zebra: fix loss of metric for Linux routes

* rt_netlink.c
  * netlink_route_change(): fetch metric information like
    netlink_routing_table() does and pass it further
diff --git a/zebra/rt_netlink.c b/zebra/rt_netlink.c
index 7652f80..eb9eae3 100644
--- a/zebra/rt_netlink.c
+++ b/zebra/rt_netlink.c
@@ -768,6 +768,8 @@
 
   int index;
   int table;
+  int metric;
+
   void *dest;
   void *gate;
   void *src;
@@ -825,6 +827,7 @@
     }
 
   index = 0;
+  metric = 0;
   dest = NULL;
   gate = NULL;
   src = NULL;
@@ -843,6 +846,9 @@
   if (tb[RTA_PREFSRC])
     src = RTA_DATA (tb[RTA_PREFSRC]);
 
+  if (h->nlmsg_type == RTM_NEWROUTE && tb[RTA_PRIORITY])
+    metric = *(int *) RTA_DATA(tb[RTA_PRIORITY]);
+
   if (rtm->rtm_family == AF_INET)
     {
       struct prefix_ipv4 p;
@@ -861,7 +867,7 @@
         }
 
       if (h->nlmsg_type == RTM_NEWROUTE)
-        rib_add_ipv4 (ZEBRA_ROUTE_KERNEL, 0, &p, gate, src, index, table, 0, 0);
+        rib_add_ipv4 (ZEBRA_ROUTE_KERNEL, 0, &p, gate, src, index, table, metric, 0);
       else
         rib_delete_ipv4 (ZEBRA_ROUTE_KERNEL, 0, &p, gate, index, table);
     }
@@ -889,7 +895,7 @@
         }
 
       if (h->nlmsg_type == RTM_NEWROUTE)
-        rib_add_ipv6 (ZEBRA_ROUTE_KERNEL, 0, &p, gate, index, table, 0, 0);
+        rib_add_ipv6 (ZEBRA_ROUTE_KERNEL, 0, &p, gate, index, table, metric, 0);
       else
         rib_delete_ipv6 (ZEBRA_ROUTE_KERNEL, 0, &p, gate, index, table);
     }