On Mon, 2016-06-06 at 23:20 +0200, Florian Westphal wrote: > since initial revision of cbq in 2004 iproute2 never implemented > support for TCA_CBQ_OVL_STRATEGY, which is what needs to be set to > activate the class->drop() call (TC_CBQ_OVL_DROP strategy must be > set by userspace). > > So lets remove this. We can even do this in a backwards compatible > way by switching ovl_drop to perform a dequeue+drop on the leaf. > > A followup commit can then remove all .drop qdisc methods since this > was the only caller. > > Signed-off-by: Florian Westphal <f...@strlen.de> > --- > On a related note, iproute2 doesn't support the TCA_CBQ_POLICE > attribute either. If we'd remove that too we could then get rid > of __parent and reshape_fail in struct Qdisc. > > However, in TCA_CBQ_POLICE case there is no way to replace > the functionality, i.e. we'd have to -EOPNOTSUPP or ignore > TCA_CBQ_POLICE if some other non-iproute2 tool presents it to us. > > AFAICS TCA_CBQ_POLICE doesn't work all that well even if userspace > would set it, one needs to: > > add a class > attach a qdisc to the class (default pfifo doesn't work as > q->handle is 0 and cbq_set_police() is a no-op in this case) > re-'add' the same class (tc class change ...) again > > user must also specifiy a defmap (e.g. 'split 1:0 defmap 3f'), since > this 'police' feature relies on its presence > the added qdisc (or the leaves) must be one of bfifo, pfifo, tbf or > netem as only these implement qdisc_reshape_fail() call. > > If all of these conditions are met, then instead of drop the leaf > qdiscs mentioned above would attempt to re-enqueue the skb in the > cbq TC_PRIO_BESTEFFORT class if their limit is reached. > > I think it would be safe to just ignore TCA_CBQ_POLICE and change the > qdiscs to drop right away. > > Does anyone have a reason to leave this in the tree? Thanks! > > diff --git a/net/sched/sch_cbq.c b/net/sched/sch_cbq.c > index baafddf..df79791 100644 > --- a/net/sched/sch_cbq.c > +++ b/net/sched/sch_cbq.c > @@ -542,9 +542,14 @@ static void cbq_ovl_lowprio(struct cbq_class *cl) > > static void cbq_ovl_drop(struct cbq_class *cl) > { > - if (cl->q->ops->drop) > - if (cl->q->ops->drop(cl->q)) > - cl->qdisc->q.qlen--; > + struct sk_buff *skb = cl->q->ops->dequeue(cl->q); > + > + if (skb) { > + cl->deficit -= qdisc_pkt_len(skb); > + cl->qdisc->q.qlen--; > + qdisc_drop(skb, cl->qdisc); > + } > + > cl->xstats.overactions++; > cbq_ovl_classic(cl); > }
A drop() is not equivalent to a dequeue() followed by qdisc_drop() for statistics. dequeue() will update stats of _sent_ packets/bytes, while drop() should not.