Re: CAN ISO-TP

[Patrick Menschel <menschel.p@posteo.de>]

Am 10.05.21 um 20:04 schrieb Patrick Menschel:
> Am 10.05.21 um 12:02 schrieb Bartosz Zdanowicz:
>> pt., 7 maj 2021 o 09:59 Patrick Menschel <menschel.p@posteo.de> napisał(a):
>>> try to enable CAN_ISOTP_WAIT_TX_DONE via socket.setsockopt() .
>>> https://github.com/raspberrypi/linux/blob/rpi-5.10.y/net/can/isotp.c#L14
>>>
>>> https://gitlab.com/Menschel/socketcan/-/blob/master/socketcan/socketcan.py#L583
>>>
>>> and wrap tx into a try-except block.
>>>
>>> try:
>>>     self.process_data(socket=socket)
>>> except OSError as e:
>>>     print(e)
>>>
>>> With this you actually have a chance to do error handling on tx path
>>> instead of hitting an already present error of the previous op.
>>>
>> I used following code:
>>
>> import isotp
>> import time
>> s = isotp.socket()
>> s._socket.settimeout(2)
>> s.set_opts(s.flags.WAIT_TX_DONE)
>> s.bind("can0", isotp.Address(rxid=1, txid=2))
>>
>> s.send(b"aaaaaaaaa") -> returns immediately with number of bytes
>> s.send(b"aaaaaaaaa") -> same OS error as above (Error 70)
>>
> 
> OK,
> 
> this is really strange. I have no clue how that is possible unless it's
> on kernel side.
> 
> I have to write a test for it later.

I can confirm this behaviour, it is definetly kernel-side of the socket.

tests/test_socketcan.py::TestCanIsoTpSocket::test_should_fail_missing_flow_control_on_transfer

--------------------------------------------------------------------------------------------------
live log call
--------------------------------------------------------------------------------------------------
2021-05-11 18:14:00 [    INFO] Return value of IsoTpSend without flow
control: 64 (test_socketcan.py:720)
2021-05-11 18:14:01 [   ERROR] Return value of IsoTpSend without flow
control: None, Raised [Errno 70] Communication error on send
(test_socketcan.py:718)

Apparently there is another message thread for this and something was fixed.

https://marc.info/?i=97e2ddd5-cc8b-9c7b-6198-2eceee39dfd4%20()%20hartkopp%20!%20net

Funny thing is, it does not care about the wait_tx_done flag, this
happens with and without it.

Regards,
Patrick