[Xorp-hackers] multicast source filter API in linux

[Pavlin Radoslavov]

Sachin K <sachinutd at gmail.com> wrote:

> When I set the source filter using the setsockopt() call for the
> following scenario
> mode: INCLUDE
> number of sources: 3
> sources: s1, s2, s3
> Group: G
> 
> The kernel first sends out a TO_EX{} report for G and then a TO_IN{s1,
> s2, s3} report for G.
> 
> Does anybody know why linux does this?

The only reason that comes to mind is if in your code you actually
join first the group G (for any source), and then you modify the
source filter to INCLUDE mode.
I just tried it with Linux kernel 2.6.20 and TO_EX{} IGMPv3 report
is sent when you use the traditional mechanism for joining (*,G).

If this is not the case, then hopefully the folks on this list who
are familiar with the host-side kernel IGMPv3 implementations can
provide a better explanation.

Regards,
Pavlin

> Thanks,
> Sachin
> 
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