Enable SOA serial autoincrement

SOA serial autoincrement is a requirement for major DNS features,
e.g. zone transfers or DNSSEC. Enable it by default in named.conf
both for new and upgraded installations. Name of the bind-dyndb-ldap
option is "serial_autoincrement".

From now on, idnsSOAserial attribute also has to be put to
replication agreement exclude list as serial will be incremented
on each DNS server separately and won't be shared. Exclude list
has to be updated both for new replication agreements and the
current ones.

Minimum number of connections for bind-dyndb-ldap has been rised
to 4 connections, the setting will be updated during package upgrade.

https://fedorahosted.org/freeipa/ticket/2554

install/tools/ipa-upgradeconfig

@@ -302,7 +302,7 @@ def upgrade_httpd_selinux(fstore):
     http = httpinstance.HTTPInstance(fstore)
     http.configure_selinux_for_httpd()
 
-def enable_psearch_for_named():
+def named_enable_psearch():
     """
     From IPA 3.0, persistent search is a preferred mechanism for new DNS zone
     detection and is also needed for other features (DNSSEC, SOA serial
@@ -322,11 +322,13 @@ def enable_psearch_for_named():
         return
 
     try:
-        psearch = bindinstance.named_conf_get_directive('psearch').lower()
+        psearch = bindinstance.named_conf_get_directive('psearch')
     except IOError, e:
         root_logger.debug('Cannot retrieve psearch option from %s: %s',
                 bindinstance.NAMED_CONF, e)
         return
+    else:
+        psearch = None if psearch is None else psearch.lower()
     if not sysupgrade.get_upgrade_state('named.conf', 'psearch_enabled'):
         if psearch != "yes":
             try:
@@ -343,7 +345,8 @@ def enable_psearch_for_named():
     # make sure number of connections is right
     minimum_connections = 2
     if psearch == 'yes':
-        minimum_connections = 3
+        # serial_autoincrement increased the minimal number of connections to 4
+        minimum_connections = 4
     try:
         connections = bindinstance.named_conf_get_directive('connections')
     except IOError, e:
@@ -373,6 +376,59 @@ def enable_psearch_for_named():
         root_logger.debug('No changes made')
     return changed
 
+def named_enable_serial_autoincrement():
+    """
+    Serial autoincrement is a requirement for zone transfers or DNSSEC. It
+    should be enabled both for new installs and upgraded servers.
+
+    When some change in named.conf is done, this functions returns True
+    """
+    changed = False
+
+    root_logger.info('[Enabling serial autoincrement in DNS]')
+
+    if not bindinstance.named_conf_exists():
+        # DNS service may not be configured
+        root_logger.debug('DNS not configured')
+        return changed
+
+    try:
+        psearch = bindinstance.named_conf_get_directive('psearch')
+        serial_autoincrement = bindinstance.named_conf_get_directive(
+                                    'serial_autoincrement')
+    except IOError, e:
+        root_logger.debug('Cannot retrieve psearch option from %s: %s',
+                bindinstance.NAMED_CONF, e)
+        return changed
+    else:
+        psearch = None if psearch is None else psearch.lower()
+        serial_autoincrement = None if serial_autoincrement is None \
+                else serial_autoincrement.lower()
+
+    # enable SOA serial autoincrement
+    if not sysupgrade.get_upgrade_state('named.conf', 'autoincrement_enabled'):
+        if psearch != "yes":    # psearch is required
+            root_logger.debug('Persistent search is disabled, '
+                    'serial autoincrement cannot be enabled')
+        else:
+            if serial_autoincrement != 'yes':
+                try:
+                    bindinstance.named_conf_set_directive('serial_autoincrement', 'yes')
+                except IOError, e:
+                    root_logger.error('Cannot enable serial_autoincrement in %s: %s',
+                            bindinstance.NAMED_CONF, e)
+                    return changed
+                else:
+                    root_logger.debug('Serial autoincrement enabled')
+                    changed = True
+            else:
+                root_logger.debug('Serial autoincrement is alredy enabled')
+        sysupgrade.set_upgrade_state('named.conf', 'autoincrement_enabled', True)
+    else:
+        root_logger.debug('Skip serial autoincrement check')
+
+    return changed
+
 def main():
     """
     Get some basics about the system. If getting those basics fail then
@@ -435,9 +491,11 @@ def main():
 
     cleanup_kdc(fstore)
     upgrade_ipa_profile(krbctx.default_realm)
-    changed = enable_psearch_for_named()
-    if changed:
+    changed_psearch = named_enable_psearch()
+    changed_autoincrement = named_enable_serial_autoincrement()
+    if changed_psearch or changed_autoincrement:
         # configuration has changed, restart the name server
+        root_logger.info('Changes to named.conf have been made, restart named')
         bindinstance.BindInstance(fstore).restart()
 
 if __name__ == '__main__':