ospf_spf_process_stubs: use LSA pos to find OSFP interface

This is better than a prefix lookup as prefixes may not be
unique, that is, the same prefix can exist on several interfaces.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/ospfd/ospf_spf.c b/ospfd/ospf_spf.c
index 26fe485..6682951 100644
--- a/ospfd/ospf_spf.c
+++ b/ospfd/ospf_spf.c
@@ -973,6 +973,7 @@
       u_char *lim;
       struct router_lsa_link *l;
       struct router_lsa *rlsa;
+      int lsa_pos = 0;
 
       if (IS_DEBUG_OSPF_EVENT)
         zlog_debug ("ospf_process_stubs():processing router LSA, id: %s",
@@ -994,7 +995,8 @@
                 (l->m[0].tos_count * OSPF_ROUTER_LSA_TOS_SIZE));
 
           if (l->m[0].type == LSA_LINK_TYPE_STUB)
-            ospf_intra_add_stub (rt, l, v, area, parent_is_root);
+	    ospf_intra_add_stub (rt, l, v, area, parent_is_root, lsa_pos);
+	  lsa_pos++;
         }
     }