Re: [RFC] WARNING: at net/mac80211/ieee80211_rate.h:159 rate_lowest_index()

[Vladimir Koutny <vlado@work.ksp.sk>]

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>> [...]
>>
>> The question is how sta->supp_rates should be initialized:
>>
>> - we could initialize it to our sta's rates, but then we could
>>   probably transmit to a station at unsupported rate
> 
> isn't this what is done right now, and the rateset is zero sometimes and then 
> we get the warning?

Yes, kind-of. It is initialized to the rateset of an ibss we are part of,
which is the one of ibss we are joining to, or our supported rateset if we
create a new one. However, it is 0 before one of those 2 actions happen, and
then we get the warning.

> this might be wrong anyways: as you said it could make us send frames at an 
> unsupported rate.

Actually, this can happen even now:
- we join an g-ibss, thus setting the rateset to 1-54
- we receive a data frame from a b-only station -> we assign all 1-54 rates to it
- we send something to this station
Probably not a big issue, as a) we will update the sta-rateset on its beacon,
and b) I would expect that such an ibss would adapt to 1-11 only in the
presence of b-only station..

> 
>> - add new ibss station only on received beacon, not on a data frame;
>>   currently, beacons are ignored for this purpose (they just update
>>   the bss list later on)
> 
> i think stations should be added on reception of both beacons and data frames.

Or, do we need this information _before_ joining/creating a new ibss?
Couldn't we just ignore all STAs around until we have a reason not to?

> 
>> - something else (like 1Mbps only)?
> 
> what about the rate of the currently received data frame (and maybe any other 
> rates we could safely deduce from that)?

Yes, that would be a reasonable option - providing that we have the rate
(which we should - there is a WARN_ON(1) in rx-path if it is not set correctly)

As I think about that, I would suggest:
- no sta info is being collected prior to join/create
- sta entry is added/updated on each beacon with reported rateset
- sta entry is added/updated on data frames with just the received-rate

Vlado

> 
> bruno


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