On Tue, Nov 07, 2017 at 05:37:32PM -0500, Vivien Didelot wrote:
> Hi Andrew,
>
> Andrew Lunn <and...@lunn.ch> writes:
>
> >> In a switch case, they all translate to programming a MDB entry for
> >> a given switch port, right?
> >
> > No, in fact it is the exact opposite.
>
> Yes, they do. The proof is you call dsa_port_mdb_add.
Note that i always say switchdev.
switchdev has no concept of the CPU port. All switchdev has is the
concept of the external ports.
So when there is a join on the br0 interface, the bridge code will
iterative over each port in the bridge, and make a switchdev call to
each of the external ports in the bridge asking it to forward
multicast traffic for a group to the host.
Now, deep down in DSA, we can translate this to a dsa_port_mdb_add, on
the CPU port. And we do that for every call the bridge makes for each
of the external ports in the bridge.
However, a pure switchdev device won't do that. It does not have a CPU
port. It probably needs to add a match/action rule to its tables for
the actual external port saying to forward the frame out the slow
path.
> Still, what I see here _from a switch driver point of view_ is either
> program an MDB entry on a user port, or on its CPU port.
I agree with this, if you make one change:
_from a DSA switch driver point of view_
However, in the general case, this is not true. We need an API which
works for Mellonex and Netranome as well, systems without a CPU port.
Andrew
