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 612FDC433FE for ; Tue, 12 Oct 2021 10:41:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 49C3F61078 for ; Tue, 12 Oct 2021 10:41:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236077AbhJLKni convert rfc822-to-8bit (ORCPT ); Tue, 12 Oct 2021 06:43:38 -0400 Received: from relay-b03.edpnet.be ([212.71.1.220]:45128 "EHLO relay-b03.edpnet.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235937AbhJLKng (ORCPT ); Tue, 12 Oct 2021 06:43:36 -0400 X-ASG-Debug-ID: 1634035293-15c4351aa511a50e0001-xx1T2L Received: from zotac.vandijck-laurijssen.be (94.105.120.149.dyn.edpnet.net [94.105.120.149]) by relay-b03.edpnet.be with ESMTP id 15nhFsRu6fTeBmie; Tue, 12 Oct 2021 12:41:33 +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 4CAD2169F842; Tue, 12 Oct 2021 12:41:33 +0200 (CEST) Date: Tue, 12 Oct 2021 12:41:32 +0200 From: Kurt Van Dijck To: Oleksij Rempel Cc: Zhang Changzhong , Oliver Hartkopp , Maxime Jayat , Robin van der Gracht , linux-kernel@vger.kernel.org, Oleksij Rempel , Marc Kleine-Budde , kernel@pengutronix.de, netdev@vger.kernel.org, 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: <20211012104132.GA14010@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 , Oliver Hartkopp , Maxime Jayat , Robin van der Gracht , linux-kernel@vger.kernel.org, Oleksij Rempel , Marc Kleine-Budde , kernel@pengutronix.de, netdev@vger.kernel.org, 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> <7b1b2e47-46e6-acec-5858-fae77266cec8@huawei.com> <20211012102131.GA14971@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8BIT In-Reply-To: <20211012102131.GA14971@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: 1634035293 X-Barracuda-URL: https://212.71.1.220:443/cgi-mod/mark.cgi X-Virus-Scanned: by bsmtpd at edpnet.be X-Barracuda-Scan-Msg-Size: 4655 X-Barracuda-BRTS-Status: 1 X-Barracuda-Spam-Score: 0.50 X-Barracuda-Spam-Status: No, SCORE=0.50 using global scores of TAG_LEVEL=1000.0 QUARANTINE_LEVEL=1000.0 KILL_LEVEL=7.0 tests=BSF_RULE7568M X-Barracuda-Spam-Report: Code version 3.2, rules version 3.2.3.93216 Rule breakdown below pts rule name description ---- ---------------------- -------------------------------------------------- 0.50 BSF_RULE7568M Custom Rule 7568M Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 12 Oct 2021 12:21:31 +0200, Oleksij Rempel wrote: > On Mon, Oct 11, 2021 at 06:40:15PM +0800, Zhang Changzhong wrote: > > On 2021/10/11 14:35, 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. > > >>>> > > >>>>> > > >>>>>> > > >>>>>> Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol") > > >>>>>> Signed-off-by: Zhang Changzhong > > >>>>>> --- > > >>>>>> net/can/j1939/transport.c | 7 +++++-- > > >>>>>> 1 file changed, 5 insertions(+), 2 deletions(-) > > >>>>>> > > >>>>>> diff --git a/net/can/j1939/transport.c b/net/can/j1939/transport.c > > >>>>>> index bb5c4b8..eedaeaf 100644 > > >>>>>> --- a/net/can/j1939/transport.c > > >>>>>> +++ b/net/can/j1939/transport.c > > >>>>>> @@ -1789,6 +1789,7 @@ static void j1939_xtp_rx_dpo(struct j1939_priv *priv, struct sk_buff *skb, > > >>>>>> static void j1939_xtp_rx_dat_one(struct j1939_session *session, > > >>>>>> struct sk_buff *skb) > > >>>>>> { > > >>>>>> + enum j1939_xtp_abort abort = J1939_XTP_ABORT_FAULT; > > >>>>>> struct j1939_priv *priv = session->priv; > > >>>>>> struct j1939_sk_buff_cb *skcb, *se_skcb; > > >>>>>> struct sk_buff *se_skb = NULL; > > >>>>>> @@ -1803,9 +1804,11 @@ static void j1939_xtp_rx_dat_one(struct j1939_session *session, > > >>>>>> > > >>>>>> skcb = j1939_skb_to_cb(skb); > > >>>>>> dat = skb->data; > > >>>>>> - if (skb->len <= 1) > > >>>>>> + if (skb->len != 8) { > > >>>>>> /* makes no sense */ > > >>>>>> + abort = J1939_XTP_ABORT_UNEXPECTED_DATA; > > >>>>>> goto out_session_cancel; > > >>>>> > > >>>>> 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. > > > > > > So, "DUT discards the BAM transport" sounds for me as local action. > > > Complete TP would be dropped locally. > > > > Yeah, you are right. With this patch receivers drop BAM transport locally > > because j1939_session_cancel() only send abort message in RTS/CTS transport. > > > > For RTS/CTS transport, SAE-J1939-82 also has similar requirements: > > "RTS/CTS Transport: Data field size of Transport Data packets for RTS/CTS > > (DUT as Responder)"..."Verify DUT behavior, e.g., sends a TP.CM_CTS to have > > packets resent or sends a TP.Conn_Abort, when it receives TP.DT data packets > > with less than 8 bytes" (section A.3.6, Row 18) > > You are right. Sounds plausible. If we find some device in the field > which will need a workaround to support less than 8byte, then we will > need to add some UAPI to configure it. By default we should follow the > spec. @Kurt, do you have anything against it? Zhang Changzhong suggested that this is part of compliance testing nowadays. That obsoletes all technical arguments, and you have no choice than to adapt. Kurt