Remove the active prefix cache in struct rib_entry. I need the space

and it also makes less sense to track this with ECMP or add-path.
Replace the re->active access with prefix_best(re) which does the
check on the spot.
Feedback and OK tb@

5 files changed, 45 insertions, 35 deletions

diff --git a/usr.sbin/bgpd/rde.c b/usr.sbin/bgpd/rde.c
index e220e105624..6d857333807 100644
--- a/usr.sbin/bgpd/rde.c
+++ b/usr.sbin/bgpd/rde.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: rde.c,v 1.542 2022/03/21 13:33:20 claudio Exp $ */
+/*	$OpenBSD: rde.c,v 1.543 2022/03/21 17:35:56 claudio Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -2400,7 +2400,7 @@ rde_dump_rib_as(struct prefix *p, struct rde_aspath *asp, pid_t pid, int flags,
 	rib.validation_state = p->validation_state;
 	rib.flags = 0;
 	re = prefix_re(p);
-	if (re != NULL && re->active == p)
+	if (re != NULL && prefix_best(re) == p)
 		rib.flags |= F_PREF_BEST;
 	if (!peer->conf.ebgp)
 		rib.flags |= F_PREF_INTERNAL;
@@ -2502,7 +2502,7 @@ rde_dump_filter(struct prefix *p, struct ctl_show_rib_request *req, int adjout)
 	re = prefix_re(p);
 	if (asp == NULL)	/* skip pending withdraw in Adj-RIB-Out */
 		return;
-	if ((req->flags & F_CTL_BEST) && re != NULL && re->active != p)
+	if ((req->flags & F_CTL_BEST) && re != NULL && prefix_best(re) != p)
 		return;
 	if ((req->flags & F_CTL_INVALID) &&
 	    (asp->flags & F_ATTR_PARSE_ERR) == 0)
@@ -3713,11 +3713,11 @@ rde_softreconfig_in(struct rib_entry *re, void *bula)
 static void
 rde_softreconfig_out(struct rib_entry *re, void *bula)
 {
-	struct prefix		*p = re->active;
+	struct prefix		*p;
 	struct rde_peer		*peer;
 	uint8_t			 aid = re->prefix->aid;
 
-	if (p == NULL)
+	if ((p = prefix_best(re)) == NULL)
 		/* no valid path for prefix */
 		return;
 
@@ -3750,12 +3750,10 @@ rde_softreconfig_sync_reeval(struct rib_entry *re, void *arg)
 			if (p->flags & PREFIX_NEXTHOP_LINKED)
 				nexthop_unlink(p);
 		}
-		re->active = NULL;
 		return;
 	}
 
 	/* evaluation process is turned on, so evaluate all prefixes again */
-	re->active = NULL;
 	prefixes = re->prefix_h;
 	LIST_INIT(&re->prefix_h);
 
@@ -3777,8 +3775,10 @@ rde_softreconfig_sync_reeval(struct rib_entry *re, void *arg)
 static void
 rde_softreconfig_sync_fib(struct rib_entry *re, void *bula)
 {
-	if (re->active)
-		rde_send_kroute(re_rib(re), re->active, NULL);
+	struct prefix *p;
+
+	if ((p = prefix_best(re)) != NULL)
+		rde_send_kroute(re_rib(re), p, NULL);
 }
 
 static void
diff --git a/usr.sbin/bgpd/rde.h b/usr.sbin/bgpd/rde.h
index eebe96aeb32..09c0871358a 100644
--- a/usr.sbin/bgpd/rde.h
+++ b/usr.sbin/bgpd/rde.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: rde.h,v 1.249 2022/03/21 13:33:20 claudio Exp $ */
+/*	$OpenBSD: rde.h,v 1.250 2022/03/21 17:35:56 claudio Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Claudio Jeker <claudio@openbsd.org> and
@@ -43,7 +43,6 @@ RB_HEAD(rib_tree, rib_entry);
 struct rib_entry {
 	RB_ENTRY(rib_entry)	 rib_e;
 	struct prefix_list	 prefix_h;
-	struct prefix		*active;	/* for fast access */
 	struct pt_entry		*prefix;
 	uint16_t		 rib_id;
 	uint16_t		 lock;
@@ -499,8 +498,10 @@ communities_unref(struct rde_community *comm)
 int	community_to_rd(struct community *, uint64_t *);
 
 /* rde_decide.c */
-int	prefix_eligible(struct prefix *);
-void	prefix_evaluate(struct rib_entry *, struct prefix *, struct prefix *);
+int		 prefix_eligible(struct prefix *);
+struct prefix	*prefix_best(struct rib_entry *);
+void		 prefix_evaluate(struct rib_entry *, struct prefix *,
+		     struct prefix *);
 
 /* rde_filter.c */
 void	rde_apply_set(struct filter_set_head *, struct rde_peer *,
diff --git a/usr.sbin/bgpd/rde_decide.c b/usr.sbin/bgpd/rde_decide.c
index a28d98188f6..0c88165e23d 100644
--- a/usr.sbin/bgpd/rde_decide.c
+++ b/usr.sbin/bgpd/rde_decide.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: rde_decide.c,v 1.89 2022/03/03 13:06:15 claudio Exp $ */
+/*	$OpenBSD: rde_decide.c,v 1.90 2022/03/21 17:35:56 claudio Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Claudio Jeker <claudio@openbsd.org>
@@ -443,6 +443,23 @@ prefix_eligible(struct prefix *p)
 	return 1;
 }
 
+struct prefix *
+prefix_best(struct rib_entry *re)
+{
+	struct prefix	*xp;
+	struct rib	*rib;
+
+	rib = re_rib(re);
+	if (rib->flags & F_RIB_NOEVALUATE)
+		/* decision process is turned off */
+		return NULL;
+
+	xp = LIST_FIRST(&re->prefix_h);
+	if (xp != NULL && !prefix_eligible(xp))
+		xp = NULL;
+	return xp;
+}
+
 /*
  * Find the correct place to insert the prefix in the prefix list.
  * If the active prefix has changed we need to send an update also special
@@ -453,7 +470,7 @@ prefix_eligible(struct prefix *p)
 void
 prefix_evaluate(struct rib_entry *re, struct prefix *new, struct prefix *old)
 {
-	struct prefix	*xp;
+	struct prefix	*xp, *active;
 	struct rib	*rib;
 
 	rib = re_rib(re);
@@ -463,19 +480,11 @@ prefix_evaluate(struct rib_entry *re, struct prefix *new, struct prefix *old)
 			LIST_REMOVE(old, entry.list.rib);
 		if (new != NULL)
 			LIST_INSERT_HEAD(&re->prefix_h, new, entry.list.rib);
-		if (re->active) {
-			/*
-			 * During reloads it is possible that the decision
-			 * process is turned off but prefixes are still
-			 * active. Clean up now to ensure that the RIB
-			 * is consistant.
-			 */
-			rde_generate_updates(rib, NULL, re->active, 0);
-			re->active = NULL;
-		}
 		return;
 	}
 
+	active = prefix_best(re);
+
 	if (old != NULL)
 		prefix_remove(old, re);
 
@@ -490,16 +499,15 @@ prefix_evaluate(struct rib_entry *re, struct prefix *new, struct prefix *old)
 	 * If the active prefix changed or the active prefix was removed
 	 * and added again then generate an update.
 	 */
-	if (re->active != xp || (old != NULL && xp == old)) {
+	if (active != xp || (old != NULL && xp == old)) {
 		/*
 		 * Send update withdrawing re->active and adding xp
 		 * but remember that xp may be NULL aka ineligible.
 		 * Additional decision may be made by the called functions.
 		 */
-		rde_generate_updates(rib, xp, re->active, 0);
+		rde_generate_updates(rib, xp, active, 0);
 		if ((rib->flags & F_RIB_NOFIB) == 0)
-			rde_send_kroute(rib, xp, re->active);
-		re->active = xp;
+			rde_send_kroute(rib, xp, active);
 		return;
 	}
 
@@ -510,5 +518,5 @@ prefix_evaluate(struct rib_entry *re, struct prefix *new, struct prefix *old)
 	 */
 	if (rde_evaluate_all())
 		if ((new != NULL && prefix_eligible(new)) || old != NULL)
-			rde_generate_updates(rib, re->active, NULL, 1);
+			rde_generate_updates(rib, prefix_best(re), NULL, 1);
 }
diff --git a/usr.sbin/bgpd/rde_peer.c b/usr.sbin/bgpd/rde_peer.c
index c3c0647537e..94148550c27 100644
--- a/usr.sbin/bgpd/rde_peer.c
+++ b/usr.sbin/bgpd/rde_peer.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: rde_peer.c,v 1.13 2022/02/06 09:51:19 claudio Exp $ */
+/*	$OpenBSD: rde_peer.c,v 1.14 2022/03/21 17:35:56 claudio Exp $ */
 
 /*
  * Copyright (c) 2019 Claudio Jeker <claudio@openbsd.org>
@@ -308,6 +308,7 @@ static void
 rde_up_dump_upcall(struct rib_entry *re, void *ptr)
 {
 	struct rde_peer		*peer = ptr;
+	struct prefix		*p;
 
 	if (peer->state != PEER_UP)
 		return;
@@ -319,10 +320,10 @@ rde_up_dump_upcall(struct rib_entry *re, void *ptr)
 		    aid2str(re->prefix->aid));
 
 	/* no eligible prefix, not even for 'evaluate all' */
-	if (re->active == NULL)
+	if ((p = prefix_best(re)) == NULL)
 		return;
 
-	up_generate_updates(out_rules, peer, re->active, NULL);
+	up_generate_updates(out_rules, peer, p, NULL);
 }
 
 static void
diff --git a/usr.sbin/bgpd/rde_rib.c b/usr.sbin/bgpd/rde_rib.c
index 0be448ce6f5..0ccdffdd39e 100644
--- a/usr.sbin/bgpd/rde_rib.c
+++ b/usr.sbin/bgpd/rde_rib.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: rde_rib.c,v 1.235 2022/03/21 13:33:20 claudio Exp $ */
+/*	$OpenBSD: rde_rib.c,v 1.236 2022/03/21 17:35:56 claudio Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Claudio Jeker <claudio@openbsd.org>
@@ -1523,7 +1523,7 @@ prefix_evaluate_all(struct prefix *p, enum nexthop_state state,
 		 */
 		if (state == NEXTHOP_REACH) {
 			if ((re_rib(re)->flags & F_RIB_NOFIB) == 0 &&
-			    p == re->active)
+			    p == prefix_best(re))
 				rde_send_kroute(re_rib(re), p, NULL);
 		}
 		return;