net: bridge: guard the switchdev replay helpers against a NULL notifier block

There is a desire to make the object and FDB replay helpers optional
when moving them inside the bridge driver. For example a certain driver
might not offload host MDBs and there is no case where the replay
helpers would be of immediate use to it.

So it would be nice if we could allow drivers to pass NULL pointers for
the atomic and blocking notifier blocks, and the replay helpers to do
nothing in that case.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/br_fdb.c

@@ -760,6 +760,9 @@ int br_fdb_replay(const struct net_device *br_dev, const struct net_device *dev,
 	unsigned long action;
 	int err = 0;
 
+	if (!nb)
+		return 0;
+
 	if (!netif_is_bridge_master(br_dev))
 		return -EINVAL;
 

net/bridge/br_mdb.c

@@ -617,6 +617,9 @@ int br_mdb_replay(struct net_device *br_dev, struct net_device *dev,
 
 	ASSERT_RTNL();
 
+	if (!nb)
+		return 0;
+
 	if (!netif_is_bridge_master(br_dev) || !netif_is_bridge_port(dev))
 		return -EINVAL;
 

net/bridge/br_vlan.c

@@ -1856,6 +1856,9 @@ int br_vlan_replay(struct net_device *br_dev, struct net_device *dev,
 
 	ASSERT_RTNL();
 
+	if (!nb)
+		return 0;
+
 	if (!netif_is_bridge_master(br_dev))
 		return -EINVAL;