I just did a frame dump from my OpenWRT device to look at what was going
on at the 802.11 level.
To be honest, I barely know what I'm doing.
I took a good capture where 4-address frames were off on the client and
then one where 4-address frames were on and the wlan0 interface was on
the bridge.
I'm looking at both captures here in Wireshark and I see the probes, the
initial authentication and association request/replies.
Then the EAPOL process is supposed to occur, and I see that go down okay
in the successful capture.
But in the bad capture, there is no reply from the client. The AP sends
out message 1 of 4 in the EAPOL negotiation and the station never responds.
But there are two things in the failed negotiation that I've noticed.
The first is that in the bad/fail capture there is a weird null-data
frame sent from the station to the AP. I'm not sure what this is all
about. The only thing I know about these frames is that they can be used
for power management notifications (hey AP, I'm going to sleep until
further notice). I don't see any PM flags in this frame. However, I
notice that it's flags are 0x03 (00000011). Is this a notification that
the client wants to do WDS? Because that's what the docs here I'm
reading online says those flags are used for:
https://www.safaribooksonline.com/library/view/80211-wireless-networks/0596100523/ch04.html
See Table 4-2. Use of the address fields in data frames
And then I look at the EAPOL frame the OpenWRT host sends to my station
after the null-data frame. It's the first EAPOL frame in the negotiation
process and it's flags are 0x02 (00000010). Isn't that supposed to be 11?
I think OpenWRT might be broken here. I'm going to check with people
over there and see what they have to say about this. It may be that the
wpa_supplicant on the station is ignoring the EAPOL frames because this
flag is wrong. But like I said, I don't know WTF I'm doing.
Captures available on request if anyone wants to look.
On 2/17/16 20:16, J Mo wrote:
I decided to grab another 802.11 adapter and test with it. This time a
rtl8192cu (ALFA AWUS036NHR). Same behavior. No change.
Here is what happens when I run the Debian ifup script in verbose mode:
user@host-->sudo ifup -v br0
Configuring interface br0=br0 (inet)
iw dev wlan0 set 4addr on
iw dev wlan0 set power_save off
/bin/run-parts --exit-on-error --verbose /etc/network/if-pre-up.d
run-parts: executing /etc/network/if-pre-up.d/bridge
Waiting for a max of 5 seconds for wlan0 to become available.
Waiting for br0 to get ready (MAXWAIT is 2 seconds).
run-parts: executing /etc/network/if-pre-up.d/ethtool
run-parts: executing /etc/network/if-pre-up.d/vlan
run-parts: executing /etc/network/if-pre-up.d/wireless-tools
run-parts: executing /etc/network/if-pre-up.d/wpasupplicant
wpa_supplicant: wpa-bridge br0
wpa_supplicant: wpa-driver nl80211,wext (default)
wpa_supplicant: /sbin/wpa_supplicant -s -B -P
/run/wpa_supplicant.wlan0.pid -i wlan0 -b br0 -D nl80211,wext -C
/run/wpa_supplicant
Starting /sbin/wpa_supplicant...
wpa_supplicant: creating sendsigs omission pidfile:
/run/sendsigs.omit.d/wpasupplicant.wpa_supplicant.wlan0.pid
wpa_supplicant: ctrl_interface socket located at
/run/wpa_supplicant/wlan0
wpa_supplicant: configuring network block -- 0
wpa_supplicant: wpa-ssid "POTATONET" -- OK
wpa_supplicant: wpa-psk ***** -- OK
wpa_supplicant: enabling network block 0 -- OK
/bin/ip addr add 192.168.130.251/255.255.255.0 broadcast
192.168.130.255 dev br0 label br0
/bin/ip link set dev br0 up
/bin/run-parts --exit-on-error --verbose /etc/network/if-up.d
run-parts: executing /etc/network/if-up.d/000resolvconf
run-parts: executing /etc/network/if-up.d/arping
run-parts: executing /etc/network/if-up.d/avahi-autoipd
run-parts: executing /etc/network/if-up.d/clamav-freshclam-ifupdown
run-parts: executing /etc/network/if-up.d/ethtool
run-parts: executing /etc/network/if-up.d/ip
run-parts: executing /etc/network/if-up.d/mountnfs
run-parts: executing /etc/network/if-up.d/openssh-server
run-parts: executing /etc/network/if-up.d/upstart
run-parts: executing /etc/network/if-up.d/wpasupplicant
It is notable that if I remove the "pre-up iw dev wlan0 set 4addr on"
parameter from the interfaces config file under br0, I get this error
when attempting to bring the interface up:
Waiting for a max of 0 seconds for wlan0 to become available.
can't add wlan0 to bridge br0: Operation not supported
So that's the point where the wlan0 interface gets bridged onto br0.
This indicates that the bridge is definitely exists and wlan0 is a
member prior to wpa_supplicant being invoked.
On 2/17/16 02:05, J Mo wrote:
I will go look and verify the order of operations for the Debian
networking system, but I am under the impression that it brings up
the wlan interface (via bridge_ports), does all bridging, and then
processes the wpa-* commands.
In other words, it's already doing what you suggested.
Also, wpa_supplicant gives errors if either the 802.11 interface (-i
wlan0) or bridge interface (-b br0) wasn't up at the time it was
launched, so I don't think it's even possible to get the order wrong
without obvious signs. I just don't think that's the issue here.
Still, I'll take your advice and double check. I think I can debug
the ifup/down scripts a little more than what I've already done, but
I don't think order of operation is an issue.
One thing to note is that if I bridge the wlan0 interface and let an
AP-reauth fail and then take the bridge off, wpa_supplicant starts
working again. Put the bridge back on and it breaks again, etc. I can
do this live with brctl without restarting wpa_supplicant and it will
start and stop working.
I don't even understand why wpa_supplicant needs to know about the
bridge in this situation, but whatever!
FYI By "official method", I mean the ideal config setup with an
"interfaces" config like this:
allow-auto wlan0
iface wlan0 inet manual
allow-auto br0
iface br0 inet dhcp
bridge_ports wlan0
bridge_stp off
bridge_waitport 5
bridge_fd 0
wpa-ssid POTATONET
wpa-psk xxxxxxx
wpa-iface wlan0
wpa-bridge br0
pre-up iw dev wlan0 set 4addr on
pre-up iw dev wlan0 set power_save off
On 2/17/16 00:49, Simon Malthieu wrote:
Hi,
Have you tried to add wlan0 to the bridge **before**
wpa_supplicant (with the -b option) is launched ?
wpa_supplicant opens a socket to listen to EAPOL frames
in the bridge, and it does not seem to work if the interface
is not in the bridge at start.
Regards,
Simon
On 17/02/2016 04:30, J Mo wrote:
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.
--
To unsubscribe from this list: send the line "unsubscribe
linux-wireless" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe
linux-wireless" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe
linux-wireless" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe
linux-wireless" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-wireless" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
