bgp: T3967: add support for conditional advertisement

The BGP conditional advertisement feature uses the non-exist-map or the
exist-map and the advertise-map keywords of the neighbor advertise-map command
in order to track routes by the route prefix.

non-exist-map
=============
* If a route prefix is not present in the output of non-exist-map command, then
  advertise the route specified by the advertise-map command.

* If a route prefix is present in the output of non-exist-map command, then do
  not advertise the route specified by the addvertise-map command.

exist-map
=========
* If a route prefix is present in the output of exist-map command, then
  advertise the route specified by the advertise-map command.

* If a route prefix is not present in the output of exist-map command, then do
  not advertise the route specified by the advertise-map command.

This feature is useful when some prefixes are advertised to one of its peers
only if the information from the other peer is not present (due to failure in
peering session or partial reachability etc).

The conditional BGP announcements are sent in addition to the normal
announcements that a BGP router sends to its peer.

CLI nodes can be found under:
* set protocols bgp neighbor <ip> address-family <afi> conditional-advertisement
* set protocols bgp peer-group <p> address-family <afi> conditional-advertisement

4 files changed, 157 insertions, 15 deletions

diff --git a/data/templates/frr/bgpd.frr.tmpl b/data/templates/frr/bgpd.frr.tmpl
index 9bb42fd2d..45e0544b7 100644
--- a/data/templates/frr/bgpd.frr.tmpl
+++ b/data/templates/frr/bgpd.frr.tmpl
@@ -146,6 +146,17 @@
 {%       if afi_config.as_override is defined %}
   neighbor {{ neighbor }} as-override
 {%       endif %}
+{%       if afi_config.conditionally_advertise is defined and afi_config.conditionally_advertise is not none %}
+{%         if afi_config.conditionally_advertise.advertise_map is defined and afi_config.conditionally_advertise.advertise_map is not none %}
+{%           set exist_non_exist_map = 'exist-map' %}
+{%           if afi_config.conditionally_advertise.exist_map is defined and afi_config.conditionally_advertise.exist_map is not none %}
+{%             set exist_non_exist_map = 'exist-map ' ~ afi_config.conditionally_advertise.exist_map %}
+{%           elif afi_config.conditionally_advertise.non_exist_map is defined and afi_config.conditionally_advertise.non_exist_map is not none %}
+{%             set exist_non_exist_map = 'non-exist-map ' ~ afi_config.conditionally_advertise.non_exist_map %}
+{%           endif %}
+  neighbor {{ neighbor }} advertise-map {{ afi_config.conditionally_advertise.advertise_map }} {{ exist_non_exist_map }}
+{%         endif %}
+{%       endif %}
 {%       if afi_config.remove_private_as is defined %}
   neighbor {{ neighbor }} remove-private-AS
 {%       endif %}
diff --git a/interface-definitions/include/bgp/neighbor-afi-ipv4-ipv6-common.xml.i b/interface-definitions/include/bgp/neighbor-afi-ipv4-ipv6-common.xml.i
index 498662b0a..f3fc4444c 100644
--- a/interface-definitions/include/bgp/neighbor-afi-ipv4-ipv6-common.xml.i
+++ b/interface-definitions/include/bgp/neighbor-afi-ipv4-ipv6-common.xml.i
@@ -11,6 +11,61 @@
     <valueless/>
   </properties>
 </leafNode>
+<node name="conditionally-advertise">
+  <properties>
+    <help>Use route-map to conditionally advertise routes</help>
+  </properties>
+  <children>
+    <leafNode name="advertise-map">
+      <properties>
+        <help>Route-map to conditionally advertise routes</help>
+        <completionHelp>
+          <path>policy route-map</path>
+        </completionHelp>
+        <valueHelp>
+          <format>txt</format>
+          <description>Route map name</description>
+        </valueHelp>
+        <constraint>
+          <regex>^[-_a-zA-Z0-9.]+$</regex>
+        </constraint>
+        <constraintErrorMessage>Name of route-map can only contain alpha-numeric letters, hyphen and underscores</constraintErrorMessage>
+      </properties>
+    </leafNode>
+    <leafNode name="exist-map">
+      <properties>
+        <help>Advertise routes only if prefixes in exist-map are installed in BGP table</help>
+        <completionHelp>
+          <path>policy route-map</path>
+        </completionHelp>
+        <valueHelp>
+          <format>txt</format>
+          <description>Route map name</description>
+        </valueHelp>
+        <constraint>
+          <regex>^[-_a-zA-Z0-9.]+$</regex>
+        </constraint>
+        <constraintErrorMessage>Name of route-map can only contain alpha-numeric letters, hyphen and underscores</constraintErrorMessage>
+      </properties>
+    </leafNode>
+    <leafNode name="non-exist-map">
+      <properties>
+        <help>Advertise routes only if prefixes in non-exist-map are not installed in BGP table</help>
+        <completionHelp>
+          <path>policy route-map</path>
+        </completionHelp>
+        <valueHelp>
+          <format>txt</format>
+          <description>Route map name</description>
+        </valueHelp>
+        <constraint>
+          <regex>^[-_a-zA-Z0-9.]+$</regex>
+        </constraint>
+        <constraintErrorMessage>Name of route-map can only contain alpha-numeric letters, hyphen and underscores</constraintErrorMessage>
+      </properties>
+    </leafNode>
+  </children>
+</node>
 #include <include/bgp/afi-allowas-in.xml.i>
 <leafNode name="as-override">
   <properties>
diff --git a/smoketest/scripts/cli/test_protocols_bgp.py b/smoketest/scripts/cli/test_protocols_bgp.py
index 22cc3785f..d7230baf4 100755
--- a/smoketest/scripts/cli/test_protocols_bgp.py
+++ b/smoketest/scripts/cli/test_protocols_bgp.py
@@ -59,11 +59,14 @@ neighbor_config = {
         'no_cap_nego'  : '',
         'port'         : '667',
         'cap_strict'   : '',
+        'advertise_map': route_map_in,
+        'non_exist_map': route_map_out,
         'pfx_list_in'  : prefix_list_in,
         'pfx_list_out' : prefix_list_out,
         'no_send_comm_std' : '',
         },
     '192.0.2.3' : {
+        'advertise_map': route_map_in,
         'description'  : 'foo bar baz',
         'remote_as'    : '200',
         'passive'      : '',
@@ -72,6 +75,8 @@ neighbor_config = {
         'peer_group'   : 'foo',
         },
     '2001:db8::1' : {
+        'advertise_map': route_map_in,
+        'exist_map'    : route_map_out,
         'cap_dynamic'  : '',
         'cap_ext_next' : '',
         'remote_as'    : '123',
@@ -104,6 +109,8 @@ neighbor_config = {
 
 peer_group_config = {
     'foo' : {
+        'advertise_map': route_map_in,
+        'exist_map'    : route_map_out,
         'bfd'          : '',
         'remote_as'    : '100',
         'passive'      : '',
@@ -113,6 +120,7 @@ peer_group_config = {
         'ttl_security': '5',
         },
     'foo-bar' : {
+        'advertise_map': route_map_in,
         'description'  : 'foo peer bar group',
         'remote_as'    : '200',
         'shutdown'     : '',
@@ -122,8 +130,9 @@ peer_group_config = {
         'pfx_list_out' : prefix_list_out,
         'no_send_comm_ext' : '',
         },
-    'baz' : {
     'foo-bar_baz' : {
+        'advertise_map': route_map_in,
+        'non_exist_map': route_map_out,
         'bfd_profile'  : bfd_profile,
         'cap_dynamic'  : '',
         'cap_ext_next' : '',
@@ -137,23 +146,34 @@ peer_group_config = {
 }
 
 class TestProtocolsBGP(VyOSUnitTestSHIM.TestCase):
-    def setUp(self):
-        self.cli_set(['policy', 'route-map', route_map_in, 'rule', '10', 'action', 'permit'])
-        self.cli_set(['policy', 'route-map', route_map_out, 'rule', '10', 'action', 'permit'])
-        self.cli_set(['policy', 'prefix-list', prefix_list_in, 'rule', '10', 'action', 'permit'])
-        self.cli_set(['policy', 'prefix-list', prefix_list_in, 'rule', '10', 'prefix', '192.0.2.0/25'])
-        self.cli_set(['policy', 'prefix-list', prefix_list_out, 'rule', '10', 'action', 'permit'])
-        self.cli_set(['policy', 'prefix-list', prefix_list_out, 'rule', '10', 'prefix', '192.0.2.128/25'])
-
-        self.cli_set(['policy', 'prefix-list6', prefix_list_in6, 'rule', '10', 'action', 'permit'])
-        self.cli_set(['policy', 'prefix-list6', prefix_list_in6, 'rule', '10', 'prefix', '2001:db8:1000::/64'])
-        self.cli_set(['policy', 'prefix-list6', prefix_list_out6, 'rule', '10', 'action', 'deny'])
-        self.cli_set(['policy', 'prefix-list6', prefix_list_out6, 'rule', '10', 'prefix', '2001:db8:2000::/64'])
+    @classmethod
+    def setUpClass(cls):
+        super(cls, cls).setUpClass()
+
+        # ensure we can also run this test on a live system - so lets clean
+        # out the current configuration :)
+        cls.cli_delete(cls, base_path)
+
+        cls.cli_set(cls, ['policy', 'route-map', route_map_in, 'rule', '10', 'action', 'permit'])
+        cls.cli_set(cls, ['policy', 'route-map', route_map_out, 'rule', '10', 'action', 'permit'])
+        cls.cli_set(cls, ['policy', 'prefix-list', prefix_list_in, 'rule', '10', 'action', 'permit'])
+        cls.cli_set(cls, ['policy', 'prefix-list', prefix_list_in, 'rule', '10', 'prefix', '192.0.2.0/25'])
+        cls.cli_set(cls, ['policy', 'prefix-list', prefix_list_out, 'rule', '10', 'action', 'permit'])
+        cls.cli_set(cls, ['policy', 'prefix-list', prefix_list_out, 'rule', '10', 'prefix', '192.0.2.128/25'])
+
+        cls.cli_set(cls, ['policy', 'prefix-list6', prefix_list_in6, 'rule', '10', 'action', 'permit'])
+        cls.cli_set(cls, ['policy', 'prefix-list6', prefix_list_in6, 'rule', '10', 'prefix', '2001:db8:1000::/64'])
+        cls.cli_set(cls, ['policy', 'prefix-list6', prefix_list_out6, 'rule', '10', 'action', 'deny'])
+        cls.cli_set(cls, ['policy', 'prefix-list6', prefix_list_out6, 'rule', '10', 'prefix', '2001:db8:2000::/64'])
+
+    @classmethod
+    def tearDownClass(cls):
+        cls.cli_delete(cls, ['policy'])
 
+    def setUp(self):
         self.cli_set(base_path + ['local-as', ASN])
 
     def tearDown(self):
-        self.cli_delete(['policy'])
         self.cli_delete(['vrf'])
         self.cli_delete(base_path)
         self.cli_commit()
@@ -212,7 +232,13 @@ class TestProtocolsBGP(VyOSUnitTestSHIM.TestCase):
             self.assertIn(f' neighbor {peer} addpath-tx-all-paths', frrconfig)
         if 'addpath_per_as' in peer_config:
             self.assertIn(f' neighbor {peer} addpath-tx-bestpath-per-AS', frrconfig)
-
+        if 'advertise_map' in peer_config:
+            base = f' neighbor {peer} advertise-map {peer_config["advertise_map"]}'
+            if 'exist_map' in peer_config:
+                base = f'{base} exist-map {peer_config["exist_map"]}'
+            if 'non_exist_map' in peer_config:
+                base = f'{base} non-exist-map {peer_config["non_exist_map"]}'
+            self.assertIn(base, frrconfig)
 
     def test_bgp_01_simple(self):
         router_id = '127.0.0.1'
@@ -353,6 +379,20 @@ class TestProtocolsBGP(VyOSUnitTestSHIM.TestCase):
             if 'addpath_per_as' in peer_config:
                 self.cli_set(base_path + ['neighbor', peer, 'address-family', afi, 'addpath-tx-per-as'])
 
+            # Conditional advertisement
+            if 'advertise_map' in peer_config:
+                self.cli_set(base_path + ['neighbor', peer, 'address-family', afi, 'conditionally-advertise', 'advertise-map', peer_config["advertise_map"]])
+                # Either exist-map or non-exist-map needs to be specified
+                if 'exist_map' not in peer_config and 'non_exist_map' not in peer_config:
+                    with self.assertRaises(ConfigSessionError):
+                        self.cli_commit()
+                    self.cli_set(base_path + ['neighbor', peer, 'address-family', afi, 'conditionally-advertise', 'exist-map', route_map_in])
+
+                if 'exist_map' in peer_config:
+                    self.cli_set(base_path + ['neighbor', peer, 'address-family', afi, 'conditionally-advertise', 'exist-map', peer_config["exist_map"]])
+                if 'non_exist_map' in peer_config:
+                    self.cli_set(base_path + ['neighbor', peer, 'address-family', afi, 'conditionally-advertise', 'non-exist-map', peer_config["non_exist_map"]])
+
         # commit changes
         self.cli_commit()
 
@@ -421,6 +461,20 @@ class TestProtocolsBGP(VyOSUnitTestSHIM.TestCase):
             if 'addpath_per_as' in config:
                 self.cli_set(base_path + ['peer-group', peer_group, 'address-family', 'ipv4-unicast', 'addpath-tx-per-as'])
 
+            # Conditional advertisement
+            if 'advertise_map' in config:
+                self.cli_set(base_path + ['peer-group', peer_group, 'address-family', 'ipv4-unicast', 'conditionally-advertise', 'advertise-map', config["advertise_map"]])
+                # Either exist-map or non-exist-map needs to be specified
+                if 'exist_map' not in config and 'non_exist_map' not in config:
+                    with self.assertRaises(ConfigSessionError):
+                        self.cli_commit()
+                    self.cli_set(base_path + ['peer-group', peer_group, 'address-family', 'ipv4-unicast', 'conditionally-advertise', 'exist-map', route_map_in])
+
+                if 'exist_map' in config:
+                    self.cli_set(base_path + ['peer-group', peer_group, 'address-family', 'ipv4-unicast', 'conditionally-advertise', 'exist-map', config["exist_map"]])
+                if 'non_exist_map' in config:
+                    self.cli_set(base_path + ['peer-group', peer_group, 'address-family', 'ipv4-unicast', 'conditionally-advertise', 'non-exist-map', config["non_exist_map"]])
+
         for peer, peer_config in neighbor_config.items():
             if 'peer_group' in peer_config:
                 self.cli_set(base_path + ['neighbor', peer, 'peer-group', peer_config['peer_group']])
diff --git a/src/conf_mode/protocols_bgp.py b/src/conf_mode/protocols_bgp.py
index 03fb17ba7..d8704727c 100755
--- a/src/conf_mode/protocols_bgp.py
+++ b/src/conf_mode/protocols_bgp.py
@@ -183,6 +183,28 @@ def verify(bgp):
                     raise ConfigError(f'Neighbor "{peer}" cannot have both ipv6-unicast and ipv6-labeled-unicast configured at the same time!')
 
                 afi_config = peer_config['address_family'][afi]
+
+                if 'conditionally_advertise' in afi_config:
+                    if 'advertise_map' not in afi_config['conditionally_advertise']:
+                        raise ConfigError('Must speficy advertise-map when conditionally-advertise is in use!')
+                    # Verify advertise-map (which is a route-map) exists
+                    verify_route_map(afi_config['conditionally_advertise']['advertise_map'], bgp)
+
+                    if ('exist_map' not in afi_config['conditionally_advertise'] and
+                        'non_exist_map' not in afi_config['conditionally_advertise']):
+                        raise ConfigError('Must either speficy exist-map or non-exist-map when ' \
+                                          'conditionally-advertise is in use!')
+
+                    if {'exist_map', 'non_exist_map'} <= set(afi_config['conditionally_advertise']):
+                        raise ConfigError('Can not specify both exist-map and non-exist-map for ' \
+                                          'conditionally-advertise!')
+
+                    if 'exist_map' in afi_config['conditionally_advertise']:
+                        verify_route_map(afi_config['conditionally_advertise']['exist_map'], bgp)
+
+                    if 'non_exist_map' in afi_config['conditionally_advertise']:
+                        verify_route_map(afi_config['conditionally_advertise']['non_exist_map'], bgp)
+
                 # Validate if configured Prefix list exists
                 if 'prefix_list' in afi_config:
                     for tmp in ['import', 'export']: