Replace DNS client based on acutil with python-dns

IPA client and server tool set used authconfig acutil module to
for client DNS operations. This is not optimal DNS interface for
several reasons:
- does not provide native Python object oriented interface
  but but rather C-like interface based on functions and
  structures which is not easy to use and extend
- acutil is not meant to be used by third parties besides
  authconfig and thus can break without notice

Replace the acutil with python-dns package which has a feature rich
interface for dealing with all different aspects of DNS including
DNSSEC. The main target of this patch is to replace all uses of
acutil DNS library with a use python-dns. In most cases, even
though the larger parts of the code are changed, the actual
functionality is changed only in the following cases:
- redundant DNS checks were removed from verify_fqdn function
  in installutils to make the whole DNS check simpler and
  less error-prone. Logging was improves for the remaining
  checks
- improved logging for ipa-client-install DNS discovery

https://fedorahosted.org/freeipa/ticket/2730
https://fedorahosted.org/freeipa/ticket/1837

1 files changed, 13 insertions, 11 deletions

diff --git a/ipapython/ipautil.py b/ipapython/ipautil.py
index 4a9db11e2..8884e7be9 100644
--- a/ipapython/ipautil.py
+++ b/ipapython/ipautil.py
@@ -41,6 +41,8 @@ import re
 import xmlrpclib
 import datetime
 import netaddr
+from dns import resolver, rdatatype
+from dns.exception import DNSException
 
 from ipapython.ipa_log_manager import *
 from ipapython import ipavalidate
@@ -611,17 +613,6 @@ def ipa_generate_password(characters=None,pwd_len=None):
         rndpwd += rndchar
     return rndpwd
 
-def parse_items(text):
-    '''Given text with items separated by whitespace or comma, return a list of those items
-
-    The returned list only contains non-empty items.
-    '''
-    split_re = re.compile('[ ,\t\n]+')
-    items = split_re.split(text)
-    for item in items[:]:
-        if not item: items.remove(item)
-    return items
-
 def user_input(prompt, default = None, allow_empty = True):
     if default == None:
         while True:
@@ -747,6 +738,17 @@ def bind_port_responder(port, socket_type=socket.SOCK_STREAM, socket_timeout=Non
     finally:
         s.close()
 
+def is_host_resolvable(fqdn):
+    for rdtype in (rdatatype.A, rdatatype.AAAA):
+        try:
+            resolver.query(fqdn, rdtype)
+        except DNSException:
+            continue
+        else:
+            return True
+
+    return False
+
 def get_ipa_basedn(conn):
     """
     Get base DN of IPA suffix in given LDAP server.