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>

3 files changed, 16 insertions, 10 deletions

diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index 727d6e9a9685..965fa5b1a274 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -317,7 +317,7 @@ void fib_flush_external(struct net *net);
 
 /* Exported by fib_semantics.c */
 int ip_fib_check_default(__be32 gw, struct net_device *dev);
-int fib_sync_down_dev(struct net_device *dev, unsigned long event);
+int fib_sync_down_dev(struct net_device *dev, unsigned long event, bool force);
 int fib_sync_down_addr(struct net *net, __be32 local);
 int fib_sync_up(struct net_device *dev, unsigned int nh_flags);
 void fib_select_multipath(struct fib_result *res);
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 690bcbc59f26..457b2cd75b85 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -1110,9 +1110,10 @@ static void nl_fib_lookup_exit(struct net *net)
         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 @@ static int fib_inetaddr_event(struct notifier_block *this, unsigned long event,
                         /* 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 @@ static int fib_netdev_event(struct notifier_block *this, unsigned long event, vo
         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 @@ static int fib_netdev_event(struct notifier_block *this, unsigned long event, vo
                 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);
diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 064bd3caaa4f..2aa5b5e7da75 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -1281,7 +1281,13 @@ int fib_sync_down_addr(struct net *net, __be32 local)
         return ret;
 }
 
-int fib_sync_down_dev(struct net_device *dev, unsigned long event)
+/* Event              force Flags           Description
+ * NETDEV_CHANGE      0     LINKDOWN        Carrier OFF, not for scope host
+ * NETDEV_DOWN        0     LINKDOWN|DEAD   Link down, not for scope host
+ * NETDEV_DOWN        1     LINKDOWN|DEAD   Last address removed
+ * NETDEV_UNREGISTER  1     LINKDOWN|DEAD   Device removed
+ */
+int fib_sync_down_dev(struct net_device *dev, unsigned long event, bool force)
 {
         int ret = 0;
         int scope = RT_SCOPE_NOWHERE;
@@ -1290,8 +1296,7 @@ int fib_sync_down_dev(struct net_device *dev, unsigned long event)
         struct hlist_head *head = &fib_info_devhash[hash];
         struct fib_nh *nh;
 
-        if (event == NETDEV_UNREGISTER ||
-            event == NETDEV_DOWN)
+        if (force)
                 scope = -1;
 
         hlist_for_each_entry(nh, head, nh_hash) {