On Fri, Jul 26, 2019 at 12:01:32PM +0200, Péter Bertalan Zoltán wrote: > I am sorry if the answer to this question is trivial, I am rather new to > OpenBSD and have a lot to learn. > > I have an 'Intel Centrino Advanced-N 6205' network card that I am trying > to put into monitor mode on a fixed channel using ifconfig. However, I > am experiencing this peculiar behaviour (at least to me): > > ---snip--- > # ifconfig iwn0 > iwn0: flags=8847<UP,BROADCAST,DEBUG,RUNNING,SIMPLEX,MULTICAST> mtu 1500 > lladdr aa:bb:cc:dd:ee:ff > index 2 priority 4 llprio 3 > groups: wlan egress > media: IEEE802.11 autoselect (HT-MCS1 mode 11n) > status: active > ieee80211: nwid my-AP chan 11 bssid 11:22:33:44:55:66 -33dBm > wpakey wpaprotos wpa2 wpaakms psk wpaciphers ccmp > wpagroupcipher ccmp > inet 192.168.43.125 netmask 0xffffff00 broadcast 192.168.43.255 > # ifconfig iwn0 -nwid -inet <-- As far as I understand, I can disconnect > like this? But sometimes it does > nothing. > # ifconfig iwn0 > iwn0: flags=8847<UP,BROADCAST,DEBUG,RUNNING,SIMPLEX,MULTICAST> mtu 1500 > lladdr aa:bb:cc:dd:ee:ff > index 2 priority 4 llprio 3 > groups: wlan egress > media: IEEE802.11 autoselect (DS1) > status: no network > ieee80211: nwid "" > # ifconfig iwn0 mediaopt monitor chan 4 > # ifconfig iwn0 > iwn0: flags=8847<UP,BROADCAST,DEBUG,RUNNING,SIMPLEX,MULTICAST> mtu 1500 > lladdr aa:bb:cc:dd:ee:ff > index 2 priority 4 llprio 3 > groups: wlan egress > media: IEEE802.11 autoselect monitor > status: active > ieee80211: nwid my-AP chan 1 bssid 11:22:33:44:55:66 > ---snip--- > > What is going on? Why is my nwid set back again to my AP? Furthermore, > why am I on channel 1 when I selected channel 4? Now when I disable the > device: > > ---snip--- > # ifconfig iwn0 down && ifconfig iwn0 > iwn0: flags=8806<BROADCAST,DEBUG,SIMPLEX,MULTICAST> mtu 1500 > lladdr aa:bb:cc:dd:ee:ff > index 2 priority 4 llprio 3 > groups: wlan egress > media: IEEE802.11 autoselect monitor > status: no network > ieee80211: nwid "" chan 4 > ---snip--- > > So the channel is actually set to 4, but when I enable the interface > again, it resets to my AP and to channel 1. I am greatly confused as to > why I keep reconnecting to my AP... Neither `ifconfig iwn0 joinlist` nor > `/etc/hostname.iwn0` contains any line related to 'my-AP'. > > Sometimes, when I don't set the channel, I get some high channel like > 149 assigned. I am not sure what '(DS1)' means; I didn't find anything > in ifconfig(8), but it is not there after a fresh boot. Is it related? > > I am sure I am doing something wrong. Thank you very much in advance for > shedding some light on what.
This is a cosmetic issue. 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. I would be happy about patches which make monitor mode less confusing to use but I won't fix trivial things like this myself because there are more important things which need fixing in the wireless stack.
