Added nat_source flag for networks.

In some more complex clouds there can not only be more than one valid network
on a server that NAT can attach to, there can also be more than one valid
network from which to get a NAT address. Allow flagging a network so that it
can be found.

Change-Id: I3d8dd6d734a1013d2d4a43e11c3538c3a345820b

doc/source/user/config/network-config.rst

@@ -58,3 +58,10 @@ by looking for a network that has subnets that have a gateway_ip. But it's
 possible to have more than one network that satisfies that condition, so the
 user might want to tell programs which one to pick. There can be only one
 `nat_destination` per cloud.
+
+`nat_source` is a boolean field that indicates which network floating
+ips should be requested from. It defaults to false. Normally this can be
+inferred by looking for a network that is attached to a router. But it's
+possible to have more than one network that satisfies that condition, so the
+user might want to tell programs which one to pick. There can be only one
+`nat_source` per cloud.

openstack/config/cloud_config.py

@@ -583,3 +583,10 @@ class CloudConfig(object):
             if net['nat_destination']:
                 return net['name']
         return None
+
+    def get_nat_source(self):
+        """Get network used for NAT source."""
+        for net in self.config['networks']:
+            if net.get('nat_source'):
+                return net['name']
+        return None

openstack/config/loader.py

@@ -550,6 +550,7 @@ class OpenStackConfig(object):
             network = dict(
                 name=name,
                 routes_externally=get_boolean(net.get('routes_externally')),
+                nat_source=get_boolean(net.get('nat_source')),
                 nat_destination=get_boolean(net.get('nat_destination')),
                 default_interface=get_boolean(net.get('default_interface')),
             )

openstack/tests/unit/config/base.py

@@ -102,6 +102,7 @@ USER_CONF = {
             'networks': [{
                 'name': 'a-public',
                 'routes_externally': True,
+                'nat_source': True,
             }, {
                 'name': 'another-public',
                 'routes_externally': True,

openstack/tests/unit/config/test_config.py

@@ -225,6 +225,7 @@ class TestConfig(base.TestCase):
         self.assertEqual(
             ['a-private', 'another-private', 'split-no-default'],
             cc.get_internal_networks())
+        self.assertEqual('a-public', cc.get_nat_source())
         self.assertEqual('another-private', cc.get_nat_destination())
         self.assertEqual('another-public', cc.get_default_network())
         self.assertEqual(
@@ -240,6 +241,7 @@ class TestConfig(base.TestCase):
         cc = c.get_one_cloud('_test-cloud-domain-scoped_')
         self.assertEqual([], cc.get_external_networks())
         self.assertEqual([], cc.get_internal_networks())
+        self.assertIsNone(cc.get_nat_source())
         self.assertIsNone(cc.get_nat_destination())
         self.assertIsNone(cc.get_default_network())
 
@@ -1020,6 +1022,7 @@ class TestBackwardsCompatibility(base.TestCase):
             'networks': [
                 {'name': 'private', 'routes_externally': False,
                  'nat_destination': False, 'default_interface': False,
+                 'nat_source': False,
                  'routes_ipv4_externally': False,
                  'routes_ipv6_externally': False},
             ]

releasenotes/notes/nat-source-field-7c7db2a724616d59.yaml

@@ -0,0 +1,6 @@
+---
+features:
+  - Added nat_source flag for networks. In some more complex clouds there
+    can not only be more than one valid network on a server that NAT can
+    attach to, there can also be more than one valid network from which to
+    get a NAT address. Allow flagging a network so that it can be found.