On 01.07.2011 14:50, Bhupesh SHARMA wrote:

>>> See details here:
>>> https://lists.berlios.de/pipermail/socketcan-users/2010-
>>> January/001226.html
>>>
>>> If it's not on the socketlayer it's worth checking the driver ;-)
>>>
>>
>> However, I did some ugly hacks and now I can run candump with -d
>> option.
>> I see the DROPCOUNT messages like this:
>> DROPCOUNT: dropped 1 CAN frame on 'can0' socket (total drops 1)

Do you see this once or continuous with increasing 'total drops' ?

>>
>> Pardon my limited knowledge on this option, but how can I determine
>> whether
>> this packet was dropped by the driver or the user-space application.

The drop that can be monitored with the '-d' option are the CAN frames that
are lost because of the userspace application was not able to consume the
entire data 'in-time'.

> Forgot to add the `ip -d -s link show can0` output:
> 
> 2: can0: <NOARP,UP,LOWER_UP,ECHO> mtu 16 qdisc pfifo_fast state UNKNOWN qlen 
> 10
>     link/can
>     can state ERROR-ACTIVE restart-ms 0
>     bitrate 988095 sample-point 0.750
>     tq 253 prop-seg 1 phase-seg1 1 phase-seg2 1 sjw 1
>     c_can: tseg1 2..16 tseg2 1..8 sjw 1..4 brp 1..1024 brp-inc 1
>     clock 83000000
>     re-started bus-errors arbit-lost error-warn error-pass bus-off
>     0          0          0          0          0          0
>     RX: bytes  packets  errors  dropped overrun mcast
>     1380496    172562   0       0       0       0
>     TX: bytes  packets  errors  dropped carrier collsns
>     0          0        0       0       0       0
> 
> I can decipher from this dump that the packet dropped and errors
> is 0 while DROPCOUNT messages are still present in `candump -d` output.

The dropped counter in the netdevice has a different meaning.

> 
> Any idea, where there frames are being dropped?

Yes - see above (in the socket receive buffer to the userspace app).

Regards,
Oliver
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