[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PER] Re: socket, mcast looping back frames -> IPv6 br
From: |
Samuel Thibault |
Subject: |
Re: [Qemu-devel] [PER] Re: socket, mcast looping back frames -> IPv6 broken |
Date: |
Wed, 6 Mar 2013 14:15:25 +0100 |
User-agent: |
Mutt/1.5.21+34 (58baf7c9f32f) (2010-12-30) |
Stefan Hajnoczi, le Wed 06 Mar 2013 13:29:37 +0100, a écrit :
> On Tue, Mar 05, 2013 at 05:35:10PM +0100, Samuel Thibault wrote:
> > The reason why IPv6 does not work when using -net socket,mcast=foo is
> > that since qemu explicitly sets IP_MULTICAST_LOOP to 1, it receives its
> > own frames. When the IPv6 stack performs duplicate addresse detection
> > (DAD) through a multicasted announce, it receives its own announcement,
> > and thus believes another machine has the same address.
>
> The reason for IP_MULTICAST_LOOP is to allow QEMU processes running on
> the same host to communicate with each other.
Sure, I've seen the comment, I wasn't suggesting to drop that :)
> > AIUI, on a real physical network network boards do not receive the
> > multicasts they send, so the issue does not happen. Perhaps some boards
> > even filter out any frame with its own MAC as source, eliminating the
> > issue altogether.
> >
> > As a result, we should probably perform this kind of dropping, I'm just
> > wondering at which level that would be preferable.
> >
> > - We could do that in qemu_send_packet_async_with_flags, thus fixing the
> > issue for all kinds of frame transporters.
> >
> > - Or we could do that for the only case that matters, mcast, in
> > net_socket_send_dgram (which will thus do it for the unicast udp case
> > too).
> >
> > What do people think about it?
>
> We should fix the layer that introduces the problem. Therefore I think
> the fix needs to be net/socket.c.
Ok.
> Unfortunately net/socket.c does not have the concept of a link-layer
> address, so we cannot easily filter out multicast packets coming from
> our NIC's address.
>
> Are you aware of a way to filter out just the packets sent by *this*
> process?
I haven't seen any in the Linux source code. One thing that should
work, however, is to use recvfrom, and drop whatever comes from our
sockname.
Samuel
- [Qemu-devel] socket,mcast looping back frames -> IPv6 broken, Samuel Thibault, 2013/03/05
- Re: [Qemu-devel] socket,mcast looping back frames -> IPv6 broken, Stefan Hajnoczi, 2013/03/06
- Re: [Qemu-devel] [PER] Re: socket, mcast looping back frames -> IPv6 broken,
Samuel Thibault <=
- Re: [Qemu-devel] [PER] Re: socket, mcast looping back frames -> IPv6 broken, Stefan Hajnoczi, 2013/03/07
- Re: [Qemu-devel] [PER] Re: socket, mcast looping back frames -> IPv6 broken, Samuel Thibault, 2013/03/07
- Re: [Qemu-devel] [PER] Re: socket, mcast looping back frames -> IPv6 broken, Stefan Hajnoczi, 2013/03/08
- Re: [Qemu-devel] [PER] Re: socket, mcast looping back frames -> IPv6 broken, Samuel Thibault, 2013/03/08
- Re: [Qemu-devel] [PER] Re: socket, mcast looping back frames -> IPv6 broken, Samuel Thibault, 2013/03/08
Re: [Qemu-devel] [PER] Re: socket, mcast looping back frames -> IPv6 broken, Samuel Thibault, 2013/03/10