On Sat, Jul 13, 2019 at 5:54 AM Eric Dumazet <eric.duma...@gmail.com> wrote:
>
>
>
> On 7/12/19 10:17 PM, Cong Wang wrote:
> > For qdisc's that support TC filters and set TCQ_F_CAN_BYPASS,
> > notably fq_codel, it makes no sense to let packets bypass the TC
> > filters we setup in any scenario, otherwise our packets steering
> > policy could not be enforced.
> >
> > This can be easily reproduced with the following script:
> >
> > ip li add dev dummy0 type dummy
> > ifconfig dummy0 up
> > tc qd add dev dummy0 root fq_codel
> > tc filter add dev dummy0 parent 8001: protocol arp basic action mirred
> > egress redirect dev lo
> > tc filter add dev dummy0 parent 8001: protocol ip basic action mirred
> > egress redirect dev lo
> > ping -I dummy0 192.168.112.1
> >
> > Without this patch, packets are sent directly to dummy0 without
> > hitting any of the filters. With this patch, packets are redirected
> > to loopback as expected.
> >
> > This fix is not perfect, it only unsets the flag but does not set it back
> > because we have to save the information somewhere in the qdisc if we
> > really want that.
> >
> > Fixes: 4b549a2ef4be ("fq_codel: Fair Queue Codel AQM")
> > Cc: Eric Dumazet <eduma...@google.com>
> > Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
> > ---
> > net/sched/cls_api.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
> > index 638c1bc1ea1b..5c800b0c810b 100644
> > --- a/net/sched/cls_api.c
> > +++ b/net/sched/cls_api.c
> > @@ -2152,6 +2152,7 @@ static int tc_new_tfilter(struct sk_buff *skb, struct
> > nlmsghdr *n,
> > tfilter_notify(net, skb, n, tp, block, q, parent, fh,
> > RTM_NEWTFILTER, false, rtnl_held);
> > tfilter_put(tp, fh);
> > + q->flags &= ~TCQ_F_CAN_BYPASS;
> > }
> >
> > errout:
> >
>
> Strange, because sfq and fq_codel are roughly the same for TCQ_F_CAN_BYPASS
> handling.
>
> Why is fq_codel_bind() not effective ?
Because I don't have class id set in the filter.
>
> If not effective, sfq had the same issue, so the Fixes: tag needs to be
> refined,
> maybe to commit 23624935e0c4 net_sched: TCQ_F_CAN_BYPASS generalization
>
Yeah, I think it is probably a better commit here.
Thanks.
