bridge: notify applications if address of bridge device changes

The mac address of the bridge device may be changed when a new interface
is added to the bridge. If this happens, then the bridge needs to call
the network notifiers to tickle any other systems that care. Since bridge
can be a module, this also means exporting the notifier function.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/bridge/br_stp_if.c

diff --git a/net/bridge/br_stp_if.c b/net/bridge/br_stp_if.c
index 79372d4..5593f5a 100644
--- a/net/bridge/br_stp_if.c
+++ b/net/bridge/br_stp_if.c
@@ -204,7 +204,7 @@
 static const unsigned short br_mac_zero_aligned[ETH_ALEN >> 1];
 
 /* called under bridge lock */
-void br_stp_recalculate_bridge_id(struct net_bridge *br)
+bool br_stp_recalculate_bridge_id(struct net_bridge *br)
 {
 	const unsigned char *br_mac_zero =
 			(const unsigned char *)br_mac_zero_aligned;
@@ -222,8 +222,11 @@
 
 	}
 
-	if (compare_ether_addr(br->bridge_id.addr, addr))
-		br_stp_change_bridge_id(br, addr);
+	if (compare_ether_addr(br->bridge_id.addr, addr) == 0)
+		return false;	/* no change */
+
+	br_stp_change_bridge_id(br, addr);
+	return true;
 }
 
 /* called under bridge lock */