Re: [Qemu-devel] [PER] Re: socket, mcast looping back frames -> IPv6 broken

[Stefan Hajnoczi]

On Mon, Apr 01, 2013 at 11:32:29AM +0200, Samuel Thibault wrote:
> Mike Lovell, le Mon 01 Apr 2013 00:35:03 -0600, a écrit :
> > On 03/08/2013 05:47 AM, Samuel Thibault wrote:
> > >Samuel Thibault, le Fri 08 Mar 2013 10:08:55 +0100, a écrit :
> > >>There does exist some unique address, which is returned by recvfrom,
> > >>I'll have a look at how to get access to it.
> > >Ah, no, it's not unique... It's just the host IP address and the same
> > >port as the multicast address, so it'll be the same for all qemus on the
> > >same host.  I've checked how Linux bounces the datagram, it's through
> > >the loopback interface, and thus dispatched over all listeners without
> > >distinction. I don't see any way to get the information that the packet
> > >comes from us, except using the ethernet content.
> > 
> > one solution is to actually use two sockets. one that is bound to the
> > multicast address, which receives the multicast packets, and another that is
> > just bound to any ephemeral udp port, which is used for sending packets.
> 
> Mmm, that should work indeed.
> 
> > if the group is interested is a solution like this, i can probably make some
> > time over the next couple days to cook up a patch. thoughts?
> 
> Yes, please.

Yeah, great.  It's a real problem that people are hitting so it would be
worth fixing.

Stefan