From 62e0bee8206491690bd6b6b72fc38d9694d5083f Mon Sep 17 00:00:00 2001
From: Miguel Lavalle <miguel.lavalle@verizonmedia.com>
Date: Sun, 26 May 2019 19:15:25 -0500
Subject: [PATCH] Support multiple external networks in L3 agent

Change [1] removed the deprecated option external_network_bridge. Per
commit message in change [2], "l3 agent can handle any networks by
setting the neutron parameter external_network_bridge and
gateway_external_network_id to empty". So the consequence of [1] was to
introduce a regression whereby multiple external networks are not
supported by the L3 agent anymore.

This change proposes a new simplified rule. If
gateway_external_network_id is defined, that is the network that the L3
agent will use. If not and multiple external networks exist, the L3
agent will handle any of them.

[1] https://review.opendev.org/#/c/567369/
[2] https://review.opendev.org/#/c/59359

Change-Id: Idd766bd069eda85ab6876a78b8b050ee5ab66cf6
Closes-Bug: #1824571
(cherry picked from commit 0b3f5f429d2e495eb78d78d46186092ac735e0d5)
---
 neutron/agent/l3/agent.py                 |  9 +++-----
 neutron/tests/unit/agent/l3/test_agent.py | 25 +++++------------------
 2 files changed, 8 insertions(+), 26 deletions(-)

diff --git a/neutron/agent/l3/agent.py b/neutron/agent/l3/agent.py
index 92621d58524..ba057a0adea 100644
--- a/neutron/agent/l3/agent.py
+++ b/neutron/agent/l3/agent.py
@@ -36,7 +36,6 @@ from oslo_utils import excutils
 from oslo_utils import timeutils
 from osprofiler import profiler
 
-from neutron._i18n import _
 from neutron.agent.common import resource_processing_queue as queue
 from neutron.agent.common import utils as common_utils
 from neutron.agent.l3 import dvr
@@ -368,12 +367,10 @@ class L3NATAgent(ha.AgentMixin,
         except oslo_messaging.RemoteError as e:
             with excutils.save_and_reraise_exception() as ctx:
                 if e.exc_type == 'TooManyExternalNetworks':
+                    # At this point we know gateway_external_network_id is not
+                    # defined. Since there are more than one external network,
+                    # we will handle all of them
                     ctx.reraise = False
-                    msg = _(
-                        "The 'gateway_external_network_id' option must be "
-                        "configured for this agent as Neutron has more than "
-                        "one external network.")
-                    raise Exception(msg)
 
     def _create_router(self, router_id, router):
         args = []
diff --git a/neutron/tests/unit/agent/l3/test_agent.py b/neutron/tests/unit/agent/l3/test_agent.py
index 2ecf102f21e..e458c161507 100644
--- a/neutron/tests/unit/agent/l3/test_agent.py
+++ b/neutron/tests/unit/agent/l3/test_agent.py
@@ -24,7 +24,6 @@ import netaddr
 from neutron_lib.agent import constants as agent_consts
 from neutron_lib.api.definitions import portbindings
 from neutron_lib import constants as lib_constants
-from neutron_lib import exceptions as exc
 from neutron_lib.exceptions import l3 as l3_exc
 from oslo_config import cfg
 from oslo_log import log
@@ -2889,12 +2888,11 @@ class TestBasicRouterOperations(BasicRouterOperationsFramework):
                   'external_gateway_info': {'network_id': 'aaa'}}
 
         agent.router_info = {}
-        self.plugin_api.get_external_network_id.side_effect = (
-            exc.TooManyExternalNetworks())
-        self.assertRaises(exc.TooManyExternalNetworks,
-                          agent._process_router_if_compatible,
-                          router)
-        self.assertNotIn(router['id'], agent.router_info)
+        e = oslo_messaging.RemoteError()
+        e.exc_type = 'TooManyExternalNetworks'
+        agent.plugin_rpc.get_external_network_id.side_effect = e
+        agent._process_router_if_compatible(router)
+        self.assertIn(router['id'], agent.router_info)
 
     def test_process_router_if_compatible_with_ext_net_in_conf(self):
         agent = l3_agent.L3NATAgent(HOSTNAME, self.conf)
@@ -2912,19 +2910,6 @@ class TestBasicRouterOperations(BasicRouterOperationsFramework):
                           router)
         self.assertNotIn(router['id'], agent.router_info)
 
-    def test_process_router_if_compatible_with_no_bridge_no_ext_net(self):
-        agent = l3_agent.L3NATAgent(HOSTNAME, self.conf)
-        self.plugin_api.get_external_network_id.return_value = 'aaa'
-
-        router = {'id': _uuid(),
-                  'routes': [],
-                  'admin_state_up': True,
-                  'external_gateway_info': {'network_id': 'aaa'}}
-
-        agent.router_info = {}
-        agent._process_router_if_compatible(router)
-        self.assertIn(router['id'], agent.router_info)
-
     def test_nonexistent_interface_driver(self):
         self.conf.set_override('interface_driver', None)
         self.assertRaises(SystemExit, l3_agent.L3NATAgent,