netdev - Re: cpsw_switch: unable to selectively forward multicast

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Message-ID: <YpHCzCTAx5sBCyDi@e495>
Date:   Sat, 28 May 2022 08:35:56 +0200
From:   Markus Klotzbuecher <mk@...o.de>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org
Subject: Re: cpsw_switch: unable to selectively forward multicast

On Fri, May 27, 2022 at 03:32:37PM +0200, Andrew Lunn wrote:
>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.

Ok, good to know, thank you!

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

Markus