Re: IEEE80211 Acknowledgement

[Alexandre Becholey <alexandre@shockfish.com>]

Ivo van Doorn wrote:
> On Monday 04 May 2009, Johannes Berg wrote:
>   
>> On Mon, 2009-05-04 at 18:55 +0200, Ivo van Doorn wrote:
>>     
>>> On Monday 04 May 2009, Johannes Berg wrote:
>>>       
>>>> On Mon, 2009-05-04 at 18:35 +0200, Ivo van Doorn wrote:
>>>>
>>>>         
>>>>> Well I believe the idea would be that (I'll see if I can dig up a reference
>>>>> to the initial discussion about this feature on this list) the driver sets a flag
>>>>> that mac80211 needs to keep a list of all frames send out to the driver and
>>>>> listens for ACK's.
>>>>>
>>>>> As soon as a ACK was passed from driver to mac80211 it could check if
>>>>> the corresponding frame 
>>>>>           
>>>>       ^^^^^^^^^^^^^^^^^^^
>>>>
>>>> Here's the problem. What I'm saying is that there's no way to knowing
>>>> what the "corresponding frame" is.
>>>>         
>>> Hmm, so would there be any alternatives of fixing this problem?
>>>       
>> The proper way of fixing this would be a firmware upgrade ;)
>>
>> Working around it would be possible if the driver queued only a single
>> frame to the hardware, when it knew the frame needed ACK status, and
>> flushed all queues before that frame, so it knows exactly about the
>> frame... This has HUGE overhead and performance impact though, and
>> requires lots of work in mac80211 to not request status for every frame
>> to start with.
>>
>> Since this breaks hostapd operation quite significantly, and I don't see
>> hostapd changing to accommodate this since that essentially breaks the
>> ability to be spec compliant (I'm fairly certain some places require
>> checking for ACK).
>>
>> An easier way would be to fake a ACK reception in the driver for every
>> frame...
>>     
>
> Ok, well I'll go with this route then. Since firmware upgrades for
> older hardware like rt73usb sounds very unlikely. And for rt2500usb
> it is plain impossible (no firmware ;))
>
> Alexandre: Well that seems to make your project a lot easier...
>
> Ivo
>   


Thanks for your answers! I'm gonna try it that way :)

Alexandre