Give instance default hostname if hostname is empty

Instance hostname is generated by displayname, currently, displayname
can be '----', and other Non-ASCII character such as Chinese characters,
sanitize_hostname will return empty in such cases.

This patch adds a helper function _default_host_name to give an instance
default name if sanitize_hostname returns empty hostname. And,
sanitize_hostname will truncated to 63 if the host name is too long.

Also Window, Linux, and Dnsmasq have different limitation:

Windows: 255 (net_bios limit to 15, but window will truncate it)
Linux: 64
Dnsmasq: 63

Due to nova-network will leverage dnsmasq to set hostname, so we chose
63.

Besides, added more test cases to cover sanitize_hostname.

DocImpact
Change-Id: I443b51e0576cf657d96e498d6700bfc34d987301
Closes-Bug: #1495388
Co-authored-by: Alex Xu <hejie.xu@intel.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/nova/tests/unit/test_utils.py b/nova/tests/unit/test_utils.py
index f4482b19a2..ca68a3e01e 100644
--- a/nova/tests/unit/test_utils.py
+++ b/nova/tests/unit/test_utils.py
@@ -94,6 +94,40 @@ class GenericUtilsTestCase(test.NoDBTestCase):
         hostname = "<}\x1fh\x10e\x08l\x02l\x05o\x12!{>"
         self.assertEqual("hello", utils.sanitize_hostname(hostname))
 
+    def test_hostname_has_default(self):
+        hostname = u"\u7684hello"
+        defaultname = "Server-1"
+        self.assertEqual("hello", utils.sanitize_hostname(hostname,
+                                                          defaultname))
+
+    def test_hostname_empty_has_default(self):
+        hostname = u"\u7684"
+        defaultname = "Server-1"
+        self.assertEqual(defaultname, utils.sanitize_hostname(hostname,
+                                                              defaultname))
+
+    def test_hostname_empty_has_default_too_long(self):
+        hostname = u"\u7684"
+        defaultname = "a" * 64
+        self.assertEqual("a" * 63, utils.sanitize_hostname(hostname,
+                                                           defaultname))
+
+    def test_hostname_empty_no_default(self):
+        hostname = u"\u7684"
+        self.assertEqual("", utils.sanitize_hostname(hostname))
+
+    def test_hostname_empty_minus_period(self):
+        hostname = "---..."
+        self.assertEqual("", utils.sanitize_hostname(hostname))
+
+    def test_hostname_with_space(self):
+        hostname = " a b c "
+        self.assertEqual("a-b-c", utils.sanitize_hostname(hostname))
+
+    def test_hostname_too_long(self):
+        hostname = "a" * 64
+        self.assertEqual(63, len(utils.sanitize_hostname(hostname)))
+
     def test_generate_password(self):
         password = utils.generate_password()
         self.assertTrue([c for c in password if c in '0123456789'])