[B.A.T.M.A.N.] Bad link quality if routers are connected by 2 interfaces

[B.A.T.M.A.N.] Bad link quality if routers are connected by 2 interfaces

[Clemens John]

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Hi,

in our Freifunk network we are experiencing some kind of strange behaviour if 
two routers can see each other by wire and wireless at the same time. Then the 
link quality in the originator table drops from normally >250 to somewhat 
around 130 or less on both interfaces.

Because we have no idea why this happens but think this is kind of unwanted 
behaviour I´m asking here if we did something wrong or if we missed some 
configuration in this case.

We are using B.A.T.M.A.N. adv 2013.4.0.

Kind Regards
Clemens John
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Re: [B.A.T.M.A.N.] Bad link quality if routers are connected by 2 interfaces

[Simon Wunderlich]

Hi,
> Hi,
> 
> in our Freifunk network we are experiencing some kind of strange behaviour
> if two routers can see each other by wire and wireless at the same time.
> Then the link quality in the originator table drops from normally >250 to
> somewhat around 130 or less on both interfaces.
> 
> Because we have no idea why this happens but think this is kind of unwanted
> behaviour I´m asking here if we did something wrong or if we missed some
> configuration in this case.

this is certainly not the expected behaviour. Are you building a bridge loop 
by any chance? Please explain your configuration (batctl if, brctl show, ...) 
and check if you have a high amount of broadcasts somehow.

Cheers,
    Simon

Re: [B.A.T.M.A.N.] Bad link quality if routers are connected by 2 interfaces

[Clemens John]

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Am Montag, 4. November 2013, 11:28:20 schrieben Sie:
> this is certainly not the expected behaviour. Are you building a bridge loop
> by any chance? Please explain your configuration (batctl if, brctl show,
> ...) and check if you have a high amount of broadcasts somehow.

Sorry for my late answer. I was busy during the week and didnt find the time to 
look into out setup in detail till now.

We have two wireless interfaces wlan0 and wlan0-1. We also have two ethernet 
interfaces eth0.1 and eth0.3 and one VPN interface ffolVPN.

The interfaces wlan0 and eth0.1 are the interfaces used for clients. They are 
bridged together with bat0:
root@RosenplatzVPN:~# brctl show
bridge name   bridge id                     STP enabled     interfaces
br-mesh          8000.a0f3c15b54a6   no                    bat0
                                                                                 eth0.1
                                                                                 wlan0

The interfaces wlan0-1 and eth0.3 are the interfaces we use for meshing with 
other routers in the same "mesh cloud". These are the interfaces both routers 
are connected by each other. The vpn interface ffolVPN is used to connect with 
outher "mesh clouds" but the two routers in this case are not connected by 
this interface. On the interfaces wlan0-1, eth0.3 and ffolVPN runs Batman 
advanced:
root@RosenplatzVPN:~# batctl if
eth0.3: active
wlan0-1: active
ffolVPN: active

To analyze the amount of broadcast traffic I did a tcpdump on the Batman 
interfaces wlan0-1 and eth0.3. For me there seems to be a big amount of 
broadcast traffic, but I don´t know the normal level of brodcasts so I can´t 
compare which amount is right and which is wrong. But maybe you can so I 
uploaded the files for you. You can analyze them using wireshark or some other 
tool:
* https://dev.freifunk-ol.de/tcpdumps/eth0.3.dump
* https://dev.freifunk-ol.de/tcpdumps/wlan0-1.dump

If you need more data just ask and I will try to provide it.

Kind regards
Clemens
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Re: [B.A.T.M.A.N.] Bad link quality if routers are connected by 2 interfaces

[Simon Wunderlich]

Hey Clemens,

> Am Montag, 4. November 2013, 11:28:20 schrieben Sie:
> > this is certainly not the expected behaviour. Are you building a bridge
> > loop by any chance? Please explain your configuration (batctl if, brctl
> > show, ...) and check if you have a high amount of broadcasts somehow.
> 
> Sorry for my late answer. I was busy during the week and didnt find the
> time to look into out setup in detail till now.
> 
> We have two wireless interfaces wlan0 and wlan0-1. We also have two
> ethernet interfaces eth0.1 and eth0.3 and one VPN interface ffolVPN.
> 
> The interfaces wlan0 and eth0.1 are the interfaces used for clients. They
> are bridged together with bat0:
> root@RosenplatzVPN:~# brctl show
> bridge name   bridge id                     STP enabled     interfaces
> br-mesh          8000.a0f3c15b54a6   no                    bat0
>                                                                            
>      eth0.1 wlan0
> 
> The interfaces wlan0-1 and eth0.3 are the interfaces we use for meshing
> with other routers in the same "mesh cloud". These are the interfaces both
> routers are connected by each other. The vpn interface ffolVPN is used to
> connect with outher "mesh clouds" but the two routers in this case are not
> connected by this interface. On the interfaces wlan0-1, eth0.3 and ffolVPN
> runs Batman advanced:
> root@RosenplatzVPN:~# batctl if
> eth0.3: active
> wlan0-1: active
> ffolVPN: active
> 
> To analyze the amount of broadcast traffic I did a tcpdump on the Batman
> interfaces wlan0-1 and eth0.3. For me there seems to be a big amount of
> broadcast traffic, but I don´t know the normal level of brodcasts so I
> can´t compare which amount is right and which is wrong. But maybe you can
> so I uploaded the files for you. You can analyze them using wireshark or
> some other tool:
> * https://dev.freifunk-ol.de/tcpdumps/eth0.3.dump
> * https://dev.freifunk-ol.de/tcpdumps/wlan0-1.dump
> 
> If you need more data just ask and I will try to provide it.

Thanks for the explanation and the dumps! I had a look at your dumps, but it 
doesn't look like a bridge loop - the number of broadcasts is normal. I don't 
have a clue yet where this behaviour comes from. I'd like to make a few more 
suggestions for debugging:

 * can you please make a debug log of batman-adv on the two nodes at the same 
time (batctl ll batman && batctl l > logfile.$hostname or something like this)

 * what are the MAC addresses of these two nodes?
As far as I see in the debug output, on one node there is:
 * Ethernet fa:d1:11:af:fd:15
 * WLAN fa:d1:11:af:fd:16

However, a2:f3:c1:5b:54:a6 is used as Ethernet source address for sending in 
both eth0.3 and wlan0-1 dumps. Is it possible that there is a mac address 
conflict?

Cheers,
    Simon

Re: [B.A.T.M.A.N.] Bad link quality if routers are connected by 2 interfaces

[Clemens John]

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Am Freitag, 8. November 2013, 10:51:26 schrieben Sie:
> However, a2:f3:c1:5b:54:a6 is used as Ethernet source address for sending in
> both eth0.3 and wlan0-1 dumps. Is it possible that there is a mac address
> conflict?

Hi Simon,

this seems to be the right hint. I checked this and we really had a mac 
address conflict on the interfaces wlan0-1 and eth0.3 we used for meshing. This 
was due to a fix for some mac adress problem in our firmware that seems to be 
outdated now.

On my router the problem is fixed. We will check our other hardware also but I 
think we have a good chance that solving the mac adress conflicts will also 
solve this link quality problem. If not, I´ll ask again.

Thank you!
Clemens
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Re: [B.A.T.M.A.N.] Bad link quality if routers are connected by 2 interfaces

[Simon Wunderlich]

> Am Freitag, 8. November 2013, 10:51:26 schrieben Sie:
> > However, a2:f3:c1:5b:54:a6 is used as Ethernet source address for sending
> > in both eth0.3 and wlan0-1 dumps. Is it possible that there is a mac
> > address conflict?
> 
> Hi Simon,
> 
> this seems to be the right hint. I checked this and we really had a mac
> address conflict on the interfaces wlan0-1 and eth0.3 we used for meshing.
> This was due to a fix for some mac adress problem in our firmware that
> seems to be outdated now.
> 
> On my router the problem is fixed. We will check our other hardware also
> but I think we have a good chance that solving the mac adress conflicts
> will also solve this link quality problem. If not, I´ll ask again.

Would be nice to hear if the problem was resolved, also we can reference to 
that later when somebody asks again for "my TQ dropped to half, why?" :)

Thanks,
    Simon

Re: [B.A.T.M.A.N.] Bad link quality if routers are connected by 2 interfaces

[Clemens John]

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Am Dienstag, 12. November 2013, 20:57:16 schrieben Sie:
> Would be nice to hear if the problem was resolved, also we can reference to
> that later when somebody asks again for "my TQ dropped to half, why?" :)

Yes resolving the conflict solves the problem. 

Kind Regards
Clemens
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#Clemens John <clemens-john@gmx.de>
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