Netdev Archive on lore.kernel.org
 help / color / Atom feed
From: Cong Wang <xiyou.wangcong@gmail.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Linux Kernel Network Developers <netdev@vger.kernel.org>,
	Eric Dumazet <edumazet@google.com>
Subject: Re: [Patch net] net_sched: unset TCQ_F_CAN_BYPASS when adding filters
Date: Sat, 13 Jul 2019 19:23:30 -0700
Message-ID: <CAM_iQpUwAcqyFw0dGAJWvKWaGzV2YGD_oJHYrae3aCt-BE9ong@mail.gmail.com> (raw)
In-Reply-To: <8733195c-ac70-4a2a-db2f-b9bdfd05a703@gmail.com>

On Sat, Jul 13, 2019 at 5:54 AM Eric Dumazet <eric.dumazet@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 <edumazet@google.com>
> > Signed-off-by: Cong Wang <xiyou.wangcong@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.

      reply index

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-12 20:17 Cong Wang
2019-07-13 12:54 ` Eric Dumazet
2019-07-14  2:23   ` Cong Wang [this message]

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CAM_iQpUwAcqyFw0dGAJWvKWaGzV2YGD_oJHYrae3aCt-BE9ong@mail.gmail.com \
    --to=xiyou.wangcong@gmail.com \
    --cc=edumazet@google.com \
    --cc=eric.dumazet@gmail.com \
    --cc=netdev@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Netdev Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/netdev/0 netdev/git/0.git
	git clone --mirror https://lore.kernel.org/netdev/1 netdev/git/1.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 netdev netdev/ https://lore.kernel.org/netdev \
		netdev@vger.kernel.org netdev@archiver.kernel.org
	public-inbox-index netdev


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.netdev


AGPL code for this site: git clone https://public-inbox.org/ public-inbox