[Olsr-dev] Smartgateway

Henning Rogge (spam-protected)
Fri Dec 9 11:45:12 CET 2011

On 12/09/2011 11:39 AM, Teco Boot wrote:
> I tested a bit more.
> I took GW function on 173 down.
> Then, 173 started use tunnel to 179, which is no GW anymore (wrong).
> 179 lost tunnel to 173 and default routes, because 173 stopped announcing
> as SGW. 179 sends ICMP net unreachable to 173, as reply on packets to
> Internet.
> An olsrd restart on 179 did remove the SGW tunnel on 173 (because no link to
> 179: cleanup HNA&  SGW).
> During a reproduction, I had some trouble when verifying self advertised HNA.
> Same for self advertised SGW info. It would be nice to include this in the
> txtinfo output.
> With tcpdump, the SGW is shown as (0/32), HNA info in packet
> was 0000 0000 0007 5903. I think /32 is shown if first mask bit(s) is(are) 0.
> Could be improved.
You mean /0 instead of /32, right?

The SmartGw use a "shortcut" in the OLSR.org code to place additional 
information into the HNA. OLSR.org ignores bytes 2-4 if the 
first byte is zero, so this three bytes are used for propagating data 
about the internet gateway.

Not a nice solution, but the 'best/easiest' I came up with for OLSRv1.

> More debugging:
> When default route on 179 goes down, it takes some seconds before a HNA without
> the SGW info is advertised. But then, the HNA&  SGW entries on the 173 must be
> cleaned up. Or after time-out. It didn't. Maybe it is caused by lack of info
> similar to txtinfo not showing HNA's that overlap an own HNA with same info?

There is some kind of filter in the OLSR.org code for not accepting HNAs 
which collide with local ones, but I have to look it up again to say how 
it works.

Henning Rogge

Diplom-Informatiker Henning Rogge , Fraunhofer-Institut für
Kommunikation, Informationsverarbeitung und Ergonomie FKIE
Kommunikationssysteme (KOM)
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