Use default reverse zone consistently

When a new reverse zone is to be generated based on an IP address without
a network prefix length, we need to use some default value. While netaddr
library default ones (32b for IPv4 and 128b for IPv6) are not very sensible
we should use the defaults already applied in installers. That is 24b for
IPv6 and 64 for IPv6.

Test case has been added to cover the new default.

https://fedorahosted.org/freeipa/ticket/2461

ipalib/plugins/dns.py

@@ -33,7 +33,8 @@ from ipalib.plugins.baseldap import *
 from ipalib import _, ngettext
 from ipalib.util import (validate_zonemgr, normalize_zonemgr,
         validate_hostname, validate_dns_label, validate_domain_name,
-        get_dns_forward_zone_update_policy, get_dns_reverse_zone_update_policy)
+        get_dns_forward_zone_update_policy, get_dns_reverse_zone_update_policy,
+        get_reverse_zone_default)
 from ipapython.ipautil import valid_ip, CheckedIPAddress, is_host_resolvable
 
 __doc__ = _("""
@@ -254,6 +255,14 @@ def _create_zone_serial():
     return int(time.time())
 
 def _reverse_zone_name(netstr):
+    try:
+        netaddr.IPAddress(netstr)
+    except (netaddr.AddrFormatError, ValueError):
+        pass
+    else:
+        # use more sensible default prefix than netaddr default
+        return unicode(get_reverse_zone_default(netstr))
+
     net = netaddr.IPNetwork(netstr)
     items = net.ip.reverse_dns.split('.')
     if net.version == 4:

ipalib/util.py

@@ -27,6 +27,7 @@ import time
 import socket
 import re
 import decimal
+import netaddr
 from types import NoneType
 from weakref import WeakKeyDictionary
 from dns import resolver, rdatatype
@@ -172,6 +173,12 @@ def normalize_zonemgr(zonemgr):
 
     return zonemgr
 
+def normalize_zone(zone):
+    if zone[-1] != '.':
+        return zone + '.'
+    else:
+        return zone
+
 def validate_dns_label(dns_label, allow_underscore=False):
     label_chars = r'a-z0-9'
     underscore_err_msg = ''
@@ -487,6 +494,17 @@ def get_dns_reverse_zone_update_policy(realm, reverse_zone, rrtypes=('PTR',)):
 
     return policy
 
+def get_reverse_zone_default(ip_address):
+    ip = netaddr.IPAddress(ip_address)
+    items = ip.reverse_dns.split('.')
+
+    if ip.version == 4:
+        items = items[1:]   # /24 for IPv4
+    elif ip.version == 6:
+        items = items[16:]  # /64 for IPv6
+
+    return normalize_zone('.'.join(items))
+
 def validate_rdn_param(ugettext, value):
     try:
         rdn = RDN(value)