netdev - Re: [PATCH net-next 1/6] net: dsa: Fix SWITCHDEV_ATTR_ID_PORT_PARENT

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Date:   Wed, 27 Sep 2017 13:15:33 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Andrew Lunn <andrew@...n.ch>, David Miller <davem@...emloft.net>
Cc:     Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 1/6] net: dsa: Fix
 SWITCHDEV_ATTR_ID_PORT_PARENT_ID

Hello!

On 9/27/2017 1:25 AM, Andrew Lunn wrote:

> SWITCHDEV_ATTR_ID_PORT_PARENT_ID is used by the software bridge when
> determining which ports to flood a packet out. If the packet
> originated from a switch, it assumes the switch has already flooded
> the packet out the switches ports, so the bridge should not flood the
> packet itself out switch ports. Ports on the same switch are expected
> to return the same parent ID when SWITCHDEV_ATTR_ID_PORT_PARENT_ID is
> called.
> 
> DSA gets this wrong with clusters of switches. As far as the software
> bridge is concerned, the cluster is all one switch. A packet from any
> switch in the cluster can be assumed to of been flooded as needed out

    s/of/have/?

> all ports of the cluster, not just the switch it originated
> from. Hence all ports of a cluster should return the same parent. The
> old implementation did not, each switch in the cluster had its own ID.
> 
> Also wrong was that the ID was not unique if multiple DSA instances
> are in operation.
> 
> Use the tree ID as the parent ID, which is the same for all switches
> in a cluster and unique across switch clusters.
> 
> Signed-off-by: Andrew Lunn <andrew@...n.ch>
> ---
> v2: Swap from MAC address to dst->tree
[...]

MBR, Sergei