switchdev: Add support for flood control

Allow devices supporting this feature to control the flooding of unknown
unicast traffic, by making switchdev infrastructure propagate this setting
to the switch driver.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/switchdev.txt

@@ -298,6 +298,9 @@ packets up to the bridge driver for flooding.  This is not ideal as the number
 of ports scale in the L2 domain as the device is much more efficient at
 flooding packets that software.
 
+If supported by the device, flood control can be offloaded to it, preventing
+certain netdevs from flooding unicast traffic for which there is no FDB entry.
+
 IGMP Snooping
 ^^^^^^^^^^^^^
 

net/switchdev/switchdev.c

@@ -746,7 +746,7 @@ int switchdev_port_bridge_getlink(struct sk_buff *skb, u32 pid, u32 seq,
 		.id = SWITCHDEV_ATTR_ID_PORT_BRIDGE_FLAGS,
 	};
 	u16 mode = BRIDGE_MODE_UNDEF;
-	u32 mask = BR_LEARNING | BR_LEARNING_SYNC;
+	u32 mask = BR_LEARNING | BR_LEARNING_SYNC | BR_FLOOD;
 	int err;
 
 	err = switchdev_port_attr_get(dev, &attr);
@@ -817,6 +817,9 @@ static int switchdev_port_br_setlink_protinfo(struct net_device *dev,
 			err = switchdev_port_br_setflag(dev, attr,
 							BR_LEARNING_SYNC);
 			break;
+		case IFLA_BRPORT_UNICAST_FLOOD:
+			err = switchdev_port_br_setflag(dev, attr, BR_FLOOD);
+			break;
 		default:
 			err = -EOPNOTSUPP;
 			break;