Add support defaultNamingContext and add --basedn to migrate-ds

There are two sides to this, the server and client side.

On the server side we attempt to add a defaultNamingContext on already
installed servers. This will fail on older 389-ds instances but the
failure is not fatal. New installations on versions of 389-ds that
support this attribute will have it already defined.

On the client side we need to look for both defaultNamingContext and
namingContexts. We still need to check that the defaultNamingContext
is an IPA server (info=IPAV2).

The migration change also takes advantage of this and adds a new
option which allows one to provide a basedn to use instead of trying
to detect it.

https://fedorahosted.org/freeipa/ticket/1919
https://fedorahosted.org/freeipa/ticket/2314

ipalib/plugins/migration.py

@@ -62,6 +62,10 @@ enable it:
 
  ipa config-mod --enable-migration=TRUE
 
+If a base DN is not provided with --basedn then IPA will use either
+the value of defaultNamingContext if it is set or the first value
+in namingContexts set in the root of the remote LDAP server.
+
 EXAMPLES:
 
  The simplest migration, accepting all defaults:
@@ -353,14 +357,14 @@ class migrate_ds(Command):
         Str('usercontainer?',
             cli_name='user_container',
             label=_('User container'),
-            doc=_('RDN of container for users in DS'),
+            doc=_('RDN of container for users in DS relative to base DN'),
             default=u'ou=people',
             autofill=True,
         ),
         Str('groupcontainer?',
             cli_name='group_container',
             label=_('Group container'),
-            doc=_('RDN of container for groups in DS'),
+            doc=_('RDN of container for groups in DS relative to base DN'),
             default=u'ou=groups',
             autofill=True,
         ),
@@ -431,6 +435,11 @@ class migrate_ds(Command):
             doc=_('Continuous operation mode. Errors are reported but the process continues'),
             default=False,
         ),
+        Str('basedn?',
+            cli_name='base_dn',
+            label=_('Base DN'),
+            doc=_('Base DN on remote LDAP server'),
+        ),
     )
 
     has_output = (
@@ -526,14 +535,14 @@ can use their Kerberos accounts.''')
             try:
                 (entries, truncated) = ds_ldap.find_entries(
                     search_filter, ['*'], search_bases[ldap_obj_name],
-                    ds_ldap.SCOPE_ONELEVEL,
+                    _ldap.SCOPE_ONELEVEL,
                     time_limit=0, size_limit=-1,
                     search_refs=True    # migrated DS may contain search references
                 )
             except errors.NotFound:
                 if not options.get('continue',False):
                     raise errors.NotFound(
-                        reason=_('Container for %(container)s not found') % {'container': ldap_obj_name}
+                        reason=_('Container for %(container)s not found at %(search_base)s') % {'container': ldap_obj_name, 'search_base': search_bases[ldap_obj_name]}
                     )
                 else:
                     truncated = False
@@ -627,6 +636,8 @@ can use their Kerberos accounts.''')
 
         config = ldap.get_ipa_config()[1]
 
+        ds_base_dn = options.get('basedn')
+
         # check if migration mode is enabled
         if config.get('ipamigrationenabled', ('FALSE', ))[0] == 'FALSE':
             return dict(result={}, failed={}, enabled=False)
@@ -635,15 +646,19 @@ can use their Kerberos accounts.''')
         ds_ldap = ldap2(shared_instance=False, ldap_uri=ldapuri, base_dn='')
         ds_ldap.connect(bind_dn=options['binddn'], bind_pw=bindpw)
 
-        # retrieve DS base DN
-        (entries, truncated) = ds_ldap.find_entries(
-            '', ['namingcontexts'], '', ds_ldap.SCOPE_BASE,
-            size_limit=-1, time_limit=0,
-        )
-        try:
-            ds_base_dn = entries[0][1]['namingcontexts'][0]
-        except (IndexError, KeyError), e:
-            raise StandardError(str(e))
+        if not ds_base_dn:
+            # retrieve base DN from remote LDAP server
+            (entries, truncated) = ds_ldap.find_entries(
+                '', ['namingcontexts', 'defaultnamingcontext'], '',
+                _ldap.SCOPE_BASE, size_limit=-1, time_limit=0,
+            )
+            if 'defaultnamingcontext' in entries[0][1]:
+                ds_base_dn = entries[0][1]['defaultnamingcontext'][0]
+            else:
+                try:
+                    ds_base_dn = entries[0][1]['namingcontexts'][0]
+                except (IndexError, KeyError), e:
+                    raise StandardError(str(e))
 
         # migrate!
         (migrated, failed) = self.migrate(