Re: [RFA] timestamp field

My wireshark timeline code is out for early review.

https://code.wireshark.org/review/#/c/13694

Simon

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On January 20, 2016 11:40:14 PM Johannes Berg <[email protected]> 
wrote:

> On Wed, 2016-01-20 at 09:46 -0800, Simon Barber wrote:
>> I like this proposal. One aspect that is missing is to define the
>> meaning of the timestamp with aggregates. Should this field be
>> present for all subframes, or just the first/last? Should the
>> timestamp refer to the subframes, or the whole A-MPDU? Currently what
>> I see in different generators is the MACTIME field is either the same
>> for all subframes, and always refers to the whole A-MPDU - not
>> individual subframes. For one generator the MACTIME was 0 for
>> subframes after the 1st. Sometimes the signal strength is only
>> present on the last subframe.
>
> Yeah, I had actually noticed this - our device also has the PHY
> acquisition timestamp of the A-MPDU, in all the frames. We should
> probably elide it in all but the first, but if we somehow lost the
> first frame that would be bad. I'm not even sure you can identify that
> today at all though.
>
> I don't think we can *standardise* the behaviour, but perhaps providing
> flags for the different behaviours would at least help you identify it?
>
> Any thoughts what flags would be useful?
>
>> Macbooks generate radtiotap files with incorrect rate fields for
>> subframes with CRC errors.
>
> That's a bit odd. Talk to Broadcom? ;-)
>
>> If you look in the wireshark gerrit, you will see I have been porting
>> my timeline viewer code over to the current devel mainline.
>>
>
> Very nice! :)
>
> johannes