[systemd-devel] udev breaks hostap linkage of raw/user interfaces, causing wpa_supplicant problems

Kay Sievers kay at vrfy.org
Sun Mar 15 07:38:50 PDT 2015

On Sun, Mar 15, 2015 at 1:40 PM, Thomas Richter <thor at math.tu-berlin.de> wrote:
> udev seems to create a problem here with the hostap (prism2) kernel driver.
> Unlike many wifi devices, the hostap device driver always creates paired
> interfaces, a raw interface (wifiX) and a network interface (wlanX) that
> represents the configured network.
> Unfortunately, udev (or hostap?) does not seem to be aware of this linkage,
> and hence, if you have two wifi radios in your system, may rename the second
> (wlanX) without the first (wifiX), and hence causing a name mismatch between
> the two.
> In general, this is not a problem, however, wpa_supplicant seems to depend
> on the linkage of the names. Hence, if wifiX does not match wlanX,
> wpa_supplicant will be unable to provide a WPA2 connection over a hostap
> driven wifi connection.
> Even worse, the complete procedure is completely untransparent to the user,
> i.e. neither wpa_supplicant (nor network-manager, depending on
> wpa_supplicant) nor network-manager provide a useful error message.
> Any chance of fixing this problem? Is this "only" a configuration issue? Is
> this an issue of hostap? Is this an issue of wpa_supplicant?

What does:
  $ grep . /sys/class/net/*/name_assign_type


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