From d7fc0e677e8c6804e00e770b4bd2c080c7ba028a Mon Sep 17 00:00:00 2001
From: Don Slice <dslice@cumulusnetworks.com>
Date: Tue, 3 Dec 2019 14:02:20 +0000
Subject: [PATCH] zebra: send RA lifetime of 0 before ceasing to advertise RAs

Problem reported by testing agency that RFC4861 section 6.2.5
states that a router should send an RA with a lifetime of 0
before ceasing to send RAs on the interface, or when the interace
is shutdown, or the router is shutdown.  This fix adds that capability.

Ticket: CM-27061
Signed-off-by: Don Slice <dslice@cumulusnetworks.com>
---
 zebra/interface.c |  2 ++
 zebra/main.c      |  3 +++
 zebra/rtadv.c     | 48 ++++++++++++++++++++++++++++++++++++++++++-----
 zebra/rtadv.h     |  2 ++
 4 files changed, 50 insertions(+), 5 deletions(-)

diff --git a/zebra/interface.c b/zebra/interface.c
index 20b05dfb3..bcb833b8d 100644
--- a/zebra/interface.c
+++ b/zebra/interface.c
@@ -1977,6 +1977,8 @@ DEFUN (shutdown_if,
 	struct zebra_if *if_data;
 
 	if (ifp->ifindex != IFINDEX_INTERNAL) {
+		/* send RA lifetime of 0 before stopping. rfc4861/6.2.5 */
+		rtadv_stop_ra(ifp);
 		ret = if_unset_flags(ifp, IFF_UP);
 		if (ret < 0) {
 			vty_out(vty, "Can't shutdown interface\n");
diff --git a/zebra/main.c b/zebra/main.c
index 731c4e161..e0408c0bc 100644
--- a/zebra/main.c
+++ b/zebra/main.c
@@ -145,6 +145,9 @@ static void sigint(void)
 	atomic_store_explicit(&zrouter.in_shutdown, true,
 			      memory_order_relaxed);
 
+	/* send RA lifetime of 0 before stopping. rfc4861/6.2.5 */
+	rtadv_stop_ra_all();
+
 	frr_early_fini();
 
 	zebra_dplane_pre_finish();
diff --git a/zebra/rtadv.c b/zebra/rtadv.c
index 0adf654aa..5dd6012f6 100644
--- a/zebra/rtadv.c
+++ b/zebra/rtadv.c
@@ -166,7 +166,8 @@ static int rtadv_recv_packet(struct zebra_vrf *zvrf, int sock, uint8_t *buf,
 #define RTADV_MSG_SIZE 4096
 
 /* Send router advertisement packet. */
-static void rtadv_send_packet(int sock, struct interface *ifp)
+static void rtadv_send_packet(int sock, struct interface *ifp,
+			      ipv6_nd_suppress_ra_status stop)
 {
 	struct msghdr msg;
 	struct iovec iov;
@@ -252,7 +253,10 @@ static void rtadv_send_packet(int sock, struct interface *ifp)
 		zif->rtadv.AdvDefaultLifetime != -1
 			? zif->rtadv.AdvDefaultLifetime
 			: MAX(1, 0.003 * zif->rtadv.MaxRtrAdvInterval);
-	rtadv->nd_ra_router_lifetime = htons(pkt_RouterLifetime);
+
+	/* send RA lifetime of 0 before stopping. rfc4861/6.2.5 */
+	rtadv->nd_ra_router_lifetime =
+		(stop == RA_SUPPRESS) ? htons(0) : htons(pkt_RouterLifetime);
 	rtadv->nd_ra_reachable = htonl(zif->rtadv.AdvReachableTime);
 	rtadv->nd_ra_retransmit = htonl(0);
 
@@ -512,7 +516,7 @@ static int rtadv_timer(struct thread *thread)
 							ifp->name);
 
 					rtadv_send_packet(rtadv_get_socket(zvrf),
-							  ifp);
+							  ifp, RA_ENABLE);
 				} else {
 					zif->rtadv.AdvIntervalTimer -= period;
 					if (zif->rtadv.AdvIntervalTimer <= 0) {
@@ -526,7 +530,7 @@ static int rtadv_timer(struct thread *thread)
 								.MaxRtrAdvInterval;
 						rtadv_send_packet(
 							  rtadv_get_socket(zvrf),
-							  ifp);
+							  ifp, RA_ENABLE);
 					}
 				}
 			}
@@ -556,7 +560,7 @@ static void rtadv_process_solicit(struct interface *ifp)
 	if ((zif->rtadv.UseFastRexmit)
 	    || (zif->rtadv.AdvIntervalTimer <=
 		(zif->rtadv.MaxRtrAdvInterval - MIN_DELAY_BETWEEN_RAS))) {
-		rtadv_send_packet(rtadv_get_socket(zvrf), ifp);
+		rtadv_send_packet(rtadv_get_socket(zvrf), ifp, RA_ENABLE);
 		zif->rtadv.AdvIntervalTimer = zif->rtadv.MaxRtrAdvInterval;
 	} else
 		zif->rtadv.AdvIntervalTimer = MIN_DELAY_BETWEEN_RAS;
@@ -911,6 +915,8 @@ static void ipv6_nd_suppress_ra_set(struct interface *ifp,
 	if (status == RA_SUPPRESS) {
 		/* RA is currently enabled */
 		if (zif->rtadv.AdvSendAdvertisements) {
+			rtadv_send_packet(rtadv_get_socket(zvrf), ifp,
+					  RA_SUPPRESS);
 			zif->rtadv.AdvSendAdvertisements = 0;
 			zif->rtadv.AdvIntervalTimer = 0;
 			zvrf->rtadv.adv_if_count--;
@@ -1012,6 +1018,38 @@ stream_failure:
 	return;
 }
 
+/*
+ * send router lifetime value of zero in RAs on this interface since we're
+ * ceasing to advertise and want to let our neighbors know.
+ * RFC 4861 secion 6.2.5
+ */
+void rtadv_stop_ra(struct interface *ifp)
+{
+	struct zebra_if *zif;
+	struct zebra_vrf *zvrf;
+
+	zif = ifp->info;
+	zvrf = vrf_info_lookup(ifp->vrf_id);
+
+	if (zif->rtadv.AdvSendAdvertisements)
+		rtadv_send_packet(rtadv_get_socket(zvrf), ifp, RA_SUPPRESS);
+}
+
+/*
+ * send router lifetime value of zero in RAs on all interfaces since we're
+ * ceasing to advertise globally and want to let all of our neighbors know
+ * RFC 4861 secion 6.2.5
+ */
+void rtadv_stop_ra_all(void)
+{
+	struct vrf *vrf;
+	struct interface *ifp;
+
+	RB_FOREACH (vrf, vrf_name_head, &vrfs_by_name)
+		FOR_ALL_INTERFACES (vrf, ifp)
+			rtadv_stop_ra(ifp);
+}
+
 void zebra_interface_radv_disable(ZAPI_HANDLER_ARGS)
 {
 	zebra_interface_radv_set(client, hdr, msg, zvrf, 0);
diff --git a/zebra/rtadv.h b/zebra/rtadv.h
index 409959d08..63cec9443 100644
--- a/zebra/rtadv.h
+++ b/zebra/rtadv.h
@@ -140,6 +140,8 @@ typedef enum {
 
 extern void rtadv_init(struct zebra_vrf *zvrf);
 extern void rtadv_terminate(struct zebra_vrf *zvrf);
+extern void rtadv_stop_ra(struct interface *ifp);
+extern void rtadv_stop_ra_all(void);
 extern void rtadv_cmd_init(void);
 extern void zebra_interface_radv_disable(ZAPI_HANDLER_ARGS);
 extern void zebra_interface_radv_enable(ZAPI_HANDLER_ARGS);
-- 
2.39.5