conf: Undeprecate and move the 'dhcp_domain' option

The metadata service makes use of the deprecated '[DEFAULT] dhcp_domain'
option when providing a hostname to the instance. This is used by
cloud-init to configure the hostname in the instance. This use was not
captured when the option was initially deprecated. This option is now
undeprecated and moved to the '[api]' group to ensure it won't be
removed alongside the other nova-network options.

Change-Id: I3940ebd1888d8019716e7d4eb6d4a413a37b9b78
Closes-Bug: #1698010

7 files changed, 47 insertions, 31 deletions

diff --git a/nova/api/metadata/base.py b/nova/api/metadata/base.py
index e3e25fe541..42e76a86b7 100644
--- a/nova/api/metadata/base.py
+++ b/nova/api/metadata/base.py
@@ -528,8 +528,10 @@ class InstanceMetadata(object):
         return self._check_version(required, requested, OPENSTACK_VERSIONS)
 
     def _get_hostname(self):
-        if CONF.dhcp_domain:
-            return '.'.join([self.instance.hostname, CONF.dhcp_domain])
+        # TODO(stephenfin): At some point in the future, we may wish to
+        # retrieve this information from neutron.
+        if CONF.api.dhcp_domain:
+            return '.'.join([self.instance.hostname, CONF.api.dhcp_domain])
 
         return self.instance.hostname
 
diff --git a/nova/conf/api.py b/nova/conf/api.py
index 574370e68e..a36e9e2f1b 100644
--- a/nova/conf/api.py
+++ b/nova/conf/api.py
@@ -209,6 +209,30 @@ running nova-metadata API service per cell, you should also configure each
 Neutron metadata-agent to point to the corresponding nova-metadata API
 service.
 """),
+    cfg.StrOpt("dhcp_domain",
+        deprecated_group="DEFAULT",
+        default="novalocal",
+        help="""
+Domain name used to configure FQDN for instances.
+
+This option has two purposes:
+
+#. For *neutron* and *nova-network* users, it is used to configure a
+   fully-qualified domain name for instance hostnames. If unset, only the
+   hostname without a domain will be configured.
+#. (Deprecated) For *nova-network* users, this option configures the DNS
+   domains used for the DHCP server. Refer to the ``--domain`` option of the
+   ``dnsmasq`` utility for more information. Like *nova-network* itself, this
+   purpose is deprecated.
+
+Possible values:
+
+* Any string that is a valid domain name.
+
+Related options:
+
+* ``use_neutron``
+"""),
 ]
 
 file_opts = [
diff --git a/nova/conf/network.py b/nova/conf/network.py
index 4ab64c1c7b..5e63231962 100644
--- a/nova/conf/network.py
+++ b/nova/conf/network.py
@@ -465,24 +465,6 @@ Related options:
 
 * ``use_neutron``
 """),
-    cfg.StrOpt("dhcp_domain",
-        default="novalocal",
-        deprecated_for_removal=True,
-        deprecated_since='15.0.0',
-        deprecated_reason="""
-nova-network is deprecated, as are any related configuration options.
-""",
-        help="""
-This option allows you to specify the domain for the DHCP server.
-
-Possible values:
-
-* Any string that is a valid domain name.
-
-Related options:
-
-* ``use_neutron``
-"""),
     cfg.StrOpt("l3_lib",
         default="nova.network.l3.LinuxNetL3",
         deprecated_for_removal=True,
diff --git a/nova/network/linux_net.py b/nova/network/linux_net.py
index da06724d0b..9abecc546d 100644
--- a/nova/network/linux_net.py
+++ b/nova/network/linux_net.py
@@ -1007,8 +1007,8 @@ def restart_dhcp(context, dev, network_ref, fixedips):
 
     # dnsmasq currently gives an error for an empty domain,
     # rather than ignoring.  So only specify it if defined.
-    if CONF.dhcp_domain:
-        cmd.append('--domain=%s' % CONF.dhcp_domain)
+    if CONF.api.dhcp_domain:
+        cmd.append('--domain=%s' % CONF.api.dhcp_domain)
 
     dns_servers = CONF.dns_server
     if CONF.use_network_dns_servers:
@@ -1096,20 +1096,20 @@ def _host_dhcp(fixedip):
         net = _host_dhcp_network(fixedip.virtual_interface_id)
         return '%s,%s.%s,%s,net:%s' % (fixedip.virtual_interface.address,
                                hostname,
-                               CONF.dhcp_domain,
+                               CONF.api.dhcp_domain,
                                fixedip.address,
                                net)
     else:
         return '%s,%s.%s,%s' % (fixedip.virtual_interface.address,
                                hostname,
-                               CONF.dhcp_domain,
+                               CONF.api.dhcp_domain,
                                fixedip.address)
 
 
 def _host_dns(fixedip):
     return '%s\t%s.%s' % (fixedip.address,
                           fixedip.instance.hostname,
-                          CONF.dhcp_domain)
+                          CONF.api.dhcp_domain)
 
 
 def _host_dhcp_opts(vif_id=None, gateway=None):
diff --git a/nova/tests/unit/network/test_linux_net.py b/nova/tests/unit/network/test_linux_net.py
index d40598487a..f184f8ffa9 100644
--- a/nova/tests/unit/network/test_linux_net.py
+++ b/nova/tests/unit/network/test_linux_net.py
@@ -734,10 +734,10 @@ class LinuxNetworkTestCase(test.NoDBTestCase):
 
         dev = 'br100'
 
-        default_domain = CONF.dhcp_domain
+        default_domain = CONF.api.dhcp_domain
         for domain in ('', default_domain):
             executes = []
-            self.flags(dhcp_domain=domain)
+            self.flags(dhcp_domain=domain, group='api')
             fixedips = self._get_fixedips(network_ref)
             linux_net.restart_dhcp(self.context, dev, network_ref, fixedips)
             expected = ['env',
@@ -761,8 +761,8 @@ class LinuxNetworkTestCase(test.NoDBTestCase):
             '--no-hosts',
             '--leasefile-ro']
 
-            if CONF.dhcp_domain:
-                expected.append('--domain=%s' % CONF.dhcp_domain)
+            if CONF.api.dhcp_domain:
+                expected.append('--domain=%s' % CONF.api.dhcp_domain)
 
             if extra_expected:
                 expected += extra_expected
diff --git a/nova/tests/unit/test_metadata.py b/nova/tests/unit/test_metadata.py
index d8fe323956..a1ec39896a 100644
--- a/nova/tests/unit/test_metadata.py
+++ b/nova/tests/unit/test_metadata.py
@@ -311,14 +311,14 @@ class MetadataTestCase(test.TestCase):
         self._test_security_groups()
 
     def test_local_hostname(self):
-        self.flags(dhcp_domain=None)
+        self.flags(dhcp_domain=None, group='api')
         md = fake_InstanceMetadata(self, self.instance.obj_clone())
         data = md.get_ec2_metadata(version='2009-04-04')
         self.assertEqual(data['meta-data']['local-hostname'],
             self.instance['hostname'])
 
     def test_local_hostname_fqdn(self):
-        self.flags(dhcp_domain='fakedomain')
+        self.flags(dhcp_domain='fakedomain', group='api')
         md = fake_InstanceMetadata(self, self.instance.obj_clone())
         data = md.get_ec2_metadata(version='2009-04-04')
         self.assertEqual('%s.fakedomain' % self.instance['hostname'],
diff --git a/releasenotes/notes/undeprecate-dhcp_domain-opt-77c9154c5b06e0ff.yaml b/releasenotes/notes/undeprecate-dhcp_domain-opt-77c9154c5b06e0ff.yaml
new file mode 100644
index 0000000000..794431fd1c
--- /dev/null
+++ b/releasenotes/notes/undeprecate-dhcp_domain-opt-77c9154c5b06e0ff.yaml
@@ -0,0 +1,8 @@
+---
+other:
+  - |
+    The ``dhcp_domain`` option has been undeprecated and moved to the ``[api]``
+    group. It is used by the metadata service to configure fully-qualified
+    domain names for instances, in addition to its role configuring DHCP
+    services for *nova-network*. This use case was missed when deprecating the
+    option initially.