From 0e3451e5cf761d877f5b99f8ac8acad0236dd4ab Mon Sep 17 00:00:00 2001
From: Renato Westphal <renato@opensourcerouting.org>
Date: Tue, 13 Jun 2017 10:32:24 -0300
Subject: [PATCH] ldpd: fix issues with dual-stack adjacencies

Handling configuration changes from single-stack mode to dual-stack mode
(and vice-versa) is tricky. This patch attempts to solve all issues that
might happen on such circumstances.

Signed-off-by: Renato Westphal <renato@opensourcerouting.org>
---
 ldpd/adjacency.c | 22 ++++++----------------
 ldpd/hello.c     | 17 ++++++++++++-----
 2 files changed, 18 insertions(+), 21 deletions(-)

diff --git a/ldpd/adjacency.c b/ldpd/adjacency.c
index 3ec57f1589..89314aa2c3 100644
--- a/ldpd/adjacency.c
+++ b/ldpd/adjacency.c
@@ -109,17 +109,19 @@ adj_new(struct in_addr lsr_id, struct hello_source *source,
 	return (adj);
 }
 
-static void
-adj_del_single(struct adj *adj)
+void
+adj_del(struct adj *adj, uint32_t notif_status)
 {
+	struct nbr	*nbr = adj->nbr;
+
 	log_debug("%s: lsr-id %s, %s (%s)", __func__, inet_ntoa(adj->lsr_id),
 	    log_hello_src(&adj->source), af_name(adj_get_af(adj)));
 
 	adj_stop_itimer(adj);
 
 	RB_REMOVE(global_adj_head, &global.adj_tree, adj);
-	if (adj->nbr)
-		RB_REMOVE(nbr_adj_head, &adj->nbr->adj_tree, adj);
+	if (nbr)
+		RB_REMOVE(nbr_adj_head, &nbr->adj_tree, adj);
 	switch (adj->source.type) {
 	case HELLO_LINK:
 		RB_REMOVE(ia_adj_head, &adj->source.link.ia->adj_tree, adj);
@@ -130,15 +132,6 @@ adj_del_single(struct adj *adj)
 	}
 
 	free(adj);
-}
-
-void
-adj_del(struct adj *adj, uint32_t notif_status)
-{
-	struct nbr	*nbr = adj->nbr;
-	struct adj	*atmp;
-
-	adj_del_single(adj);
 
 	/*
 	 * If the neighbor still exists but none of its remaining
@@ -146,8 +139,6 @@ adj_del(struct adj *adj, uint32_t notif_status)
 	 * then delete it.
 	 */
 	if (nbr && nbr_adj_count(nbr, nbr->af) == 0) {
-		RB_FOREACH_SAFE(adj, nbr_adj_head, &nbr->adj_tree, atmp)
-			adj_del_single(adj);
 		session_shutdown(nbr, notif_status, 0, 0);
 		nbr_del(nbr);
 	}
@@ -194,7 +185,6 @@ adj_itimer(struct thread *thread)
 			tnbr_del(leconf, adj->source.target);
 			return (0);
 		}
-		adj->source.target->adj = NULL;
 	}
 
 	adj_del(adj, S_HOLDTIME_EXP);
diff --git a/ldpd/hello.c b/ldpd/hello.c
index dd67f68f70..d17e80008e 100644
--- a/ldpd/hello.c
+++ b/ldpd/hello.c
@@ -214,6 +214,7 @@ recv_hello(struct in_addr lsr_id, struct ldp_msg *msg, int af,
 		    __func__, inet_ntoa(lsr_id));
 		return;
 	}
+	ds_tlv = (tlvs_rcvd & F_HELLO_TLV_RCVD_DS) ? 1 : 0;
 
 	/* implicit transport address */
 	if (!(tlvs_rcvd & F_HELLO_TLV_RCVD_ADDR))
@@ -291,11 +292,21 @@ recv_hello(struct in_addr lsr_id, struct ldp_msg *msg, int af,
 		source.link.src_addr = *src;
 	}
 
+	debug_hello_recv("%s lsr-id %s transport-address %s holdtime %u%s",
+	    log_hello_src(&source), inet_ntoa(lsr_id), log_addr(af, &trans_addr),
+	     holdtime, (ds_tlv) ? " (dual stack TLV present)" : "");
+
 	adj = adj_find(lsr_id, &source);
+	if (adj && adj->ds_tlv != ds_tlv) {
+		/*
+		 * Transient condition, ignore packet and wait until adjacency
+		 * times out.
+		 */
+		return;
+	}
 	nbr = nbr_find_ldpid(lsr_id.s_addr);
 
 	/* check dual-stack tlv */
-	ds_tlv = (tlvs_rcvd & F_HELLO_TLV_RCVD_DS) ? 1 : 0;
 	if (ds_tlv && trans_pref != leconf->trans_pref) {
 		/*
 	 	 * RFC 7552 - Section 6.1.1:
@@ -420,10 +431,6 @@ recv_hello(struct in_addr lsr_id, struct ldp_msg *msg, int af,
 	else
 		adj_stop_itimer(adj);
 
-	debug_hello_recv("%s lsr-id %s transport-address %s holdtime %u%s",
-	    log_hello_src(&source), inet_ntoa(lsr_id), log_addr(af, &trans_addr),
-	     holdtime, (ds_tlv) ? " (dual stack TLV present)" : "");
-
 	if (nbr && nbr->state == NBR_STA_PRESENT && !nbr_pending_idtimer(nbr) &&
 	    nbr_session_active_role(nbr) && !nbr_pending_connect(nbr))
 		nbr_establish_connection(nbr);