From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Abeni Subject: Re: [PATCH net-next v3 1/5] tc/act: user space can't use TC_ACT_REDIRECT directly Date: Wed, 25 Jul 2018 17:48:23 +0200 Message-ID: References: <82c5852909788fef3c7b5c29d6ad8c90b60c7170.1532437050.git.pabeni@redhat.com> <20180725115652.GD2164@nanopsycho> <5d38822b635a18b102810a14883e65479f3841ab.camel@redhat.com> <20180725130330.GJ2164@nanopsycho> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Jamal Hadi Salim , netdev@vger.kernel.org, Cong Wang , Daniel Borkmann , Marcelo Ricardo Leitner , Eyal Birger , "David S. Miller" To: Jiri Pirko Return-path: Received: from mx3-rdu2.redhat.com ([66.187.233.73]:44494 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728360AbeGYRAl (ORCPT ); Wed, 25 Jul 2018 13:00:41 -0400 In-Reply-To: <20180725130330.GJ2164@nanopsycho> Sender: netdev-owner@vger.kernel.org List-ID: 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: > > Hi, > > > > 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. > 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. Thanks, Paolo