How to disassociate a wireless interface with an access point?

Question

I'm trying to make a script that sleeps my wireless card in linux. For that I'm using the deepsleep command of iwpriv:

iwpriv wlan0 deepsleep 1

The problem is that this command only works if the wireless card is disconnected and disassociated. When it's connected there is no problem because if I disconnect, it disassociates automatically. But if it's disconnected, sometimes it associates (but not connects) automatically to unencrypted networks, so I cannot run the iwpriv command. The only fix I have found is to change the mode first to Ad-Hoc and then to Managed before sleep the card:

iwconfig wlan0 mode ad-hoc
iwconfig wlan0 mode managed
iwpriv wlan0 deepsleep 1

But I think it's a bit tricky.

Does exist a more direct way to disassociate a wireless card in linux?

Answer 1

I don't have a fix, but you could try setting the ESSID of the card to a random string and hope that no access points nearby use that ESSID. That should prevent autoconnecting to any unencrypted network found. Not a solution, but maybe a better band-aid.

Answer 2

Won't it disassociate if you do ifconfig wlan0 down?

Answer 3

Many drivers use the convention that associating with the NULL AP disconnects from the current AP. Add to this a brief delay, and you might have what you want. For example,

iwconfig wlan0 ap 00:00:00:00:00:00
sleep 1
iwpriv wlan0 deepsleep 1

Typically, it shouldn't take more than 250-500 milliseconds to disconnect from an AP, but a fractional sleep command (e.g. sleep 0.25) isn't portable.