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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C119EC433EF for ; Mon, 11 Oct 2021 07:18:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A723960EE3 for ; Mon, 11 Oct 2021 07:18:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234395AbhJKHUr convert rfc822-to-8bit (ORCPT ); Mon, 11 Oct 2021 03:20:47 -0400 Received: from relay-b01.edpnet.be ([212.71.1.221]:32958 "EHLO relay-b01.edpnet.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234336AbhJKHUp (ORCPT ); Mon, 11 Oct 2021 03:20:45 -0400 X-ASG-Debug-ID: 1633936723-15c4341a8713e36d0001-xx1T2L Received: from zotac.vandijck-laurijssen.be (94.105.120.149.dyn.edpnet.net [94.105.120.149]) by relay-b01.edpnet.be with ESMTP id cJ4FK3WM5awVTL4L; Mon, 11 Oct 2021 09:18:43 +0200 (CEST) X-Barracuda-Envelope-From: dev.kurt@vandijck-laurijssen.be X-Barracuda-Effective-Source-IP: 94.105.120.149.dyn.edpnet.net[94.105.120.149] X-Barracuda-Apparent-Source-IP: 94.105.120.149 Received: from x1.vandijck-laurijssen.be (x1.vandijck-laurijssen.be [IPv6:fd01::1a1d:eaff:fe02:d339]) by zotac.vandijck-laurijssen.be (Postfix) with ESMTPSA id A2409169E195; Mon, 11 Oct 2021 09:18:43 +0200 (CEST) Date: Mon, 11 Oct 2021 09:18:42 +0200 From: Kurt Van Dijck To: Oleksij Rempel Cc: Zhang Changzhong , Maxime Jayat , Robin van der Gracht , linux-kernel@vger.kernel.org, Oleksij Rempel , netdev@vger.kernel.org, Marc Kleine-Budde , kernel@pengutronix.de, Oliver Hartkopp , Jakub Kicinski , linux-can@vger.kernel.org, "David S. Miller" Subject: Re: [PATCH net] can: j1939: j1939_xtp_rx_dat_one(): cancel session if receive TP.DT with error length Message-ID: <20211011071842.GA22069@x1.vandijck-laurijssen.be> X-ASG-Orig-Subj: Re: [PATCH net] can: j1939: j1939_xtp_rx_dat_one(): cancel session if receive TP.DT with error length Mail-Followup-To: Oleksij Rempel , Zhang Changzhong , Maxime Jayat , Robin van der Gracht , linux-kernel@vger.kernel.org, Oleksij Rempel , netdev@vger.kernel.org, Marc Kleine-Budde , kernel@pengutronix.de, Oliver Hartkopp , Jakub Kicinski , linux-can@vger.kernel.org, "David S. Miller" References: <1632972800-45091-1-git-send-email-zhangchangzhong@huawei.com> <20210930074206.GB7502@x1.vandijck-laurijssen.be> <1cab07f2-593a-1d1c-3a29-43ee9df4b29e@huawei.com> <20211008110007.GE29653@pengutronix.de> <556a04ed-c350-7b2b-5bbe-98c03846630b@huawei.com> <20211011063507.GI29653@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8BIT In-Reply-To: <20211011063507.GI29653@pengutronix.de> User-Agent: Mutt/1.5.22 (2013-10-16) X-Barracuda-Connect: 94.105.120.149.dyn.edpnet.net[94.105.120.149] X-Barracuda-Start-Time: 1633936723 X-Barracuda-URL: https://212.71.1.221:443/cgi-mod/mark.cgi X-Virus-Scanned: by bsmtpd at edpnet.be X-Barracuda-Scan-Msg-Size: 2176 X-Barracuda-BRTS-Status: 1 X-Barracuda-Spam-Score: 0.00 X-Barracuda-Spam-Status: No, SCORE=0.00 using global scores of TAG_LEVEL=1000.0 QUARANTINE_LEVEL=1000.0 KILL_LEVEL=7.0 tests= X-Barracuda-Spam-Report: Code version 3.2, rules version 3.2.3.93191 Rule breakdown below pts rule name description ---- ---------------------- -------------------------------------------------- Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 11 Oct 2021 08:35:07 +0200, Oleksij Rempel wrote: > On Sat, Oct 09, 2021 at 04:43:56PM +0800, Zhang Changzhong wrote: > > On 2021/10/8 19:00, Oleksij Rempel wrote: > > > On Fri, Oct 08, 2021 at 05:22:12PM +0800, Zhang Changzhong wrote: > > >> Hi Kurt, > > >> Sorry for the late reply. > > >> > > >> On 2021/9/30 15:42, Kurt Van Dijck wrote: > > >>> On Thu, 30 Sep 2021 11:33:20 +0800, Zhang Changzhong wrote: > > >>>> According to SAE-J1939-21, the data length of TP.DT must be 8 bytes, so > > >>>> cancel session when receive unexpected TP.DT message. > > >>> > > >>> SAE-j1939-21 indeed says that all TP.DT must be 8 bytes. > > >>> However, the last TP.DT may contain up to 6 stuff bytes, which have no meaning. > > >>> If I remember well, they are even not 'reserved'. > > >> > > >> Agree, these bytes are meaningless for last TP.DT. > > >> > > >>> > > >>>> [...] > > >>> > > >>> I think this is a situation of > > >>> "be strict on what you send, be tolerant on what you receive". > > >>> > > >>> Did you find a technical reason to abort a session because the last frame didn't > > >>> bring overhead that you don't use? > > >> > > >> No technical reason. The only reason is that SAE-J1939-82 requires responder > > >> to abort session if any TP.DT less than 8 bytes (section A.3.4, Row 7). > > > > > > Do you mean: "BAM Transport: Ensure DUT discards BAM transport when > > > TP.DT data packets are not correct size" ... "Verify DUT discards the > > > BAM transport if any TP.DT data packet has less than 8 bytes"? > > > > Yes. > > OK, then I have some problems to understand this part: > - 5.10.2.4 Connection Closure > The “connection abort” message is not allowed to be used by responders in the > case of a global destination (i.e. BAM). > > My assumption would be: In case of broadcast transfer, multiple MCU are > receivers. If one of MCU was not able to get complete TP.DT, it should > not abort BAM for all. There is indeed no action defined to abort at BAM. > > So, "DUT discards the BAM transport" sounds for me as local action. > Complete TP would be dropped locally. exact. Kurt