net: ipv6/l3mdev: Move host route on saved address if necessary

Commit f1705ec197e70 allows IPv6 addresses to be retained on a link down.
The address can have a cached host route which can point to the wrong
FIB table if the L3 enslavement is changed (e.g., route can point to local
table instead of VRF table if device is added to an L3 domain).

On link up check the table of the cached host route against the FIB
table associated with the device and correct if needed.

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/addrconf.c

@@ -3170,9 +3170,35 @@ static void addrconf_gre_config(struct net_device *dev)
 }
 #endif
 
+#if IS_ENABLED(CONFIG_NET_L3_MASTER_DEV)
+/* If the host route is cached on the addr struct make sure it is associated
+ * with the proper table. e.g., enslavement can change and if so the cached
+ * host route needs to move to the new table.
+ */
+static void l3mdev_check_host_rt(struct inet6_dev *idev,
+				  struct inet6_ifaddr *ifp)
+{
+	if (ifp->rt) {
+		u32 tb_id = l3mdev_fib_table(idev->dev) ? : RT6_TABLE_LOCAL;
+
+		if (tb_id != ifp->rt->rt6i_table->tb6_id) {
+			ip6_del_rt(ifp->rt);
+			ifp->rt = NULL;
+		}
+	}
+}
+#else
+static void l3mdev_check_host_rt(struct inet6_dev *idev,
+				  struct inet6_ifaddr *ifp)
+{
+}
+#endif
+
 static int fixup_permanent_addr(struct inet6_dev *idev,
 				struct inet6_ifaddr *ifp)
 {
+	l3mdev_check_host_rt(idev, ifp);
+
 	if (!ifp->rt) {
 		struct rt6_info *rt;