[Xorp-hackers] IGMP version used on an interface

[Pavlin Radoslavov]

> I have a multicast router with multiple interfaces, each connected to
> different network. Each network uses a different version of IGMP. I am
> running Linux on the router.
> 
> If the user space multicast routing daemon had to send a group
> specific query on all interfaces then how to know which interface is
> using what version of IGMP?
> 
> Is there any ioctl or getsockopt call to know that on linux?

Inside of XORP each interface is explicitly configured with the IGMP
version number so XORP itself uses that information when dealing
with each subnet. All the router-side IGMP machinery is implemented
in user space, so the kernel doesn't know the version used by XORP
on each interface.

The host-side IGMP machinery however is implemented inside the
kernel. I believe it is system-specific whether/how you can
configure or access the IGMP host version on each interface.
E.g., on Linux "cat /proc/net/igmp" will give you the Querier
version on each interface.
Hitoshi Asaeda (CC-ed in this email) should know better about the
IGMP host-side story.

Regards,
Pavlin