mdns: T5615: Allow controlling IP version to use for mDNS repeater

This commit adds a new configuration option to the mDNS repeater service
to allow controlling which IP version to use for mDNS repeater.

Additionally, publishing AAAA record over IPv4 and A record over IPv6 is
disabled as suggested.

See:
- https://github.com/lathiat/avahi/issues/117#issuecomment-1651475104
- https://bugzilla.redhat.com/show_bug.cgi?id=669627#c2

(cherry picked from commit e66f7075ee12ae3107d29efaf683442c3535e8b9)

4 files changed, 111 insertions, 16 deletions

diff --git a/data/templates/mdns-repeater/avahi-daemon.j2 b/data/templates/mdns-repeater/avahi-daemon.j2
index e0dfd897e..d562c048f 100644
--- a/data/templates/mdns-repeater/avahi-daemon.j2
+++ b/data/templates/mdns-repeater/avahi-daemon.j2
@@ -1,7 +1,7 @@
 ### Autogenerated by service_mdns-repeater.py ###
 [server]
-use-ipv4=yes
-use-ipv6=yes
+use-ipv4={{ 'yes' if ip_version in ['ipv4', 'both'] else 'no' }}
+use-ipv6={{ 'yes' if ip_version in ['ipv6', 'both'] else 'no' }}
 allow-interfaces={{ interface | join(', ') }}
 {% if browse_domain is vyos_defined and browse_domain | length %}
 browse-domains={{ browse_domain | join(', ') }}
@@ -17,6 +17,8 @@ disable-user-service-publishing=yes
 publish-addresses=no
 publish-hinfo=no
 publish-workstation=no
+publish-aaaa-on-ipv4=no
+publish-a-on-ipv6=no
 
 [reflector]
 enable-reflector=yes
diff --git a/interface-definitions/service-mdns-repeater.xml.in b/interface-definitions/service-mdns-repeater.xml.in
index 653dbbbe4..67870946c 100644
--- a/interface-definitions/service-mdns-repeater.xml.in
+++ b/interface-definitions/service-mdns-repeater.xml.in
@@ -15,6 +15,31 @@
             <children>
               #include <include/generic-disable-node.xml.i>
               #include <include/generic-interface-multi.xml.i>
+              <leafNode name="ip-version">
+                <properties>
+                  <help>IP address version to use</help>
+                  <valueHelp>
+                    <format>_ipv4</format>
+                    <description>Use only IPv4 address</description>
+                  </valueHelp>
+                  <valueHelp>
+                    <format>_ipv6</format>
+                    <description>Use only IPv6 address</description>
+                  </valueHelp>
+                  <valueHelp>
+                    <format>both</format>
+                    <description>Use both IPv4 and IPv6 address</description>
+                  </valueHelp>
+                  <completionHelp>
+                    <list>ipv4 ipv6 both</list>
+                  </completionHelp>
+                  <constraint>
+                    <regex>(ipv[46]|both)</regex>
+                  </constraint>
+                  <constraintErrorMessage>IP Version must be literal 'ipv4', 'ipv6' or 'both'</constraintErrorMessage>
+                </properties>
+                <defaultValue>both</defaultValue>
+              </leafNode>
               <leafNode name="browse-domain">
                 <properties>
                   <help>mDNS browsing domains in addition to the default one</help>
diff --git a/smoketest/scripts/cli/test_service_mdns-repeater.py b/smoketest/scripts/cli/test_service_mdns-repeater.py
index 9a9839025..f2fb3b509 100755
--- a/smoketest/scripts/cli/test_service_mdns-repeater.py
+++ b/smoketest/scripts/cli/test_service_mdns-repeater.py
@@ -19,6 +19,7 @@ import unittest
 from base_vyostest_shim import VyOSUnitTestSHIM
 
 from configparser import ConfigParser
+from vyos.configsession import ConfigSessionError
 from vyos.utils.process import process_named_running
 
 base_path = ['service', 'mdns', 'repeater']
@@ -27,6 +28,20 @@ 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)
+
+        # 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()
+
     def tearDown(self):
         # Check for running process
         self.assertTrue(process_named_running('avahi-daemon'))
@@ -34,24 +49,23 @@ class TestServiceMDNSrepeater(VyOSUnitTestSHIM.TestCase):
         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
         self.assertFalse(process_named_running('avahi-daemon'))
 
-    def test_service(self):
+    def test_service_dual_stack(self):
         # mDNS browsing domains in addition to the default one (local)
         domains = ['dom1.home.arpa', 'dom2.home.arpa']
 
         # mDNS services to be repeated
         services = ['_ipp._tcp', '_smb._tcp', '_ssh._tcp']
 
-        # 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 + ['dum20', 'address', '192.0.2.5/30'])
-
-        self.cli_set(base_path + ['interface', 'dum10'])
+        self.cli_set(base_path + ['ip-version', 'both'])
         self.cli_set(base_path + ['interface', 'dum20'])
+        self.cli_set(base_path + ['interface', 'dum30'])
 
         for domain in domains:
             self.cli_set(base_path + ['browse-domain', domain])
@@ -65,10 +79,56 @@ class TestServiceMDNSrepeater(VyOSUnitTestSHIM.TestCase):
         conf = ConfigParser(delimiters='=')
         conf.read(config_file)
 
-        self.assertEqual(conf['server']['allow-interfaces'], 'dum10, dum20')
+        self.assertEqual(conf['server']['use-ipv4'], 'yes')
+        self.assertEqual(conf['server']['use-ipv6'], 'yes')
+        self.assertEqual(conf['server']['allow-interfaces'], 'dum20, dum30')
         self.assertEqual(conf['server']['browse-domains'], ', '.join(domains))
         self.assertEqual(conf['reflector']['enable-reflector'], 'yes')
         self.assertEqual(conf['reflector']['reflect-filters'], ', '.join(services))
 
+    def test_service_ipv4(self):
+        # partcipating interfaces should have IPv4 addresses
+        self.cli_set(base_path + ['ip-version', 'ipv4'])
+        self.cli_set(base_path + ['interface', 'dum10'])
+        self.cli_set(base_path + ['interface', 'dum40'])
+
+        # exception is raised if partcipating interfaces do not have IPv4 address
+        with self.assertRaises(ConfigSessionError):
+            self.cli_commit()
+        self.cli_delete(base_path + ['interface', 'dum40'])
+        self.cli_set(base_path + ['interface', 'dum20'])
+        self.cli_commit()
+
+        # Validate configuration values
+        conf = ConfigParser(delimiters='=')
+        conf.read(config_file)
+
+        self.assertEqual(conf['server']['use-ipv4'], 'yes')
+        self.assertEqual(conf['server']['use-ipv6'], 'no')
+        self.assertEqual(conf['server']['allow-interfaces'], 'dum10, dum20')
+        self.assertEqual(conf['reflector']['enable-reflector'], 'yes')
+
+    def test_service_ipv6(self):
+        # partcipating interfaces should have IPv6 addresses
+        self.cli_set(base_path + ['ip-version', 'ipv6'])
+        self.cli_set(base_path + ['interface', 'dum10'])
+        self.cli_set(base_path + ['interface', 'dum30'])
+
+        # exception is raised if partcipating interfaces do not have IPv4 address
+        with self.assertRaises(ConfigSessionError):
+            self.cli_commit()
+        self.cli_delete(base_path + ['interface', 'dum10'])
+        self.cli_set(base_path + ['interface', 'dum40'])
+        self.cli_commit()
+
+        # Validate configuration values
+        conf = ConfigParser(delimiters='=')
+        conf.read(config_file)
+
+        self.assertEqual(conf['server']['use-ipv4'], 'no')
+        self.assertEqual(conf['server']['use-ipv6'], 'yes')
+        self.assertEqual(conf['server']['allow-interfaces'], 'dum30, dum40')
+        self.assertEqual(conf['reflector']['enable-reflector'], 'yes')
+
 if __name__ == '__main__':
     unittest.main(verbosity=2)
diff --git a/src/conf_mode/service_mdns-repeater.py b/src/conf_mode/service_mdns-repeater.py
index a2c90b537..d4b8ef8c4 100755
--- a/src/conf_mode/service_mdns-repeater.py
+++ b/src/conf_mode/service_mdns-repeater.py
@@ -18,7 +18,7 @@ import os
 
 from json import loads
 from sys import exit
-from netifaces import ifaddresses, interfaces, AF_INET
+from netifaces import ifaddresses, interfaces, AF_INET, AF_INET6
 
 from vyos.config import Config
 from vyos.ifconfig.vrrp import VRRP
@@ -36,18 +36,22 @@ def get_config(config=None):
         conf = config
     else:
         conf = Config()
+
     base = ['service', 'mdns', 'repeater']
-    mdns = conf.get_config_dict(base, key_mangling=('-', '_'), get_first_key=True)
+    if not conf.exists(base):
+        return None
+
+    mdns = conf.get_config_dict(base, key_mangling=('-', '_'),
+                                no_tag_node_value_mangle=True,
+                                get_first_key=True,
+                                with_recursive_defaults=True)
 
     if mdns:
         mdns['vrrp_exists'] = conf.exists('high-availability vrrp')
     return mdns
 
 def verify(mdns):
-    if not mdns:
-        return None
-
-    if 'disable' in mdns:
+    if not mdns or 'disable' in mdns:
         return None
 
     # We need at least two interfaces to repeat mDNS advertisments
@@ -60,10 +64,14 @@ def verify(mdns):
         if interface not in interfaces():
             raise ConfigError(f'Interface "{interface}" does not exist!')
 
-        if AF_INET not in ifaddresses(interface):
+        if mdns['ip_version'] in ['ipv4', 'both'] and AF_INET not in ifaddresses(interface):
             raise ConfigError('mDNS repeater requires an IPv4 address to be '
                                   f'configured on interface "{interface}"')
 
+        if mdns['ip_version'] in ['ipv6', 'both'] and AF_INET6 not in ifaddresses(interface):
+            raise ConfigError('mDNS repeater requires an IPv6 address to be '
+                                  f'configured on interface "{interface}"')
+
     return None
 
 # Get VRRP states from interfaces, returns only interfaces where state is MASTER