bgpd: Add CLI knob to enable graceful restart for BGP notifications

N-bit flag should be exchanged in BGP OPEN messages, not only when the
bgpd is restarted/started.

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>

bgpd/bgp_open.c

@@ -1435,12 +1435,17 @@ static void bgp_peer_send_gr_capability(struct stream *s, struct peer *peer,
 	restart_time = peer->bgp->restart_time;
 	if (peer->bgp->t_startup) {
 		SET_FLAG(restart_time, GRACEFUL_RESTART_R_BIT);
-		SET_FLAG(restart_time, GRACEFUL_RESTART_N_BIT);
 		SET_FLAG(peer->cap, PEER_CAP_GRACEFUL_RESTART_R_BIT_ADV);
-		SET_FLAG(peer->cap, PEER_CAP_GRACEFUL_RESTART_N_BIT_ADV);
-
 		if (BGP_DEBUG(graceful_restart, GRACEFUL_RESTART))
-			zlog_debug("[BGP_GR] Sending R-Bit/N-Bit for peer: %s",
+			zlog_debug("[BGP_GR] Sending R-Bit for peer: %s",
+				   peer->host);
+	}
+
+	if (CHECK_FLAG(peer->bgp->flags, BGP_FLAG_GRACEFUL_NOTIFICATION)) {
+		SET_FLAG(restart_time, GRACEFUL_RESTART_N_BIT);
+		SET_FLAG(peer->cap, PEER_CAP_GRACEFUL_RESTART_N_BIT_ADV);
+		if (BGP_DEBUG(graceful_restart, GRACEFUL_RESTART))
+			zlog_debug("[BGP_GR] Sending N-Bit for peer: %s",
 				   peer->host);
 	}
 

bgpd/bgp_vty.c

@@ -123,6 +123,10 @@ FRR_CFG_DEFAULT_BOOL(BGP_SUPPRESS_DUPLICATES,
 	{ .val_bool = false, .match_version = "< 7.6", },
 	{ .val_bool = true },
 );
+FRR_CFG_DEFAULT_BOOL(BGP_GRACEFUL_NOTIFICATION,
+	{ .val_bool = false, .match_version = "< 8.3", },
+	{ .val_bool = true },
+);
 
 DEFINE_HOOK(bgp_inst_config_write,
 		(struct bgp *bgp, struct vty *vty),
@@ -569,6 +573,8 @@ int bgp_get_vty(struct bgp **bgp, as_t *as, const char *name,
 			SET_FLAG((*bgp)->flags, BGP_FLAG_EBGP_REQUIRES_POLICY);
 		if (DFLT_BGP_SUPPRESS_DUPLICATES)
 			SET_FLAG((*bgp)->flags, BGP_FLAG_SUPPRESS_DUPLICATES);
+		if (DFLT_BGP_GRACEFUL_NOTIFICATION)
+			SET_FLAG((*bgp)->flags, BGP_FLAG_GRACEFUL_NOTIFICATION);
 
 		ret = BGP_SUCCESS;
 	}
@@ -2868,6 +2874,24 @@ DEFUN (no_bgp_graceful_restart_preserve_fw,
 	return CMD_SUCCESS;
 }
 
+DEFPY (bgp_graceful_restart_notification,
+	bgp_graceful_restart_notification_cmd,
+	"[no$no] bgp graceful-restart notification",
+	NO_STR
+	BGP_STR
+	"Graceful restart capability parameters\n"
+	"Indicate Graceful Restart support for BGP NOTIFICATION messages\n")
+{
+	VTY_DECLVAR_CONTEXT(bgp, bgp);
+
+	if (no)
+		UNSET_FLAG(bgp->flags, BGP_FLAG_GRACEFUL_NOTIFICATION);
+	else
+		SET_FLAG(bgp->flags, BGP_FLAG_GRACEFUL_NOTIFICATION);
+
+	return CMD_SUCCESS;
+}
+
 DEFUN (bgp_graceful_restart_disable,
 	bgp_graceful_restart_disable_cmd,
 	"bgp graceful-restart-disable",
@@ -17258,6 +17282,14 @@ int bgp_config_write(struct vty *vty)
 			vty_out(vty, " bgp graceful-restart restart-time %u\n",
 				bgp->restart_time);
 
+		if (!!CHECK_FLAG(bgp->flags, BGP_FLAG_GRACEFUL_NOTIFICATION) !=
+		    SAVE_BGP_GRACEFUL_NOTIFICATION)
+			vty_out(vty, " %sbgp graceful-restart notification\n",
+				CHECK_FLAG(bgp->flags,
+					   BGP_FLAG_GRACEFUL_NOTIFICATION)
+					? ""
+					: "no ");
+
 		if (bgp->select_defer_time != BGP_DEFAULT_SELECT_DEFERRAL_TIME)
 			vty_out(vty,
 				" bgp graceful-restart select-defer-time %u\n",
@@ -17890,6 +17922,7 @@ void bgp_vty_init(void)
 			&no_bgp_graceful_restart_select_defer_time_cmd);
 	install_element(BGP_NODE, &bgp_graceful_restart_preserve_fw_cmd);
 	install_element(BGP_NODE, &no_bgp_graceful_restart_preserve_fw_cmd);
+	install_element(BGP_NODE, &bgp_graceful_restart_notification_cmd);
 
 	install_element(BGP_NODE, &bgp_graceful_restart_disable_eor_cmd);
 	install_element(BGP_NODE, &no_bgp_graceful_restart_disable_eor_cmd);

bgpd/bgpd.h

@@ -488,6 +488,8 @@ struct bgp {
 #define BGP_FLAG_SUPPRESS_FIB_PENDING (1 << 26)
 #define BGP_FLAG_SUPPRESS_DUPLICATES (1 << 27)
 #define BGP_FLAG_PEERTYPE_MULTIPATH_RELAX (1 << 29)
+/* Indicate Graceful Restart support for BGP NOTIFICATION messages */
+#define BGP_FLAG_GRACEFUL_NOTIFICATION (1 << 30)
 
 	/* BGP default address-families.
 	 * New peers inherit enabled afi/safis from bgp instance.

doc/user/bgp.rst

@@ -947,6 +947,15 @@ However, it MUST defer route selection for an address family until it either.
    expires. The stale path timer is started when the router receives a Route-Refresh
    BoRR message.
 
+.. clicmd:: bgp graceful-restart notification
+
+   Indicate Graceful Restart support for BGP NOTIFICATION messages.
+
+   After changing this parameter, you have to reset the peers in order to advertise
+   N-bit in Graceful Restart capability.
+
+   Enabled by default.
+
 .. _bgp-per-peer-graceful-restart:
 
 BGP Per Peer Graceful Restart