Re: [PATCH net 2/3] can: j1939: j1939_can_recv(): ignore messages with invalid source address

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On 2021/10/22 18:23, Oleksij Rempel wrote:
> On Thu, Oct 21, 2021 at 10:04:16PM +0800, Zhang Changzhong wrote:
>> According to SAE-J1939-82 2015 (A.3.6 Row 2), a receiver should never
>> send TP.CM_CTS to the global address, so we can add a check in
>> j1939_can_recv() to drop messages with invalid source address.
>>
>> Fixes: 9d71dd0c7009 ("can: add support of SAE J1939 protocol")
>> Signed-off-by: Zhang Changzhong <zhangchangzhong@xxxxxxxxxx>
> 
> NACK. This will break Address Claiming, where first message is SA == 0xff

I know that 0xfe can be used as a source address, but which message has a source
address of 0xff?

According to SAE-J1939-81 2017 4.2.2.8:

  The network address 255, also known as the Global address, is permitted in the
  Destination Address field of the SAE J1939 message identifier but never in the
  Source Address field.

> 
>> ---
>>  net/can/j1939/main.c | 4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> diff --git a/net/can/j1939/main.c b/net/can/j1939/main.c
>> index 08c8606..4f1e4bb 100644
>> --- a/net/can/j1939/main.c
>> +++ b/net/can/j1939/main.c
>> @@ -75,6 +75,10 @@ static void j1939_can_recv(struct sk_buff *iskb, void *data)
>>  	skcb->addr.pgn = (cf->can_id >> 8) & J1939_PGN_MAX;
>>  	/* set default message type */
>>  	skcb->addr.type = J1939_TP;
>> +	if (!j1939_address_is_valid(skcb->addr.sa))
>> +		/* ignore messages whose sa is broadcast address */
>> +		goto done;
>> +
>>  	if (j1939_pgn_is_pdu1(skcb->addr.pgn)) {
>>  		/* Type 1: with destination address */
>>  		skcb->addr.da = skcb->addr.pgn;
>> -- 
>> 2.9.5
>>
>>
>>
> 



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