nl80211, wext, dhclient

Dan Williams dcbw at redhat.com
Fri Sep 4 14:54:42 EDT 2015


On Fri, 2015-09-04 at 20:47 +0200, Simon Kitching wrote:
> On 09/04/2015 06:26 PM, Dan Williams wrote:
> > On Fri, 2015-09-04 at 15:25 +0200, Simon Kitching wrote:
> >> Hi,
> >>
> >> I've noticed some odd behaviour I hope someone here can explain.
> >>
> >> I can get dhcpcd/dhclient to initialise an interface with wpa_supplicant
> >> using "-Dwext" but not "-Dnl80211" (ie the default). Is that expected
> >> behaviour?
> >>
> >> System: Lenovo thinkpad with intel 7265 wireless. OS: debian8 or
> >> linux-from-scratch (both show the same behaviour), systemd-based but all
> >> network-related daemons disabled.
> >>
> >> If I run
> >>     wpa_supplicant -c.. -iwlp3s0
> >> then the interface does not reach RUNNING state (according to ifconfig).
> > Posting the debug logging from wpa_supplicant (pass '-dddt' to it to
> > enable debug logging) and the config file network block would be
> > necessary to figure out what's going on.  Also, what kernel version?
> >
> > Dan
> >
> >> Running "dhcpcd wlp3s0" afterwards reports "link not up" and eventually
> >> exits. Running "dhclient wlp3s0" just hangs.
> >>
> >> If I add "-Dwext" to the wpa_supplicant options, then the interface
> >> reaches state RUNNING, and dhcpcd/dhclient allocate an address for it.
> 
> Ok, found the triggering factor. The nl80211 driver doesn't work with a 
> hidden SSID. As soon as I switched my router to broadcast the id (and 
> updated wpa_supplicant config to match), that driver works fine. Is that 
> expected?

Does it work if you remove ap_scan=2 from the config file?  That's
typically not needed when you have "scan_ssid=1" and a non-broken
driver.

Dan

> Attached is a targz file with the requested logging. There are traces 
> for three cases:
> * wext with hidden SSID (works)
> * nl80211 with hidden SSID (doesn't work; just stops at "link not ready")
> * nl80211 with public SSID (works)
> and the wpa_supplicant.conf files are there too. Note that I've manually 
> changed the SSID name in the files.
> 
> (and yes I know that hiding the SSID doesn't really add much security).
> 
> These traces are all from a system running kernel 3.19.
> 
> Thanks & Regards,
> Simon




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