ospfd: Remember network LSA sequence numbers across up/downs of an interface

* ospf_interface.h: (struct ospf_if_params) add field for saved network LSA
  seqnum
* ospf_interfa.c: (ospf_new_if_params) init network_lsa_seqnum field to
  initial seqnum - doesnt matter though.
* ospf_lsa.c: (ospf_network_lsa_new) check for any saved sequence number,
  and use if it exists.  Save the result back. This should help avoid needless
  round of LSUpdate/LSRequests when a neighbour has to tell the originator
  "uhm, i have something newer than that already".
* ospf_vty.c: (show_ip_ospf_interface_sub) Show the saved network LSA seqnum

ospfd/ospf_interface.c

@@ -531,6 +531,8 @@ ospf_new_if_params (void)
 
   oip->auth_crypt = list_new ();
   
+  oip->network_lsa_seqnum = htonl(OSPF_INITIAL_SEQUENCE_NUMBER);
+
   return oip;
 }
 
@@ -569,7 +571,8 @@ ospf_free_if_params (struct interface *ifp, struct in_addr addr)
       !OSPF_IF_PARAM_CONFIGURED (oip, type) &&
       !OSPF_IF_PARAM_CONFIGURED (oip, auth_simple) &&
       !OSPF_IF_PARAM_CONFIGURED (oip, auth_type) &&
-      listcount (oip->auth_crypt) == 0)
+      listcount (oip->auth_crypt) == 0 &&
+      ntohl (oip->network_lsa_seqnum) != OSPF_INITIAL_SEQUENCE_NUMBER)
     {
       ospf_del_if_params (oip);
       rn->info = NULL;

ospfd/ospf_interface.h

@@ -73,6 +73,9 @@ struct ospf_if_params
   
   DECLARE_IF_PARAM (struct list *, auth_crypt);    /* List of Auth cryptographic data. */
   DECLARE_IF_PARAM (int, auth_type);               /* OSPF authentication type */
+  
+  /* Other, non-configuration state */
+  u_int32_t network_lsa_seqnum;		/* Network LSA seqnum */
 };
 
 enum
@@ -167,6 +170,7 @@ struct ospf_interface
 
   /* Configured varables. */
   struct ospf_if_params *params;
+  
   u_int32_t crypt_seqnum;		/* Cryptographic Sequence Number */ 
   u_int32_t output_cost;	        /* Acutual Interface Output Cost */
 

ospfd/ospf_lsa.c

@@ -1048,6 +1048,7 @@ ospf_network_lsa_new (struct ospf_interface *oi)
   struct stream *s;
   struct ospf_lsa *new;
   struct lsa_header *lsah;
+  struct ospf_if_params *oip;
   int length;
 
   /* If there are no neighbours on this network (the net is stub),
@@ -1087,6 +1088,22 @@ ospf_network_lsa_new (struct ospf_interface *oi)
   memcpy (new->data, lsah, length);
   stream_free (s);
   
+  /* Remember prior network LSA sequence numbers, even if we stop
+   * originating one for this oi, to try avoid re-originating LSAs with a
+   * prior sequence number, and thus speed up adjency forming & convergence.
+   */
+  if ((oip = ospf_lookup_if_params (oi->ifp, oi->address->u.prefix4)))
+    {
+      new->data->ls_seqnum = oip->network_lsa_seqnum;
+      new->data->ls_seqnum = lsa_seqnum_increment (new);
+    }
+  else
+    {
+      oip = ospf_get_if_params (oi->ifp, oi->address->u.prefix4);
+      ospf_if_update_params (oi->ifp, oi->address->u.prefix4);
+    }
+  oip->network_lsa_seqnum = new->data->ls_seqnum;
+  
   return new;
 }
 
@@ -1125,6 +1142,7 @@ ospf_network_lsa_refresh (struct ospf_lsa *lsa, struct ospf_interface *oi)
 {
   struct ospf_area *area = lsa->area;
   struct ospf_lsa *new;
+  struct ospf_if_params *oip;
 
   assert (lsa->data);
 
@@ -1135,7 +1153,10 @@ ospf_network_lsa_refresh (struct ospf_lsa *lsa, struct ospf_interface *oi)
   new = ospf_network_lsa_new (oi);
   if (new == NULL)
     return -1;
-  new->data->ls_seqnum = lsa_seqnum_increment (lsa);
+  
+  oip = ospf_lookup_if_params (oi->ifp, oi->address->u.prefix4);
+  assert (oip != NULL);
+  oip->network_lsa_seqnum = new->data->ls_seqnum = lsa_seqnum_increment (lsa);
 
   ospf_lsa_install (area->ospf, oi, new);
 

ospfd/ospf_vty.c

@@ -2934,6 +2934,12 @@ show_ip_ospf_interface_sub (struct vty *vty, struct ospf *ospf,
 	    }
 	}
       
+      /* Next network-LSA sequence number we'll use, if we're elected DR */
+      if (oi->params && ntohl (oi->params->network_lsa_seqnum)
+                          != OSPF_INITIAL_SEQUENCE_NUMBER)
+        vty_out (vty, "  Saved Network-LSA sequence number 0x%x%s",
+                 ntohl (oi->params->network_lsa_seqnum), VTY_NEWLINE);
+      
       vty_out (vty, "  Multicast group memberships:");
       if (OI_MEMBER_CHECK(oi, MEMBER_ALLROUTERS)
           || OI_MEMBER_CHECK(oi, MEMBER_DROUTERS))