hostapd error

[Jouni Malinen]

On Fri, Mar 25, 2016 at 05:49:57PM -0700, Ben Greear wrote:
> On 03/25/2016 05:24 PM, Ann Lo wrote:
> >Thanks for your information and suggestion. Using -dd option, there
> >are more information from hostapd, including:
> >
> >nl80211: Beacon set failed: -16 (Device or resource busy)
> >
> >Further investigation result is that this happens in the following scenario:
> >1) hostapd runs OK at channel 36 using 80 MHz width.
> >2) wpa_supplicant (using the same radio) tries to connect to a remote
> >AP on channel 36 using 20 MHz width.
> >3) hostapd is restarted at this point.
> >4) When hostapd comes up again, it gets the above error.
> >5) At this point, wpa_supplicant connects successfully.
> >
> >The radio requires AP and client using the same channel. Does this
> >mean that the channel width must be the same?
> 
> Channel width does not need to be the same, but the primary channel
> must be.
> 
> You probably need a patch I put into hostapd to force not switching
> the primary channel when running multiple interfaces on a single radio.
> 
> https://github.com/greearb/hostap-ct/commit/cd25b893c97da95b5b7cda0e61ea7bcf5355bc16

Instead of that configuration parameter that can be used to disable
mandatory 40 MHz co-existence requirements, shouldn't this be handled
automatically by detecting that another local vif of the same radio
prevents the switch and based on that, prevent the switch? I'd be fine
doing this based on the local concurrent use constraints, but it would
be difficult to justify parameters that can be misused.

-- 
Jouni Malinen                                            PGP id EFC895FA