[BRIDGE]: linkstate handling

This makes bridge port status reflect both the state of the interface
from software (up/down) and the carrier.  It makes STP handle link failure
(cable breakage, etc).  The original concept comes from a 
Mark Ruijter <bridge@siennax.com> who implemented it differently.
My way is simpler and requires no polling.

Obviously, this link state detection will only work if the network card
handles the events properly.
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@redhat.com>

net/bridge/br_if.c

@@ -344,7 +344,8 @@ int br_add_if(struct net_bridge *br, struct net_device *dev)
 
 		spin_lock_bh(&br->lock);
 		br_stp_recalculate_bridge_id(br);
-		if ((br->dev->flags & IFF_UP) && (dev->flags & IFF_UP))
+		if ((br->dev->flags & IFF_UP) 
+		    && (dev->flags & IFF_UP) && netif_carrier_ok(dev))
 			br_stp_enable_port(p);
 		spin_unlock_bh(&br->lock);
 

net/bridge/br_notify.c

@@ -19,58 +19,59 @@
 
 static int br_device_event(struct notifier_block *unused, unsigned long event, void *ptr);
 
-struct notifier_block br_device_notifier =
-{
+struct notifier_block br_device_notifier = {
 	.notifier_call = br_device_event
 };
 
 static int br_device_event(struct notifier_block *unused, unsigned long event, void *ptr)
 {
-	struct net_device *dev;
-	struct net_bridge_port *p;
+	struct net_device *dev = ptr;
+	struct net_bridge_port *p = dev->br_port;
 	struct net_bridge *br;
 
-	dev = ptr;
-	p = dev->br_port;
-
 	if (p == NULL)
 		return NOTIFY_DONE;
 
 	br = p->br;
+	if ( !(br->dev->flags & IFF_UP))
+		return NOTIFY_DONE;
 
+	if (event == NETDEV_CHANGEMTU) {
+		dev_set_mtu(br->dev, br_min_mtu(br));
+		return NOTIFY_DONE;
+	}
+
+	spin_lock_bh(&br->lock);
 	switch (event) {
 	case NETDEV_CHANGEADDR:
-		spin_lock_bh(&br->lock);
 		br_fdb_changeaddr(p, dev->dev_addr);
-		if (br->dev->flags & IFF_UP)
 		br_stp_recalculate_bridge_id(br);
-		spin_unlock_bh(&br->lock);
 		break;
 
-	case NETDEV_CHANGEMTU:
-		dev_set_mtu(br->dev, br_min_mtu(br));
+	case NETDEV_CHANGE:	/* device is up but carrier changed */
+		if (netif_carrier_ok(dev)) {
+			if (p->state == BR_STATE_DISABLED)
+				br_stp_enable_port(p);
+		} else {
+			if (p->state != BR_STATE_DISABLED)
+				br_stp_disable_port(p);
+		}
 		break;
 
 	case NETDEV_DOWN:
-		if (br->dev->flags & IFF_UP) {
-			spin_lock_bh(&br->lock);
 		br_stp_disable_port(p);
-			spin_unlock_bh(&br->lock);
-		}
 		break;
 
 	case NETDEV_UP:
-		if (br->dev->flags & IFF_UP) {
-			spin_lock_bh(&br->lock);
+		if (netif_carrier_ok(dev)) 
 			br_stp_enable_port(p);
-			spin_unlock_bh(&br->lock);
-		}
 		break;
 
 	case NETDEV_UNREGISTER:
 		br_del_if(br, dev);
 		break;
 	} 
+	spin_unlock_bh(&br->lock);
 
 	return NOTIFY_DONE;
 }

net/bridge/br_stp_if.c

@@ -52,7 +52,7 @@ void br_stp_enable_bridge(struct net_bridge *br)
 	br_config_bpdu_generation(br);
 
 	list_for_each_entry(p, &br->port_list, list) {
-		if (p->dev->flags & IFF_UP)
+		if ((p->dev->flags & IFF_UP) && netif_carrier_ok(p->dev))
 			br_stp_enable_port(p);
 
 	}