bgpd: Add Notification CEASE BFD Down message

Related: https://datatracker.ietf.org/doc/html/draft-ietf-idr-bfd-subcode

When BFD Down notification comes and BGP is configured to track on BFD events,
send BGP Cease/BFD Down notification to the peer.

If RFC 8538 is enabled (Notification support for Graceful-Restart), notification
should be encapsulated into Hard Reset message.

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

bgpd/bgp_bfd.c

@@ -40,6 +40,7 @@
 #include "bgpd/bgp_bfd.h"
 #include "bgpd/bgp_debug.h"
 #include "bgpd/bgp_vty.h"
+#include "bgpd/bgp_packet.h"
 
 DEFINE_MTYPE_STATIC(BGPD, BFD_CONFIG, "BFD configuration data");
 
@@ -68,6 +69,12 @@ static void bfd_session_status_update(struct bfd_session_params *bsp,
 			return;
 		}
 		peer->last_reset = PEER_DOWN_BFD_DOWN;
+
+		/* draft-ietf-idr-bfd-subcode */
+		if (BGP_IS_VALID_STATE_FOR_NOTIF(peer->status))
+			bgp_notify_send(peer, BGP_NOTIFY_CEASE,
+					BGP_NOTIFY_CEASE_BFD_DOWN);
+
 		BGP_EVENT_ADD(peer, BGP_Stop);
 	}
 

bgpd/bgp_debug.c

@@ -170,6 +170,7 @@ static const struct message bgp_notify_cease_msg[] = {
 	 "/Connection Collision Resolution"},
 	{BGP_NOTIFY_CEASE_OUT_OF_RESOURCE, "/Out of Resources"},
 	{BGP_NOTIFY_CEASE_HARD_RESET, "/Hard Reset"},
+	{BGP_NOTIFY_CEASE_BFD_DOWN, "/BFD Down"},
 	{0}};
 
 static const struct message bgp_notify_route_refresh_msg[] = {

bgpd/bgp_packet.c

@@ -814,6 +814,7 @@ bool bgp_notify_send_hard_reset(struct peer *peer, uint8_t code,
 		case BGP_NOTIFY_CEASE_ADMIN_SHUTDOWN:
 		case BGP_NOTIFY_CEASE_PEER_UNCONFIG:
 		case BGP_NOTIFY_CEASE_HARD_RESET:
+		case BGP_NOTIFY_CEASE_BFD_DOWN:
 			return true;
 		case BGP_NOTIFY_CEASE_ADMIN_RESET:
 			/* Provide user control:

bgpd/bgpd.h

@@ -1870,6 +1870,7 @@ struct bgp_nlri {
 #define BGP_NOTIFY_CEASE_COLLISION_RESOLUTION    7
 #define BGP_NOTIFY_CEASE_OUT_OF_RESOURCE         8
 #define BGP_NOTIFY_CEASE_HARD_RESET 9
+#define BGP_NOTIFY_CEASE_BFD_DOWN 10
 
 /* BGP_NOTIFY_ROUTE_REFRESH_ERR sub codes (RFC 7313). */
 #define BGP_NOTIFY_ROUTE_REFRESH_INVALID_MSG_LEN 1

tests/topotests/bfd_bgp_cbit_topo3/r3/bgpd.conf

@@ -14,6 +14,7 @@ router bgp 102
  neighbor 2001:db8:1::1 remote-as external
  neighbor 2001:db8:1::1 update-source 2001:db8:4::1
  neighbor 2001:db8:1::1 bfd
+ neighbor 2001:db8:1::1 bfd check-control-plane-failure
  neighbor 2001:db8:1::1 ebgp-multihop 5
  !
  address-family ipv4 unicast

tests/topotests/bgp_bfd_down_cease_notification/r1/bfdd.conf

@@ -0,0 +1,6 @@
+bfd
+ peer 192.168.255.2 interface r1-eth0
+ exit
+ !
+exit
+!

tests/topotests/bgp_bfd_down_cease_notification/r1/bgpd.conf

@@ -0,0 +1,9 @@
+router bgp 65001
+ no bgp ebgp-requires-policy
+ neighbor 192.168.255.2 remote-as external
+ neighbor 192.168.255.2 timers 3 10
+ neighbor 192.168.255.2 bfd
+ address-family ipv4
+  redistribute connected
+ exit-address-family
+!

tests/topotests/bgp_bfd_down_cease_notification/r1/zebra.conf

@@ -0,0 +1,9 @@
+!
+interface lo
+ ip address 172.16.255.1/32
+!
+interface r1-eth0
+ ip address 192.168.255.1/24
+!
+ip forwarding
+!

tests/topotests/bgp_bfd_down_cease_notification/r2/bfdd.conf

@@ -0,0 +1,6 @@
+bfd
+ peer 192.168.255.1 interface r2-eth0
+ exit
+ !
+exit
+!

tests/topotests/bgp_bfd_down_cease_notification/r2/bgpd.conf

@@ -0,0 +1,9 @@
+router bgp 65002
+ no bgp ebgp-requires-policy
+ neighbor 192.168.255.1 remote-as external
+ neighbor 192.168.255.1 timers 3 10
+ neighbor 192.168.255.1 bfd
+ address-family ipv4
+  redistribute connected
+ exit-address-family
+!

tests/topotests/bgp_bfd_down_cease_notification/r2/zebra.conf

@@ -0,0 +1,9 @@
+!
+interface lo
+ ip address 172.16.255.2/32
+!
+interface r2-eth0
+ ip address 192.168.255.2/24
+!
+ip forwarding
+!

tests/topotests/bgp_bfd_down_cease_notification/test_bgp_bfd_down_cease_notification.py

@@ -0,0 +1,124 @@
+#!/usr/bin/env python
+
+#
+# bgp_bfd_down_cease_notification.py
+#
+# Copyright (c) 2022 by
+# Donatas Abraitis <donatas@opensourcerouting.org>
+#
+# Permission to use, copy, modify, and/or distribute this software
+# for any purpose with or without fee is hereby granted, provided
+# that the above copyright notice and this permission notice appear
+# in all copies.
+#
+# THE SOFTWARE IS PROVIDED "AS IS" AND NETDEF DISCLAIMS ALL WARRANTIES
+# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NETDEF BE LIABLE FOR
+# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY
+# DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
+# WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
+# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+# OF THIS SOFTWARE.
+#
+
+"""
+Check if Cease/BFD Down notification message is sent/received
+when the BFD is down.
+"""
+
+import os
+import sys
+import json
+import pytest
+import functools
+
+CWD = os.path.dirname(os.path.realpath(__file__))
+sys.path.append(os.path.join(CWD, "../"))
+
+# pylint: disable=C0413
+from lib import topotest
+from lib.topogen import Topogen, TopoRouter, get_topogen
+from lib.common_config import kill_router_daemons, step
+
+pytestmark = [pytest.mark.bfdd, pytest.mark.bgpd]
+
+
+def build_topo(tgen):
+    for routern in range(1, 3):
+        tgen.add_router("r{}".format(routern))
+
+    switch = tgen.add_switch("s1")
+    switch.add_link(tgen.gears["r1"])
+    switch.add_link(tgen.gears["r2"])
+
+
+def setup_module(mod):
+    tgen = Topogen(build_topo, mod.__name__)
+    tgen.start_topology()
+
+    router_list = tgen.routers()
+
+    for i, (rname, router) in enumerate(router_list.items(), 1):
+        router.load_config(
+            TopoRouter.RD_ZEBRA, os.path.join(CWD, "{}/zebra.conf".format(rname))
+        )
+        router.load_config(
+            TopoRouter.RD_BGP, os.path.join(CWD, "{}/bgpd.conf".format(rname))
+        )
+        router.load_config(
+            TopoRouter.RD_BFD, os.path.join(CWD, "{}/bfdd.conf".format(rname))
+        )
+
+    tgen.start_router()
+
+
+def teardown_module(mod):
+    tgen = get_topogen()
+    tgen.stop_topology()
+
+
+def test_bgp_bfd_down_notification():
+    tgen = get_topogen()
+
+    if tgen.routers_have_failure():
+        pytest.skip(tgen.errors)
+
+    r2 = tgen.gears["r2"]
+
+    def _bgp_converge():
+        output = json.loads(r2.vtysh_cmd("show ip bgp neighbor 192.168.255.1 json"))
+        expected = {
+            "192.168.255.1": {
+                "bgpState": "Established",
+                "addressFamilyInfo": {"ipv4Unicast": {"acceptedPrefixCounter": 2}},
+                "peerBfdInfo": {"status": "Up"},
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    def _bgp_bfd_down_notification():
+        output = json.loads(r2.vtysh_cmd("show ip bgp neighbor 192.168.255.1 json"))
+        expected = {
+            "192.168.255.1": {
+                "lastNotificationReason": "Cease/BFD Down",
+            }
+        }
+        return topotest.json_cmp(output, expected)
+
+    step("Initial BGP converge")
+    test_func = functools.partial(_bgp_converge)
+    _, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert result is None, "Failed to see BGP convergence on R2"
+
+    step("Kill bfdd on R2")
+    kill_router_daemons(tgen, "r2", ["bfdd"])
+
+    step("Check if we received Cease/BFD Down notification message")
+    test_func = functools.partial(_bgp_bfd_down_notification)
+    _, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert result is None, "Failed to see BGP Cease/BFD Down notification message on R2"
+
+
+if __name__ == "__main__":
+    args = ["-s"] + sys.argv[1:]
+    sys.exit(pytest.main(args))