Merge pull request #18518 from opensourcerouting/fix/backport_18498_10.0stable/10.0

bgpd: Retain the routes if we do a clear with N-bit set for Graceful-Restart (backport)

2 files changed, 39 insertions, 19 deletions

diff --git a/bgpd/bgp_packet.c b/bgpd/bgp_packet.c
index 24742b4c07..f372d419b6 100644
--- a/bgpd/bgp_packet.c
+++ b/bgpd/bgp_packet.c
@@ -1037,6 +1037,13 @@ static void bgp_notify_send_internal(struct peer_connection *connection,
 	/* Add packet to peer's output queue */
 	stream_fifo_push(connection->obuf, s);
 
+	/* If Graceful-Restart N-bit (Notification) is exchanged,
+	 * and it's not a Hard Reset, let's retain the routes.
+	 */
+	if (bgp_has_graceful_restart_notification(peer) && !hard_reset &&
+	    CHECK_FLAG(peer->sflags, PEER_STATUS_NSF_MODE))
+		SET_FLAG(peer->sflags, PEER_STATUS_NSF_WAIT);
+
 	bgp_peer_gr_flags_update(peer);
 	BGP_GR_ROUTER_DETECT_AND_SEND_CAPABILITY_TO_ZEBRA(peer->bgp,
 							  peer->bgp->peer);
diff --git a/tests/topotests/bgp_gr_notification/test_bgp_gr_notification.py b/tests/topotests/bgp_gr_notification/test_bgp_gr_notification.py
index 2ffcb723ec..9e886771f9 100644
--- a/tests/topotests/bgp_gr_notification/test_bgp_gr_notification.py
+++ b/tests/topotests/bgp_gr_notification/test_bgp_gr_notification.py
@@ -165,8 +165,8 @@ def test_bgp_administrative_reset_gr():
         }
         return topotest.json_cmp(output, expected)
 
-    def _bgp_check_gr_notification_stale():
-        output = json.loads(r1.vtysh_cmd("show bgp ipv4 unicast 172.16.255.2/32 json"))
+    def _bgp_check_gr_notification_stale(router, prefix):
+        output = json.loads(router.vtysh_cmd(f"show bgp ipv4 unicast {prefix} json"))
         expected = {
             "paths": [
                 {
@@ -177,34 +177,47 @@ def test_bgp_administrative_reset_gr():
         }
         return topotest.json_cmp(output, expected)
 
-    def _bgp_clear_r1_and_shutdown():
-        r2.vtysh_cmd(
-            """
-            clear ip bgp 192.168.255.1
-            configure terminal
-             router bgp
-              neighbor 192.168.255.1 shutdown
-            """
-        )
-
     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("Reset and shutdown R1")
-    _bgp_clear_r1_and_shutdown()
+    step("Reset and delay the session establishement for R1")
+    r1.vtysh_cmd(
+        """
+        configure terminal"
+        router bgp
+         neighbor 192.168.255.2 timers delayopen 60
+        """
+    )
+    r2.vtysh_cmd(
+        """
+        configure terminal"
+        router bgp
+         neighbor 192.168.255.1 timers delayopen 60
+        """
+    )
+    r2.vtysh_cmd("clear ip bgp 192.168.255.1")
+
+    step("Check if stale routes are retained on R1")
+    test_func = functools.partial(
+        _bgp_check_gr_notification_stale, r1, "172.16.255.2/32"
+    )
+    _, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert result is None, "Failed to see retained stale routes on R1"
+
+    step("Check if stale routes are retained on R2")
+    test_func = functools.partial(
+        _bgp_check_gr_notification_stale, r2, "172.16.255.1/32"
+    )
+    _, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
+    assert result is None, "Failed to see retained stale routes on R2"
 
     step("Check if Hard Reset notification wasn't sent from R2")
     test_func = functools.partial(_bgp_check_hard_reset)
     _, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
     assert result is None, "Failed to send Administrative Reset notification from R2"
 
-    step("Check if stale routes are retained on R1")
-    test_func = functools.partial(_bgp_check_gr_notification_stale)
-    _, result = topotest.run_and_expect(test_func, None, count=60, wait=0.5)
-    assert result is None, "Failed to see retained stale routes on R1"
-
 
 if __name__ == "__main__":
     args = ["-s"] + sys.argv[1:]