Re: IGMP problem with 2.5 kernels

Niels den Otter (
Mon, 3 Mar 2003 14:49:04 +0100

On Wednesday, 12 February 2003, Niels den Otter wrote:
> On Monday, 10 February 2003, Niels den Otter wrote:
> > I have tried to run several IP Multicast applications (SDR, Vat,...)
> > with on 2.5 kernels (now running 2.5.59bk3) without succes. Same
> > applications appear to work on 2.4 kernels.
> >
> > What seems to be happening is that the application binds to the lo
> > interface instead of eth0 so that no IGMP queries are send out on
> > the ethernet interface. I have a small application that tries to
> > listen to address and here is /proc/net/igmp with and
> > without the app running:
> Did more debugging and disabled my loopback interface to ensure the
> mcast apps don't bind to this interface. strace shows all applications
> go wrong with the same error. Is this kernel related?

In the meantime I have had verious discussion on this subject with
Antonio Querubin and others and I don't know any solution yet.

Is anyone able to use multicast applications on recent 2.5 kernels and
make it send out IGMP joins on an ethernet device?

RFC 1112 says
If the upper-layer protocol chooses not to identify an outgoing
interface, a default interface should be used, preferably under the
control of system management.

In Linux 2.4 kernels this seems to work with adding a route for on the desired ethernet interface. This doesn't work in 2.5
kernels however.

Anyone who knows what the problem is and how it can be solved?


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