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

On 3/18/2021 4:18 PM, Vladimir Oltean wrote:

From: Vladimir Oltean <vladimir.oltean@nxp.com>

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@nxp.com>

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