WPA_Supplicant: no unicast with wpa encryption

[mkettn@technik-emden.de]

Hello,

I want to use wpa_supplicant to encrypt a ad-hoc network with WPA.
Each device is also a router (using babeld). 
With encryption the support for unicast packages drops. I've used
tshark to monitor the traffic of two devices (A and B):

when A wants to ping B it broadcasts a ask for the MAC-address of B.
B sends the MAC-address successfully but A doesn't care.

I see the reply of B in tshark (running on B), but the ARP-package
doesn't show up on tshark on A.

this only happens with wpa_supplicant enabled.

The wpa_supplicant.conf looks like this:
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1

# use 'ap_scan=2' on all devices connected to the network
ap_scan=2

network={
    ssid="mesh-wpa"
    mode=1
    frequency=2432
    proto=WPA
    key_mgmt=WPA-NONE
    pairwise=NONE
    group=TKIP
    psk="secret passphrase"
}


and the /etc/network/interfaces like this:
auto lo

iface lo inet loopback
iface eth0 inet dhcp

allow-hotplug wlan0
iface wlan0 inet static
    address 192.168.13.37
    netmask 255.255.255.255

    # Load WPA-Supplicant for WPA in Ad-Hoc Mode
    wpa-driver wext
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

iface default inet dhcp


I'm using two RaspberryPis with Raspbian Linux 3.6.11+.
Here is the device descriptor of the wlan usb stick:
lsusb -v -d 0cf3:9271 - http://pastebin.com/nfvVp80u

the output of wpa_supplicant -i wlan0 -D wext
-c /etc/wpa_supplicant/wpa_supplicant.conf brings:

ioctl[SIOCSIWPMKSA]: Invalid argument
ioctl[SIOCSIWENCODEEXT]: Invalid argument
ioctl[SIOCSIWENCODEEXT]: Invalid argument
wlan0: Trying to associate with SSID 'mesh-wpa'
ioctl[SIOCSIWGENIE]: Operation not supported
wlan0: Association request to the driver failed
wlan0: CTRL-EVENT-CONNECTED - Connection to 00:00:00:00:00:00 completed
(auth) [id=-1 id_str=] wlan0: Trying to associate with SSID 'mesh-wpa'
ioctl[SIOCSIWENCODEEXT]: Invalid argument
ioctl[SIOCSIWENCODEEXT]: Invalid argument
ioctl[SIOCSIWGENIE]: Operation not supported
wlan0: Association request to the driver failed
wlan0: CTRL-EVENT-CONNECTED - Connection to 00:00:00:00:00:00 completed
(reauth) [id=0 id_str=]

-Mark