udev iw add interface rename issue

Question

I need to put wifi interface into additional monitor state.

If I don't use udev rule and wifi interface named by kernel as wlan0 (default):

$ iw dev wlan0 interface add mon0 type monitor

in this case I don't have any problem and everything works. I can see mon0 interface in iwconfig output.

mon0      IEEE 802.11  Mode:Monitor  Frequency:2.412 GHz  
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Power Management:on

wlan0     IEEE 802.11  ESSID:off/any  
          Mode:Managed  Access Point: Not-Associated   
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:on

If I'm using udev rule and wifi interface named as wbrd0:

70-wireless.rule file:

SUBSYSTEM=="net", ACTION=="add", ATTRS{address}=="xx:xx:xx:xx:xx:xx", NAME="wbrd0"

$ iw dev wbrd0 interface add mon0 type monitor

In this case iwconfig output looks like this:

rename4   IEEE 802.11  Mode:Monitor  Frequency:2.412 GHz  
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Power Management:on

wbrd0     IEEE 802.11  ESSID:off/any  
          Mode:Managed  Access Point: Not-Associated   
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:on

As you can see there's no mon0 interface and instead it's renamed as rename4. I think it's because of udev rule, udev is trying to name new monitor interface as wbrd0 instead of mon0. Probably there's something I'm missing in udev documentation. Though I know that it works with default udev rules but I cannot find a place where it is.

I have a workaround, I can just rename rename4 interface with:

$ ip link set rename4 name mon0

But it's really dirty there should be a better way.

So my question is how to write udev rule which will create a monitor interface from existing wbrd0?

OR

How to find a place in default udev rule which is renaming monitor interface into mon0 when I'm not using my 70-wireless.rule?

udev iw add interface rename issue

0 Answers0