Until now AS-ext LSA were always announced with the router as nexthop.

Change this so that the real nexthop is announced if the following
conditions are met:
 - the nexthop is reachable via an OSPF enabled interface
 - the interface is a broadcast or NBMA interface
It does not make sense to announce the nexthop of a point-to-point link
since the traffic has to go through this box anyway. This is closer to
what other systems implement.

1 files changed, 36 insertions, 16 deletions

diff --git a/usr.sbin/ospfd/rde.c b/usr.sbin/ospfd/rde.c
index 4848b820076..88c1d7a4350 100644
--- a/usr.sbin/ospfd/rde.c
+++ b/usr.sbin/ospfd/rde.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: rde.c,v 1.81 2009/06/06 07:31:26 eric Exp $ */
+/*	$OpenBSD: rde.c,v 1.82 2009/10/05 08:20:26 claudio Exp $ */
 
 /*
  * Copyright (c) 2004, 2005 Claudio Jeker <claudio@openbsd.org>
@@ -56,6 +56,7 @@ int		 rde_req_list_exists(struct rde_nbr *, struct lsa_hdr *);
 void		 rde_req_list_del(struct rde_nbr *, struct lsa_hdr *);
 void		 rde_req_list_free(struct rde_nbr *);
 
+struct iface	*rde_asext_lookup(u_int32_t, int);
 struct lsa	*rde_asext_get(struct rroute *);
 struct lsa	*rde_asext_put(struct rroute *);
 
@@ -1033,24 +1034,32 @@ rde_req_list_free(struct rde_nbr *nbr)
 /*
  * as-external LSA handling
  */
-struct lsa *
-rde_asext_get(struct rroute *rr)
+struct iface *
+rde_asext_lookup(u_int32_t prefix, int plen)
 {
 	struct area	*area;
 	struct iface	*iface;
 
-	LIST_FOREACH(area, &rdeconf->area_list, entry)
+	LIST_FOREACH(area, &rdeconf->area_list, entry) {
 		LIST_FOREACH(iface, &area->iface_list, entry) {
 			if ((iface->addr.s_addr & iface->mask.s_addr) ==
-			    rr->kr.prefix.s_addr && iface->mask.s_addr ==
-			    prefixlen2mask(rr->kr.prefixlen)) {
-				/* already announced as (stub) net LSA */
-				log_debug("rde_asext_get: %s/%d is net LSA",
-				    inet_ntoa(rr->kr.prefix), rr->kr.prefixlen);
-				return (NULL);
-			}
+			    (prefix & iface->mask.s_addr) && (plen == -1 ||
+			    iface->mask.s_addr == prefixlen2mask(plen)))
+				return (iface);
 		}
+	}
+	return (NULL);
+}
 
+struct lsa *
+rde_asext_get(struct rroute *rr)
+{
+	if (rde_asext_lookup(rr->kr.prefix.s_addr, rr->kr.prefixlen)) {
+		/* already announced as (stub) net LSA */
+		log_debug("rde_asext_get: %s/%d is net LSA",
+		    inet_ntoa(rr->kr.prefix), rr->kr.prefixlen);
+		return (NULL);
+	}
 	/* update of seqnum is done by lsa_merge */
 	return (orig_asext_lsa(rr, DEFAULT_AGE));
 }
@@ -1138,6 +1147,7 @@ struct lsa *
 orig_asext_lsa(struct rroute *rr, u_int16_t age)
 {
 	struct lsa	*lsa;
+	struct iface	*iface;
 	u_int16_t	 len;
 
 	len = sizeof(struct lsa_hdr) + sizeof(struct lsa_asext);
@@ -1166,12 +1176,22 @@ orig_asext_lsa(struct rroute *rr, u_int16_t age)
 
 	/*
 	 * nexthop -- on connected routes we are the nexthop,
-	 * on all other cases we announce the true nexthop.
-	 * XXX this is wrong as the true nexthop may be outside
-	 * of the ospf cloud and so unreachable. For now we force
-	 * all traffic to be directed to us.
+	 * in other cases we may announce the true nexthop if the
+	 * nexthop is reachable via an OSPF enabled interface but only
+	 * broadcast & NBMA interfaces are considered in that case.
+	 * It does not make sense to announce the nexthop of a point-to-point
+	 * link since the traffic has to go through this box anyway.
+	 * Some implementations actually check that there are multiple
+	 * neighbors on the particular segment, we skip that check.
 	 */
-	lsa->data.asext.fw_addr = 0;
+	iface = rde_asext_lookup(rr->kr.nexthop.s_addr, -1);
+	if (rr->kr.flags & F_CONNECTED)
+		lsa->data.asext.fw_addr = 0;
+	else if (iface && (iface->type == IF_TYPE_BROADCAST ||
+	    iface->type == IF_TYPE_NBMA))
+		lsa->data.asext.fw_addr = rr->kr.nexthop.s_addr;
+	else
+		lsa->data.asext.fw_addr = 0;
 
 	lsa->data.asext.metric = htonl(rr->metric);
 	lsa->data.asext.ext_tag = htonl(rr->kr.ext_tag);