From ee2c84b2f0cc13d71122bd2ee0640bb13aa8040e Mon Sep 17 00:00:00 2001
From: Christian Poessinger <christian@poessinger.com>
Date: Sun, 12 Dec 2021 10:06:17 +0100
Subject: bgp: T4069: add "parameters fast-convergence" CLI option

Whenever BGP peer address becomes unreachable we must bring down the BGP
session immediately. Currently only single-hop EBGP sessions are brought down
immediately. IBGP and multi-hop EBGP sessions wait for hold-timer expiry to
bring down the sessions.

This new configuration option helps user to teardown BGP sessions immediately
whenever peer becomes unreachable.

This configuration is available at the bgp level. When enabled, configuration
is applied to all the neighbors configured in that bgp instance.
---
 data/templates/frr/bgpd.frr.tmpl                               | 3 +++
 interface-definitions/include/bgp/protocol-common-config.xml.i | 6 ++++++
 smoketest/scripts/cli/test_protocols_bgp.py                    | 2 ++
 3 files changed, 11 insertions(+)

diff --git a/data/templates/frr/bgpd.frr.tmpl b/data/templates/frr/bgpd.frr.tmpl
index cae53d09c..351e4a7ed 100644
--- a/data/templates/frr/bgpd.frr.tmpl
+++ b/data/templates/frr/bgpd.frr.tmpl
@@ -510,6 +510,9 @@ router bgp {{ local_as }} {{ 'vrf ' ~ vrf if vrf is defined and vrf is not none
 {%       endfor %}
 {%     endif %}
 {%   endif %}
+{%   if parameters.fast_convergence is defined %}
+  bgp fast-convergence
+{%   endif %}
 {%   if parameters.graceful_restart is defined %}
  bgp graceful-restart {{ 'stalepath-time ' ~ parameters.graceful_restart.stalepath_time if parameters.graceful_restart.stalepath_time is defined }}
 {%   endif %}
diff --git a/interface-definitions/include/bgp/protocol-common-config.xml.i b/interface-definitions/include/bgp/protocol-common-config.xml.i
index 351ee8eda..5dd4e522b 100644
--- a/interface-definitions/include/bgp/protocol-common-config.xml.i
+++ b/interface-definitions/include/bgp/protocol-common-config.xml.i
@@ -1363,6 +1363,12 @@
         <valueless/>
       </properties>
     </leafNode>
+    <leafNode name="fast-convergence">
+      <properties>
+        <help>Teardown sessions immediately whenever peer becomes unreachable</help>
+        <valueless/>
+      </properties>
+    </leafNode>
     <node name="graceful-restart">
       <properties>
         <help>Graceful restart capability parameters</help>
diff --git a/smoketest/scripts/cli/test_protocols_bgp.py b/smoketest/scripts/cli/test_protocols_bgp.py
index 8282d507a..2693ca5ba 100755
--- a/smoketest/scripts/cli/test_protocols_bgp.py
+++ b/smoketest/scripts/cli/test_protocols_bgp.py
@@ -241,6 +241,7 @@ class TestProtocolsBGP(VyOSUnitTestSHIM.TestCase):
         self.cli_set(base_path + ['parameters', 'bestpath', 'compare-routerid'])
 
         self.cli_set(base_path + ['parameters', 'conditional-advertisement', 'timer', cond_adv_timer])
+        self.cli_set(base_path + ['parameters', 'fast-convergence'])
 
         # AFI maximum path support
         self.cli_set(base_path + ['address-family', 'ipv4-unicast', 'maximum-paths', 'ebgp', max_path_v4])
@@ -258,6 +259,7 @@ class TestProtocolsBGP(VyOSUnitTestSHIM.TestCase):
         self.assertIn(f' bgp log-neighbor-changes', frrconfig)
         self.assertIn(f' bgp default local-preference {local_pref}', frrconfig)
         self.assertIn(f' bgp conditional-advertisement timer {cond_adv_timer}', frrconfig)
+        self.assertIn(f' bgp fast-convergence', frrconfig)
         self.assertIn(f' bgp graceful-restart stalepath-time {stalepath_time}', frrconfig)
         self.assertIn(f' bgp graceful-shutdown', frrconfig)
         self.assertIn(f' bgp bestpath as-path multipath-relax', frrconfig)
-- 
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