[PATCH net-next 07/14] net: dsa: Add ability to program multicast filter for CPU port

[Florian Fainelli <f.fainelli@gmail.com>]

When the switch ports operate as individual network devices, the switch
driver might have configured the switch to flood multicast all the way
to the CPU port. This is really undesireable as it can lead to receiving
a lot of unwanted traffic that the network stack needs to filter in
software.

For each valid multicast address, program it into the switch's MDB only
when the host is interested in receiving such traffic, e.g: running an
multicast application.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
---
 net/dsa/slave.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index a3fcc1d01615..33f6b88b6fd6 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -68,6 +68,39 @@ static int dsa_slave_get_iflink(const struct net_device *dev)
 	return dsa_slave_to_master(dev)->ifindex;
 }
 
+static int dsa_slave_sync_unsync_mdb_addr(struct net_device *dev,
+					  const unsigned char *addr, bool add)
+{
+	struct switchdev_obj_port_mdb mdb = {
+		.obj = {
+			.id = SWITCHDEV_OBJ_ID_HOST_MDB,
+			.flags = SWITCHDEV_F_DEFER,
+		},
+		.vid = 0,
+	};
+	int ret = -EOPNOTSUPP;
+
+	ether_addr_copy(mdb.addr, addr);
+	if (add)
+		ret = switchdev_port_obj_add(dev, &mdb.obj, NULL);
+	else
+		ret = switchdev_port_obj_del(dev, &mdb.obj);
+
+	return ret;
+}
+
+static int dsa_slave_sync_mdb_addr(struct net_device *dev,
+				   const unsigned char *addr)
+{
+	return dsa_slave_sync_unsync_mdb_addr(dev, addr, true);
+}
+
+static int dsa_slave_unsync_mdb_addr(struct net_device *dev,
+				     const unsigned char *addr)
+{
+	return dsa_slave_sync_unsync_mdb_addr(dev, addr, false);
+}
+
 static int dsa_slave_open(struct net_device *dev)
 {
 	struct net_device *master = dsa_slave_to_master(dev);
@@ -126,6 +159,8 @@ static int dsa_slave_close(struct net_device *dev)
 
 	dev_mc_unsync(master, dev);
 	dev_uc_unsync(master, dev);
+	__hw_addr_unsync_dev(&dev->mc, dev, dsa_slave_unsync_mdb_addr);
+
 	if (dev->flags & IFF_ALLMULTI)
 		dev_set_allmulti(master, -1);
 	if (dev->flags & IFF_PROMISC)
@@ -150,7 +185,17 @@ static void dsa_slave_change_rx_flags(struct net_device *dev, int change)
 static void dsa_slave_set_rx_mode(struct net_device *dev)
 {
 	struct net_device *master = dsa_slave_to_master(dev);
+	struct dsa_port *dp = dsa_slave_to_port(dev);
 
+	/* If the port is bridged, the bridge takes care of sending
+	 * SWITCHDEV_OBJ_ID_HOST_MDB to program the host's MC filter
+	 */
+	if (netdev_mc_empty(dev) || dp->bridge_dev)
+		goto out;
+
+	__hw_addr_sync_dev(&dev->mc, dev, dsa_slave_sync_mdb_addr,
+			   dsa_slave_unsync_mdb_addr);
+out:
 	dev_mc_sync(master, dev);
 	dev_uc_sync(master, dev);
 }
@@ -1395,6 +1440,11 @@ static int dsa_slave_changeupper(struct net_device *dev,
 
 	if (netif_is_bridge_master(info->upper_dev)) {
 		if (info->linking) {
+			/* Remove existing MC addresses that might have been
+			 * programmed
+			 */
+			__hw_addr_unsync_dev(&dev->mc, dev,
+					     dsa_slave_unsync_mdb_addr);
 			err = dsa_port_bridge_join(dp, info->upper_dev);
 			err = notifier_from_errno(err);
 		} else {
-- 
2.17.1