[B.A.T.M.A.N.] Bridge changing source mac address prevents batman-adv from connecting

[B.A.T.M.A.N.] Bridge changing source mac address prevents batman-adv from connecting

[Ilario Gelmetti]

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Hi all!
I'm using batman-adv (2014.2.0) on two devices running OpenWrt
(LibreMesh) connected using a third device running a proprietary
firmware in bridge mode (AirOS), this is the topology:
http://i.imgur.com/ELMi5RC.png

mac3E80 OpenWrt batman----cable----macE3E7 AirOS station----wireless--
--macE434 AP OpenWrt batman

using tcpdump on the OpenWrt devices I can see batman packets flowing:
on mac3E80 I can see:
http://sprunge.us/iePM
while on macE434 I can see:
http://sprunge.us/DIAX
as you can see the problem is that macE434 sees packets from mac3E80
*approaching with the wrong mac address*, the mac address of macE3E7 so
I think it discards the packages when source mac address is different
from mac address specified inside the packet.
Is this only a security check?
How could I get things work?
Thanks,
Ilario


-- 
Ilario Gelmetti
iochesonome@gmail.com
ilario.gelmetti@sns.it


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Re: [B.A.T.M.A.N.] Bridge changing source mac address prevents batman-adv from connecting

[Gui Iribarren]

On 20/06/14 10:58, Ilario Gelmetti wrote:
> Hi all! I'm using batman-adv (2014.2.0) on two devices running
> OpenWrt (LibreMesh) connected using a third device running a
> proprietary firmware in bridge mode (AirOS), this is the topology: 
> http://i.imgur.com/ELMi5RC.png
> 
> mac3E80 OpenWrt batman----cable----macE3E7 AirOS
> station----wireless-- --macE434 AP OpenWrt batman
> 
> using tcpdump on the OpenWrt devices I can see batman packets
> flowing: on mac3E80 I can see: http://sprunge.us/iePM while on
> macE434 I can see: http://sprunge.us/DIAX as you can see the
> problem is that macE434 sees packets from mac3E80 *approaching with
> the wrong mac address*, the mac address of macE3E7 so


Yeah, AirOS in "WDS mode" does tricky stuff.

The problem is, in principle, you shouldn't be able to bridge a wifi
interface in client mode.

http://wiki.openwrt.org/doc/howto/clientmode?s[]=bridged&s[]=client

Your AirOS client device is expecting the AP to be in "4addr" mode,
which vanilla openwrt is not.

You should either
a) keep stock airOS on both client and ap, (what i've done so far,
when bumped into this problem)
b) flash openwrt to both "client" and "ap", and use adhoc between them
c) or dig into doing WDS on openwrt (i guess it's possible but i
haven't tried)

Nothing to do with batman-adv, though :)


> I think it discards the packages when source mac address is
> different from mac address specified inside the packet. Is this
> only a security check? How could I get things work? Thanks, Ilario
> 
> 

Re: [B.A.T.M.A.N.] Bridge changing source mac address prevents batman-adv from connecting

[Bastian]

Hi,

we have a similar situation at freifunk-berlin. Because of problems with 
weather-radar we are forced to use DFS/802.11h compliant hardware. We 
chose ubnt nanostations with AirOS in WDS/transparent-bridge mode.
If you want to *bridge* two networks, you need some form of WDS. Basic 
AP<->STA does not have enough fields for additional MAC-addresses of 
devices behind the STA.

So either you run OpenWRT with batadv+bmx6 on both NanoStations, or you 
use AirOS in WDS-mode on both NanoStations and run batadv+bm6 with 
ethernet-node behind those NS5. Mixing AirOS and OpenWRT (with or 
without bridge mode) will - as far as i know - always break anything 
that relies on correct MAC-adresses, like batman-adv or IPv6-NDP.

Regards.
Bastian


On 06/20/2014 03:58 PM, Ilario Gelmetti wrote:
> Hi all!
> I'm using batman-adv (2014.2.0) on two devices running OpenWrt
> (LibreMesh) connected using a third device running a proprietary
> firmware in bridge mode (AirOS), this is the topology:
> http://i.imgur.com/ELMi5RC.png
>
> mac3E80 OpenWrt batman----cable----macE3E7 AirOS station----wireless--
> --macE434 AP OpenWrt batman
>
> using tcpdump on the OpenWrt devices I can see batman packets flowing:
> on mac3E80 I can see:
> http://sprunge.us/iePM
> while on macE434 I can see:
> http://sprunge.us/DIAX
> as you can see the problem is that macE434 sees packets from mac3E80
> *approaching with the wrong mac address*, the mac address of macE3E7 so
> I think it discards the packages when source mac address is different
> from mac address specified inside the packet.
> Is this only a security check?
> How could I get things work?
> Thanks,
> Ilario
>
>