[Olsr-dev] process unspec. link quality information

[Henning Rogge]

Am Friday 03 April 2009 11:54:48 schrieb Peter Tarjan:
> ---------------------------------------------------------------------------
>------------------------------ static void
> create_lq_hello(struct lq_hello_message *lq_hello, struct interface *outif)
> ...
>   OLSR_FOR_ALL_LINK_ENTRIES(walker) {
>
>     // allocate a neighbour entry
>     struct lq_hello_neighbor *neigh = olsr_malloc_lq_hello_neighbor("Build
> LQ_HELLO");
>
>     // a) this neighbor interface IS NOT visible via the output interface
>     if (!ipequal(&walker->local_iface_addr, &outif->ip_addr))
>       neigh->link_type = UNSPEC_LINK;
> ---------------------------------------------------------------------------
>------------------------------
> I wondered when I looked into the code, why
> this information was even included in a HELLO packet.
You need this information to discover all 2-hop neighbors. Imagine an router 
with one interface connected to a router with multiple interfaces.

> In my network scenario B sends HELLO packets from both interfaces. Every
> HELLO packet lists all the links regardless which interface it is broadcast
> on.
Yes, that's correct.

> When these packets are processed, A is considering the first information
> that can be found in the packet about the LQ information of the link
> directed to it. So if there is an UNSPEC link first and later a SYM_NEIGH
> to A, UNSPEC link information is considered.
I had to look at the situation a little bit more closely and finally got that 
you are correct with your patch. The problem with this situation is that we 
have an OLSR instance with two interfaces receivable by the same interface of 
a second OLSR (for example two WLAN cards with the same channel).

I will pushed your patch and added a few more comments.

Henning

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