From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3241BFA372A for ; Thu, 17 Oct 2019 16:34:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0E6A921835 for ; Thu, 17 Oct 2019 16:33:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2408009AbfJQQd6 (ORCPT ); Thu, 17 Oct 2019 12:33:58 -0400 Received: from out30-56.freemail.mail.aliyun.com ([115.124.30.56]:58056 "EHLO out30-56.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730640AbfJQQd6 (ORCPT ); Thu, 17 Oct 2019 12:33:58 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R431e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01422;MF=zhiyuan2048@linux.alibaba.com;NM=1;PH=DS;RN=8;SR=0;TI=SMTPD_---0TfKEPAy_1571330034; Received: from houzhiyuandeMacBook-Pro.local(mailfrom:zhiyuan2048@linux.alibaba.com fp:SMTPD_---0TfKEPAy_1571330034) by smtp.aliyun-inc.com(127.0.0.1); Fri, 18 Oct 2019 00:33:55 +0800 Subject: Re: [PATCH net] net: sched: act_mirred: drop skb's dst_entry in ingress redirection To: Eyal Birger Cc: Cong Wang , Jamal Hadi Salim , Jiri Pirko , "David S . Miller" , Linux Kernel Network Developers , LKML , shmulik.ladkani@gmail.com References: <20191012071620.8595-1-zhiyuan2048@linux.alibaba.com> <20191016151307.40f63896@jimi> From: Zhiyuan Hou Message-ID: Date: Fri, 18 Oct 2019 00:33:53 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.1.2 MIME-Version: 1.0 In-Reply-To: <20191016151307.40f63896@jimi> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/10/16 8:13 下午, Eyal Birger wrote: > Hi, > > On Wed, 16 Oct 2019 01:22:01 +0800 > Zhiyuan Hou wrote: > >> On 2019/10/15 1:57 上午, Cong Wang wrote: >>> On Sat, Oct 12, 2019 at 12:16 AM Zhiyuan Hou >>> wrote: >>>> diff --git a/net/sched/act_mirred.c b/net/sched/act_mirred.c >>>> index 9ce073a05414..6108a64c0cd5 100644 >>>> --- a/net/sched/act_mirred.c >>>> +++ b/net/sched/act_mirred.c >>>> @@ -18,6 +18,7 @@ >>>> #include >>>> #include >>>> #include >>>> +#include >>>> #include >>>> #include >>>> #include >>>> @@ -298,8 +299,10 @@ static int tcf_mirred_act(struct sk_buff >>>> *skb, const struct tc_action *a, >>>> >>>> if (!want_ingress) >>>> err = dev_queue_xmit(skb2); >>>> - else >>>> + else { >>>> + skb_dst_drop(skb2); >>>> err = netif_receive_skb(skb2); >>>> + } >>> Good catch! > Indeed! Thanks for fixing this! > >>> I don't want to be picky, but it seems this is only needed >>> when redirecting from egress to ingress, right? That is, >>> ingress to ingress, or ingress to egress is okay? If not, >>> please fix all the cases while you are on it? >> Sure. But I think this patch is also needed when redirecting from >> ingress to ingress. Because we cannot assure that a skb has null dst >> in ingress redirection path. For example, if redirecting a skb from >> loopback's ingress to other device's ingress, the skb will take a >> dst. >> >> As commit logs point out, skb with valid dst cannot be made routing >> decision in following process. original dst may cause skb loss or >> other unexpected behavior. > On the other hand, removing the dst on ingress-to-ingress redirection > may remove LWT information on incoming packets, which may be undesired. Sorry, I do not understand why lwt information is needed on ingress-to-ingress redirection. lwt is used on output path, isn't it? Can you please give more information? > Eyal.