hostapd + WPA2 + ath9k + compat-wireless = fail(?)

Jouni Malinen j at
Mon Jan 30 18:34:28 EST 2012

On Sun, Jan 15, 2012 at 12:42:52AM +0100, Mihai Moldovan wrote:
> hostapd: git
> ath9k: in-kernel, compat-wireless
> Whenever I start hostapd, STAs try to connect but can't due to some
> EAPOL timeout in handshake phase 1 when using compat-wireless.
> The 3.2 and 3.0.2 in-kernel ath9k drivers work fine though.

Which kernel version and compat-wireless version combinations have you
seen issues with?

> -nl80211: Setup AP - device_ap_sme=0 use_monitor=1
> +nl80211: Setup AP - device_ap_sme=0 use_monitor=0
> Why is the old driver creating a monitor, while the new one is not? (Cf.
> my thesis "hostapd does not see traffic")

mac80211 added recently support for AP mode operations without requiring
the monitor interface. hostapd will automatically stop using monitor
interface when the driver is detected to support the new mechanism.

> Also, the older version is using a 100ms timeout, while the new version
> raised that to 1000ms... but it still fails.

This depends on whether TX status indication is available for EAPOL
frames. This was available through the monitor interface, but may not be
available in some cases with the new mechanism if you use new enough
compat-wireless with a kernel version that does not support the needed
socket extensions.

> Do you see anything else?

I haven't seen this issue in my tests, but I don't really test with
compat-wireless, so I could easily have missed some combination of
versions that do not get handled correctly. It looks like the issue
would be in either the way EAPOL frames are sent or received which
sounds a bit odd since I would have expected some other areas to be more
like to be broken than this..

Jouni Malinen                                            PGP id EFC895FA

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