bridge: Change local fdb entries whenever mac address of bridge device changes

Vlan code may need fdb change when changing mac address of bridge device
even if it is caused by the mac address changing of a bridge port.

Example configuration:
  ip link set eth0 address 12:34:56:78:90:ab
  ip link set eth1 address aa:bb:cc:dd:ee:ff
  brctl addif br0 eth0
  brctl addif br0 eth1 # br0 will have mac address 12:34:56:78:90:ab
  bridge vlan add dev br0 vid 10 self
  bridge vlan add dev eth0 vid 10
We will have fdb entry such that f->dst == NULL, f->vlan_id == 10 and
f->addr == 12:34:56:78:90:ab at this time.
Next, change the mac address of eth0 to greater value.
  ip link set eth0 address ee:ff:12:34:56:78
Then, mac address of br0 will be recalculated and set to aa:bb:cc:dd:ee:ff.
However, an entry aa:bb:cc:dd:ee:ff will not be created and we will be not
able to communicate using br0 on vlan 10.

Address this issue by deleting and adding local entries whenever
changing the mac address of the bridge device.

If there already exists an entry that has the same address, for example,
in case that br_fdb_changeaddr() has already inserted it,
br_fdb_change_mac_address() will simply fail to insert it and no
duplicated entry will be made, as it was.

This approach also needs br_add_if() to call br_fdb_insert() before
br_stp_recalculate_bridge_id() so that we don't create an entry whose
dst == NULL in this function to preserve previous behavior.

Note that this is a slight change in behavior where the bridge device can
receive the traffic to the new address before calling
br_stp_recalculate_bridge_id() in br_add_if().
However, it is not a problem because we have already the address on the
new port and such a way to insert new one before recalculating bridge id
is taken in br_device_event() as well.

Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Acked-by: Vlad Yasevich <vyasevic@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/br_device.c

@@ -187,7 +187,6 @@ static int br_set_mac_address(struct net_device *dev, void *p)
 
 	spin_lock_bh(&br->lock);
 	if (!ether_addr_equal(dev->dev_addr, addr->sa_data)) {
-		br_fdb_change_mac_address(br, addr->sa_data);
 		/* Mac address will be changed in br_stp_change_bridge_id(). */
 		br_stp_change_bridge_id(br, addr->sa_data);
 	}

net/bridge/br_if.c

@@ -389,6 +389,9 @@ int br_add_if(struct net_bridge *br, struct net_device *dev)
 	if (br->dev->needed_headroom < dev->needed_headroom)
 		br->dev->needed_headroom = dev->needed_headroom;
 
+	if (br_fdb_insert(br, p, dev->dev_addr, 0))
+		netdev_err(dev, "failed insert local address bridge forwarding table\n");
+
 	spin_lock_bh(&br->lock);
 	changed_addr = br_stp_recalculate_bridge_id(br);
 
@@ -404,9 +407,6 @@ int br_add_if(struct net_bridge *br, struct net_device *dev)
 
 	dev_set_mtu(br->dev, br_min_mtu(br));
 
-	if (br_fdb_insert(br, p, dev->dev_addr, 0))
-		netdev_err(dev, "failed insert local address bridge forwarding table\n");
-
 	kobject_uevent(&p->kobj, KOBJ_ADD);
 
 	return 0;

net/bridge/br_stp_if.c

@@ -194,6 +194,8 @@ void br_stp_change_bridge_id(struct net_bridge *br, const unsigned char *addr)
 
 	wasroot = br_is_root_bridge(br);
 
+	br_fdb_change_mac_address(br, addr);
+
 	memcpy(oldaddr, br->bridge_id.addr, ETH_ALEN);
 	memcpy(br->bridge_id.addr, addr, ETH_ALEN);
 	memcpy(br->dev->dev_addr, addr, ETH_ALEN);