dyndns: New option dyndns_update_ptr

https://fedorahosted.org/sssd/ticket/1832

While some servers, such as FreeIPA allow the PTR record to be
synchronized when the forward record is updated, other servers,
including Active Directory, require that the PTR record is synchronized
manually.

This patch adds a new option, dyndns_update_ptr that automatically
generates appropriate DNS update message for updating the reverse zone.

This option is off by default in the IPA provider.

Also renames be_nsupdate_create_msg to be_nsupdate_create_fwd_msg

src/config/SSSDConfig/__init__.py.in

@@ -129,6 +129,7 @@ option_strings = {
     'dyndns_ttl' : _("The TTL to apply to the client's DNS entry after updating it"),
     'dyndns_iface' : _("The interface whose IP should be used for dynamic DNS updates"),
     'dyndns_refresh_interval' : _("How often to periodically update the client's DNS entry"),
+    'dyndns_update_ptr' : _("Whether the provider should explicitly update the PTR record as well"),
 
     # [provider/ipa]
     'ipa_domain' : _('IPA domain'),

src/config/SSSDConfigTest.py

@@ -511,6 +511,7 @@ def testListOptions(self):
             'dyndns_ttl',
             'dyndns_iface',
             'dyndns_refresh_interval',
+            'dyndns_update_ptr',
             'override_gid',
             'case_sensitive',
             'override_homedir',
@@ -858,6 +859,7 @@ def testRemoveProvider(self):
             'dyndns_ttl',
             'dyndns_iface',
             'dyndns_refresh_interval',
+            'dyndns_update_ptr',
             'override_gid',
             'case_sensitive',
             'override_homedir',

src/config/etc/sssd.api.conf

@@ -126,6 +126,7 @@ dyndns_update = bool, None, false
 dyndns_ttl = int, None, false
 dyndns_iface = str, None, false
 dyndns_refresh_interval = int, None, false
+dyndns_update_ptr = bool, None, false
 
 # Special providers
 [provider/permit]

src/man/sssd-ipa.5.xml

@@ -219,6 +219,26 @@
                     </listitem>
                 </varlistentry>
 
+                <varlistentry>
+                    <term>dyndns_update_ptr (bool)</term>
+                    <listitem>
+                        <para>
+                            Whether the PTR record should also be explicitly
+                            updated when updating the client's DNS records.
+                            Applicable only when dyndns_update is true.
+                        </para>
+                        <para>
+                            This options should be False in most IPA
+                            deployments as the IPA server generates the
+                            PTR records automatically when forward records
+                            are changed.
+                        </para>
+                        <para>
+                            Default: False (disabled)
+                        </para>
+                    </listitem>
+                </varlistentry>
+
                 <varlistentry>
                     <term>ipa_hbac_search_base (string)</term>
                     <listitem>