[Xorp-hackers] OLSR assert

Ben Greear greearb at candelatech.com
Wed Sep 30 14:33:26 PDT 2009


On 09/30/2009 01:56 PM, Bruce Simpson wrote:
> Ben Greear wrote:
>>
>> The more I look, the weirder it seems..but I may be mis-interpreting
>> things.
>
> It really takes some visualization to get through, I sat up with a good
> book on graph theory to work it all out. "Introduction to Graph Theory"
> by Trudeau is really good to have around.
>
> Some of the naming in the RFC is counterintuitive. E.g. an MPR set is
> the set of relays chosen by the local node, an MPR selector set is the
> set of neighbours which choose the local node as a relay.
>
> All of this is happening in near-real-time, or at least as close to real
> time as you can get with the link state update quantization. So the
> regression tests can sometimes fail on slow machines due to timer aliasing.

My regression tests are more horrible yet...I'm using 'real' routers :)

But, I'm not exhaustively checking that route propagating works properly
in all directions at this point.

>> The code looks quite tricky..and reading the pertinent subsection of
>> the RFC
>> is not helping too much.
>
> No worries. I had to read it about 3 times incrementally before it sank
> in, and even then I had what you might call a minor nervous breakdown.

Here's an attached patch that seems to fix things.  I believe the main error
was checking for (!is_mpr()) in consider_remaining_cand_mprs

I can't see why that check helps anything, and it was excluding from consideration the mpr
that was needed to find the 2-hop neighbor in my setup.

With the attached patch, no more crashes and routes seem to be propagating properly,
though I haven't done a full verification of the (large amount of) routes.


Most of the patch is debugging, but since I fear I'll be visiting this again
someday, I'm leaving that in my tree...

Considering OLSR seems to be at least mostly working, maybe you could commit
the two patches I posted a few days ago that enables other ppl to build OLSR?

Thanks,
Ben


-- 
Ben Greear <greearb at candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

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