Hello everyone
I am having a very difficult time with a wireless bridging problem.
My objective is to use a Debian GNU/Linux host as a wireless ethernet
bridge between itself, some hosts connected through a switch on it's
eth0 port, and an OpenWRT router.
I have a test setup consisting of a laptop, a small PC (802.11 client),
and the OpenWRT AP/router.
The wifi client system is an amd64(intel) with one 802.11 interface and
a 1000BASE-T interface. The 802.11 hardware here is an Intel 3160. The
OS is Debian GNU/Linux unstable with kernel 4.3.0-1-amd64 and
wpasupplicant package version 2.3-2.3.
The 802.11 AP is a TP-Link TL-WR710N which is based off the Atheros ar9331.
My problem is the moment I bridge the wlan0 interface on the 802.11 PC
client, wpa_supplicant stops doing it's job. It stops responding to any
EAPOL frames from the AP, even though it seems to be receiving them.
It is noteworthy that the bridging works. I am able to get a DHCP lease
on the laptop from the OpenWRT AP/router via bridging though the PC.
Traffic passes both way and everything works great until the next WPA
rekey event comes along (every 10 minutes by default for OpenWRT), and
then the client gets deauth'ed from the AP because it fails to respond.
The only way I can get this to work is to first bring up my wlan0
interface on the PC so that wpa_supplicant authenticates itself
correctly. Once the 802.11 layer 2 is up, I manually use brctl to bridge
in the eth0 and wlan0 ports on the PC. Everything works fine until the
AP wants to rekey or the client needs to re-auth for some reason.
Here is what my setup looks like:
The OpenWRT device setup is pretty standard. The only thing required for
the bridging is the addition of the "option wds 1" parameter under the
wifi-iface in the "wireless" config file. The wds parameter enables
4-address frames to allow the bridging. In case it's relevant, I'm doing
WPA2 PSK AES/CCMP.
My PC/client /etc/network/interfaces file looks kind of like this:
allow-hotplug eth0
iface eth0 inet manual
auto wlan0
iface wlan0 inet manual
wpa-debug-level 2
wpa-ssid POTATONET
wpa-psk XXXXXXXXX
pre-up iw dev wlan0 set 4addr on
pre-up iw dev wlan0 set power_save off
allow-auto br0
# iface br0 inet dhcp
iface br0 inet manual
# bridge_ports wlan0
bridge_ports none
bridge_stp off
bridge_waitport 0
bridge_fd 0
# wpa-iface wlan0
# wpa-bridge br0
I bring up wlan0 and br0:
sudo ifup wlan0
sudo ifup br0
At this point, the wlan0 port should be associated to the AP, even
though I don't have any layer 3 interfaces on the PC yet. If I force a
re-authentication from the AP it works fine. WPA rekey works fine.
I do this to bridge up the interfaces:
sudo brctl addif br0 eth0
sudo brctl addif br0 wlan0
From this point on, wpa_supplicant stops working correctly. However,
the bridge works and ethernet frames are being passed between the laptop
off of PC port eth0 and the OpenWRT AP. Everything is fine until the WPA
rekey happens and then the wlan0 interface goes down and stops working.
I did a tcpdump to find out what was going on and discovered that once
the AP asked for re-authentication from the client, no traffic was going
out of the wlan0 interface on the client PC. This was supported by
ifconfig TX counters. wpa_supplicant stops replying to the AP on the
wlan0 interface.
It should be noted at this point that I am aware wpa_supplicant is
supposed to need the "-b" argument in this kind of setup, which is what
the commented-out "wpa-bridge" parameter in the "interfaces" file above
is for, but it didn't work. I verified the arguments given to
wpa_supplicant were correct via ps:
/sbin/wpa_supplicant -s -B -P /run/wpa_supplicant.wlan0.pid -i wlan0 -b
br0 -D nl80211,wext -C /run/wpa_supplicant
Additional notes and observations:
Just to be clear, I have inspected the macaddr and arp tables on both
the OpenWRT AP and the laptop and the MACs are correct. The wireless
bridging is definitely working as expected. Let me know if you want
output from these commands, but I don't think they are relevant.
The default WPA rekey timer is every 10 minutes on OpenWRT, but I can
force the AP to re-authenticate the client by doing this:
ubus call hostapd.wlan0 del_client '{"addr":"34:de:1a:zz:zz:zz",
"reason":1, "deauth":true, "ban_time":0}'
Finally, here is some debugging output (wpa_supplicant -ddd) from the
client PC during a failed re-auth with the AP.
http://jmomo.net/files/wpa_probs.txt
What do?
If additional debugging is needed, let me know what to do. If this is a
Debian package problem, let me know and I'll go open a bug there.
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