[Xorp-hackers] Multicast routing

[Pavlin Radoslavov]

> 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?

Do you see the multicast forwarding entries in the kernel with
commands "netstat -gn" (for *BSD) or "cat /proc/net/ip_mr_cache"
(for Linux), and do they have the right iif and oif set?
Also, I presume that you used TTL of 1 for mfcc_ttls.

If yes, then your program has done the right thing.
In that case, make sure that the TTL of the multicast data packets
as originated by the sender is at least 2. The default TTL is 1 and
such packets won't be forwarded.
Finally, if this didn't help, check whether there are any firewall
rules that might be stopping the multicast packets.

Regards,
Pavlin