[ovs-discuss] Multicast snooping turned off on interfaces with a multicast querier/router

[Flavio Leitner]

On Thu, Aug 30, 2018 at 04:35:40PM -0700, Ben Pfaff wrote:
> This test was part of the original commit by Flavio.
> 
> Flavio, do you have any information?

Hi,

> On Thu, Aug 30, 2018 at 03:17:04PM -0700, Ajit Warrier wrote:
> > I confirmed from the source code that it is intentional. The snooping is
> > disabled on ports with routers attached in:
> > 
> > lib/mcast-snooping.c:mcast_snooping_add_group()
> > 
> > 
> >     /* Avoid duplicate packets. */
> >     if (mcast_snooping_mrouter_lookup(ms, vlan, port)
> >         || mcast_snooping_port_lookup(&ms->fport_list, port)) {
> >         return false;
> >     }
> > 
> > It would be nice to know why this is so.

It's been a while, but IIRC it tracks three situations: ports with flood
enabled, ports with mcast router attached and ports with mcast clients.
There is a list for each situation.

You most probably see the mcast router in the mdb/show, but yeah, it
doesn't mix the types because then you would see the same packet being
forwarded because of the mcast router and another copy because of the
mcast host client.

I recall that there was a restriction when sending reports, but I
suspect we could fix the code to allow mcast hosts and routers in
the same port.

Could you tell more about your requirements?
Thanks
fbl

> > Thanks,
> > Ajit.
> > 
> > On Thu, 30 Aug 2018 at 14:06 Ben Pfaff <blp at ovn.org> wrote:
> > 
> > > On Tue, Aug 28, 2018 at 01:05:42PM -0700, Ajit Warrier wrote:
> > > > I have a setup where an embedded device runs OVS on a bridge connecting
> > > two
> > > > interfaces (1 and 2). Interface 1 is connected to a multicast router
> > > > sending IGMP queries periodically. Now if I open a multicast socket on a
> > > > device on interface 1, I see the IGMP join going into the embedded device
> > > > with OVS, but the command:
> > > >
> > > > ovs-appctl mdb/show br0
> > > >
> > > > does not list that multicast flow. Opening a multicast socket on a device
> > > > connected to interface 2 works as expected - I get an entry for that flow
> > > > in the above command.
> > >
> > > We've had a multicast snooping fixes over time.  If you're not using the
> > > latest release, please consider upgrading.
> > >
> 
> > _______________________________________________
> > discuss mailing list
> > discuss at openvswitch.org
> > https://mail.openvswitch.org/mailman/listinfo/ovs-discuss
> 
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-- 
Flavio