Re: [B.A.T.M.A.N.] lost connection to a client / Q: transglobal-table

Antonio Quartulli
2013-11-23T16:15:16Z

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On Sat, Nov 23, 2013 at 10:24:45AM +0100, Bastian Bittorf wrote:
> * Gui Iribarren <gui@altermundi.net> [03.11.2013 20:37]:
> > btw, even with the ebtables rule, we had to turn off DAT in a
> > scenario equivalent to yours, because the DAT cache was also acting
> > funny (DUP arp replies from each node in the cloud)
> > haven't got around to properly debug it / report it, but still, be warned :)

I think all these strange behaviours are coming from the fact that what you guys
are trying to do is not really supported by the underlying layer (batman-adv).

I think a better idea is to start thinking how to bring anycast support in
batman-adv other than trying to mess up the rest :) That would surely help the
entire community.

After the last WBM we concentrated our efforts in creating a starting point for
a "more general" solution and we collected the results in this page [*].

This page describes what you probably want to achieve at the end, so working all
together to make it possible would probably be the best option (instead of
trying to workaround unsupported setup and then asking for help to debug
inconsistent behaviours....).

> root@box:~ batctl dc
> Distributed ARP Table (bat0):
> IPv4 MAC last-seen
> * 192.168.222.61 00:21:6a:32:7c:1c 3:50
>
> after some seconds the client disappaers from DAT-cache:

As you can imagine DAT is a cache and if it does not get refreshed
often enough the content will slowly disappear. Right now the timeout is 4
minutes and this is why "after" few second your entry goes away (it is at 3:50
at that moment). If you have not yet read the documentation, [1] explains the
mechanism behind it.

>
> root@box:~ batctl tl
> Locally retrieved addresses (from bat0) announced via TT (TTVN: 2 CRC:
> 0x6023):
> Client Flags Last seen
> * 00:21:6a:32:7c:1c [....W] 0.010
>
> root@box:~ batctl dc
> Distributed ARP Table (bat0):
> IPv4 MAC last-seen
>
> after some time even the 'translocal-table' is empty, although with
> 'iw dev wlan0 station dump' i can see the active client. i'm
> normally connected, can ping/ssh the node itself but not further.
> (only hop by hop)
>
> how does batman detect, if a client is active? (can i trigger is somehow?)
> what can i do tho debug further?
>

As written in [2]:
"Every client MAC address that is recognized through the mesh interface will be
stored in a node local table called "local translation table" which will contain
all the clients the node is currently serving."

So if your client is timing out it means that no packet originated by it is
reaching your mesh interface.

If you want to debug further now you have to ask yourself what are you doing to
prevent packets to reach bat0 :-)

Cheers,

[*] http://www.open-mesh.org/projects/open-mesh/wiki/Connecting-Batman-adv-clouds
[1] http://www.open-mesh.org/projects/batman-adv/wiki/DistributedArpTable-technical
[2] http://www.open-mesh.org/projects/batman-adv/wiki/Client-announcement

--
Antonio Quartulli

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