[RFC] P2P: Handling single channel concurrency

Jouni Malinen j at w1.fi
Sun Jan 8 23:59:56 EST 2012


On Thu, Jan 05, 2012 at 11:12:23AM -0800, Reinette Chatre wrote:
> This sounds good. Maybe higher level options like "first come first
> served" could make things even easier to get this off the ground. Maybe
> even start with one default, which then does not even need a
> configuration parameter - it could just be the one default that
> wpa_supplicant supports unless there are hooks that indicate otherwise.

It sounds like a good idea to start with that and maybe even leave it
there. I'm not sure why wpa_supplicant would need to know more. In other
words, allow either STA or P2P operation to be started when nothing else
is running and reject any new command that would result in having to
stop a previously started connection (ideally with an error code
indicating the reason).

In other words, something above wpa_supplicant would take care of user
preferences on how to behave based on use cases etc. It would explicitly
need to stop previously started operations before starting the new
conflicting one - wpa_supplicant should not need extra code for that
part.

> >  In addition to this, we may add a new reason code to GROUP_REMOVE
> > event to indicate that group has been removed due to frequency conflict. This way 
> > framework/user app can come to know about it and notify user. This policing is 
> > not run-time. But this probably can be attempted as a first step.
> 
> Excellent, yes. In addition to the reason added to GROUP_REMOVE there
> should maybe also be a reason code to the STA side of things. Some logic
> may need to be added to connection managers to support this smoothly so
> that the connection manager will not keep trying to associate when
> something like an already present P2P connection prevents it from doing
> so. 

This reason code in group remove events is
P2P_GROUP_REMOVAL_UNAVAILABLE and driver can already trigger it with
EVENT_INTERFACE_UNAVAILABLE on the group interface. That event just
needs to be added to nl80211 so that this goes through (i.e., this has
been used only with some out-of-tree driver wrappers so far).

Well.. The connection manager can try, but that will be rejected
(assuming the STA network does not happen to be available on the same
channel). Anyway, connection managers will obviously need to become
more aware of concurrent operations for smoother user experience.

-- 
Jouni Malinen                                            PGP id EFC895FA


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