From: Eric Dumazet <eric.dumazet@gmail.com>
To: Cong Wang <xiyou.wangcong@gmail.com>, netdev@vger.kernel.org
Cc: Eric Dumazet <edumazet@google.com>
Subject: Re: [Patch net] net_sched: unset TCQ_F_CAN_BYPASS when adding filters
Date: Sat, 13 Jul 2019 14:54:48 +0200 [thread overview]
Message-ID: <8733195c-ac70-4a2a-db2f-b9bdfd05a703@gmail.com> (raw)
In-Reply-To: <20190712201749.28421-1-xiyou.wangcong@gmail.com>
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 ?
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
next prev parent reply other threads:[~2019-07-13 12:54 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-12 20:17 [Patch net] net_sched: unset TCQ_F_CAN_BYPASS when adding filters Cong Wang
2019-07-13 12:54 ` Eric Dumazet [this message]
2019-07-14 2:23 ` Cong Wang
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