=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D----------=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D-----=
-----=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D----------=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
Hello list,
In net/mac80211/scan.c, function ieee80211_bss_info_update() passes
incoming scan results to the generic wireless layer, with indication of
the received signal level, but no indication of signal validity.
Before ieee80211_bss_info_update() is called, rx_status->flag can be set
to RX_FLAG_NO_SIGNAL_VAL by the ath9k driver and it won't be taken into
account in the wireless layer.
Even later in ieee80211_bss_info_update(), rx_status->flag can also be set
to RX_FLAG_NO_SIGNAL_VAL, and the wireless layer won't be aware of this.
I stumbled on this because, when using ath9k (WLE350NX) to do a passive sca=
n
off-channel, the beacons received in a 30ms window after channel change sho=
w
a signal level +10dB above the real value. So I was looking for a way to
tell the above layers that the signal is invalid. RX_FLAG_NO_SIGNAL_VAL see=
ms
to fit, but is not conveyed up to iw or wpa_supplicant.
In fact I did not find any such thing in net/wireless/nl80211.c, function
nl80211_send_bss().
Any suggestion? Did I miss something?
Regards,
Jean-Pierre
On Wed, 2018-02-14 at 10:10 +0000, Jean Pierre TOSONI wrote:
> >
> > However, it looks like you're right and ieee80211_bss_info_update()
> > doesn't take the flag into account. Bit strange that we even have
> > the flag I guess, since we treat 0 as an invalid value in various
> > places, being too high power to realistically receive anyway.
>
> The problem is that 0 is invalid as a SIGNAL_DBM value but this is
> dubious for a SIGNAL_UNSPEC value which appears to be still in use
> in a couple of drivers.
Huh, good point, that's ancient history to me and I forget :-)
> > Want to send a patch? There seem to be a few more places as well,
>
> I am working on a 3.18 kernel; so I can either make the patch from
> an old compat-wireless, or make the patch from your last tree but
> I cannot test it; are you interested anyways?
The only useful patch would be on the last tree. :-)
> > e.g.
> > in rx.c for cfg80211_report_obss_beacon() and cfg80211_rx_mgmt().
>
> There is also mlme.c, the ifmgd->ave_beacon_signal should not be updated
> with an invalid signal;
> and in the last tree, the ibss join passes an uninitialized signal
> value to cfg80211_inform_bss_frame_data().
Good catch!
johannes
On Thu, 2018-02-08 at 09:49 +0000, Jean Pierre TOSONI wrote:
> In net/mac80211/scan.c, function ieee80211_bss_info_update() passes
> incoming scan results to the generic wireless layer, with indication of
> the received signal level, but no indication of signal validity.
Well, there is an indication of validity, if the value is 0 then it's
invalid.
> Before ieee80211_bss_info_update() is called, rx_status->flag can be set
> to RX_FLAG_NO_SIGNAL_VAL by the ath9k driver and it won't be taken into
> account in the wireless layer.
> Even later in ieee80211_bss_info_update(), rx_status->flag can also be set
> to RX_FLAG_NO_SIGNAL_VAL, and the wireless layer won't be aware of this.
However, it looks like you're right and ieee80211_bss_info_update()
doesn't take the flag into account. Bit strange that we even have the
flag I guess, since we treat 0 as an invalid value in various places,
being too high power to realistically receive anyway.
> I stumbled on this because, when using ath9k (WLE350NX) to do a passive scan
> off-channel, the beacons received in a 30ms window after channel change show
> a signal level +10dB above the real value. So I was looking for a way to
> tell the above layers that the signal is invalid. RX_FLAG_NO_SIGNAL_VAL seems
> to fit, but is not conveyed up to iw or wpa_supplicant.
>
> In fact I did not find any such thing in net/wireless/nl80211.c, function
> nl80211_send_bss().
>
> Any suggestion? Did I miss something?
Want to send a patch? There seem to be a few more places as well, e.g.
in rx.c for cfg80211_report_obss_beacon() and cfg80211_rx_mgmt().
johannes
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