Re: Count dropped frames on CAN socket

[Austin Hendrix <namniart@gmail.com>]

Awesome, that's exactly what I was looking for.


Thanks!

-Austin


On 11/16/2016 01:57 AM, Oliver Hartkopp wrote:
> And here is how the dropcount stuff has been integrated in candump:
>
> https://github.com/linux-can/can-utils/commit/3c019ea61169d7f08d10d1fece95433c629eb4a6 
>
>
> Regards,
> Oliver
>
>
> On 11/16/2016 01:08 AM, Brian Silverman wrote:
>> Hi Austin,
>>
>> If you enable the (SOL_SOCKET, SO_RX_OVFL) option with setsockopt on a
>> CAN socket, you'll get a corresponding (cmsg_level == SOL_SOCKET,
>> cmsg_type == SO_RXQ_OVFL) piece of ancillary data from recvmsg. The
>> value is a uint32_t containing that exact sk_drops value. The
>> semantics for this value documented in socket(7) are wrong, but the
>> commit message adding it (3b885787ea41) gives a reasonable
>> description. In particular, the message doesn't show up at all until
>> at least one frame is dropped, and it's a total counter not a delta.
>>
>> Brian
>>
>> On Tue, Nov 15, 2016 at 6:32 PM, Austin Hendrix <namniart@gmail.com> 
>> wrote:
>>> Hi linux-can,
>>>
>>> I'm writing a program which receives CAN frames over SocketCAN. I've 
>>> found
>>> on a couple of occasions that my program has had bugs that cause it 
>>> not to
>>> empty the CAN socket receive buffer, and the kernel has dropped 
>>> incoming CAN
>>> frames.
>>>
>>> I had a look through the kernel source code, and found that the 
>>> kernel's
>>> socket framework keeps track of dropped frames in the sk_drops field 
>>> of the
>>> sock struct. Is there a way to retrieve that dropped frame counter 
>>> from my
>>> program, so that it's easier for me to detect problems like this in the
>>> future? (I've looked in the docs and in /proc and haven't been able 
>>> to find
>>> a way to retrieve the sk_drops counter, but it's quite possible that I
>>> missed something)
>>>
>>>
>>> Thanks,
>>>
>>> -Austin
>>>
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