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 8CCBBC433FE for ; Tue, 12 Oct 2021 10:21:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 740156101D for ; Tue, 12 Oct 2021 10:21:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235951AbhJLKXr (ORCPT ); Tue, 12 Oct 2021 06:23:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58964 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235903AbhJLKXr (ORCPT ); Tue, 12 Oct 2021 06:23:47 -0400 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C8AFFC061570 for ; Tue, 12 Oct 2021 03:21:45 -0700 (PDT) Received: from ptx.hi.pengutronix.de ([2001:67c:670:100:1d::c0]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1maEuc-0003e5-Fb; Tue, 12 Oct 2021 12:21:34 +0200 Received: from ore by ptx.hi.pengutronix.de with local (Exim 4.92) (envelope-from ) id 1maEuZ-0004HC-3P; Tue, 12 Oct 2021 12:21:31 +0200 Date: Tue, 12 Oct 2021 12:21:31 +0200 From: Oleksij Rempel To: Zhang Changzhong Cc: 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: <20211012102131.GA14971@pengutronix.de> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <7b1b2e47-46e6-acec-5858-fae77266cec8@huawei.com> X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-IRC: #ptxdist @freenode X-Accept-Language: de,en X-Accept-Content-Type: text/plain X-Uptime: 12:17:56 up 236 days, 13:41, 138 users, load average: 0.08, 0.29, 0.41 User-Agent: Mutt/1.10.1 (2018-07-13) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c0 X-SA-Exim-Mail-From: ore@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: netdev@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org 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? Regards, Oleksij -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |