[Xorp-hackers] Multicast routing

[Sachin K]

Hi all,

I have added VIFs on all physical interfaces and getting the required
IGMP messages to userspace.

Now I add an MFC entry depending on IGMP message using setsockopt and
MRT_ADD_MFC.  Does this mean that kernel would do the multicast
routing looking at the MFC? or do I need to do something more than
adding an MFC entry.

For example:

[Host A]<--------> vif0 [Router] vif1 <-------> [Host B]

[Router] adds vif0 and vif1 and is ready to process IGMP messages.

[Host A] sends an IGMP membership report for (S,G) = (Host B, 232.10.10.10)

[Router] adds an MFC entry with Iif = vif1 and Oif = vif0.

[Host B] is sending multicast packets to 232.10.10.10.

But [Host A] is not getting any packets. Note that I am running only
my code on [Router], it has no pim or any sorts of standard routing
daemons.

What would be the problem? Do I need some more configuration on any of
the systems?

Thanks,
Sachin

On 2/15/07, Pavlin Radoslavov <pavlin at icir.org> wrote:
> > Opening RAW socket for IPPROTO_IGMP, will get all IGMP packets regardless of
> > its destination address from kernel to XORP.
>
> I doubt this will happen if the interface wasn't in ALLMULTI state
> (see my previous email on the subject).
>
> > Can i know, where it says it will only get 224.0.0.1 packets. I'm not aware
> > such a filtering in RAW socket.
>
> The 224.0.0.1 packets are received only with the RAW socket because
> every host is a member of the 224.0.0.1 (ALL-SYSTEMS) multicast
> group (the kernel itself joins that group). For groups that have
> been joined the interface doesn't need to be in ALLMULTI state.
>
> Regards,
> Pavlin
>
> > Thanks,
> > Regards,
> > Suresh kannan.
> >
> >
> > On 2/15/07, Sachin K <sachinutd at gmail.com> wrote:
> > >
> > > How does the XORP multicast router sniff IGMP/MLD messages from the
> > > network?
> > >
> > > I checked the some routers' code. Most of them just open a RAW socket with
> > > protocol set to IPPROTO_IGMP. But using this the router gets the
> > > packets addressed to 224.0.0.1 only.
> > >
> > > How does it receive IGMPv2 and IGMPv3 membership reports sent by other
> > > hosts?
> > >
> > > Thanks,
> > >
> > > Sachin
> > >
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