Implements OSPF stub router option (RFC 3137).

Also fixes OSPFv3 routing table calculcation w.r.t.
errata 2078 to RFC 5340.

doc/bird.sgml

@@ -1904,6 +1904,7 @@ on nonbroadcast networks.
 <code>
 protocol ospf &lt;name&gt; {
 	rfc1583compat &lt;switch&gt;;
+	stub router &lt;switch&gt;;
 	tick &lt;num&gt;;
 	ecmp &lt;switch&gt; [limit &lt;num&gt;];
 	area &lt;id&gt; {
@@ -1983,6 +1984,15 @@ protocol ospf &lt;name&gt; {
 	 url="ftp://ftp.rfc-editor.org/in-notes/rfc1583.txt">. Default
 	 value is no.
 
+	<tag>stub router <M>switch</M></tag>
+	 This option configures the router to be a stub router, i.e.,
+	 a router that participates in the OSPF topology but does not
+	 allow transit traffic. In OSPFv2, this is implemented by
+	 advertising maximum metric for outgoing links, as suggested
+	 by RFC 3137<htmlurl url="ftp://ftp.rfc-editor.org/in-notes/rfc3137.txt">.
+	 In OSPFv3, the stub router behavior is announced by clearing
+	 the R-bit in the router LSA. Default value is no.
+
 	<tag>tick <M>num</M></tag>
 	 The routing table calculation and clean-up of areas' databases
          is not performed when a single link state

proto/ospf/config.Y

@@ -158,6 +158,7 @@ ospf_proto:
 ospf_proto_item:
    proto_item
  | RFC1583COMPAT bool { OSPF_CFG->rfc1583 = $2; }
+ | STUB ROUTER bool { OSPF_CFG->stub_router = $3; }
  | ECMP bool { OSPF_CFG->ecmp = $2 ? DEFAULT_ECMP_LIMIT : 0; }
  | ECMP bool LIMIT expr { OSPF_CFG->ecmp = $2 ? $4 : 0; if ($4 < 0) cf_error("ECMP limit cannot be negative"); }
  | TICK expr { OSPF_CFG->tick = $2; if($2<=0) cf_error("Tick must be greater than zero"); }

proto/ospf/ospf.c

@@ -167,7 +167,7 @@ ospf_area_add(struct proto_ospf *po, struct ospf_area_config *ac, int reconf)
 #ifdef OSPFv2
   oa->options = ac->type;
 #else /* OSPFv3 */
-  oa->options = OPT_R | ac->type | OPT_V6;
+  oa->options = ac->type | OPT_V6 | (po->stub_router ? 0 : OPT_R);
 #endif
 
   /*
@@ -234,6 +234,7 @@ ospf_start(struct proto *p)
   po->router_id = proto_get_router_id(p->cf);
   po->last_vlink_id = 0x80000000;
   po->rfc1583 = c->rfc1583;
+  po->stub_router = c->stub_router;
   po->ebit = 0;
   po->ecmp = c->ecmp;
   po->tick = c->tick;
@@ -690,7 +691,7 @@ ospf_area_reconfigure(struct ospf_area *oa, struct ospf_area_config *nac)
 #ifdef OSPFv2
   oa->options = nac->type;
 #else /* OSPFv3 */
-  oa->options = OPT_R | nac->type | OPT_V6;
+  oa->options = nac->type | OPT_V6 | (oa->po->stub_router ? 0 : OPT_R);
 #endif
   if (oa_is_nssa(oa) && (oa->po->areano > 1))
     oa->po->ebit = 1;
@@ -738,6 +739,7 @@ ospf_reconfigure(struct proto *p, struct proto_config *c)
   if (old->abr != new->abr)
     return 0;
 
+  po->stub_router = new->stub_router;
   po->ecmp = new->ecmp;
   po->tick = new->tick;
   po->disp_timer->recurrent = po->tick;
@@ -831,6 +833,7 @@ ospf_sh(struct proto *p)
 
   cli_msg(-1014, "%s:", p->name);
   cli_msg(-1014, "RFC1583 compatibility: %s", (po->rfc1583 ? "enable" : "disabled"));
+  cli_msg(-1014, "Stub router: %s", (po->stub_router ? "Yes" : "No"));
   cli_msg(-1014, "RT scheduler tick: %d", po->tick);
   cli_msg(-1014, "Number of areas: %u", po->areano);
   cli_msg(-1014, "Number of LSAs in DB:\t%u", po->gr->hash_entries);

proto/ospf/ospf.h

@@ -83,6 +83,7 @@ struct ospf_config
   struct proto_config c;
   unsigned tick;
   byte rfc1583;
+  byte stub_router;
   byte abr;
   int ecmp;
   list area_list;		/* list of struct ospf_area_config */
@@ -771,6 +772,7 @@ struct proto_ospf
   int areano;			/* Number of area I belong to */
   struct fib rtf;		/* Routing table */
   byte rfc1583;			/* RFC1583 compatibility */
+  byte stub_router;		/* Do not forward transit traffic */
   byte ebit;			/* Did I originate any ext lsa? */
   byte ecmp;			/* Maximal number of nexthops in ECMP route, or 0 */
   struct ospf_area *backbone;	/* If exists */

proto/ospf/rt.c

@@ -501,6 +501,10 @@ ospf_rt_spfa(struct ospf_area *oa)
 #ifdef OSPFv2
       ospf_rt_spfa_rtlinks(oa, act, act);
 #else /* OSPFv3 */
+      /* Errata 2078 to RFC 5340 4.8.1 - skip links from non-routing nodes */
+      if ((act != oa->rt) && !(rt->options & OPT_R))
+	break;
+
       for (tmp = ospf_hash_find_rt_first(po->gr, act->domain, act->lsa.rt);
 	   tmp; tmp = ospf_hash_find_rt_next(tmp))
 	ospf_rt_spfa_rtlinks(oa, act, tmp);
@@ -1839,7 +1843,7 @@ add_cand(list * l, struct top_hash_entry *en, struct top_hash_entry *par,
   if (en->lsa.type == LSA_T_RT)
     {
       struct ospf_lsa_rt *rt = en->lsa_body;
-      if (!(rt->options & OPT_V6) || !(rt->options & OPT_R))
+      if (!(rt->options & OPT_V6))
 	return;
     }
 #endif

proto/ospf/topology.c

@@ -233,6 +233,7 @@ originate_rt_lsa_body(struct ospf_area *oa, u16 *length)
   WALK_LIST(ifa, po->iface_list)
   {
     int net_lsa = 0;
+    u32 link_cost = po->stub_router ? 0xffff : ifa->cost;
 
     if ((ifa->type == OSPF_IT_VLINK) && (ifa->voa == oa) &&
 	(!EMPTY_LIST(ifa->neigh_list)))
@@ -268,8 +269,7 @@ originate_rt_lsa_body(struct ospf_area *oa, u16 *length)
 	     * this address as a next-hop.
 	     */
 	    ln->data = ipa_to_u32(ifa->addr->ip);
-
-	    ln->metric = ifa->cost;
+	    ln->metric = link_cost;
 	    ln->padding = 0;
 	    i++;
 	  }
@@ -283,7 +283,7 @@ originate_rt_lsa_body(struct ospf_area *oa, u16 *length)
 	    ln->type = LSART_NET;
 	    ln->id = ipa_to_u32(ifa->drip);
 	    ln->data = ipa_to_u32(ifa->addr->ip);
-	    ln->metric = ifa->cost;
+	    ln->metric = link_cost;
 	    ln->padding = 0;
 	    i++;
 	    net_lsa = 1;
@@ -298,7 +298,7 @@ originate_rt_lsa_body(struct ospf_area *oa, u16 *length)
 	  ln->type = LSART_VLNK;
 	  ln->id = neigh->rid;
 	  ln->data = ipa_to_u32(ifa->addr->ip);
-	  ln->metric = ifa->cost;
+	  ln->metric = link_cost;
 	  ln->padding = 0;
 	  i++;
         }