What is the proper error response to send during an ISO-TP timeout?

[brandonros]

The question isn't specific to your code base, but I can tell by the high quality of your code and thorough understanding of all of the protocols at play, you probably stand a good chance of helping.

tuneutils/src/protocols/isotp/can.rs

Line 48 in 84586db

return Err(Error::Timeout);

I have my own version of an ISO-TP/CAN/UDS server in node.js

Sometimes, the device I'm interfacing with fails to properly complete an ISO-TP request. Whether it is taking too long for flow control frame or the consecutive frames themselves not coming across quickly enough, I'm not sure if me acting as the ECU is supposed to send:

a) no response

or b) a 0x7F failure (with what error response code? I can't find one that I would expect to exist for "general failure/please retry")

Are CAN interfaces not supposed to be so generally unreliable? Do I maybe have a bigger problem with my drivers?

[jcmnn]

Are you getting no response when sending multi-frame packets? When sending frames too quickly with certain interfaces, some of them might get dropped.

When sending the flow control frame, zero all the fields for the shortest delay (so the frame will be 03 00 00.

Some ECUs drop frames that aren't padded to 8 bytes (pad it with 0s).
So instead of sending e.g. 40 13 32 45 65, send 40 13 32 45 65 00 00 00.