netdev - Re: cpsw_switch: unable to selectively forward multicast

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Message-ID: <YpDS9Vg4Z+sdAfIp@lunn.ch>
Date:   Fri, 27 May 2022 15:32:37 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Markus Klotzbuecher <mk@...o.de>
Cc:     netdev@...r.kernel.org
Subject: Re: cpsw_switch: unable to selectively forward multicast

On Fri, May 27, 2022 at 08:43:25AM +0200, Markus Klotzbuecher wrote:
> Hi Andrew,
> 
> thank you for your feedback.
> 
> On Wed, May 25, 2022 at 11:05:14PM +0200, Andrew Lunn wrote:
> >On Wed, May 25, 2022 at 11:30:40AM +0200, Markus Klotzbuecher wrote:
> >> Hi All,
> >> 
> >> I'm using multiple am335x based devices connected in a daisy chain
> >> using cpsw_new in switch mode:
> >> 
> >>              /-br0-\          /-br0-\         /-br0-\
> >>             |       |        |       |       |       |
> >>         ---swp0    swp1-----swp0    swp1----swp0    swp1
> >>             |       |        |       |       |       |
> >>              \-----/          \-----/         \-----/
> >>                #1               #2              #3
> >> 
> >> The bridge is configured as described in cpsw_switchdev.rst
> >> [1]. Regular unicast traffic works fine, however I am unable to get
> >> traffic to multicast groups to be forwarded in both directions via the
> >> switches.
> >
> >Do you have listens reporting they are interested in the traffic via
> >IGMP? Do you have an IGMP quirer in your network? Without these, IGMP
> >snooping will not work.
> 
> The userspace application running on each device in the chain calls
> setsockopt + IP_ADD_MEMBERSHIP and peer devices receive IGMP packets
> such as
> 
>  7 10.399981403 192.168.178.51 ? 224.0.0.22   IGMPv3 62 Membership Report / Join group 239.253.253.239 for any sources
>  8 10.399981403 192.168.178.51 ? 224.0.0.22   IGMPv3 56 Membership Report / Join group 239.253.253.239 for any sources
> 
> and corresponding bridge mdb records appear for swpX and br0
> subsequently. Shouldn't this suffice for multicast to work or do I
> really need an additional IGMP querier? I realize that these mdb
> entries will expire, however multicast traffic isn't forwarded even
> temporarily and manually adding the same entries as 'permanent' didn't
> help either.

Hi Markus

You should have a quierer, in order to have reliable IGMP
snooping. However, that is a secondary issues, since it should work
with permanent mdb entries.

Unfortunately, i don't know the cpsw driver, so you need the TI guys
to help you.

   Andrew