Re: [B.A.T.M.A.N.] BLAII + gw_mode, DHCP sometimes gets dropped

[Simon Wunderlich <simon.wunderlich@s2003.tu-chemnitz.de>]

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Hello Guido,

On Tue, Jul 03, 2012 at 05:07:17PM -0300, Guido Iribarren wrote:
> Hello there again,
> I have observed a problem since updating to 2012.2 and enabled BLAII
> 
> I'm compiling logs to understand what's happening, but as always,
> reading logs only gets me more lost :(
> So here i am again begging for help

There are some debug levels for BLA as well, and you can now get the
claimlist with batctl (which is basically the list of clients a gateway
feels responsible for) - this may help for debugging. But first,
we should clarify some more details for your setup.

> 
> the setup is the same I described in yesterday's attachment, but
> what's not pictured is an ethernet cable between colmena-casa and
> f8d11504758.
> f8d11504758 is the only router that connects to the internet (through
> WAN cable), and it's also the only one that has dnsmasq running and
> gw_mode=server.
> All the other nodes have gw_mode=client
> 
> All of the nodes have bridge_loop_avoidance=1
> (even though there are no other utp connections, so it could in fact
> be enabled only on colmena-casa and f8d11504758)
> 
> with this setup, dhcp requests from the mesh sometimes get "lost",
> either they don't reach f8d11504758 or the reply doesn't get out

Questions:
 * which node runs the DHCP server? colmena-casa, f8d11504758 or something else?
 * at which point is DHCP getting lost? is the DISCOVER/REQUEST from the client
   getting lost, or the reply from the server?
 * Can you specify "sometimes" a little bit more? What are the circumstances, how
   often does it happen?

> 
> this didn't happen with batman 2012.1 , setup as indicated by the BLAI
> wiki page (batctl if add br-lan)
> furthermore, with batman 2012.2 , BLAII activated, but gw_mode=off in
> all nodes, DHCP also works fine.

Mhm, that's rather strange ... we had a similar problem when ap isolation
was activated. Do you have this feature turned on?

So DHCP is only having problems when gw-mode is turned on colmena-casa
and f8d11504758?

> 
> So, a few questions arise:
> is it a problem to activate bridge_loop_avoidance=1 in all nodes,
> regardless of the fact that they "need" it or not? (that is, it is
> activated on nodes that don't have any ethernet cables connected and
> couldn't possibly create a bridge loop)

No, that it is not a problem - you can activate it everywhere. It will
just send some additional control packets on bat0, but won't do anything
as long as it does not detect other gateways.

> 
> would it make a difference, if I add br-lan to bat0 (batctl if add
> br-lan) the way I used to do with batman 2012.1 ?

That won't help, because the design of BLA changed and the old BLA has been
removed. Please keep the bridge out of bat0. :)

Cheers,
	Simon

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