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

Thomas Richter thor at math.tu-berlin.de
Mon Mar 16 00:26:00 PDT 2015

Hi folks,

> 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?
> Either way, it took me several hours of figuring out what was wrong....

One day passed, no useful pointers. Folks, sorry to say, but it is
unacceptable if udev *breaks* the prism wifi.

So long,

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