First STA scan results are ignored if P2P_FIND is issued immediately after STA scan

Jouni Malinen j
Tue Mar 26 01:49:55 PDT 2013

On Tue, Mar 26, 2013 at 12:51:36PM +0530, Sreenath wrote:
> With the latest wpa_supplicant I have found an issue that the first STA 
> scan results are not processed if P2P_FIND is issued immediately in P2P 
> interface after issuing a STA scan in STA interface. However the 
> subsequent STA scan results are processed during ongoing P2P_FIND operation.

That is by design, i.e., wpa_supplicant tries to do what it is asked to
do. P2P_FIND issued during the station scan is interpreted as a request
to start P2P device discovery. Since processing of the station scan
results could start a longer operation (association with an AP), those
results are dropped to allow the requested P2P_FIND to start.

> So as a work around / fix, if the processing of pending P2P operation is 
> removed from function - '_wpa_supplicant_event_scan_results()' 
> everything works fine as STA results will be processed always and 
> pending P2P operation will be taken cared by the function - 
> "wpas_p2p_continue_after_scan()" called after 
> "wpa_supplicant_event_scan_results()" inside 'EVENT_SCAN_RESULTS' event 
> handling in "wpa_supplicant_event()".
> So kindly verify and update me, if the above modification is valid.

Why would you issue the P2P_FIND command here in the first place? I
think the real fix would be to not issue that if you want to get the
station interface doing something more quickly. In concurrent operation
case the interfaces will be competing for the same radio resource and if
you try to start multiple operations at the same time, these will need
to be ordered somehow and the current wpa_supplicant design is to try to
follow the last control interface command first to match the behavior
with single interface (last operation may stop earlier operations).

Jouni Malinen                                            PGP id EFC895FA

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