azure: avoid re-running cloud-init when instance-id is byte-swapped (#84)

Azure stores the instance ID with an incorrect byte ordering for the
first three hyphen delimited parts. This results in invalid
is_new_instance checks forcing Azure datasource to recrawl the metadata
service.

When persisting instance-id from the metadata service, swap the
instance-id string byte order such that it is consistent with
that returned by dmi information. Check whether the instance-id
string is a byte-swapped match when determining correctly whether 
the Azure platform instance-id has actually changed. 

2 files changed, 40 insertions, 3 deletions

diff --git a/tests/unittests/test_datasource/test_azure.py b/tests/unittests/test_datasource/test_azure.py
index 59e351de..a809fd87 100644
--- a/tests/unittests/test_datasource/test_azure.py
+++ b/tests/unittests/test_datasource/test_azure.py
@@ -477,7 +477,7 @@ scbus-1 on xpt0 bus 0
             'public-keys': [],
         })
 
-        self.instance_id = 'test-instance-id'
+        self.instance_id = 'D0DF4C54-4ECB-4A4B-9954-5BDF3ED5C3B8'
 
         def _dmi_mocks(key):
             if key == 'system-uuid':
@@ -645,7 +645,7 @@ scbus-1 on xpt0 bus 0
             'azure_data': {
                 'configurationsettype': 'LinuxProvisioningConfiguration'},
             'imds': NETWORK_METADATA,
-            'instance-id': 'test-instance-id',
+            'instance-id': 'D0DF4C54-4ECB-4A4B-9954-5BDF3ED5C3B8',
             'local-hostname': u'myhost',
             'random_seed': 'wild'}
 
@@ -1091,6 +1091,24 @@ scbus-1 on xpt0 bus 0
         self.assertTrue(ret)
         self.assertEqual('value', dsrc.metadata['test'])
 
+    def test_instance_id_endianness(self):
+        """Return the previous iid when dmi uuid is the byteswapped iid."""
+        ds = self._get_ds({'ovfcontent': construct_valid_ovf_env()})
+        # byte-swapped previous
+        write_file(
+            os.path.join(self.paths.cloud_dir, 'data', 'instance-id'),
+            '544CDFD0-CB4E-4B4A-9954-5BDF3ED5C3B8')
+        ds.get_data()
+        self.assertEqual(
+            '544CDFD0-CB4E-4B4A-9954-5BDF3ED5C3B8', ds.metadata['instance-id'])
+        # not byte-swapped previous
+        write_file(
+            os.path.join(self.paths.cloud_dir, 'data', 'instance-id'),
+            '644CDFD0-CB4E-4B4A-9954-5BDF3ED5C3B8')
+        ds.get_data()
+        self.assertEqual(
+            'D0DF4C54-4ECB-4A4B-9954-5BDF3ED5C3B8', ds.metadata['instance-id'])
+
     def test_instance_id_from_dmidecode_used(self):
         ds = self._get_ds({'ovfcontent': construct_valid_ovf_env()})
         ds.get_data()
@@ -1292,7 +1310,7 @@ class TestAzureBounce(CiTestCase):
 
         def _dmi_mocks(key):
             if key == 'system-uuid':
-                return 'test-instance-id'
+                return 'D0DF4C54-4ECB-4A4B-9954-5BDF3ED5C3B8'
             elif key == 'chassis-asset-tag':
                 return '7783-7084-3265-9085-8269-3286-77'
             raise RuntimeError('should not get here')
diff --git a/tests/unittests/test_datasource/test_azure_helper.py b/tests/unittests/test_datasource/test_azure_helper.py
index bd17f636..007df09f 100644
--- a/tests/unittests/test_datasource/test_azure_helper.py
+++ b/tests/unittests/test_datasource/test_azure_helper.py
@@ -170,6 +170,25 @@ class TestGoalStateParsing(CiTestCase):
         goal_state = self._get_goal_state(instance_id=instance_id)
         self.assertEqual(instance_id, goal_state.instance_id)
 
+    def test_instance_id_byte_swap(self):
+        """Return true when previous_iid is byteswapped current_iid"""
+        previous_iid = "D0DF4C54-4ECB-4A4B-9954-5BDF3ED5C3B8"
+        current_iid = "544CDFD0-CB4E-4B4A-9954-5BDF3ED5C3B8"
+        self.assertTrue(
+            azure_helper.is_byte_swapped(previous_iid, current_iid))
+
+    def test_instance_id_no_byte_swap_same_instance_id(self):
+        previous_iid = "D0DF4C54-4ECB-4A4B-9954-5BDF3ED5C3B8"
+        current_iid = "D0DF4C54-4ECB-4A4B-9954-5BDF3ED5C3B8"
+        self.assertFalse(
+            azure_helper.is_byte_swapped(previous_iid, current_iid))
+
+    def test_instance_id_no_byte_swap_diff_instance_id(self):
+        previous_iid = "D0DF4C54-4ECB-4A4B-9954-5BDF3ED5C3B8"
+        current_iid = "G0DF4C54-4ECB-4A4B-9954-5BDF3ED5C3B8"
+        self.assertFalse(
+            azure_helper.is_byte_swapped(previous_iid, current_iid))
+
     def test_certificates_xml_parsed_and_fetched_correctly(self):
         http_client = mock.MagicMock()
         certificates_url = 'TestCertificatesUrl'