Only set default network interface flat if enabled in config

This patch updates the driver factory logic which sets a default for the
network interface when there is not one set in the config file. Before
this patch the logic forces "flat" as the default network interface for
all hardware types and classic drivers even if flat isn't enabled in the
config file, resulting in a misleading error.

This patch changes the code to only set "flat" as the default for
classic drivers if its enabled in the enabled_network_interfaces
configuration option in the config file, and to not override a default
for hardware types at all because the default for hardware types should
either come from the config file or from the hardware type's
supported_network_interfaces list.

Change-Id: Ia8676d3483ddc78df8766dc1baaf2db6b5686050
Closes-Bug: #1744332

4 files changed, 41 insertions, 4 deletions

diff --git a/ironic/common/driver_factory.py b/ironic/common/driver_factory.py
index a51e7bc54..9ab997a8e 100644
--- a/ironic/common/driver_factory.py
+++ b/ironic/common/driver_factory.py
@@ -175,10 +175,19 @@ def default_interface(driver_or_hw_type, interface_type,
                                   hardware_type.AbstractHardwareType)
     # Explicit interface defaults
     additional_defaults = {
-        'network': 'flat' if CONF.dhcp.dhcp_provider == 'neutron' else 'noop',
         'storage': 'noop'
     }
 
+    if not is_hardware_type:
+        # For non hardware types we need to set a fallback for the network
+        # interface however hardware_types specify their own defaults if not in
+        # the config file.
+        if (CONF.dhcp.dhcp_provider == 'neutron' and
+                'flat' in CONF.enabled_network_interfaces):
+            additional_defaults['network'] = 'flat'
+        elif 'noop' in CONF.enabled_network_interfaces:
+            additional_defaults['network'] = 'noop'
+
     # The fallback default from the configuration
     impl_name = getattr(CONF, 'default_%s_interface' % interface_type)
     if impl_name is None:
diff --git a/ironic/drivers/fake_hardware.py b/ironic/drivers/fake_hardware.py
index 6cf6f0d56..5d0776f22 100644
--- a/ironic/drivers/fake_hardware.py
+++ b/ironic/drivers/fake_hardware.py
@@ -80,3 +80,10 @@ class FakeHardware(hardware_type.AbstractHardwareType):
     def supported_vendor_interfaces(self):
         """List of classes of supported rescue interfaces."""
         return [fake.FakeVendorB, fake.FakeVendorA]
+
+    @property
+    def supported_network_interfaces(self):
+        # import late to avoid circular imports
+        from ironic.drivers.modules.network import flat
+        from ironic.drivers.modules.network import noop
+        return [flat.FlatNetwork, noop.NoopNetwork]
diff --git a/ironic/tests/unit/common/test_driver_factory.py b/ironic/tests/unit/common/test_driver_factory.py
index 12cb0dbe7..9d7cbd5dc 100644
--- a/ironic/tests/unit/common/test_driver_factory.py
+++ b/ironic/tests/unit/common/test_driver_factory.py
@@ -480,7 +480,8 @@ class CheckAndUpdateNodeInterfacesTestCase(db_base.DbTestCase):
 class DefaultInterfaceTestCase(db_base.DbTestCase):
     def setUp(self):
         super(DefaultInterfaceTestCase, self).setUp()
-        self.config(enabled_hardware_types=['manual-management'])
+        self.config(enabled_hardware_types=['manual-management'],
+                    enabled_drivers=['fake'])
         self.driver = driver_factory.get_hardware_type('manual-management')
 
     def test_from_config(self):
@@ -493,16 +494,27 @@ class DefaultInterfaceTestCase(db_base.DbTestCase):
         iface = driver_factory.default_interface(self.driver, 'storage')
         self.assertEqual('noop', iface)
 
-    def test_network_from_additional_defaults(self):
+    def test_network_from_additional_defaults_hardware_type(self):
         self.config(default_network_interface=None)
         self.config(dhcp_provider='none', group='dhcp')
+        self.config(enabled_network_interfaces=['neutron'])
         iface = driver_factory.default_interface(self.driver, 'network')
+        self.assertEqual('neutron', iface)
+
+    def test_network_from_additional_defaults(self):
+        self.config(default_network_interface=None)
+        self.config(dhcp_provider='none', group='dhcp')
+        iface = driver_factory.default_interface(
+            driver_factory.get_driver_or_hardware_type('fake'),
+            'network')
         self.assertEqual('noop', iface)
 
     def test_network_from_additional_defaults_neutron_dhcp(self):
         self.config(default_network_interface=None)
         self.config(dhcp_provider='neutron', group='dhcp')
-        iface = driver_factory.default_interface(self.driver, 'network')
+        iface = driver_factory.default_interface(
+            driver_factory.get_driver_or_hardware_type('fake'),
+            'network')
         self.assertEqual('flat', iface)
 
     def test_calculated_with_one(self):
diff --git a/releasenotes/notes/only_default_flat_network_if_enabled-b5c6ea415239a53c.yaml b/releasenotes/notes/only_default_flat_network_if_enabled-b5c6ea415239a53c.yaml
new file mode 100644
index 000000000..5a8fd2029
--- /dev/null
+++ b/releasenotes/notes/only_default_flat_network_if_enabled-b5c6ea415239a53c.yaml
@@ -0,0 +1,9 @@
+---
+fixes:
+  - |
+    Fixes a bug seen when no ``default_network_interface`` is set, because the
+    conductor tries use the ``flat`` network interface instead even if it is
+    not included in the conductor's ``enabled_network_interfaces`` config
+    option.  Resulting in `Failed to register hardware types` error. See
+    `bug 1744332 <https://bugs.launchpad.net/ironic/+bug/1744332>`_
+    for more information.
\ No newline at end of file