[Xorp-users] Multicast problem

[Ben Greear]

Bruce M Simpson wrote:
> Ben Greear wrote:
>> ...
>> Is there a way to check to see if it's actually doing good things
>> in xorpsh?
> 
>  > show route table ipv4 multicast fib2mrib
> 
> ...should tell you.
> 
>>
>> On a more basic level, can you let me know if this is close to how
>> this scenario *should* work:
>>
>> * kernel mcast sends the pkts to the pimreg device, which shows up on
>>  the mcast socket in mfea_mrouter.
>>
>> * Some piece of xorp (haven't found what yet) then makes a kernel
>>  call to set up the MFC for this particular route.
> 
> The interaction with the multicast FIB happens in the MFEA (which is now 
> mostly merged with the FEA). libmrt might also be worth a look.
> 
>>
>>
>>  I'm guessing fib2mrib or similar logic must query xorp's understanding
>>  of the routing tables to set up the MFC correctly?
> 
> fib2mrib takes the unicast FIB contents and puts it into the multicast 
> RIB, so that RPF checks can happen on each interface when a channel is 
> brought up in PIM.
> 
> Otherwise we'd have a situation where traffic could be forwarded back 
> across the same interface twice, resulting in a packet explosion.
> 
> Normally the RPF checks happen in kernel using interface indexes as the 
> key.

I see the whole-pkt being sent to the PIMSM_4 module..do you happen to
know the method that handles this message?  I want to start tracing
that code next...

As far as I can tell, the fib2mrib routes look right, though I didn't
verify every route...

Thanks,
Ben

-- 
Ben Greear <greearb at candelatech.com>
Candela Technologies Inc  http://www.candelatech.com