"channel [21] (157) is disabled for use in AP mode"

[Krishna Chaitanya]

On Sun, Apr 28, 2013 at 4:27 PM, Marty <marty at heavyreckoning.com> wrote:
>
> On 04/28/2013 06:05 AM, Zack Buhman wrote:
> > I'd like to use channel 157, as I've done in the past. I've read
> > [1] that 157 is perfectly valid to use in the US. Apparently
> > hostapd disagrees with this assesment.
> >
> > I'm using hostapd hostapd v2.0 [2] using the nl80211 driver on
> > ath9k hardware.
> >
> > iw reg get: http://ix.io/5o7 iw list: http://ix.io/5o6 hostapd -dd
> > /etc/hostapd/hostapd.conf: http://ix.io/5o8
> >
> > I'm not quite understanding how hostapd came to the conclusion that
> > I can't use channel 157, and, more importantly, how I can fix
> > this.
> >
> > [1]
> > https://en.wikipedia.org/wiki/List_of_WLAN_channels#5.C2.A0GHz_.28802.11a.2Fh.2Fj.2Fn.29.5B13.5D
> >
> >
> [2] http://w1.fi/releases/hostapd-2.0.tar.gz
> >
>
> This appears to be the important message in the debug output you listed:
>
> channel [21] (157) is disabled for use in AP mode, flags: 0x77 NO-IBSS
> PASSIVE-SCAN
>
> I'm not up to speed on it, but it appears that while allowed for use
> for other purposes, like DFS and TPS, it cannot be used for an access
> point channel because no BSS in the sense an AP uses one is used on
> that channel.  I think this might be because there have been
> interference issues with satellite and radar in the 5-5.8Ghz band and
> so use of some channels in the 5Ghz range have to be selected
> dynamically to avoid interference with existing critical systems.  So
> you shouldn't manually select them, but instead need a layer that
> handles that dynamic channel selection.  Reference 802.11h
>

But in US >149 are non-DFS channels, isn't it (DFS falg is not set)?
Then why it shows as only passive scanning as if its a DFS channel

from the reg rules the chanel is enabled so only reason channel can be
disabled is if there is some error with the retrieving the reg rules in the
cfg80211??? dmesg might help.