netdev - Re: [PATCH v4 net-next 0/6] IGMP snooping for local traffic

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Message-Id: <20171110.134221.272876658800963354.davem@davemloft.net>
Date:   Fri, 10 Nov 2017 13:42:21 +0900 (KST)
From:   David Miller <davem@...emloft.net>
To:     andrew@...n.ch
Cc:     vivien.didelot@...oirfairelinux.com, f.fainelli@...il.com,
        netdev@...r.kernel.org
Subject: Re: [PATCH v4 net-next 0/6] IGMP snooping for local traffic

From: Andrew Lunn <andrew@...n.ch>
Date: Thu,  9 Nov 2017 23:10:56 +0100

> 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...
> 
> This version fixes up the nitpick from Nikolay, removes an unrelated
> white space change, and adds in a patch adding a few const attributes
> to a couple of functions taking a port parameter, in order to stop the
> following patch produces warnings.
> 
> Acked-by: Stephen Hemminger <stephen@...workplumber.org>

Series applied, thanks Andrew.