ospfd: Optimize and improve SPF nexthop calculation

Maintain router LSA positions in OSPF interface.
Find the OSPF interface in nexthop_calculation using
the position in the router LSA. This is possible because
the only time nexthop_calculation needs to look up interfaces
is when dealing with its own Router LSA.

This has the following advantages:
 - Multiple PtP interfaces with the same IP address between two routers.
 - Use Unnumbered PtP on just one end of the link.
 - Faster OI lookup for the OSPF interface and only
   done once for PtoP links.

*ospf_interface.h: (struct ospf_interface) Add storage for
		   storing router LSA position.

*ospf_interface.c: (ospf_if_lookup_by_lsa_pos)
		   lookup OSPF I/F in an area using LSA position.

*ospf_lsa.c: (router_lsa_link_set) record Router LSA position.

*ospf_spf.c: (ospf_spf_next) Count and pass along lsa position.
	     (ospf_nexthop_calculation) Add lsa position argument.
	     call ospf_if_lookup_by_lsa_pos() for OSFP interface handle.
	     Clean up and remove all calls ospf_if_is_configured() the
	     rest. Adjust a few debug logs.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>

ospfd/ospf_interface.c

@@ -392,6 +392,21 @@ ospf_if_exists (struct ospf_interface *oic)
   return NULL;
 }
 
+/* Lookup OSPF interface by router LSA posistion */
+struct ospf_interface *
+ospf_if_lookup_by_lsa_pos (struct ospf_area *area, int lsa_pos)
+{
+  struct listnode *node;
+  struct ospf_interface *oi;
+
+  for (ALL_LIST_ELEMENTS_RO (area->oiflist, node, oi))
+    {
+      if (lsa_pos >= oi->lsa_pos_beg && lsa_pos < oi->lsa_pos_end)
+	return oi;
+    }
+  return NULL;
+}
+
 struct ospf_interface *
 ospf_if_lookup_by_local_addr (struct ospf *ospf,
 			      struct interface *ifp, struct in_addr address)
@@ -801,6 +816,9 @@ ospf_if_down (struct ospf_interface *oi)
     return 0;
 
   OSPF_ISM_EVENT_EXECUTE (oi, ISM_InterfaceDown);
+  /* delete position in router LSA */
+  oi->lsa_pos_beg = 0;
+  oi->lsa_pos_end = 0;
   /* Shutdown packet reception and sending */
   ospf_if_stream_unset (oi);
 

ospfd/ospf_interface.h

@@ -127,6 +127,10 @@ struct ospf_interface
   /* OSPF Area. */
   struct ospf_area *area;
 
+  /* Position range in Router LSA */
+  uint16_t lsa_pos_beg; /* inclusive, >= */
+  uint16_t lsa_pos_end; /* exclusive, <  */
+
   /* Interface data from zebra. */
   struct interface *ifp;
   struct ospf_vl_data *vl_data;		/* Data for Virtual Link */
@@ -244,6 +248,8 @@ extern int ospf_if_down (struct ospf_interface *);
 
 extern int ospf_if_is_up (struct ospf_interface *);
 extern struct ospf_interface *ospf_if_exists (struct ospf_interface *);
+extern struct ospf_interface *ospf_if_lookup_by_lsa_pos (struct ospf_area *,
+							 int);
 extern struct ospf_interface *ospf_if_lookup_by_local_addr (struct ospf *,
 							    struct interface
 							    *,

ospfd/ospf_lsa.c

@@ -670,6 +670,7 @@ router_lsa_link_set (struct stream *s, struct ospf_area *area)
 	{
 	  if (oi->state != ISM_Down)
 	    {
+	      oi->lsa_pos_beg = links;
 	      /* Describe each link. */
 	      switch (oi->type)
 		{
@@ -691,6 +692,7 @@ router_lsa_link_set (struct stream *s, struct ospf_area *area)
 		case OSPF_IFTYPE_LOOPBACK:
 		  links += lsa_link_loopback_set (s, oi); 
 		}
+	      oi->lsa_pos_end = links;
 	    }
 	}
     }

ospfd/ospf_spf.c

@@ -490,13 +490,15 @@ ospf_spf_add_parent (struct vertex *v, struct vertex *w,
 static unsigned int
 ospf_nexthop_calculation (struct ospf_area *area, struct vertex *v,
                           struct vertex *w, struct router_lsa_link *l,
-                          unsigned int distance)
+                          unsigned int distance, int lsa_pos)
 {
   struct listnode *node, *nnode;
   struct vertex_nexthop *nh;
   struct vertex_parent *vp;
   struct ospf_interface *oi = NULL;
   unsigned int added = 0;
+  char buf1[BUFSIZ];
+  char buf2[BUFSIZ];
 
   if (IS_DEBUG_OSPF_EVENT)
     {
@@ -515,6 +517,27 @@ ospf_nexthop_calculation (struct ospf_area *area, struct vertex *v,
          the OSPF interface connecting to the destination network/router.
       */
 
+      /* we *must* be supplied with the link data */
+      assert (l != NULL);
+      oi = ospf_if_lookup_by_lsa_pos (area, lsa_pos);
+      if (!oi)
+	{
+	  zlog_debug("%s: OI not found in LSA: lsa_pos:%d link_id:%s link_data:%s",
+		     __func__, lsa_pos,
+		     inet_ntop (AF_INET, &l->link_id, buf1, BUFSIZ),
+		     inet_ntop (AF_INET, &l->link_data, buf2, BUFSIZ));
+	  return 0;
+	}
+
+      if (IS_DEBUG_OSPF_EVENT)
+	{
+	  zlog_debug("%s: considering link:%s "
+		     "type:%d link_id:%s link_data:%s",
+		     __func__, oi->ifp->name, l->m[0].type,
+		     inet_ntop (AF_INET, &l->link_id, buf1, BUFSIZ),
+		     inet_ntop (AF_INET, &l->link_data, buf2, BUFSIZ));
+	}
+
       if (w->type == OSPF_VERTEX_ROUTER)
         {
           /* l  is a link from v to w
@@ -522,23 +545,10 @@ ospf_nexthop_calculation (struct ospf_area *area, struct vertex *v,
            */
           struct router_lsa_link *l2 = NULL;
 
-          /* we *must* be supplied with the link data */
-          assert (l != NULL);
-          
-          if (IS_DEBUG_OSPF_EVENT)
-            {
-              char buf1[BUFSIZ];
-              char buf2[BUFSIZ];
-              
-              zlog_debug("ospf_nexthop_calculation(): considering link "
-                        "type %d link_id %s link_data %s",
-                        l->m[0].type,
-                        inet_ntop (AF_INET, &l->link_id, buf1, BUFSIZ),
-                        inet_ntop (AF_INET, &l->link_data, buf2, BUFSIZ));
-            }
-
           if (l->m[0].type == LSA_LINK_TYPE_POINTOPOINT)
             {
+	      struct in_addr nexthop;
+
               /* If the destination is a router which connects to
                  the calculating router via a Point-to-MultiPoint
                  network, the destination's next hop IP address(es)
@@ -549,17 +559,19 @@ ospf_nexthop_calculation (struct ospf_area *area, struct vertex *v,
                  provides an IP address of the next hop router.
 
                  At this point l is a link from V to W, and V is the
-                 root ("us").  Find the local interface associated 
+                 root ("us"). If it is a point-to-multipoint interface,
-                 with l (its address is in l->link_data).  If it
+		 then look through the links in the opposite direction (W to V).
-                 is a point-to-multipoint interface, then look through
+		 If any of them have an address that lands within the
-                 the links in the opposite direction (W to V).  If
-                 any of them have an address that lands within the
                  subnet declared by the PtMP link, then that link
                  is a constituent of the PtMP link, and its address is
                  a nexthop address for V.
               */
-              oi = ospf_if_is_configured (area->ospf, &l->link_data);
+	      if (oi->type == OSPF_IFTYPE_POINTOPOINT)
-              if (oi && oi->type == OSPF_IFTYPE_POINTOMULTIPOINT)
+		{
+		  added = 1;
+		  nexthop.s_addr = 0; /* Nexthop not required */
+		}
+	      else if (oi->type == OSPF_IFTYPE_POINTOMULTIPOINT)
 		{
 		  struct prefix_ipv4 la;
 
@@ -573,44 +585,27 @@ ospf_nexthop_calculation (struct ospf_area *area, struct vertex *v,
 		      la.prefix = l2->link_data;
 
 		      if (prefix_cmp ((struct prefix *) &la,
-                                      oi->address) == 0)
+				      oi->address) != 0)
+			continue;
 		      /* link_data is on our PtMP network */
-                        break;
+		      added = 1;
-                    }
+		      nexthop = l2->link_data;
-                } /* end l is on point-to-multipoint link */
-              else
-                {
-                  /* l is a regular point-to-point link.
-                     Look for a link from W to V.
-                   */
-                  while ((l2 = ospf_get_next_link (w, v, l2)))
-                    {
-                      oi = ospf_if_is_configured (area->ospf,
-                                                  &(l2->link_data));
-
-                      if (oi == NULL)
-                        continue;
-
-                      if (!IPV4_ADDR_SAME (&oi->address->u.prefix4,
-                                           &l->link_data))
-                        continue;
-
 		      break;
 		    }
 		}
 
-              if (oi && l2)
+              if (added)
                 {
                   /* found all necessary info to build nexthop */
                   nh = vertex_nexthop_new ();
                   nh->oi = oi;
-                  nh->router = l2->link_data;
+                  nh->router = nexthop;
                   ospf_spf_add_parent (v, w, nh, distance);
                   return 1;
                 }
               else
-                zlog_info("ospf_nexthop_calculation(): "
+		zlog_info("%s: could not determine nexthop for link %s",
-                          "could not determine nexthop for link");
+			  __func__, oi->ifp->name);
             } /* end point-to-point link from V to W */
           else if (l->m[0].type == LSA_LINK_TYPE_VIRTUALLINK)
             {
@@ -643,19 +638,13 @@ ospf_nexthop_calculation (struct ospf_area *area, struct vertex *v,
       else
         {
           assert(w->type == OSPF_VERTEX_NETWORK);
-          oi = ospf_if_is_configured (area->ospf, &(l->link_data));
+
-          if (oi)
-            {
 	  nh = vertex_nexthop_new ();
 	  nh->oi = oi;
-              nh->router.s_addr = 0;
+	  nh->router.s_addr = 0; /* Nexthop not required */
 	  ospf_spf_add_parent (v, w, nh, distance);
 	  return 1;
         }
-        }
-      zlog_info("ospf_nexthop_calculation(): "
-                "Unknown attached link");
-      return 0;
     } /* end V is the root */
   /* Check if W's parent is a network connected to root. */
   else if (v->type == OSPF_VERTEX_NETWORK)
@@ -736,7 +725,7 @@ ospf_spf_next (struct vertex *v, struct ospf_area *area,
   u_char *lim;
   struct router_lsa_link *l = NULL;
   struct in_addr *r;
-  int type = 0;
+  int type = 0, lsa_pos=-1, lsa_pos_next=0;
 
   /* If this is a router-LSA, and bit V of the router-LSA (see Section
      A.4.2:RFC2328) is set, set Area A's TransitCapability to TRUE.  */
@@ -765,6 +754,8 @@ ospf_spf_next (struct vertex *v, struct ospf_area *area,
         {
           l = (struct router_lsa_link *) p;
 
+	  lsa_pos = lsa_pos_next; /* LSA link position */
+	  lsa_pos_next++;
           p += (OSPF_ROUTER_LSA_LINK_SIZE +
                 (l->m[0].tos_count * OSPF_ROUTER_LSA_TOS_SIZE));
 
@@ -886,7 +877,7 @@ ospf_spf_next (struct vertex *v, struct ospf_area *area,
           w = ospf_vertex_new (w_lsa);
 
           /* Calculate nexthop to W. */
-          if (ospf_nexthop_calculation (area, v, w, l, distance))
+          if (ospf_nexthop_calculation (area, v, w, l, distance, lsa_pos))
             pqueue_enqueue (w, candidate);
           else if (IS_DEBUG_OSPF_EVENT)
             zlog_debug ("Nexthop Calc failed");
@@ -906,7 +897,7 @@ ospf_spf_next (struct vertex *v, struct ospf_area *area,
             {
 	      /* Found an equal-cost path to W.  
                * Calculate nexthop of to W from V. */
-              ospf_nexthop_calculation (area, v, w, l, distance);
+	      ospf_nexthop_calculation (area, v, w, l, distance, lsa_pos);
             }
            /* less than. */
 	  else
@@ -916,7 +907,7 @@ ospf_spf_next (struct vertex *v, struct ospf_area *area,
                * valid nexthop it will call spf_add_parents, which
                * will flush the old parents
                */
-              if (ospf_nexthop_calculation (area, v, w, l, distance))
+	      if (ospf_nexthop_calculation (area, v, w, l, distance, lsa_pos))
                 /* Decrease the key of the node in the heap.
                  * trickle-sort it up towards root, just in case this
                  * node should now be the new root due the cost change.