multicast and multiple nics

[iprebeg at freebsd.org]

On Thu, Jul 23, 2009 at 12:47:01PM +0200, Giulio Ferro wrote:
> Thanks for the reply.
>
> iprebeg at freebsd.org wrote:
>>> I want to run ushare (/usr/ports/ushare). This program sends
>>> multicast packets to multicast address 239.255.255.250
>>>
>>> The packets should go to the lan, so I add the route:
>>> route add 224/4 -iface re0
>>>
>>> In order to do the test I switch off the firewall (/etc/rc.d/pf stop)
>>>
>>> I start the service, but no packets can be seen leaving the interface re0
>>> with tcpdump.
>>>     
>>
>> Can you try to sniff with other machine in that lan?
>>   
>
> Yes. Other machines can multicast without problem but nothing
> multicast shows originating from the freebsd box.
>>   
>>> Even If I ping a multicast address directly I can see no packets at all:
>>>
>>> ping -I 192.168.2.1 239.255.255.250
>>>     
> I forgot mentioning that I can run this command from my linux box
> and tcpdump from the same machine show the packets going to and fro.
>
>>
>> Please, try to use mcastread like this
>>
>> mcastread -v4 -s 192.168.2.1 re0 239.255.255.250 1337
>>   
> mcastread -v4 -s 192.168.2.1 re0 239.255.255.250 1337
> mcastread: trying 239.255.255.250
> mcastread: using (S,G)=(192.168.2.1,239.255.255.250)
>
> And stays there..

It is ok for mcastread to stay like this, but in normal situation, 
you should see two IGMPv3 reports leaving re0. Maybe it is related 
to re driver. Can you try the same on adapter that uses different
driver?

>
>> or mcastsend like this
>>
>> mcastsend -i re0 239.255.255.250 1337
>>   
> This results in an error:
> mcastsend: setsockopt(IP_MULTICAST_IF): Can't assign requested address
>
>

You can use it without "-i re0" part and maybe experiment with and
without routes.

> Is there something else I can try?
>
> Thanks again...

You're most welcome.

>
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