Re: command ip -details -statistics link show wlan0

[Wolfgang Grandegger <wg@grandegger.com>]

Hi Ernast,

On 05/15/2013 08:58 PM, Ernast Sevo wrote:
> Hello,
> 
>  I am quite new to socket can and I had a question about the output of
> the command: ip -details -statistics link show can0. When I run the
> above command I get the following output:
> 
> 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
>     3956387    948121    11      0           11          0
>     TX: bytes  packets  errors  dropped carrier collsns
>     100        44       0       0       0       0
> 
> 
> I see that I received 11 errors packets (all of them being rx overrun
> errors) and that no packets were dropped. Does the dropped field refer
> to packets lost in userspace (i.e because they weren't being read fast
> enough and the socket receive buffer overflowed) or does the dropped
> packet field refer to dropped packets being dropped somewhere other
> than userspace?

They refer to packets dropped in the driver for some reason, maily
because memory is short (ENOMEM). The overrun errors above are reported
by the hardware due to messages arrived but there was no space to store
it. Messages dropped because the socket buffer was full can be reported
with the candump option "-d" as shown here:

https://gitorious.org/linux-can/can-utils/blobs/master/candump.c#line549

Hope that helps.

Wolfgang.