Re: [PATCH] mac80211: add support for userspace to handle auth frames on adhoc ifaces

[Will Hawkins <hawkinsw@opentechinstitute.org>]

On 06/14/2012 12:53 PM, Johannes Berg wrote:
> On Thu, 2012-06-14 at 14:46 +0200, Nicolas Cavallari wrote:
>> On 14/06/2012 13:24, Johannes Berg wrote:
>>> On Thu, 2012-06-14 at 10:00 +0200, Nicolas Cavallari wrote:
>>>
>>>> I just have a question here : when auth frames are not delivered to
>>>> userspace, mac80211 will respond to them, and also uses them to detect
>>>> node reboot. If you register for auth frames, mac80211 will still send
>>>> auth frames as soon as a new station is seen, which might be confusing
>>>> for user space. Is that ok to do this ? Or should userspace have more
>>>> control over how mac80211 sends auth frames ?
>>>
>>> Please read the code. If userspace registers for them, mac80211 will
>>> never do anything with the frame.
>>
>> I didn't say the contrary. But if you read ieee80211_ibss_finish_sta(),
>> you see that mac80211 sends auth frames to each discovered station, even
>> if userspace want to handle auth frames. This seems strange to be able
>> to receive and handle auth frames from userspace while mac80211 sends
>> them behind userspace's back.
> 
> Oops, sorry, yes. I forgot all about that code!
> 
> I suppose we'd have to check whether userspace is handling
> authentication?

Could use the control_port flag to check for that condition?

> 
>>>> There is also another thing to consider if you want to send auth frames
>>>> from userspace, as CMD_FRAME requires a frequency, which in IBSS mode,
>>>> can change anytime without userspace being notified. If you only have to
>>>> answer to received auth frames, this is easier as you can reuse the
>>>> frequency given by nl80211 when receiving the auth frame. But if you
>>>> want to send a auth frame independently, how do you get the frequency to
>>>> use ?
>>>
>>> You check the BSS info, that's trivial.
>>
>> There is no GET_BSS from userspace. when merging IBSS, only the new
>> BSSID is notified. The only way to get this info from userspace would be
>> to dump the scan result and check the "we joined that ibss" flag, and
>> this isn't race-free. That, or using fixed_freq.
> 
> Yeah, I guess that's true -- we should probably just allow not giving a
> frequency attribute at all and then it only works if you're
> connected/... but uses the right frequency.
> 
> johannes
> 
>