Add a new type HostDomain.

HostDomain is like HostAddress with the support of
_ character - RFC1033

openstack services are failing to start when a hostname with underscore
_ is provided.

Example:

```
overcloud-novacompute_edge1-0.internalapi.localdomain
overcloud-novacompute_edge1-0.internalapi
```

Nova use `HostAddressOpt` to define `live_migration_inbound_addr`,
and if a hostname with underscore is present in the config file
then the service fail to start.

Example:

```
/etc/nova/nova.conf
live_migration_inbound_addr =
overcloud-novacompute_edge1-0.internalapi.localdomain
```

FQDN is a domain name that specifies its exact
location in the tree hierarchy of the Domain Name System (DNS).

Underscore are allowed by RFC1033 [1][2][3]. Indeed, while a hostname may not
contain other characters, such as the underscore character (_), other
DNS names may contain the underscore.[1][2].
Systems such as DomainKeys and service records use the underscore.

These changes allow us to use underscore with the `HostDomain`.

[1] https://www.ietf.org/rfc/rfc1912.txt
[2] https://www.ietf.org/rfc/rfc1033.txt
[3] http://domainkeys.sourceforge.net/underscore.html

Co-authored-by: Daniel Bengtsson <dbengt@redhat.com>
Change-Id: I0a0670207f96a987996d329e5efa9a5eb2ce000c
Closes-Bug: #1892044

3 files changed, 76 insertions, 4 deletions

diff --git a/oslo_config/tests/test_types.py b/oslo_config/tests/test_types.py
index 644a239..8ab4a09 100644
--- a/oslo_config/tests/test_types.py
+++ b/oslo_config/tests/test_types.py
@@ -766,6 +766,27 @@ class HostAddressTypeTests(TypeTestHelper, unittest.TestCase):
         self.assertConvertedValue('abc.0-0', 'abc.0-0')
 
 
+class HostDomainTypeTests(TypeTestHelper, unittest.TestCase):
+    type = types.HostDomain()
+
+    def test_invalid_host_addresses(self):
+        self.assertInvalid('-1')
+        self.assertInvalid('3.14')
+        self.assertInvalid('10.0')
+        self.assertInvalid('host..name')
+        self.assertInvalid('org.10')
+        self.assertInvalid('0.0.00')
+
+    def test_valid_host_addresses(self):
+        self.assertConvertedValue('_foo', '_foo')
+        self.assertConvertedValue('host_name', 'host_name')
+        self.assertConvertedValue(
+            'overcloud-novacompute_edge1-0.internalapi.localdomain',
+            'overcloud-novacompute_edge1-0.internalapi.localdomain')
+        self.assertConvertedValue('host_01.co.uk', 'host_01.co.uk')
+        self.assertConvertedValue('_site01001', '_site01001')
+
+
 class HostnameTypeTests(TypeTestHelper, unittest.TestCase):
     type = types.Hostname()
 
@@ -796,8 +817,8 @@ class HostnameTypeTests(TypeTestHelper, unittest.TestCase):
         self.assertInvalid("h'ost'")
         self.assertInvalid("h'ost")
         self.assertInvalid("h$ost")
-        self.assertInvalid("h%ost")
         self.assertInvalid("host_01.co.uk")
+        self.assertInvalid("h%ost")
         self.assertInvalid("host;name=99")
         self.assertInvalid('___site0.1001')
         self.assertInvalid('_site01001')
@@ -808,6 +829,7 @@ class HostnameTypeTests(TypeTestHelper, unittest.TestCase):
     def test_invalid_hostnames_with_numeric_characters(self):
         self.assertInvalid("10.0.0.0")
         self.assertInvalid("3.14")
+        self.assertInvalid('___site0.1001')
         self.assertInvalid("org.10")
         self.assertInvalid('0.0.00')
 
diff --git a/oslo_config/types.py b/oslo_config/types.py
index dfd89bc..a1f75c9 100644
--- a/oslo_config/types.py
+++ b/oslo_config/types.py
@@ -761,11 +761,12 @@ class Hostname(ConfigType):
     :param type_name: Type name to be used in the sample config file.
 
     """
+    HOSTNAME_REGEX = '(?!-)[A-Z0-9-]{1,63}(?<!-)$'
 
     def __init__(self, type_name='hostname value'):
         super(Hostname, self).__init__(type_name=type_name)
 
-    def __call__(self, value):
+    def __call__(self, value, regex=HOSTNAME_REGEX):
         """Check hostname is valid.
 
         Ensures that each segment
@@ -789,7 +790,7 @@ class Hostname(ConfigType):
                              % value)
         if value.endswith("."):
             value = value[:-1]
-        allowed = re.compile("(?!-)[A-Z0-9-]{1,63}(?<!-)$", re.IGNORECASE)
+        allowed = re.compile(regex, re.IGNORECASE)
         if not re.search('[a-zA-Z-]', value.split(".")[-1]):
             raise ValueError('%s contains no non-numeric characters in the '
                              'top-level domain part of the host name and is '
@@ -844,7 +845,8 @@ class HostAddress(ConfigType):
             try:
                 value = self.hostname(value)
             except ValueError:
-                raise ValueError("%s is not a valid host address" % (value,))
+                raise ValueError(
+                    "%s is not a valid host address" % (value,))
         return value
 
     def __repr__(self):
@@ -857,6 +859,45 @@ class HostAddress(ConfigType):
         return value
 
 
+class HostDomain(HostAddress):
+    """Host Domain type.
+
+    Like HostAddress with the support of _ character.
+
+    :param version: defines which version should be explicitly
+                    checked (4 or 6) in case of an IP address
+    :param type_name: Type name to be used in the sample config file.
+    """
+    # DOMAIN_REGEX is HOSTNAME_REGEX with the _ character added
+    DOMAIN_REGEX = '(?!-)[A-Z0-9-_]{1,63}(?<!-)$'
+
+    def __call__(self, value):
+        """Checks if is a valid IP/hostname.
+
+        If not a valid IP, makes sure it is not a mistyped IP before
+        performing checks for it as a hostname.
+
+        """
+
+        try:
+            value = super(HostDomain, self).__call__(value)
+        except ValueError:
+            # Check if domain is valid
+            # Add support of underscore
+            # https://www.ietf.org/rfc/rfc1912,
+            # http://domainkeys.sourceforge.net/underscore.html
+            # https://bugs.launchpad.net/oslo.config/+bug/1892044
+            try:
+                value = self.hostname(value, regex=self.DOMAIN_REGEX)
+            except ValueError:
+                raise ValueError(
+                    "%s is not a valid host address" % (value,))
+        return value
+
+    def __repr__(self):
+        return 'HostDomain'
+
+
 class URI(ConfigType):
 
     """URI type
diff --git a/releasenotes/notes/add-HostDomain-implement-rfc1033-c985a3054f824e9d.yaml b/releasenotes/notes/add-HostDomain-implement-rfc1033-c985a3054f824e9d.yaml
new file mode 100644
index 0000000..1f8d153
--- /dev/null
+++ b/releasenotes/notes/add-HostDomain-implement-rfc1033-c985a3054f824e9d.yaml
@@ -0,0 +1,9 @@
+---
+features:
+  - |
+    Add ``HostDomain`` to handle address with underscore. Underscore are
+    allowed in domain by RFC1033 [1][2][3].
+
+    - [1] https://www.ietf.org/rfc/rfc1912.txt
+    - [2] https://www.ietf.org/rfc/rfc1033.txt
+    - [3] http://domainkeys.sourceforge.net/underscore.html