[Olsr-dev] mDns plugin improvement

[ZioPRoTo (Saverio Proto)]

> Let's try to comply to standards. We should not break nodes that
> discards mDNS packets not having TTL=225. And support protocols
> that have TTL=1.

I still do not see this problem.
I agree application should generate packets with TTL=255. But routers
should not be able to alter the TTL value of the IP packets as usual ?
If packet is not originated on the local link then TTL !=255, and this
is okay with the standard.

> Packet rate of mDNS would be low, so hash calculation looks
> acceptable to me. This is the way SMF works.
> http://tools.ietf.org/html/rfc6621#section-6.2.2
> I prefer having the standards based method implemented. In
> IETF, we had a long discussion. With this outcome.

The rate of mDNS packet is not low if you have a big network.
We have hundreds of end devices connected that generate a huge amount
of mDNS traffic !

Look at the size of our network:
http://tuscolomesh.ninux.org/images/topology.png
and IPv6
http://cleopatra.ninux.org/topology.png

we run both networks on top of devices that have small CPU and memory
resources. Mostly Ubiquiti NanoStation M5. We already have issues with
CPU spikes to 100%. We have two olsrd running one for IPv4 and one for
IPv6


> It would be nice having only one copy of the mDNS (or whatever
> multicast) packet flooded. This needs some coordination between
> the leaf routers. Could be active / backup election. Could be an
> extended dup detection in the flooding mechanism, with a plugin.

agreed this is a problem that the patch do not solve.

Saverio