From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jiri Pirko Subject: Re: [PATCH net-next v3 1/5] tc/act: user space can't use TC_ACT_REDIRECT directly Date: Thu, 26 Jul 2018 09:43:00 +0200 Message-ID: <20180726074300.GE2222@nanopsycho> References: <82c5852909788fef3c7b5c29d6ad8c90b60c7170.1532437050.git.pabeni@redhat.com> <20180725115652.GD2164@nanopsycho> <5d38822b635a18b102810a14883e65479f3841ab.camel@redhat.com> <20180725130330.GJ2164@nanopsycho> <15b57fa8-670a-a7a3-a5f5-0685207d054f@iogearbox.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Paolo Abeni , Jamal Hadi Salim , netdev@vger.kernel.org, Cong Wang , Marcelo Ricardo Leitner , Eyal Birger , "David S. Miller" , alexei.starovoitov@gmail.com To: Daniel Borkmann Return-path: Received: from mail-wm0-f68.google.com ([74.125.82.68]:38050 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727951AbeGZJBF (ORCPT ); Thu, 26 Jul 2018 05:01:05 -0400 Received: by mail-wm0-f68.google.com with SMTP id t25-v6so942937wmi.3 for ; Thu, 26 Jul 2018 00:45:29 -0700 (PDT) Content-Disposition: inline In-Reply-To: <15b57fa8-670a-a7a3-a5f5-0685207d054f@iogearbox.net> Sender: netdev-owner@vger.kernel.org List-ID: Wed, Jul 25, 2018 at 06:29:54PM CEST, daniel@iogearbox.net wrote: >On 07/25/2018 05:48 PM, Paolo Abeni wrote: >> On Wed, 2018-07-25 at 15:03 +0200, Jiri Pirko wrote: >>> Wed, Jul 25, 2018 at 02:54:04PM CEST, pabeni@redhat.com wrote: >>>> On Wed, 2018-07-25 at 13:56 +0200, Jiri Pirko wrote: >>>>> Tue, Jul 24, 2018 at 10:06:39PM CEST, pabeni@redhat.com wrote: >>>>>> Only cls_bpf and act_bpf can safely use such value. If a generic >>>>>> action is configured by user space to return TC_ACT_REDIRECT, >>>>>> the usually visible behavior is passing the skb up the stack - as >>>>>> for unknown action, but, with complex configuration, more random >>>>>> results can be obtained. >>>>>> >>>>>> This patch forcefully converts TC_ACT_REDIRECT to TC_ACT_UNSPEC >>>>>> at action init time, making the kernel behavior more consistent. >>>>>> >>>>>> v1 -> v3: use TC_ACT_UNSPEC instead of a newly definied act value >>>>>> >>>>>> Signed-off-by: Paolo Abeni >>>>>> --- >>>>>> net/sched/act_api.c | 5 +++++ >>>>>> 1 file changed, 5 insertions(+) >>>>>> >>>>>> diff --git a/net/sched/act_api.c b/net/sched/act_api.c >>>>>> index 148a89ab789b..24b5534967fe 100644 >>>>>> --- a/net/sched/act_api.c >>>>>> +++ b/net/sched/act_api.c >>>>>> @@ -895,6 +895,11 @@ struct tc_action *tcf_action_init_1(struct net *net, struct tcf_proto *tp, >>>>>> } >>>>>> } >>>>>> >>>>>> + if (a->tcfa_action == TC_ACT_REDIRECT) { >>>>>> + net_warn_ratelimited("TC_ACT_REDIRECT can't be used directly"); >>>>> >>>>> Can't you push this warning through extack? >>>>> >>>>> But, wouldn't it be more appropriate to fail here? User is passing >>>>> invalid configuration.... >>>> >>>> Jiri, Jamal, thank you for the feedback. >>>> >>>> Please allow me to answer both of you here, since you raised similar >>>> concers. >>>> >>>> I thought about rejecting the action, but that change of behavior could >>>> break some users, as currently most kind of invalid tcfa_action values >>>> are simply accepted. >>>> >>>> If there is consensus about it, I can simply fail. >>> >>> Well it was obviously wrong to expose TC_ACT_REDIRECT to uapi and it >>> really has no meaning for anyone to use it throughout its whole history. > >That claim is completely wrong. Why? Does addition of TC_ACT_REDIRECT to uapi have any meaning? > >>> I would vote for "fail", yet I admit that I am usually alone in opinion >>> about similar uapi changes :) >> >> Since even Jamal suggested the same, unless someone else voice some >> opposition soon, in v4 I'll opt for rejecting actions using >> TC_ACT_REDIRECT. > >You should probably leave out act_bpf from that rejection as there may be >a small chance that users could potentially use it as default action. > >Thanks, >Daniel