fib: FIB crash removing labelled route (VPP-1818)

Type: fix

The crash occured trying to retreive a NULL path list to walk the path
extensions. A walk shoul not be required, because there should be no
extensins, since all paths are removed. The problem is that when the
paths were added, they were not sorted, hence neither were the
extensions and when they were updated, duplicate extensions were added,
and hence a path removal did not remove them all.
Fix is to make sure paths are sorted.

Change-Id: I069d937de8e7bc8aae3d92f588db4daff727d863
Signed-off-by: Neale Ranns <nranns@cisco.com>
(cherry picked from commit 257749c409)

src/vnet/fib/fib_table.c

@@ -580,6 +580,13 @@ fib_table_entry_path_add (u32 fib_index,
     return (fib_entry_index);
 }
 
+static int
+fib_route_path_cmp_for_sort (void * v1,
+			     void * v2)
+{
+    return (fib_route_path_cmp(v1, v2));
+}
+
 fib_node_index_t
 fib_table_entry_path_add2 (u32 fib_index,
 			   const fib_prefix_t *prefix,
@@ -598,6 +605,11 @@ fib_table_entry_path_add2 (u32 fib_index,
     {
 	fib_table_route_path_fixup(prefix, &flags, &rpaths[ii]);
     }
+    /*
+     * sort the paths provided by the control plane. this means
+     * the paths and the extension on the entry will be sorted.
+     */
+    vec_sort_with_function(rpaths, fib_route_path_cmp_for_sort);
 
     if (FIB_NODE_INDEX_INVALID == fib_entry_index)
     {
@@ -740,13 +752,6 @@ fib_table_entry_path_remove (u32 fib_index,
     vec_free(paths);
 }
 
-static int
-fib_route_path_cmp_for_sort (void * v1,
-			     void * v2)
-{
-    return (fib_route_path_cmp(v1, v2));
-}
-
 fib_node_index_t
 fib_table_entry_update (u32 fib_index,
 			const fib_prefix_t *prefix,