc_dequeue_peeked()
method instead.

Patch 1 fixes the issue for red qdisc. Patch 2 fixes it for sfb.
Patch 3 adds testcases for the two setups.

Jamal Hadi Salim (2):
  net/sched: sch_red: Replace direct dequeue call with peek and
    qdisc_dequeue_peeked
  net/sched: sch_sfb: Replace direct dequeue call with peek and
    qdisc_dequeue_peeked

Victor Nogueira (1):
  selftests/tc-testing: Add tests that force red and sfb to dequeue from
    child's gso_skb

 net/sched/sch_red.c                           |   2 +-
 net/sched/sch_sfb.c                           |   2 +-
 .../tc-testing/tc-tests/infra/qdiscs.json     | 148 ++++++++++++++++++
 3 files changed, 150 insertions(+), 2 deletions(-)

-- 
2.34.1