Provide API to check if IPA DNS is enabled on some server

Fixes: https://fedorahosted.org/freeipa/ticket/600

API.txt

@@ -467,6 +467,11 @@ option: Str('version?', exclude='webui', flags=['no_option', 'no_output'])
 output: Output('summary', (<type 'unicode'>, <type 'NoneType'>), 'User-friendly description of action performed')
 output: Entry('result', <type 'dict'>, Gettext('A dictionary representing an LDAP entry', domain='ipa', localedir=None))
 output: Output('value', <type 'unicode'>, "The primary_key value of the entry, e.g. 'jdoe' for a user")
+command: dns_is_enabled
+args: 0,0,3
+output: Output('summary', (<type 'unicode'>, <type 'NoneType'>), 'User-friendly description of action performed')
+output: Output('result', <type 'bool'>, 'True means the operation was successful')
+output: Output('value', <type 'unicode'>, "The primary_key value of the entry, e.g. 'jdoe' for a user")
 command: dns_resolve
 args: 1,0,3
 arg: Str('hostname', label=Gettext('Hostname', domain='ipa', localedir=None))

ipalib/plugins/dns.py

@@ -616,3 +616,28 @@ class dns_resolve(Command):
         return dict(result=True, value=query)
 
 api.register(dns_resolve)
+
+class dns_is_enabled(Command):
+    """
+    Checks if any of the servers has the DNS service enabled.
+    """
+    INTERNAL = True
+    has_output = output.standard_value
+
+    base_dn = 'cn=master,cn=ipa,cn=etc,%s' % api.env.basedn
+    filter = '(&(objectClass=ipaConfigObject)(cn=DNS))'
+
+    def execute(self, *args, **options):
+        ldap = self.api.Backend.ldap2
+        dns_enabled = False
+
+        try:
+            ent = ldap.find_entries(filter=filter, base_dn=base_dn)
+            if len(e):
+                dns_enabled = True
+        except Exception, e:
+            pass
+
+        return dict(result=dns_enabled, value=u'')
+
+api.register(dns_is_enabled)