Re: [B.A.T.M.A.N.] [RFC PATCH] batman-adv: mitigate issue when empty vlan is received

Sven Eckelmann
2018-05-07T06:32:28Z

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On Sonntag, 6. Mai 2018 21:55:59 CEST Leonardo Mörlein wrote:
> This patch is not a fix for the issue itself, but a fix for the
> other nodes, which are also influenced by the issue.
>
> - Some (affected) nodes send TT announcements for an empty vlan (for
> now only seen with vlan_id = 0).
> - This behaviour is a bug! Batman-adv nodes must not send TT
> announcements for empty vlans.
> - The receiving batman-adv can not handle incoming TT announcements
> with empty vlans. (The crc check routine batadv_tt_global_check_crc()
> fails.)
> - As the receiving node thinks, the crc is broken, it does a full
> table request then.
> - The announcing node sends a TT full table to the receiving node
> then, which also contains the empty vlan, so
> *batadv_tt_global_check_crc()* fails again on the receiver side.
> - This causes a lot of unneeded TT traffic. In Freifunk Hannover we
> decreased the amount of from ~20kpp/s to ~4kpp/s on our supernodes.
> We have ~800 nodes, which are connected via vpn to one of six
> supernodes. Those supernodes are connected with each other in a fully
> connected mesh.

Can you attach a (small) pcap of actual traffic which show a packet which
triggers this behavior?

Thanks,
Sven