net: switchdev: introduce helper for checking dynamically learned FDB entries

It is a bit difficult to understand what DSA checks when it tries to
avoid installing dynamically learned addresses on foreign interfaces as
local host addresses, so create a generic switchdev helper that can be
reused and is generally more readable.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/switchdev.h

@@ -238,6 +238,12 @@ switchdev_notifier_info_to_extack(const struct switchdev_notifier_info *info)
 	return info->extack;
 }
 
+static inline bool
+switchdev_fdb_is_dynamically_learned(const struct switchdev_notifier_fdb_info *fdb_info)
+{
+	return !fdb_info->added_by_user && !fdb_info->is_local;
+}
+
 #ifdef CONFIG_NET_SWITCHDEV
 
 void switchdev_deferred_process(void);

net/dsa/slave.c

@@ -2438,7 +2438,7 @@ static int dsa_slave_switchdev_event(struct notifier_block *unused,
 			 * On the other hand, FDB entries for local termination
 			 * should always be installed.
 			 */
-			if (!fdb_info->added_by_user && !fdb_info->is_local &&
+			if (switchdev_fdb_is_dynamically_learned(fdb_info) &&
 			    !dp->ds->assisted_learning_on_cpu_port)
 				return NOTIFY_DONE;