avahi: T6908: add option to define max-cache entries (#4207)

* avahi: T6908: reduce runtime overhead in smoketests by using setUpClass/tearDownClass

* avahi: T6908: add option to define mdns-repeater max-cache entries

Add CLI option to configure `cache-entries-max` entries in Avahi daemon
configuration.

Default value of 4096 for "cache-entries" CVLI node was retrieved from
source code.

data/templates/mdns-repeater/avahi-daemon.conf.j2

@@ -6,6 +6,9 @@ allow-interfaces={{ interface | join(', ') }}
 {% if browse_domain is vyos_defined and browse_domain | length %}
 browse-domains={{ browse_domain | join(', ') }}
 {% endif %}
+{% if cache_entries is vyos_defined %}
+cache-entries-max={{ cache_entries }}
+{% endif %}
 disallow-other-stacks=no
 
 [wide-area]

interface-definitions/service_mdns_repeater.xml.in

@@ -67,6 +67,23 @@
                   <multi/>
                 </properties>
               </leafNode>
+              <leafNode name="cache-entries">
+                <properties>
+                  <help>Number of resource records cached per interface</help>
+                  <valueHelp>
+                    <format>u32:0</format>
+                    <description>Disable caching</description>
+                  </valueHelp>
+                  <valueHelp>
+                    <format>u32:1-65535</format>
+                    <description>Resource records to cache per interface</description>
+                  </valueHelp>
+                  <constraint>
+                    <validator name="numeric" argument="--range 0-65535"/>
+                  </constraint>
+                </properties>
+                <defaultValue>4096</defaultValue>
+              </leafNode>
               <leafNode name="vrrp-disable">
                 <properties>
                   <help>Disables mDNS repeater on VRRP interfaces not in MASTER state</help>

smoketest/scripts/cli/test_service_mdns_repeater.py

@@ -21,36 +21,45 @@
 from configparser import ConfigParser
 from vyos.configsession import ConfigSessionError
 from vyos.utils.process import process_named_running
+from vyos.xml_ref import default_value
 
 base_path = ['service', 'mdns', 'repeater']
 intf_base = ['interfaces', 'dummy']
 config_file = '/run/avahi-daemon/avahi-daemon.conf'
 
-
 class TestServiceMDNSrepeater(VyOSUnitTestSHIM.TestCase):
-    def setUp(self):
-        # Start with a clean CLI instance
-        self.cli_delete(base_path)
+    @classmethod
+    def setUpClass(cls):
+        super(TestServiceMDNSrepeater, cls).setUpClass()
 
-        # Service required a configured IP address on the interface
-        self.cli_set(intf_base + ['dum10', 'address', '192.0.2.1/30'])
-        self.cli_set(intf_base + ['dum10', 'ipv6', 'address', 'no-default-link-local'])
-        self.cli_set(intf_base + ['dum20', 'address', '192.0.2.5/30'])
-        self.cli_set(intf_base + ['dum20', 'address', '2001:db8:0:2::5/64'])
-        self.cli_set(intf_base + ['dum30', 'address', '192.0.2.9/30'])
-        self.cli_set(intf_base + ['dum30', 'address', '2001:db8:0:2::9/64'])
-        self.cli_set(intf_base + ['dum40', 'address', '2001:db8:0:2::11/64'])
-        self.cli_commit()
+        # 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, intf_base + ['dum10', 'address', '192.0.2.1/30'])
+        cls.cli_set(cls, intf_base + ['dum10', 'ipv6', 'address', 'no-default-link-local'])
+        cls.cli_set(cls, intf_base + ['dum20', 'address', '192.0.2.5/30'])
+        cls.cli_set(cls, intf_base + ['dum20', 'address', '2001:db8:0:2::5/64'])
+        cls.cli_set(cls, intf_base + ['dum30', 'address', '192.0.2.9/30'])
+        cls.cli_set(cls, intf_base + ['dum30', 'address', '2001:db8:0:2::9/64'])
+        cls.cli_set(cls, intf_base + ['dum40', 'address', '2001:db8:0:2::11/64'])
+
+        cls.cli_commit(cls)
+
+    @classmethod
+    def tearDownClass(cls):
+        cls.cli_delete(cls, intf_base + ['dum10'])
+        cls.cli_delete(cls, intf_base + ['dum20'])
+        cls.cli_delete(cls, intf_base + ['dum30'])
+        cls.cli_delete(cls, intf_base + ['dum40'])
+
+        cls.cli_commit(cls)
 
     def tearDown(self):
         # Check for running process
         self.assertTrue(process_named_running('avahi-daemon'))
 
         self.cli_delete(base_path)
-        self.cli_delete(intf_base + ['dum10'])
-        self.cli_delete(intf_base + ['dum20'])
-        self.cli_delete(intf_base + ['dum30'])
-        self.cli_delete(intf_base + ['dum40'])
         self.cli_commit()
 
         # Check that there is no longer a running process
@@ -130,5 +139,38 @@ def test_service_ipv6(self):
         self.assertEqual(conf['server']['allow-interfaces'], 'dum30, dum40')
         self.assertEqual(conf['reflector']['enable-reflector'], 'yes')
 
+    def test_service_max_cache_entries(self):
+        cli_default_max_cache = default_value(base_path + ['cache-entries'])
+        self.cli_set(base_path)
+
+        # Need at least two interfaces
+        with self.assertRaises(ConfigSessionError):
+            self.cli_commit()
+        self.cli_set(base_path + ['interface', 'dum20'])
+
+        # Need at least two interfaces
+        with self.assertRaises(ConfigSessionError):
+            self.cli_commit()
+        self.cli_set(base_path + ['interface', 'dum30'])
+
+        self.cli_commit()
+
+        # Validate configuration values
+        conf = ConfigParser(delimiters='=')
+        conf.read(config_file)
+        self.assertEqual(conf['server']['cache-entries-max'], cli_default_max_cache)
+
+        # Set max cache entries
+        cache_entries = '1234'
+        self.cli_set(base_path + ['cache-entries', cache_entries])
+
+        self.cli_commit()
+
+        # Validate configuration values
+        conf = ConfigParser(delimiters='=')
+        conf.read(config_file)
+
+        self.assertEqual(conf['server']['cache-entries-max'], cache_entries)
+
 if __name__ == '__main__':
     unittest.main(verbosity=2)