[opennhrp-devel] multicast packets (was Re: Tunnel route traffic but after a time stops working)

[Timo T. <tim...@ik...>]

Hi,

Sonia wrote:
> Now I have RIPv2 running over GRE tunnel. The configuration file is,
> as you suggested,
> 
> interface gre1
> map 10.67.84.1/32 X.X.X.X register
> multicast nhs
> shortcut
> redirect
> 
> Right now I only need to use RIP between the NHS and my NHC. I'm able
> to receive RIP traffic and update routing tables in my NHC with RIP
> information, but multicast packets from my NHC don't reach the
> Server.
>
> I see the packet errors growing in GRE tunnel interface, so I think
> there is something wrong in the configuration. Do I need to add any
> kernel option to make it work?

Yes and no. The multicast thingy is a bit of a hack currently.
What happens is that the gre driver drops all multicast packets as
erroneous. The opennhrp grabs them with pf_packet socket and resends
them as multiple unicast packets on the lower layer (the multicast
destination is preserved though).

I had some kernel patches for native kernel multicast handling. But
I need to rework them. I'm not yet sure of schedule when that happens.
Until that is done, you'll get gre interface error for each multicast
packet.

If you run opennhrp with -v, you should see it logging messages
for each multicast packet it has relayed. Also with tcpdump you
should see: the original multicast and resent multicast packet for
each nhs.

- Timo