azure: allow azure to generate network configuration from IMDS per boot.

Azure datasource now queries IMDS metadata service for network
configuration at link local address
http://169.254.169.254/metadata/instance?api-version=2017-12-01. The
azure metadata service presents a list of macs and allocated ip addresses
associated with this instance. Azure will now also regenerate network
configuration on every boot because it subscribes to EventType.BOOT
maintenance events as well as the 'first boot'
EventType.BOOT_NEW_INSTANCE.

For testing add azure-imds --kind to cloud-init devel net_convert tool
for debugging IMDS metadata.

Also refactor _get_data into 3 discrete methods:
  - is_platform_viable: check quickly whether the datasource is
    potentially compatible with the platform on which is is running
  - crawl_metadata: walk all potential metadata candidates, returning a
    structured dict of all metadata and userdata. Raise InvalidMetaData on
    error.
  - _get_data: call crawl_metadata and process results or error. Cache
    instance data on class attributes: metadata, userdata_raw etc.

1 files changed, 371 insertions, 28 deletions

diff --git a/tests/unittests/test_datasource/test_azure.py b/tests/unittests/test_datasource/test_azure.py
index e82716eb..4e428b71 100644
--- a/tests/unittests/test_datasource/test_azure.py
+++ b/tests/unittests/test_datasource/test_azure.py
@@ -1,15 +1,21 @@
 # This file is part of cloud-init. See LICENSE file for license information.
 
+from cloudinit import distros
 from cloudinit import helpers
-from cloudinit.sources import DataSourceAzure as dsaz
+from cloudinit import url_helper
+from cloudinit.sources import (
+    UNSET, DataSourceAzure as dsaz, InvalidMetaDataException)
 from cloudinit.util import (b64e, decode_binary, load_file, write_file,
                             find_freebsd_part, get_path_dev_freebsd,
                             MountFailedError)
 from cloudinit.version import version_string as vs
-from cloudinit.tests.helpers import (CiTestCase, TestCase, populate_dir, mock,
-                                     ExitStack, PY26, SkipTest)
+from cloudinit.tests.helpers import (
+    HttprettyTestCase, CiTestCase, populate_dir, mock, wrap_and_call,
+    ExitStack, PY26, SkipTest)
 
 import crypt
+import httpretty
+import json
 import os
 import stat
 import xml.etree.ElementTree as ET
@@ -77,6 +83,106 @@ def construct_valid_ovf_env(data=None, pubkeys=None,
     return content
 
 
+NETWORK_METADATA = {
+    "network": {
+        "interface": [
+            {
+                "macAddress": "000D3A047598",
+                "ipv6": {
+                    "ipAddress": []
+                },
+                "ipv4": {
+                    "subnet": [
+                        {
+                           "prefix": "24",
+                           "address": "10.0.0.0"
+                        }
+                    ],
+                    "ipAddress": [
+                        {
+                           "privateIpAddress": "10.0.0.4",
+                           "publicIpAddress": "104.46.124.81"
+                        }
+                    ]
+                }
+            }
+        ]
+    }
+}
+
+
+class TestGetMetadataFromIMDS(HttprettyTestCase):
+
+    with_logs = True
+
+    def setUp(self):
+        super(TestGetMetadataFromIMDS, self).setUp()
+        self.network_md_url = dsaz.IMDS_URL + "instance?api-version=2017-12-01"
+
+    @mock.patch('cloudinit.sources.DataSourceAzure.readurl')
+    @mock.patch('cloudinit.sources.DataSourceAzure.EphemeralDHCPv4')
+    @mock.patch('cloudinit.sources.DataSourceAzure.net.is_up')
+    def test_get_metadata_does_not_dhcp_if_network_is_up(
+            self, m_net_is_up, m_dhcp, m_readurl):
+        """Do not perform DHCP setup when nic is already up."""
+        m_net_is_up.return_value = True
+        m_readurl.return_value = url_helper.StringResponse(
+            json.dumps(NETWORK_METADATA).encode('utf-8'))
+        self.assertEqual(
+            NETWORK_METADATA,
+            dsaz.get_metadata_from_imds('eth9', retries=3))
+
+        m_net_is_up.assert_called_with('eth9')
+        m_dhcp.assert_not_called()
+        self.assertIn(
+            "Crawl of Azure Instance Metadata Service (IMDS) took",  # log_time
+            self.logs.getvalue())
+
+    @mock.patch('cloudinit.sources.DataSourceAzure.readurl')
+    @mock.patch('cloudinit.sources.DataSourceAzure.EphemeralDHCPv4')
+    @mock.patch('cloudinit.sources.DataSourceAzure.net.is_up')
+    def test_get_metadata_performs_dhcp_when_network_is_down(
+            self, m_net_is_up, m_dhcp, m_readurl):
+        """Perform DHCP setup when nic is not up."""
+        m_net_is_up.return_value = False
+        m_readurl.return_value = url_helper.StringResponse(
+            json.dumps(NETWORK_METADATA).encode('utf-8'))
+
+        self.assertEqual(
+            NETWORK_METADATA,
+            dsaz.get_metadata_from_imds('eth9', retries=2))
+
+        m_net_is_up.assert_called_with('eth9')
+        m_dhcp.assert_called_with('eth9')
+        self.assertIn(
+            "Crawl of Azure Instance Metadata Service (IMDS) took",  # log_time
+            self.logs.getvalue())
+
+        m_readurl.assert_called_with(
+            self.network_md_url, exception_cb=mock.ANY,
+            headers={'Metadata': 'true'}, retries=2, timeout=1)
+
+    @mock.patch('cloudinit.url_helper.time.sleep')
+    @mock.patch('cloudinit.sources.DataSourceAzure.net.is_up')
+    def test_get_metadata_from_imds_empty_when_no_imds_present(
+            self, m_net_is_up, m_sleep):
+        """Return empty dict when IMDS network metadata is absent."""
+        httpretty.register_uri(
+            httpretty.GET,
+            dsaz.IMDS_URL + 'instance?api-version=2017-12-01',
+            body={}, status=404)
+
+        m_net_is_up.return_value = True  # skips dhcp
+
+        self.assertEqual({}, dsaz.get_metadata_from_imds('eth9', retries=2))
+
+        m_net_is_up.assert_called_with('eth9')
+        self.assertEqual([mock.call(1), mock.call(1)], m_sleep.call_args_list)
+        self.assertIn(
+            "Crawl of Azure Instance Metadata Service (IMDS) took",  # log_time
+            self.logs.getvalue())
+
+
 class TestAzureDataSource(CiTestCase):
 
     with_logs = True
@@ -95,8 +201,19 @@ class TestAzureDataSource(CiTestCase):
         self.patches = ExitStack()
         self.addCleanup(self.patches.close)
 
-        self.patches.enter_context(mock.patch.object(dsaz, '_get_random_seed'))
-
+        self.patches.enter_context(mock.patch.object(
+            dsaz, '_get_random_seed', return_value='wild'))
+        self.m_get_metadata_from_imds = self.patches.enter_context(
+            mock.patch.object(
+                dsaz, 'get_metadata_from_imds',
+                mock.MagicMock(return_value=NETWORK_METADATA)))
+        self.m_fallback_nic = self.patches.enter_context(
+            mock.patch('cloudinit.sources.net.find_fallback_nic',
+                       return_value='eth9'))
+        self.m_remove_ubuntu_network_scripts = self.patches.enter_context(
+            mock.patch.object(
+                dsaz, 'maybe_remove_ubuntu_network_config_scripts',
+                mock.MagicMock()))
         super(TestAzureDataSource, self).setUp()
 
     def apply_patches(self, patches):
@@ -137,7 +254,7 @@ scbus-1 on xpt0 bus 0
         ])
         return dsaz
 
-    def _get_ds(self, data, agent_command=None):
+    def _get_ds(self, data, agent_command=None, distro=None):
 
         def dsdevs():
             return data.get('dsdevs', [])
@@ -186,8 +303,11 @@ scbus-1 on xpt0 bus 0
                 side_effect=_wait_for_files)),
         ])
 
+        if distro is not None:
+            distro_cls = distros.fetch(distro)
+            distro = distro_cls(distro, data.get('sys_cfg', {}), self.paths)
         dsrc = dsaz.DataSourceAzure(
-            data.get('sys_cfg', {}), distro=None, paths=self.paths)
+            data.get('sys_cfg', {}), distro=distro, paths=self.paths)
         if agent_command is not None:
             dsrc.ds_cfg['agent_command'] = agent_command
 
@@ -260,29 +380,20 @@ fdescfs            /dev/fd          fdescfs rw              0 0
             res = get_path_dev_freebsd('/etc', mnt_list)
             self.assertIsNotNone(res)
 
-    @mock.patch('cloudinit.sources.DataSourceAzure.util.read_dmi_data')
-    def test_non_azure_dmi_chassis_asset_tag(self, m_read_dmi_data):
-        """Report non-azure when DMI's chassis asset tag doesn't match.
-
-        Return False when the asset tag doesn't match Azure's static
-        AZURE_CHASSIS_ASSET_TAG.
-        """
+    @mock.patch('cloudinit.sources.DataSourceAzure._is_platform_viable')
+    def test_call_is_platform_viable_seed(self, m_is_platform_viable):
+        """Check seed_dir using _is_platform_viable and return False."""
         # Return a non-matching asset tag value
-        nonazure_tag = dsaz.AZURE_CHASSIS_ASSET_TAG + 'X'
-        m_read_dmi_data.return_value = nonazure_tag
+        m_is_platform_viable.return_value = False
         dsrc = dsaz.DataSourceAzure(
             {}, distro=None, paths=self.paths)
         self.assertFalse(dsrc.get_data())
-        self.assertEqual(
-            "DEBUG: Non-Azure DMI asset tag '{0}' discovered.\n".format(
-                nonazure_tag),
-            self.logs.getvalue())
+        m_is_platform_viable.assert_called_with(dsrc.seed_dir)
 
     def test_basic_seed_dir(self):
         odata = {'HostName': "myhost", 'UserName': "myuser"}
         data = {'ovfcontent': construct_valid_ovf_env(data=odata),
                 'sys_cfg': {}}
-
         dsrc = self._get_ds(data)
         ret = dsrc.get_data()
         self.assertTrue(ret)
@@ -291,6 +402,82 @@ fdescfs            /dev/fd          fdescfs rw              0 0
         self.assertTrue(os.path.isfile(
             os.path.join(self.waagent_d, 'ovf-env.xml')))
 
+    def test_get_data_non_ubuntu_will_not_remove_network_scripts(self):
+        """get_data on non-Ubuntu will not remove ubuntu net scripts."""
+        odata = {'HostName': "myhost", 'UserName': "myuser"}
+        data = {'ovfcontent': construct_valid_ovf_env(data=odata),
+                'sys_cfg': {}}
+
+        dsrc = self._get_ds(data, distro='debian')
+        dsrc.get_data()
+        self.m_remove_ubuntu_network_scripts.assert_not_called()
+
+    def test_get_data_on_ubuntu_will_remove_network_scripts(self):
+        """get_data will remove ubuntu net scripts on Ubuntu distro."""
+        odata = {'HostName': "myhost", 'UserName': "myuser"}
+        data = {'ovfcontent': construct_valid_ovf_env(data=odata),
+                'sys_cfg': {}}
+
+        dsrc = self._get_ds(data, distro='ubuntu')
+        dsrc.get_data()
+        self.m_remove_ubuntu_network_scripts.assert_called_once_with()
+
+    def test_crawl_metadata_returns_structured_data_and_caches_nothing(self):
+        """Return all structured metadata and cache no class attributes."""
+        yaml_cfg = "{agent_command: my_command}\n"
+        odata = {'HostName': "myhost", 'UserName': "myuser",
+                 'UserData': {'text': 'FOOBAR', 'encoding': 'plain'},
+                 'dscfg': {'text': yaml_cfg, 'encoding': 'plain'}}
+        data = {'ovfcontent': construct_valid_ovf_env(data=odata),
+                'sys_cfg': {}}
+        dsrc = self._get_ds(data)
+        expected_cfg = {
+            'PreprovisionedVm': False,
+            'datasource': {'Azure': {'agent_command': 'my_command'}},
+            'system_info': {'default_user': {'name': u'myuser'}}}
+        expected_metadata = {
+            'azure_data': {
+                'configurationsettype': 'LinuxProvisioningConfiguration'},
+            'imds': {'network': {'interface': [{
+                'ipv4': {'ipAddress': [
+                     {'privateIpAddress': '10.0.0.4',
+                      'publicIpAddress': '104.46.124.81'}],
+                      'subnet': [{'address': '10.0.0.0', 'prefix': '24'}]},
+                'ipv6': {'ipAddress': []},
+                'macAddress': '000D3A047598'}]}},
+            'instance-id': 'test-instance-id',
+            'local-hostname': u'myhost',
+            'random_seed': 'wild'}
+
+        crawled_metadata = dsrc.crawl_metadata()
+
+        self.assertItemsEqual(
+            crawled_metadata.keys(),
+            ['cfg', 'files', 'metadata', 'userdata_raw'])
+        self.assertEqual(crawled_metadata['cfg'], expected_cfg)
+        self.assertEqual(
+            list(crawled_metadata['files'].keys()), ['ovf-env.xml'])
+        self.assertIn(
+            b'<HostName>myhost</HostName>',
+            crawled_metadata['files']['ovf-env.xml'])
+        self.assertEqual(crawled_metadata['metadata'], expected_metadata)
+        self.assertEqual(crawled_metadata['userdata_raw'], 'FOOBAR')
+        self.assertEqual(dsrc.userdata_raw, None)
+        self.assertEqual(dsrc.metadata, {})
+        self.assertEqual(dsrc._metadata_imds, UNSET)
+        self.assertFalse(os.path.isfile(
+            os.path.join(self.waagent_d, 'ovf-env.xml')))
+
+    def test_crawl_metadata_raises_invalid_metadata_on_error(self):
+        """crawl_metadata raises an exception on invalid ovf-env.xml."""
+        data = {'ovfcontent': "BOGUS", 'sys_cfg': {}}
+        dsrc = self._get_ds(data)
+        error_msg = ('BrokenAzureDataSource: Invalid ovf-env.xml:'
+                     ' syntax error: line 1, column 0')
+        with self.assertRaises(InvalidMetaDataException) as cm:
+            dsrc.crawl_metadata()
+        self.assertEqual(str(cm.exception), error_msg)
+
     def test_waagent_d_has_0700_perms(self):
         # we expect /var/lib/waagent to be created 0700
         dsrc = self._get_ds({'ovfcontent': construct_valid_ovf_env()})
@@ -314,6 +501,20 @@ fdescfs            /dev/fd          fdescfs rw              0 0
         self.assertTrue(ret)
         self.assertEqual(data['agent_invoked'], cfg['agent_command'])
 
+    def test_network_config_set_from_imds(self):
+        """Datasource.network_config returns IMDS network data."""
+        odata = {}
+        data = {'ovfcontent': construct_valid_ovf_env(data=odata)}
+        expected_network_config = {
+            'ethernets': {
+                'eth0': {'set-name': 'eth0',
+                         'match': {'macaddress': '00:0d:3a:04:75:98'},
+                         'dhcp4': True}},
+            'version': 2}
+        dsrc = self._get_ds(data)
+        dsrc.get_data()
+        self.assertEqual(expected_network_config, dsrc.network_config)
+
     def test_user_cfg_set_agent_command(self):
         # set dscfg in via base64 encoded yaml
         cfg = {'agent_command': "my_command"}
@@ -579,12 +780,34 @@ fdescfs            /dev/fd          fdescfs rw              0 0
         self.assertEqual(
             [mock.call("/dev/cd0")], m_check_fbsd_cdrom.call_args_list)
 
+    @mock.patch('cloudinit.net.generate_fallback_config')
+    def test_imds_network_config(self, mock_fallback):
+        """Network config is generated from IMDS network data when present."""
+        odata = {'HostName': "myhost", 'UserName': "myuser"}
+        data = {'ovfcontent': construct_valid_ovf_env(data=odata),
+                'sys_cfg': {}}
+
+        dsrc = self._get_ds(data)
+        ret = dsrc.get_data()
+        self.assertTrue(ret)
+
+        expected_cfg = {
+            'ethernets': {
+                'eth0': {'dhcp4': True,
+                         'match': {'macaddress': '00:0d:3a:04:75:98'},
+                         'set-name': 'eth0'}},
+            'version': 2}
+
+        self.assertEqual(expected_cfg, dsrc.network_config)
+        mock_fallback.assert_not_called()
+
     @mock.patch('cloudinit.net.get_interface_mac')
     @mock.patch('cloudinit.net.get_devicelist')
     @mock.patch('cloudinit.net.device_driver')
     @mock.patch('cloudinit.net.generate_fallback_config')
-    def test_network_config(self, mock_fallback, mock_dd,
-                            mock_devlist, mock_get_mac):
+    def test_fallback_network_config(self, mock_fallback, mock_dd,
+                                     mock_devlist, mock_get_mac):
+        """On absent IMDS network data, generate network fallback config."""
         odata = {'HostName': "myhost", 'UserName': "myuser"}
         data = {'ovfcontent': construct_valid_ovf_env(data=odata),
                 'sys_cfg': {}}
@@ -605,6 +828,8 @@ fdescfs            /dev/fd          fdescfs rw              0 0
         mock_get_mac.return_value = '00:11:22:33:44:55'
 
         dsrc = self._get_ds(data)
+        # Represent empty response from network imds
+        self.m_get_metadata_from_imds.return_value = {}
         ret = dsrc.get_data()
         self.assertTrue(ret)
 
@@ -617,8 +842,9 @@ fdescfs            /dev/fd          fdescfs rw              0 0
     @mock.patch('cloudinit.net.get_devicelist')
     @mock.patch('cloudinit.net.device_driver')
     @mock.patch('cloudinit.net.generate_fallback_config')
-    def test_network_config_blacklist(self, mock_fallback, mock_dd,
-                                      mock_devlist, mock_get_mac):
+    def test_fallback_network_config_blacklist(self, mock_fallback, mock_dd,
+                                               mock_devlist, mock_get_mac):
+        """On absent network metadata, blacklist mlx from fallback config."""
         odata = {'HostName': "myhost", 'UserName': "myuser"}
         data = {'ovfcontent': construct_valid_ovf_env(data=odata),
                 'sys_cfg': {}}
@@ -649,6 +875,8 @@ fdescfs            /dev/fd          fdescfs rw              0 0
         mock_get_mac.return_value = '00:11:22:33:44:55'
 
         dsrc = self._get_ds(data)
+        # Represent empty response from network imds
+        self.m_get_metadata_from_imds.return_value = {}
         ret = dsrc.get_data()
         self.assertTrue(ret)
 
@@ -689,9 +917,12 @@ class TestAzureBounce(CiTestCase):
             mock.patch.object(dsaz, 'get_metadata_from_fabric',
                               mock.MagicMock(return_value={})))
         self.patches.enter_context(
-            mock.patch.object(dsaz.util, 'which', lambda x: True))
+            mock.patch.object(dsaz, 'get_metadata_from_imds',
+                              mock.MagicMock(return_value={})))
         self.patches.enter_context(
-            mock.patch.object(dsaz, '_get_random_seed'))
+            mock.patch.object(dsaz.util, 'which', lambda x: True))
+        self.patches.enter_context(mock.patch.object(
+            dsaz, '_get_random_seed', return_value='wild'))
 
         def _dmi_mocks(key):
             if key == 'system-uuid':
@@ -719,9 +950,12 @@ class TestAzureBounce(CiTestCase):
             mock.patch.object(dsaz, 'set_hostname'))
         self.subp = self.patches.enter_context(
             mock.patch('cloudinit.sources.DataSourceAzure.util.subp'))
+        self.find_fallback_nic = self.patches.enter_context(
+            mock.patch('cloudinit.net.find_fallback_nic', return_value='eth9'))
 
     def tearDown(self):
         self.patches.close()
+        super(TestAzureBounce, self).tearDown()
 
     def _get_ds(self, ovfcontent=None, agent_command=None):
         if ovfcontent is not None:
@@ -927,7 +1161,7 @@ class TestLoadAzureDsDir(CiTestCase):
             str(context_manager.exception))
 
 
-class TestReadAzureOvf(TestCase):
+class TestReadAzureOvf(CiTestCase):
 
     def test_invalid_xml_raises_non_azure_ds(self):
         invalid_xml = "<foo>" + construct_valid_ovf_env(data={})
@@ -1188,6 +1422,25 @@ class TestCanDevBeReformatted(CiTestCase):
                       "(datasource.Azure.never_destroy_ntfs)", msg)
 
 
+class TestClearCachedData(CiTestCase):
+
+    def test_clear_cached_attrs_clears_imds(self):
+        """All class attributes are reset to defaults, including imds data."""
+        tmp = self.tmp_dir()
+        paths = helpers.Paths(
+            {'cloud_dir': tmp, 'run_dir': tmp})
+        dsrc = dsaz.DataSourceAzure({}, distro=None, paths=paths)
+        clean_values = [dsrc.metadata, dsrc.userdata, dsrc._metadata_imds]
+        dsrc.metadata = 'md'
+        dsrc.userdata = 'ud'
+        dsrc._metadata_imds = 'imds'
+        dsrc._dirty_cache = True
+        dsrc.clear_cached_attrs()
+        self.assertEqual(
+            [dsrc.metadata, dsrc.userdata, dsrc._metadata_imds],
+            clean_values)
+
+
 class TestAzureNetExists(CiTestCase):
 
     def test_azure_net_must_exist_for_legacy_objpkl(self):
@@ -1398,4 +1651,94 @@ class TestAzureDataSourcePreprovisioning(CiTestCase):
         self.assertEqual(m_net.call_count, 1)
 
 
+class TestRemoveUbuntuNetworkConfigScripts(CiTestCase):
+
+    with_logs = True
+
+    def setUp(self):
+        super(TestRemoveUbuntuNetworkConfigScripts, self).setUp()
+        self.tmp = self.tmp_dir()
+
+    def test_remove_network_scripts_removes_both_files_and_directories(self):
+        """Any files or directories in paths are removed when present."""
+        file1 = self.tmp_path('file1', dir=self.tmp)
+        subdir = self.tmp_path('sub1', dir=self.tmp)
+        subfile = self.tmp_path('leaf1', dir=subdir)
+        write_file(file1, 'file1content')
+        write_file(subfile, 'leafcontent')
+        dsaz.maybe_remove_ubuntu_network_config_scripts(paths=[subdir, file1])
+
+        for path in (file1, subdir, subfile):
+            self.assertFalse(os.path.exists(path),
+                             'Found unremoved: %s' % path)
+
+        expected_logs = [
+            'INFO: Removing Ubuntu extended network scripts because cloud-init'
+            ' updates Azure network configuration on the following event:'
+            ' System boot.',
+            'Recursively deleting %s' % subdir,
+            'Attempting to remove %s' % file1]
+        for log in expected_logs:
+            self.assertIn(log, self.logs.getvalue())
+
+    def test_remove_network_scripts_only_attempts_removal_if_path_exists(self):
+        """Any files or directories absent are skipped without error."""
+        dsaz.maybe_remove_ubuntu_network_config_scripts(paths=[
+            self.tmp_path('nodirhere/', dir=self.tmp),
+            self.tmp_path('notfilehere', dir=self.tmp)])
+        self.assertNotIn('/not/a', self.logs.getvalue())  # No delete logs
+
+    @mock.patch('cloudinit.sources.DataSourceAzure.os.path.exists')
+    def test_remove_network_scripts_default_removes_stock_scripts(self,
+                                                                  m_exists):
+        """Azure's stock ubuntu image scripts and artifacts are removed."""
+        # Report path absent on all to avoid delete operation
+        m_exists.return_value = False
+        dsaz.maybe_remove_ubuntu_network_config_scripts()
+        calls = m_exists.call_args_list
+        for path in dsaz.UBUNTU_EXTENDED_NETWORK_SCRIPTS:
+            self.assertIn(mock.call(path), calls)
+
+
+class TestWBIsPlatformViable(CiTestCase):
+    """White box tests for _is_platform_viable."""
+    with_logs = True
+
+    @mock.patch('cloudinit.sources.DataSourceAzure.util.read_dmi_data')
+    def test_true_on_non_azure_chassis(self, m_read_dmi_data):
+        """Return True if DMI chassis-asset-tag is AZURE_CHASSIS_ASSET_TAG."""
+        m_read_dmi_data.return_value = dsaz.AZURE_CHASSIS_ASSET_TAG
+        self.assertTrue(dsaz._is_platform_viable('doesnotmatter'))
+
+    @mock.patch('cloudinit.sources.DataSourceAzure.os.path.exists')
+    @mock.patch('cloudinit.sources.DataSourceAzure.util.read_dmi_data')
+    def test_true_on_azure_ovf_env_in_seed_dir(self, m_read_dmi_data, m_exist):
+        """Return True if ovf-env.xml exists in known seed dirs."""
+        # Non-matching Azure chassis-asset-tag
+        m_read_dmi_data.return_value = dsaz.AZURE_CHASSIS_ASSET_TAG + 'X'
+
+        m_exist.return_value = True
+        self.assertTrue(dsaz._is_platform_viable('/some/seed/dir'))
+        m_exist.called_once_with('/other/seed/dir')
+
+    def test_false_on_no_matching_azure_criteria(self):
+        """Report non-azure on unmatched asset tag, ovf-env absent and no dev.
+
+        Return False when the asset tag doesn't match Azure's static
+        AZURE_CHASSIS_ASSET_TAG, no ovf-env.xml files exist in known seed dirs
+        and no devices have a label starting with prefix 'rd_rdfe_'.
+        """
+        self.assertFalse(wrap_and_call(
+            'cloudinit.sources.DataSourceAzure',
+            {'os.path.exists': False,
+             # Non-matching Azure chassis-asset-tag
+             'util.read_dmi_data': dsaz.AZURE_CHASSIS_ASSET_TAG + 'X',
+             'util.which': None},
+            dsaz._is_platform_viable, 'doesnotmatter'))
+        self.assertIn(
+            "DEBUG: Non-Azure DMI asset tag '{0}' discovered.\n".format(
+                dsaz.AZURE_CHASSIS_ASSET_TAG + 'X'),
+            self.logs.getvalue())
+
+
 # vi: ts=4 expandtab