Make advertisement intervals for radvd configurable

Currently a global setting that is applied for all managed radvd
processes. Per-process setting could be done in the future.

For large clouds, it may be useful to increase the intervals, to reduce
multicast storms.

Co-Authored-By: Brian Haley <brian.haley@hpe.com>

DocImpact Router advertisement intervals for radvd are now configurable
Related-Bug: #1532338

Change-Id: I6cc313599f0ee12f7d51d073a22321221fca263f

neutron/agent/linux/ra.py

@@ -38,13 +38,19 @@ OPTS = [
     cfg.StrOpt('ra_confs',
                default='$state_path/ra',
                help=_('Location to store IPv6 RA config files')),
+    cfg.IntOpt('min_rtr_adv_interval',
+               default=3,
+               help=_('MinRtrAdvInterval setting for radvd.conf')),
+    cfg.IntOpt('max_rtr_adv_interval',
+               default=10,
+               help=_('MaxRtrAdvInterval setting for radvd.conf')),
 ]
 
 CONFIG_TEMPLATE = jinja2.Template("""interface {{ interface_name }}
 {
    AdvSendAdvert on;
-   MinRtrAdvInterval 3;
+   MinRtrAdvInterval {{ min_rtr_adv_interval }};
-   MaxRtrAdvInterval 10;
+   MaxRtrAdvInterval {{ max_rtr_adv_interval }};
 
    {% if constants.DHCPV6_STATELESS in ra_modes %}
    AdvOtherConfigFlag on;
@@ -106,7 +112,9 @@ class DaemonMonitor(object):
                 interface_name=interface_name,
                 prefixes=auto_config_prefixes,
                 dns_servers=dns_servers[0:MAX_RDNSS_ENTRIES],
-                constants=constants))
+                constants=constants,
+                min_rtr_adv_interval=self._agent_conf.min_rtr_adv_interval,
+                max_rtr_adv_interval=self._agent_conf.max_rtr_adv_interval))
 
         common_utils.replace_file(radvd_conf, buf.getvalue())
         return radvd_conf

neutron/tests/unit/agent/l3/test_agent.py

@@ -2246,6 +2246,20 @@ class TestBasicRouterOperations(BasicRouterOperationsFramework):
             assertFlag(managed_flag)('AdvManagedFlag on;',
                 self.utils_replace_file.call_args[0][1])
 
+    def test_generate_radvd_intervals(self):
+        self.conf.set_override('min_rtr_adv_interval', 22)
+        self.conf.set_override('max_rtr_adv_interval', 66)
+        router = l3_test_common.prepare_router_data()
+        ipv6_subnet_modes = [{'ra_mode': l3_constants.IPV6_SLAAC,
+                             'address_mode': l3_constants.IPV6_SLAAC}]
+        ri = self._process_router_ipv6_subnet_added(router,
+                                                    ipv6_subnet_modes)
+        ri.radvd._generate_radvd_conf(router[l3_constants.INTERFACE_KEY])
+        self.assertIn("MinRtrAdvInterval 22",
+                      self.utils_replace_file.call_args[0][1])
+        self.assertIn("MaxRtrAdvInterval 66",
+                      self.utils_replace_file.call_args[0][1])
+
     def test_generate_radvd_rdnss_conf(self):
         router = l3_test_common.prepare_router_data()
         ipv6_subnet_modes = [{'ra_mode': l3_constants.IPV6_SLAAC,

releasenotes/notes/advertisement-intervals-for-radvd-configurable-6d85b5fdd97a2742.yaml

@@ -0,0 +1,9 @@
+---
+fixes:
+  - Prior to Mitaka, the settings that control the frequency of
+    router advertisements transmitted by the radvd daemon were
+    not able to be adjusted. Larger deployments may wish to decrease
+    the frequency in which radvd sends multicast traffic. The 'min_rtr_adv_interval'
+    and 'max_rtr_adv_interval' settings in the L3 agent configuration file
+    map directly to the 'MinRtrAdvInterval' and 'MaxRtrAdvInterval' in the generated
+    radvd.conf file. Consult the manpage for radvd.conf for more detailed information.