Don't configure dnsmasq entries for "network" ports

Ports with device_owner like:
* floating_ip,
* DHCP,
* some types of router ports, like: HA interface interface,
* distributed ports,
don't need to be configured in the dnsmasq file.
So there is no need to reload dnsmasq every time when such port is
added/updated to the network.

This patch adds skip in such case which should improve load on the
Neutron DHCP agent.

Closes-Bug: #1913269
Change-Id: I63221507713b941c261cdf88781133149da8ab8d

neutron/agent/dhcp/agent.py

@@ -602,6 +602,8 @@ class DhcpAgent(manager.Manager):
     def port_update_end(self, context, payload):
         """Handle the port.update.end notification event."""
         updated_port = dhcp.DictModel(payload['port'])
+        if not dhcp.port_requires_dhcp_configuration(updated_port):
+            return
         if self.cache.is_port_message_stale(updated_port):
             LOG.debug("Discarding stale port update: %s", updated_port)
             return
@@ -626,6 +628,8 @@ class DhcpAgent(manager.Manager):
     def reload_allocations(self, port, network, prio=False):
         LOG.info("Trigger reload_allocations for port %s on network %s",
                  port, network)
+        if not dhcp.port_requires_dhcp_configuration(port):
+            return
         driver_action = 'reload_allocations'
         if self._is_port_on_this_agent(port):
             orig = self.cache.get_port_by_id(port['id'])
@@ -664,6 +668,8 @@ class DhcpAgent(manager.Manager):
     def port_create_end(self, context, payload):
         """Handle the port.create.end notification event."""
         created_port = dhcp.DictModel(payload['port'])
+        if not dhcp.port_requires_dhcp_configuration(created_port):
+            return
         update = DHCPResourceUpdate(created_port.network_id,
                                     payload.get('priority', DEFAULT_PRIORITY),
                                     action='_port_create',

neutron/agent/linux/dhcp.py

@@ -58,6 +58,23 @@ HOST_DHCPV6_TAG = 'tag:dhcpv6,'
 DHCP_OPT_CLIENT_ID_NUM = 61
 
 
+def port_requires_dhcp_configuration(port):
+    if not getattr(port, 'device_owner', None):
+        # We can't check if port needs dhcp entry, so it will be better
+        # to create one
+        return True
+    # TODO(slaweq): define this list as a constant in neutron_lib.constants
+    # NOTE(slaweq): Not all port types which belongs e.g. to the routers can be
+    # excluded from that list. For some of them, like router interfaces used to
+    # plug subnet to the router should be configured in dnsmasq to provide DNS
+    # naming resolution. Otherwise it may slowdown e.g. traceroutes from the VM
+    return port.device_owner not in [
+        constants.DEVICE_OWNER_ROUTER_HA_INTF,
+        constants.DEVICE_OWNER_FLOATINGIP,
+        constants.DEVICE_OWNER_DHCP,
+        constants.DEVICE_OWNER_DISTRIBUTED]
+
+
 class DictModel(collections.abc.MutableMapping):
     """Convert dict into an object that provides attribute access to values."""
 
@@ -719,6 +736,9 @@ class Dnsmasq(DhcpLocalProcess):
                        if subnet.ip_version == 6)
 
         for port in self.network.ports:
+            if not port_requires_dhcp_configuration(port):
+                continue
+
             fixed_ips = self._sort_fixed_ips_for_dnsmasq(port.fixed_ips,
                                                          v6_nets)
             # TODO(hjensas): Drop this conditional and option once distros

neutron/tests/unit/agent/linux/test_dhcp.py

@@ -308,6 +308,19 @@ class FakeRouterPort(object):
                                for ip in self.fixed_ips]
 
 
+class FakeRouterHAPort(object):
+    def __init__(self):
+        self.id = 'hahahaha-haha-haha-haha-hahahahahaha'
+        self.admin_state_up = True
+        self.device_owner = constants.DEVICE_OWNER_ROUTER_HA_INTF
+        self.mac_address = '00:00:0f:aa:aa:aa'
+        self.device_id = 'fake_router_ha_port'
+        self.dns_assignment = []
+        self.extra_dhcp_opts = []
+        self.fixed_ips = [FakeIPAllocation(
+            '169.254.169.20', 'dddddddd-dddd-dddd-dddd-dddddddddddd')]
+
+
 class FakeRouterPortNoDHCP(object):
     def __init__(self, dev_owner=constants.DEVICE_OWNER_ROUTER_INTF,
                  ip_address='192.168.0.1', domain='openstacklocal'):
@@ -694,6 +707,7 @@ class FakeDualNetwork(object):
         self.namespace = 'qdhcp-ns'
         self.ports = [FakePort1(domain=domain), FakeV6Port(domain=domain),
                       FakeDualPort(domain=domain),
+                      FakeRouterHAPort(),
                       FakeRouterPort(domain=domain)]
 
 

releasenotes/notes/do-not-create-dhcp-entries-for-all-types-of-ports-39c03b3782d2753e.yaml

@@ -0,0 +1,6 @@
+---
+other:
+  - |
+    To improve performance of the DHCP agent, it will no longer configure the DHCP server
+    for every port type created in Neutron. For example, for floating IP or router HA
+    interfaces there is no need since a client will not make a DHCP request for them