Properly implement the exponential backoff timer on session initialization

According with the section 2.5.3 of RFC 5036, an LSR must throttle its
session setup retry attempts with an exponential backoff in situations
where Initialization messages are being NAK'd (because of disagreements
on session parameters). It doesn't mention using this procedure for TCP
connection failures. With that said, start the inactive delay timer only
after receiving an appropriate notification message.

When playing the active role of the initialization process, throttle the
session setup retry attempts by not connecting to the remote peer. When
playing the passive role, throttle the session setup retry attempts by
delaying the processing of the received Initialization message.

Diff by Renato Westphal, adjusted by myself

5 files changed, 37 insertions, 12 deletions

diff --git a/usr.sbin/ldpd/init.c b/usr.sbin/ldpd/init.c
index 0a940e562dd..90937841f53 100644
--- a/usr.sbin/ldpd/init.c
+++ b/usr.sbin/ldpd/init.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: init.c,v 1.10 2013/06/01 19:28:55 claudio Exp $ */
+/*	$OpenBSD: init.c,v 1.11 2013/06/04 01:32:16 claudio Exp $ */
 
 /*
  * Copyright (c) 2009 Michele Marchetto <michele@openbsd.org>
@@ -107,7 +107,8 @@ recv_init(struct nbr *nbr, char *buf, u_int16_t len)
 	else
 		nbr->keepalive = ntohs(sess.keepalive_time);
 
-	nbr_fsm(nbr, NBR_EVT_INIT_RCVD);
+	if (!nbr_pending_idtimer(nbr))
+		nbr_fsm(nbr, NBR_EVT_INIT_RCVD);
 
 	return (ntohs(init.length));
 }
diff --git a/usr.sbin/ldpd/ldp.h b/usr.sbin/ldpd/ldp.h
index b810d19a3dd..115d23deae8 100644
--- a/usr.sbin/ldpd/ldp.h
+++ b/usr.sbin/ldpd/ldp.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: ldp.h,v 1.11 2013/06/01 01:34:57 claudio Exp $ */
+/*	$OpenBSD: ldp.h,v 1.12 2013/06/04 01:32:16 claudio Exp $ */
 
 /*
  * Copyright (c) 2009 Michele Marchetto <michele@openbsd.org>
@@ -49,6 +49,7 @@
 #define	MAX_HELLO_INTERVAL	0xffff	/* XXX */
 
 #define	INIT_DELAY_TMR		15
+#define	MAX_DELAY_TMR		120
 #define DEFAULT_NBR_TMOUT	86400	/* 24 hours */
 
 /* LDP message types */
diff --git a/usr.sbin/ldpd/ldpe.h b/usr.sbin/ldpd/ldpe.h
index 8b0976aa990..ee70736ca29 100644
--- a/usr.sbin/ldpd/ldpe.h
+++ b/usr.sbin/ldpd/ldpe.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: ldpe.h,v 1.23 2013/06/04 00:56:49 claudio Exp $ */
+/*	$OpenBSD: ldpe.h,v 1.24 2013/06/04 01:32:16 claudio Exp $ */
 
 /*
  * Copyright (c) 2004, 2005, 2008 Esben Norby <norby@openbsd.org>
@@ -60,6 +60,7 @@ struct nbr {
 
 	int			 fd;
 	int			 state;
+	int			 idtimer_cnt;
 
 	u_int16_t		 holdtime;
 	u_int16_t		 keepalive;
diff --git a/usr.sbin/ldpd/neighbor.c b/usr.sbin/ldpd/neighbor.c
index 907f7015ae2..13b2df1d0c4 100644
--- a/usr.sbin/ldpd/neighbor.c
+++ b/usr.sbin/ldpd/neighbor.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: neighbor.c,v 1.34 2013/06/04 00:56:49 claudio Exp $ */
+/*	$OpenBSD: neighbor.c,v 1.35 2013/06/04 01:32:16 claudio Exp $ */
 
 /*
  * Copyright (c) 2009 Michele Marchetto <michele@openbsd.org>
@@ -219,7 +219,6 @@ nbr_fsm(struct nbr *nbr, enum nbr_event event)
 		ldpe_imsg_compose_lde(IMSG_NEIGHBOR_DOWN, nbr->peerid, 0,
 		    NULL, 0);
 		session_close(nbr);
-		nbr_start_idtimer(nbr);
 		break;
 	case NBR_ACT_NOTHING:
 		/* do nothing */
@@ -446,13 +445,13 @@ nbr_idtimer(int fd, short event, void *arg)
 {
 	struct nbr *nbr = arg;
 
-	if (!nbr_session_active_role(nbr))
-		return;
-
 	log_debug("nbr_idtimer: neighbor ID %s peerid %lu", inet_ntoa(nbr->id),
 	    nbr->peerid);
 
-	nbr_establish_connection(nbr);
+	if (nbr_session_active_role(nbr))
+		nbr_establish_connection(nbr);
+	else if (nbr->state == NBR_STA_INITIAL)
+		nbr_fsm(nbr, NBR_EVT_INIT_RCVD);
 }
 
 void
@@ -461,7 +460,23 @@ nbr_start_idtimer(struct nbr *nbr)
 	struct timeval	tv;
 
 	timerclear(&tv);
+
 	tv.tv_sec = INIT_DELAY_TMR;
+	switch(nbr->idtimer_cnt) {
+	default:
+		/* do not further increase the counter */
+		tv.tv_sec = MAX_DELAY_TMR;
+		break;
+	case 2:
+		tv.tv_sec *= 2;
+		/* FALLTHROUGH */
+	case 1:
+		tv.tv_sec *= 2;
+		/* FALLTHROUGH */
+	case 0:
+		nbr->idtimer_cnt++;
+		break;
+	}
 
 	if (evtimer_add(&nbr->initdelay_timer, &tv) == -1)
 		fatal("nbr_start_idtimer");
@@ -561,7 +576,6 @@ nbr_establish_connection(struct nbr *nbr)
 		}
 		log_debug("nbr_establish_connection: error while "
 		    "connecting to %s", inet_ntoa(nbr->addr));
-		nbr_start_idtimer(nbr);
 		close(nbr->fd);
 		return (-1);
 	}
@@ -585,6 +599,8 @@ nbr_act_session_operational(struct nbr *nbr)
 {
 	struct lde_nbr	 rn;
 
+	nbr->idtimer_cnt = 0;
+
 	bzero(&rn, sizeof(rn));
 	rn.id.s_addr = nbr->id.s_addr;
 
diff --git a/usr.sbin/ldpd/notification.c b/usr.sbin/ldpd/notification.c
index 580167e5568..be57dd1acc4 100644
--- a/usr.sbin/ldpd/notification.c
+++ b/usr.sbin/ldpd/notification.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: notification.c,v 1.12 2013/06/01 19:42:07 claudio Exp $ */
+/*	$OpenBSD: notification.c,v 1.13 2013/06/04 01:32:16 claudio Exp $ */
 
 /*
  * Copyright (c) 2009 Michele Marchetto <michele@openbsd.org>
@@ -111,6 +111,12 @@ recv_notification(struct nbr *nbr, char *buf, u_int16_t len)
 		    notification_name(ntohl(st.status_code)));
 
 	if (st.status_code & htonl(STATUS_FATAL)) {
+		if (st.status_code == htonl(S_NO_HELLO) ||
+		    st.status_code == htonl(S_PARM_ADV_MODE) ||
+		    st.status_code == htonl(S_MAX_PDU_LEN) ||
+		    st.status_code == htonl(S_PARM_L_RANGE))
+			nbr_start_idtimer(nbr);
+
 		nbr_fsm(nbr, NBR_EVT_CLOSE_SESSION);
 		return (-1);
 	}