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 42F99C433F5 for ; Mon, 11 Oct 2021 10:40:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2C0E060EBD for ; Mon, 11 Oct 2021 10:40:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235941AbhJKKmU (ORCPT ); Mon, 11 Oct 2021 06:42:20 -0400 Received: from szxga03-in.huawei.com ([45.249.212.189]:24239 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235898AbhJKKmS (ORCPT ); Mon, 11 Oct 2021 06:42:18 -0400 Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.55]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4HSZzM53YpzQj9v; Mon, 11 Oct 2021 18:39:11 +0800 (CST) Received: from dggpeml500006.china.huawei.com (7.185.36.76) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.8; Mon, 11 Oct 2021 18:40:16 +0800 Received: from [10.174.178.240] (10.174.178.240) by dggpeml500006.china.huawei.com (7.185.36.76) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.8; Mon, 11 Oct 2021 18:40:15 +0800 Subject: Re: [PATCH net] can: j1939: j1939_xtp_rx_dat_one(): cancel session if receive TP.DT with error length To: Oleksij Rempel CC: Maxime Jayat , Robin van der Gracht , , Oleksij Rempel , , Marc Kleine-Budde , , Oliver Hartkopp , Jakub Kicinski , , "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> From: Zhang Changzhong Message-ID: <7b1b2e47-46e6-acec-5858-fae77266cec8@huawei.com> Date: Mon, 11 Oct 2021 18:40:15 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.8.0 MIME-Version: 1.0 In-Reply-To: <20211011063507.GI29653@pengutronix.de> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.240] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpeml500006.china.huawei.com (7.185.36.76) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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) Regards, Changzhong .