netdev - Re: [PATCH v3 net-next 0/5] IGMP snooping for local traffic

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Date:   Tue, 7 Nov 2017 10:01:48 +0900
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [PATCH v3 net-next 0/5] IGMP snooping for local traffic

On Tue,  7 Nov 2017 00:26:53 +0100
Andrew Lunn <andrew@...n.ch> wrote:

> The linux bridge supports IGMP snooping. It will listen to IGMP
> reports on bridge ports and keep track of which groups have been
> joined on an interface. It will then forward multicast based on this
> group membership.
> 
> When the bridge adds or removed groups from an interface, it uses
> switchdev to request the hardware add an mdb to a port, so the
> hardware can perform the selective forwarding between ports.
> 
> What is not covered by the current bridge code, is IGMP joins/leaves
> from the host on the brX interface. These are not reported via
> switchdev so that hardware knows the local host is interested in the
> multicast frames.
> 
> Luckily, the bridge does track joins/leaves on the brX interface. The
> code is obfusticated, which is why i missed it with my first attempt.
> So the first patch tries to remove this obfustication. Currently,
> there is no notifications sent when the bridge interface joins a
> group. The second patch adds them. bridge monitor then shows
> joins/leaves in the same way as for other ports of the bridge.
> 
> Then starts the work passing down to the hardware that the host has
> joined/left a group. The existing switchdev mdb object cannot be used,
> since the semantics are different. The existing
> SWITCHDEV_OBJ_ID_PORT_MDB is used to indicate a specific multicast
> group should be forwarded out that port of the switch. However here we
> require the exact opposite. We want multicast frames for the group
> received on the port to the forwarded to the host. Hence add a new
> object SWITCHDEV_OBJ_ID_HOST_MDB, a multicast database entry to
> forward to the host. This new object is then propagated through the
> DSA layers. No DSA driver changes should be needed, this should just
> work...
> 
> Andrew Lunn (5):
>   net: bridge: Rename mglist to host_joined
>   net: bridge: Send notification when host join/leaves a group
>   net: bridge: Add/del switchdev object on host join/leave
>   net: dsa: slave: Handle switchdev host mdb add/del
>   net: dsa: switch: Don't add CPU port to an mdb by default
> 
>  include/net/switchdev.h   |  1 +
>  net/bridge/br_input.c     |  2 +-
>  net/bridge/br_mdb.c       | 50 +++++++++++++++++++++++++++++++++++++++++++----
>  net/bridge/br_multicast.c | 18 ++++++++++-------
>  net/bridge/br_private.h   |  2 +-
>  net/dsa/slave.c           | 13 ++++++++++++
>  net/dsa/switch.c          |  3 ++-
>  net/switchdev/switchdev.c |  2 ++
>  8 files changed, 77 insertions(+), 14 deletions(-)

The bridge part looks good.
Acked-by: Stephen Hemminger <stephen@...workplumber.org>