Follow hostname RFCs

Updated hostname sanitization method to more closely follow RFC-952
and RFC-1123. Also moved it to nova.utils, where it seems to fit
better.

Fixes bug 885374

(Patch Set 1) Updated hostname sanitization with more efficient and
              [opinion] more readable implementation.

Change-Id: I60d7ee89867c05950bec1fd53b072a1c6247ebea

nova/tests/test_compute.py

@@ -1237,6 +1237,30 @@ class ComputeAPITestCase(BaseTestCase):
 
         db.instance_destroy(self.context, instance_id)
 
+    def test_hostname_create(self):
+        """Ensure instance hostname is set during creation."""
+        inst_type = instance_types.get_instance_type_by_name('m1.tiny')
+        (instances, _) = self.compute_api.create(self.context,
+                                                 inst_type,
+                                                 None,
+                                                 display_name='test host')
+
+        self.assertEqual('test-host', instances[0]['hostname'])
+
+    def test_hostname_update(self):
+        """Ensure instance hostname is set during an update."""
+        instance_id = self._create_instance({"display_name": "test host"})
+        instance = db.instance_get(self.context, instance_id)
+
+        expected_hostname = 'test-host'
+        actual = self.compute_api.update(self.context,
+                                         instance_id,
+                                         **dict(instance))
+
+        self.assertEqual(expected_hostname, actual['hostname'])
+
+        db.instance_destroy(self.context, instance_id)
+
     def test_set_admin_password(self):
         """Ensure instance can have its admin password set"""
         instance_id = self._create_instance()

nova/utils.py

@@ -1061,3 +1061,16 @@ def total_seconds(td):
     else:
         return ((td.days * 86400 + td.seconds) * 10 ** 6 +
                 td.microseconds) / 10.0 ** 6
+
+
+def sanitize_hostname(hostname):
+    """Return a hostname which conforms to RFC-952 and RFC-1123 specs."""
+    if isinstance(hostname, unicode):
+        hostname = hostname.encode('latin-1', 'ignore')
+
+    hostname = re.sub('[ _]', '-', hostname)
+    hostname = re.sub('[^\w.-]+', '', hostname)
+    hostname = hostname.lower()
+    hostname = hostname.strip('.-')
+
+    return hostname