[B.A.T.M.A.N.] [PATCHv2] batman-adv: improve unicast packet (re)routing

Marek Lindner lindner_marek at yahoo.de
Tue Mar 20 14:01:59 CET 2012

On Friday, March 16, 2012 18:03:28 Antonio Quartulli wrote:
> In case of a client X roaming from a generic node A to another node B, it
> is possible that a third node C gets A's OGM but not B's. At this point in
> time, if C wants to send data to X it will send a unicast packet destined
> to A. The packet header will contain A's last ttvn (C got A's OGM and so
> it knows it).
> The packet will travel towards A without being intercepted because the ttvn
> contained in its header is the newest for A.
> Once A will receive the packet, A's state will not report to be in a
> "roaming phase" (because, after a roaming, once A sends out its OGM, all
> the changes are committed and the node is considered not to be in the
> roaming state anymore) and it will match the ttvn carried by the packet.
> Therefore there is no reason for A to try to alter the packet's route,
> thus dropping the packet because the destination client is not there
> anymore.
> However, C is well aware that it's routing information towards the client X
> is outdated as it received an OGM from A saying that the client roamed
> away. Thanks to this detail, this patch introduces a small change in
> behaviour: as long as C is in the state of not knowing the new location of
> client X it will forward the traffic to its last known location using
> ttvn-1 of the destination. By using an older ttvn node A will be forced to
> re-route the packet. Intermediate nodes are also allowed to update the
> packet's destination as long as they have the information about the
> client's new location.

Applied in revision b46c60b.


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