fib: Copy the prefix before use in case the underlying entry reallocs.

Type: fix

all other uses of the fib_entry_get_preifx in the code base don't pass
the prefix into recursive functions.

Change-Id: Ic1c56acd406a733b215ee2fd98b6bed58b490a4f
Signed-off-by: Neale Ranns <nranns@cisco.com>
diff --git a/src/vnet/fib/fib_attached_export.c b/src/vnet/fib/fib_attached_export.c
index a0f4e4e..3c9c2bf 100644
--- a/src/vnet/fib/fib_attached_export.c
+++ b/src/vnet/fib/fib_attached_export.c
@@ -152,7 +152,7 @@
 		      fib_node_index_t entry_index)
 {
     fib_node_index_t *existing;
-    const fib_prefix_t *prefix;
+    fib_prefix_t prefix;
 
     /*
      * ensure we only add the exported entry once, since
@@ -168,15 +168,15 @@
 
     /*
      * this is the first time this export entry has been imported
-     * Add it to the import FIB and to the list of importeds
+     * Add it to the import FIB and to the list of importeds.
+     * make a copy of the prefix in case the underlying entry reallocs.
      */
-    prefix = fib_entry_get_prefix(entry_index);
+    fib_prefix_copy(&prefix, fib_entry_get_prefix(entry_index));
 
     /*
      * don't import entries that have the same prefix the import entry
      */
-    if (0 != fib_prefix_cmp(prefix,
-			    &import->faei_prefix))
+    if (0 != fib_prefix_cmp(&prefix, &import->faei_prefix))
     {
         const dpo_id_t *dpo;
 
@@ -185,7 +185,7 @@
         if (dpo_id_is_valid(dpo) && !dpo_is_drop(dpo))
         {
             fib_table_entry_special_dpo_add(import->faei_import_fib,
-                                            prefix,
+                                            &prefix,
                                             FIB_SOURCE_AE,
                                             (fib_entry_get_flags(entry_index) |
                                              FIB_ENTRY_FLAG_EXCLUSIVE),