ipv4: fix to not remove local route on link down

When fib_netdev_event calls fib_disable_ip on NETDEV_DOWN event
we should not delete the local routes if the local address
is still present. The confusion comes from the fact that both
fib_netdev_event and fib_inetaddr_event use the NETDEV_DOWN
constant. Fix it by returning back the variable 'force'.

Steps to reproduce:
modprobe dummy
ifconfig dummy0 192.168.168.1 up
ifconfig dummy0 down
ip route list table local | grep dummy | grep host
local 192.168.168.1 dev dummy0  proto kernel  scope host  src 192.168.168.1

Fixes: 8a3d03166f19 ("net: track link-status of ipv4 nexthops")
Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 690bcbc..457b2cd 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -1110,9 +1110,10 @@
 	net->ipv4.fibnl = NULL;
 }
 
-static void fib_disable_ip(struct net_device *dev, unsigned long event)
+static void fib_disable_ip(struct net_device *dev, unsigned long event,
+			   bool force)
 {
-	if (fib_sync_down_dev(dev, event))
+	if (fib_sync_down_dev(dev, event, force))
 		fib_flush(dev_net(dev));
 	rt_cache_flush(dev_net(dev));
 	arp_ifdown(dev);
@@ -1140,7 +1141,7 @@
 			/* Last address was deleted from this interface.
 			 * Disable IP.
 			 */
-			fib_disable_ip(dev, event);
+			fib_disable_ip(dev, event, true);
 		} else {
 			rt_cache_flush(dev_net(dev));
 		}
@@ -1157,7 +1158,7 @@
 	unsigned int flags;
 
 	if (event == NETDEV_UNREGISTER) {
-		fib_disable_ip(dev, event);
+		fib_disable_ip(dev, event, true);
 		rt_flush_dev(dev);
 		return NOTIFY_DONE;
 	}
@@ -1178,14 +1179,14 @@
 		rt_cache_flush(net);
 		break;
 	case NETDEV_DOWN:
-		fib_disable_ip(dev, event);
+		fib_disable_ip(dev, event, false);
 		break;
 	case NETDEV_CHANGE:
 		flags = dev_get_flags(dev);
 		if (flags & (IFF_RUNNING | IFF_LOWER_UP))
 			fib_sync_up(dev, RTNH_F_LINKDOWN);
 		else
-			fib_sync_down_dev(dev, event);
+			fib_sync_down_dev(dev, event, false);
 		/* fall through */
 	case NETDEV_CHANGEMTU:
 		rt_cache_flush(net);