Index: ospfd/ospf_interface.c
===================================================================
RCS file: /var/cvsroot/quagga/ospfd/ospf_interface.c,v
retrieving revision 1.21
diff -u -r1.21 ospf_interface.c
--- ospfd/ospf_interface.c	17 Feb 2004 20:07:30 -0000	1.21
+++ ospfd/ospf_interface.c	11 Mar 2004 21:44:53 -0000
@@ -933,24 +933,49 @@
       }
 
   rl = (struct router_lsa *)v->lsa;
-  
-  for (i = 0; i < ntohs (rl->links); i++)
+
+  /* use SPF determined backlink index in struct vertex
+   * for virtual link destination address
+   */
+  if (v->backlink >= 0)
     {
-      switch (rl->link[i].type)
+      if (!IPV4_ADDR_SAME (&vl_data->peer_addr,
+                           &rl->link[v->backlink].link_data))
+        changed = 1;
+      vl_data->peer_addr = rl->link[v->backlink].link_data;
+    }
+  else
+    {
+      /* This is highly odd, there is no backlink index
+       * there should be due to the ospf_spf_has_link() check
+       * in SPF. Lets warn and try pick a link anyway.
+       */
+      zlog_warn ("ospf_vl_set_params: No backlink for %s!",
+                 vl_data->vl_oi->ifp->name);
+      for (i = 0; i < ntohs (rl->links); i++)
         {
-          case LSA_LINK_TYPE_VIRTUALLINK:
-            if (IS_DEBUG_OSPF_EVENT)
-              zlog_info ("found back link through VL");
-          case LSA_LINK_TYPE_TRANSIT:
-          case LSA_LINK_TYPE_POINTOPOINT:
-            vl_data->peer_addr = rl->link[i].link_data;
-          if (IS_DEBUG_OSPF_EVENT)
-            zlog_info ("%s peer address is %s\n",
-        	           vl_data->vl_oi->ifp->name, 
-        	           inet_ntoa(vl_data->peer_addr));
-          return changed;
+          switch (rl->link[i].type)
+            {
+              case LSA_LINK_TYPE_VIRTUALLINK:
+                if (IS_DEBUG_OSPF_EVENT)
+                  zlog_info ("found back link through VL");
+              case LSA_LINK_TYPE_TRANSIT:
+              case LSA_LINK_TYPE_POINTOPOINT:
+                vl_data->peer_addr = rl->link[i].link_data;
+              if (IS_DEBUG_OSPF_EVENT)
+                zlog_info ("%s peer address is %s\n",
+                               vl_data->vl_oi->ifp->name, 
+                               inet_ntoa(vl_data->peer_addr));
+              return changed;
+            }
         }
     }
+    
+  if (IS_DEBUG_OSPF_EVENT)
+    zlog_info ("ospf_vl_set_params: %s peer address is %s\n",
+               vl_data->vl_oi->ifp->name,
+               inet_ntoa(vl_data->peer_addr));
+               
   return changed;
 }
 
Index: ospfd/ospf_spf.c
===================================================================
RCS file: /var/cvsroot/quagga/ospfd/ospf_spf.c,v
retrieving revision 1.8
diff -u -r1.8 ospf_spf.c
--- ospfd/ospf_spf.c	4 Mar 2004 17:45:01 -0000	1.8
+++ ospfd/ospf_spf.c	11 Mar 2004 21:44:53 -0000
@@ -93,6 +93,7 @@
   new->distance = 0;
   new->child = list_new ();
   new->nexthop = list_new ();
+  new->backlink = -1;
 
   return new;
 }
@@ -184,6 +185,7 @@
   return NULL;
 }
 
+/* return index of link back to V from W, or -1 if no link found */
 int
 ospf_lsa_has_link (struct lsa_header *w, struct lsa_header *v)
 {
@@ -196,15 +198,15 @@
   if (w->type == OSPF_NETWORK_LSA)
     {
       if (v->type == OSPF_NETWORK_LSA)
-        return 0;
+        return -1;
 
       nl = (struct network_lsa *) w;
       length = (ntohs (w->length) - OSPF_LSA_HEADER_SIZE - 4) / 4;
 
       for (i = 0; i < length; i++)
         if (IPV4_ADDR_SAME (&nl->routers[i], &v->id))
-          return 1;
-      return 0;
+          return i;
+      return -1;
     }
 
   /* In case of W is Router LSA. */
@@ -226,7 +228,7 @@
               if (v->type == OSPF_ROUTER_LSA &&
                   IPV4_ADDR_SAME (&rl->link[i].link_id, &v->id))
                 {
-                  return 1;
+                  return i;
                 }
               break;
             case LSA_LINK_TYPE_TRANSIT:
@@ -234,7 +236,7 @@
               if (v->type == OSPF_NETWORK_LSA &&
                   IPV4_ADDR_SAME (&rl->link[i].link_id, &v->id))
                 {
-                  return 1;
+                  return i;
                 }
               break;
             case LSA_LINK_TYPE_STUB:
@@ -245,7 +247,7 @@
             }
         }
     }
-  return 0;
+  return -1;
 }
 
 /* Add the nexthop to the list, only if it is unique.
@@ -544,6 +546,8 @@
 
   while (p < lim)
     {
+      int link = -1; /* link index for w's back link */
+      
       /* In case of V is Router-LSA. */
       if (v->lsa->type == OSPF_ROUTER_LSA)
         {
@@ -616,7 +620,7 @@
       if (IS_LSA_MAXAGE (w_lsa))
         continue;
 
-      if (!ospf_lsa_has_link (w_lsa->data, v->lsa))
+      if ( (link = ospf_lsa_has_link (w_lsa->data, v->lsa)) < 0 )
         {
           if (IS_DEBUG_OSPF_EVENT)
             zlog_info ("The LSA doesn't have a link back");
@@ -640,6 +644,9 @@
 
       /* prepare vertex W. */
       w = ospf_vertex_new (w_lsa);
+
+      /* Save W's back link index number, for use by virtual links */
+      w->backlink = link;
 
       /* calculate link cost D. */
       if (v->lsa->type == OSPF_ROUTER_LSA)
Index: ospfd/ospf_spf.h
===================================================================
RCS file: /var/cvsroot/quagga/ospfd/ospf_spf.h,v
retrieving revision 1.1.1.2
diff -u -r1.1.1.2 ospf_spf.h
--- ospfd/ospf_spf.h	25 Mar 2003 02:37:17 -0000	1.1.1.2
+++ ospfd/ospf_spf.h	11 Mar 2004 21:44:53 -0000
@@ -33,6 +33,7 @@
   struct in_addr id;
   struct lsa_header *lsa;
   u_int32_t distance;
+  int backlink;        /* link index of back-link */
   list child;
   list nexthop;
 };