The moment I started reading this I thought "this dude is playing with
aircrack". Surely enough I was right.

On Fri, Jul 26, 2019, 10:14 AM Stefan Sperling, <s...@stsp.name> wrote:

> On Fri, Jul 26, 2019 at 01:53:04PM +0200, Péter Bertalan Zoltán wrote:
> > On 2019-07-26, Stefan Sperling wrote:
> > > Internally to net80211, there are two channels: The 'default' channel
> > > (referred to as "ic_ibss_chan" in source code) and the 'desired'
> > > channel (referred to as "ic_des_chan" in source code).
> > >
> > > The default channel is initialized when the driver attaches (usually
> > > to channel 1). Monitor mode uses this default channel, which you've
> > > modified while the interface was in monitor mode.
> > > ifconfig shows this channel while the interface is down.
> > >
> > > Furthermore, the channel for each known AP is stored alongside other
> > > data such as the AP's SSID. While the interface is up, ifconfig shows
> > > the channel of the currently selected AP. This selection is ineffective
> > > in monitor mode because no connection to any AP is initiated, but data
> > > from the previous connection is still there and is being displayed.
> >
> > So as far as I understand, when I issued
> >    # ifconfig iwn0 mediaopt monitor chan 4
> > I have modified the *default channel*, which monitor mode uses? And in
> > monitor mode, what `ifconfig iwn0` shows as the AP (after 'ieee80211:')
> > can be disregarded, including the channel, because those settings are
> > ineffective in monitor mode?
>
> Yes. What ifconfig shows you here is bogus.
>
> > But this would mean that the interface is indeed set to use channel 4,
> > as desired. However:
> >
> > ---snip---
> > # airodump-ng --channel 4 iwn0
> > CH  4 ][ Elapsed: 1 min ][ 2019-07-26 13:48 ][ fixed channel iwn0: 12
> > ...
> > ---snip---
> >
> > Is this an issue with aircrack-ng? Did I misunderstand you?
>
> I have no idea what aircrack-ng is doing.
>
> You can verify the current channel with:
>   tcpdump -i iwn0 -y IEEE802_11_RADIO
>
> This shows the current channel number in radiotap headers, e.g.:
>   ... <radiotap v0, chan 4, 11n, ...> ...
>
>

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