On 02.02.21 10:05, Marc Kleine-Budde wrote:

On 2/2/21 10:00 AM, Oliver Hartkopp wrote:

quoted

quoted

quoted

IMO, can_frames in the tx path with CAN_ERR_FLAG should be dropped
if the driver can't handle them. vcan in this regard is capable of
handling those, as does the kvaser usb.

Makes sense. The implementation steps could be:
- convert can_dropped_invalid_skb() from static inline to
    regular function
- add check for CAN_ERR_FLAG and enabled CAN_CTRLMODE_TX_ERR
    to can_dropped_invalid_skb()

Which means the vcan has to support CAN_CTRLMODE_TX_ERR too.

quoted

quoted

I think it's wrong that CAN_ERR_FLAG messages would appear as regular
frame on CAN, as happens today if I understood well.

ACK

What happens if you send a valid CAN frame with CAN_ERR_FLAG set?

I did not check it but I assume the frame is sent as normal frame and
the echo'ed CAN frame would *only* go through the error message filter
bank in af_can.c.

If CAN_CTRLMODE_TX_ERR has been added to the kernel and
can_dropped_invalid_skb() is updated, then a CAN frame with CAN_ERR_FLAG set
would be either send as an error frame or dropped by can_dropped_invalid_skb().

So it would be echoed only if the driver supports CAN_CTRLMODE_TX_ERR and it's
enabled.

ACK.

So a second time Vincent found a mismatch nobody cared about so far. 
Congrats, Vincent!
(no irony here)

;-)

Best,
Oliver

quoted

This is probably not what we want for 'real' CAN devices, so we might
have to take a look at this too.

Marc