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 <zhangchangzhong@xxxxxxxxxx> > > >>>>>> --- > > >>>>>> 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