Re: [RFC] net: dsa: mv88e6xxx disable IGMP snooping on cpu port

On Mon, Mar 27, 2023 at 04:51:20PM +0200, Steffen Bätz - Innosonix GmbH wrote:

Hi Andrew,
Yes, strangely, this piece of code has stayed the same for years.
But we only face this behaviour if you add a bridge interface on top of the DSA
ports.
The setup looks like: eth0 (physical port of the imx8mn) <-> lan3/lan4 (DSA
ports of the mv88e6320)

ip link add br0 type bridge
ip link set br0 up
ip link set lan3 master br0
ip link set lan4 master br0
ip link set lan3 up
ip link set lan4 up
dhcpcd -b br0

If now you try to receive an audio multicast stream, like from 239.255.84.1,
the neighbour bridge will not forward this stream to our board. And there is no
entry in the MDB of the external switch.

Ah, O.K. That is not actually IGMP snooping. It is normal usage of
IGMP. I probably did not test that. I think all my multicast source
and sinks where on switch ports, and i tested that the switch did not
flood multicast to all ports, just ports with listeners.

So your change looks O.K, but as i said, it probably should apply to
DSA ports as well as CPU ports. And i suggest you reword the commit
message to differentiate between IGMP snooping and an IGMP listener on
the bridge.

    Andrew