Re: [RFC PATCH v2 net-next 04/16] net: dsa: sync up with bridge port's STP state when joining

[Florian Fainelli]

On 3/18/2021 4:18 PM, Vladimir Oltean wrote:
> From: Vladimir Oltean <vladimir.oltean@xxxxxxx>
> 
> It may happen that we have the following topology:
> 
> ip link add br0 type bridge stp_state 1
> ip link add bond0 type bond
> ip link set bond0 master br0
> ip link set swp0 master bond0
> ip link set swp1 master bond0
> 
> STP decides that it should put bond0 into the BLOCKING state, and
> that's that. The ports that are actively listening for the switchdev
> port attributes emitted for the bond0 bridge port (because they are
> offloading it) and have the honor of seeing that switchdev port
> attribute can react to it, so we can program swp0 and swp1 into the
> BLOCKING state.
> 
> But if then we do:
> 
> ip link set swp2 master bond0
> 
> then as far as the bridge is concerned, nothing has changed: it still
> has one bridge port. But this new bridge port will not see any STP state
> change notification and will remain FORWARDING, which is how the
> standalone code leaves it in.
> 
> Add a function to the bridge which retrieves the current STP state, such
> that drivers can synchronize to it when they may have missed switchdev
> events.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>

Reviewed-by: Florian Fainelli <f.fainelli@xxxxxxxxx>
-- 
Florian