path: root/source4/dsdb/samdb/ldb_modules/repl_meta_data.c

/*
   ldb database library

   Copyright (C) Simo Sorce  2004-2008
   Copyright (C) Andrew Bartlett <abartlet@samba.org> 2005
   Copyright (C) Andrew Tridgell 2005
   Copyright (C) Stefan Metzmacher <metze@samba.org> 2007
   Copyright (C) Matthieu Patou <mat@samba.org> 2010

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

/*
 *  Name: ldb
 *
 *  Component: ldb repl_meta_data module
 *
 *  Description: - add a unique objectGUID onto every new record,
 *               - handle whenCreated, whenChanged timestamps
 *               - handle uSNCreated, uSNChanged numbers
 *               - handle replPropertyMetaData attribute
 *
 *  Author: Simo Sorce
 *  Author: Stefan Metzmacher
 */

#include "includes.h"
#include "ldb_module.h"
#include "dsdb/samdb/samdb.h"
#include "dsdb/common/proto.h"
#include "../libds/common/flags.h"
#include "librpc/gen_ndr/ndr_misc.h"
#include "librpc/gen_ndr/ndr_drsuapi.h"
#include "librpc/gen_ndr/ndr_drsblobs.h"
#include "param/param.h"
#include "libcli/security/security.h"
#include "lib/util/dlinklist.h"
#include "dsdb/samdb/ldb_modules/util.h"
#include "lib/util/binsearch.h"
#include "lib/util/tsort.h"

struct replmd_private {
	TALLOC_CTX *la_ctx;
	struct la_entry *la_list;
	TALLOC_CTX *bl_ctx;
	struct la_backlink *la_backlinks;
	struct nc_entry {
		struct nc_entry *prev, *next;
		struct ldb_dn *dn;
		uint64_t mod_usn;
		uint64_t mod_usn_urgent;
	} *ncs;
};

struct la_entry {
	struct la_entry *next, *prev;
	struct drsuapi_DsReplicaLinkedAttribute *la;
};

struct replmd_replicated_request {
	struct ldb_module *module;
	struct ldb_request *req;

	const struct dsdb_schema *schema;

	/* the controls we pass down */
	struct ldb_control **controls;

	/* details for the mode where we apply a bunch of inbound replication meessages */
	bool apply_mode;
	uint32_t index_current;
	struct dsdb_extended_replicated_objects *objs;

	struct ldb_message *search_msg;

	uint64_t seq_num;
	bool is_urgent;
};

enum urgent_situation {
	REPL_URGENT_ON_CREATE = 1,
	REPL_URGENT_ON_UPDATE = 2,
	REPL_URGENT_ON_DELETE = 4
};


static const struct {
	const char *update_name;
	enum urgent_situation repl_situation;
} urgent_objects[] = {
		{"nTDSDSA", (REPL_URGENT_ON_CREATE | REPL_URGENT_ON_DELETE)},
		{"crossRef", (REPL_URGENT_ON_CREATE | REPL_URGENT_ON_DELETE)},
		{"attributeSchema", (REPL_URGENT_ON_CREATE | REPL_URGENT_ON_UPDATE)},
		{"classSchema", (REPL_URGENT_ON_CREATE | REPL_URGENT_ON_UPDATE)},
		{"secret", (REPL_URGENT_ON_CREATE | REPL_URGENT_ON_UPDATE)},
		{"rIDManager", (REPL_URGENT_ON_CREATE | REPL_URGENT_ON_UPDATE)},
		{NULL, 0}
};

/* Attributes looked for when updating or deleting, to check for a urgent replication needed */
static const char *urgent_attrs[] = {
		"lockoutTime",
		"pwdLastSet",
		"userAccountControl",
		NULL
};


static bool replmd_check_urgent_objectclass(const struct ldb_message_element *objectclass_el,
					enum urgent_situation situation)
{
	unsigned int i, j;
	for (i=0; urgent_objects[i].update_name; i++) {

		if ((situation & urgent_objects[i].repl_situation) == 0) {
			continue;
		}

		for (j=0; j<objectclass_el->num_values; j++) {
			const struct ldb_val *v = &objectclass_el->values[j];
			if (ldb_attr_cmp((const char *)v->data, urgent_objects[i].update_name) == 0) {
				return true;
			}
		}
	}
	return false;
}

static bool replmd_check_urgent_attribute(const struct ldb_message_element *el)
{
	if (ldb_attr_in_list(urgent_attrs, el->name)) {
		return true;
	}
	return false;
}


static int replmd_replicated_apply_next(struct replmd_replicated_request *ar);

/*
  initialise the module
  allocate the private structure and build the list
  of partition DNs for use by replmd_notify()
 */
static int replmd_init(struct ldb_module *module)
{
	struct replmd_private *replmd_private;
	struct ldb_context *ldb = ldb_module_get_ctx(module);

	replmd_private = talloc_zero(module, struct replmd_private);
	if (replmd_private == NULL) {
		ldb_oom(ldb);
		return LDB_ERR_OPERATIONS_ERROR;
	}
	ldb_module_set_private(module, replmd_private);

	return ldb_next_init(module);
}

/*
  cleanup our per-transaction contexts
 */
static void replmd_txn_cleanup(struct replmd_private *replmd_private)
{
	talloc_free(replmd_private->la_ctx);
	replmd_private->la_list = NULL;
	replmd_private->la_ctx = NULL;

	talloc_free(replmd_private->bl_ctx);
	replmd_private->la_backlinks = NULL;
	replmd_private->bl_ctx = NULL;
}


struct la_backlink {
	struct la_backlink *next, *prev;
	const char *attr_name;
	struct GUID forward_guid, target_guid;
	bool active;
};

/*
  process a backlinks we accumulated during a transaction, adding and
  deleting the backlinks from the target objects
 */
static int replmd_process_backlink(struct ldb_module *module, struct la_backlink *bl, struct ldb_request *parent)
{
	struct ldb_dn *target_dn, *source_dn;
	int ret;
	struct ldb_context *ldb = ldb_module_get_ctx(module);
	struct ldb_message *msg;
	TALLOC_CTX *tmp_ctx = talloc_new(bl);
	char *dn_string;

	/*
	  - find DN of target
	  - find DN of source
	  - construct ldb_message
              - either an add or a delete
	 */
	ret = dsdb_module_dn_by_guid(module, tmp_ctx, &bl->target_guid, &target_dn, parent);
	if (ret != LDB_SUCCESS) {
		DEBUG(2,(__location__ ": WARNING: Failed to find target DN for linked attribute with GUID %s\n",
			 GUID_string(bl, &bl->target_guid)));
		return LDB_SUCCESS;
	}

	ret = dsdb_module_dn_by_guid(module, tmp_ctx, &bl->forward_guid, &source_dn, parent);
	if (ret != LDB_SUCCESS) {
		ldb_asprintf_errstring(ldb, "Failed to find source DN for linked attribute with GUID %s\n",
				       GUID_string(bl, &bl->forward_guid));
		talloc_free(tmp_ctx);
		return ret;
	}

	msg = ldb_msg_new(tmp_ctx);
	if (msg == NULL) {
		ldb_module_oom(module);
		talloc_free(tmp_ctx);
		return LDB_ERR_OPERATIONS_ERROR;
	}

	/* construct a ldb_message for adding/deleting the backlink */
	msg->dn = target_dn;
	dn_string = ldb_dn_get_extended_linearized(tmp_ctx, source_dn, 1);
	if (!dn_string) {
		ldb_module_oom(module);
		talloc_free(tmp_ctx);
		return LDB_ERR_OPERATIONS_ERROR;
	}
	ret = ldb_msg_add_steal_string(msg, bl->attr_name, dn_string);
	if (ret != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ret;
	}
	msg->elements[0].flags = bl->active?LDB_FLAG_MOD_ADD:LDB_FLAG_MOD_DELETE;

	/* a backlink should never be single valued. Unfortunately the
	   exchange schema has a attribute
	   msExchBridgeheadedLocalConnectorsDNBL which is single
	   valued and a backlink. We need to cope with that by
	   ignoring the single value flag */
	msg->elements[0].flags |= LDB_FLAG_INTERNAL_DISABLE_SINGLE_VALUE_CHECK;

	ret = dsdb_module_modify(module, msg, DSDB_FLAG_NEXT_MODULE, parent);
	if (ret == LDB_ERR_NO_SUCH_ATTRIBUTE && !bl->active) {
		/* we allow LDB_ERR_NO_SUCH_ATTRIBUTE as success to
		   cope with possible corruption where the backlink has
		   already been removed */
		DEBUG(3,("WARNING: backlink from %s already removed from %s - %s\n",
			 ldb_dn_get_linearized(target_dn),
			 ldb_dn_get_linearized(source_dn),
			 ldb_errstring(ldb)));
		ret = LDB_SUCCESS;
	} else if (ret != LDB_SUCCESS) {
		ldb_asprintf_errstring(ldb, "Failed to %s backlink from %s to %s - %s",
				       bl->active?"add":"remove",
				       ldb_dn_get_linearized(source_dn),
				       ldb_dn_get_linearized(target_dn),
				       ldb_errstring(ldb));
		talloc_free(tmp_ctx);
		return ret;
	}
	talloc_free(tmp_ctx);
	return ret;
}

/*
  add a backlink to the list of backlinks to add/delete in the prepare
  commit
 */
static int replmd_add_backlink(struct ldb_module *module, const struct dsdb_schema *schema,
			       struct GUID *forward_guid, struct GUID *target_guid,
			       bool active, const struct dsdb_attribute *schema_attr, bool immediate)
{
	const struct dsdb_attribute *target_attr;
	struct la_backlink *bl;
	struct replmd_private *replmd_private =
		talloc_get_type_abort(ldb_module_get_private(module), struct replmd_private);

	target_attr = dsdb_attribute_by_linkID(schema, schema_attr->linkID ^ 1);
	if (!target_attr) {
		/*
		 * windows 2003 has a broken schema where the
		 * definition of msDS-IsDomainFor is missing (which is
		 * supposed to be the backlink of the
		 * msDS-HasDomainNCs attribute
		 */
		return LDB_SUCCESS;
	}

	/* see if its already in the list */
	for (bl=replmd_private->la_backlinks; bl; bl=bl->next) {
		if (GUID_equal(forward_guid, &bl->forward_guid) &&
		    GUID_equal(target_guid, &bl->target_guid) &&
		    (target_attr->lDAPDisplayName == bl->attr_name ||
		     strcmp(target_attr->lDAPDisplayName, bl->attr_name) == 0)) {
			break;
		}
	}

	if (bl) {
		/* we found an existing one */
		if (bl->active == active) {
			return LDB_SUCCESS;
		}
		DLIST_REMOVE(replmd_private->la_backlinks, bl);
		talloc_free(bl);
		return LDB_SUCCESS;
	}

	if (replmd_private->bl_ctx == NULL) {
		replmd_private->bl_ctx = talloc_new(replmd_private);
		if (replmd_private->bl_ctx == NULL) {
			ldb_module_oom(module);
			return LDB_ERR_OPERATIONS_ERROR;
		}
	}

	/* its a new one */
	bl = talloc(replmd_private->bl_ctx, struct la_backlink);
	if (bl == NULL) {
		ldb_module_oom(module);
		return LDB_ERR_OPERATIONS_ERROR;
	}

	/* Ensure the schema does not go away before the bl->attr_name is used */
	if (!talloc_reference(bl, schema)) {
		talloc_free(bl);
		ldb_module_oom(module);
		return LDB_ERR_OPERATIONS_ERROR;
	}

	bl->attr_name = target_attr->lDAPDisplayName;
	bl->forward_guid = *forward_guid;
	bl->target_guid = *target_guid;
	bl->active = active;

	/* the caller may ask for this backlink to be processed
	   immediately */
	if (immediate) {
		int ret = replmd_process_backlink(module, bl, NULL);
		talloc_free(bl);
		return ret;
	}

	DLIST_ADD(replmd_private->la_backlinks, bl);

	return LDB_SUCCESS;
}


/*
 * Callback for most write operations in this module:
 *
 * notify the repl task that a object has changed. The notifies are
 * gathered up in the replmd_private structure then written to the
 * @REPLCHANGED object in each partition during the prepare_commit
 */
static int replmd_op_callback(struct ldb_request *req, struct ldb_reply *ares)
{
	int ret;
	struct replmd_replicated_request *ac =
		talloc_get_type_abort(req->context, struct replmd_replicated_request);
	struct replmd_private *replmd_private =
		talloc_get_type_abort(ldb_module_get_private(ac->module), struct replmd_private);
	struct nc_entry *modified_partition;
	struct ldb_control *partition_ctrl;
	const struct dsdb_control_current_partition *partition;

	struct ldb_control **controls;

	partition_ctrl = ldb_reply_get_control(ares, DSDB_CONTROL_CURRENT_PARTITION_OID);

	controls = ares->controls;
	if (ldb_request_get_control(ac->req,
				    DSDB_CONTROL_CURRENT_PARTITION_OID) == NULL) {
		/*
		 * Remove the current partition control from what we pass up
		 * the chain if it hasn't been requested manually.
		 */
		controls = ldb_controls_except_specified(ares->controls, ares,
							 partition_ctrl);
	}

	if (ares->error != LDB_SUCCESS) {
		DEBUG(5,("%s failure. Error is: %s\n", __FUNCTION__, ldb_strerror(ares->error)));
		return ldb_module_done(ac->req, controls,
					ares->response, ares->error);
	}

	if (ares->type != LDB_REPLY_DONE) {
		ldb_set_errstring(ldb_module_get_ctx(ac->module), "Invalid reply type for notify\n!");
		return ldb_module_done(ac->req, NULL,
				       NULL, LDB_ERR_OPERATIONS_ERROR);
	}

	if (!partition_ctrl) {
		ldb_set_errstring(ldb_module_get_ctx(ac->module),"No partition control on reply");
		return ldb_module_done(ac->req, NULL,
				       NULL, LDB_ERR_OPERATIONS_ERROR);
	}

	partition = talloc_get_type_abort(partition_ctrl->data,
				    struct dsdb_control_current_partition);

	if (ac->seq_num > 0) {
		for (modified_partition = replmd_private->ncs; modified_partition;
		     modified_partition = modified_partition->next) {
			if (ldb_dn_compare(modified_partition->dn, partition->dn) == 0) {
				break;
			}
		}

		if (modified_partition == NULL) {
			modified_partition = talloc_zero(replmd_private, struct nc_entry);
			if (!modified_partition) {
				ldb_oom(ldb_module_get_ctx(ac->module));
				return ldb_module_done(ac->req, NULL,
						       NULL, LDB_ERR_OPERATIONS_ERROR);
			}
			modified_partition->dn = ldb_dn_copy(modified_partition, partition->dn);
			if (!modified_partition->dn) {
				ldb_oom(ldb_module_get_ctx(ac->module));
				return ldb_module_done(ac->req, NULL,
						       NULL, LDB_ERR_OPERATIONS_ERROR);
			}
			DLIST_ADD(replmd_private->ncs, modified_partition);
		}

		if (ac->seq_num > modified_partition->mod_usn) {
			modified_partition->mod_usn = ac->seq_num;
			if (ac->is_urgent) {
				modified_partition->mod_usn_urgent = ac->seq_num;
			}
		}
	}

	if (ac->apply_mode) {
		talloc_free(ares);
		ac->index_current++;

		ret = replmd_replicated_apply_next(ac);
		if (ret != LDB_SUCCESS) {
			return ldb_module_done(ac->req, NULL, NULL, ret);
		}
		return ret;
	} else {
		/* free the partition control container here, for the
		 * common path.  Other cases will have it cleaned up
		 * eventually with the ares */
		talloc_free(partition_ctrl);
		return ldb_module_done(ac->req, controls,
				       ares->response, LDB_SUCCESS);
	}
}


/*
 * update a @REPLCHANGED record in each partition if there have been
 * any writes of replicated data in the partition
 */
static int replmd_notify_store(struct ldb_module *module, struct ldb_request *parent)
{
	struct replmd_private *replmd_private =
		talloc_get_type(ldb_module_get_private(module), struct replmd_private);

	while (replmd_private->ncs) {
		int ret;
		struct nc_entry *modified_partition = replmd_private->ncs;

		ret = dsdb_module_save_partition_usn(module, modified_partition->dn,
						     modified_partition->mod_usn,
						     modified_partition->mod_usn_urgent, parent);
		if (ret != LDB_SUCCESS) {
			DEBUG(0,(__location__ ": Failed to save partition uSN for %s\n",
				 ldb_dn_get_linearized(modified_partition->dn)));
			return ret;
		}
		DLIST_REMOVE(replmd_private->ncs, modified_partition);
		talloc_free(modified_partition);
	}

	return LDB_SUCCESS;
}


/*
  created a replmd_replicated_request context
 */
static struct replmd_replicated_request *replmd_ctx_init(struct ldb_module *module,
							 struct ldb_request *req)
{
	struct ldb_context *ldb;
	struct replmd_replicated_request *ac;

	ldb = ldb_module_get_ctx(module);

	ac = talloc_zero(req, struct replmd_replicated_request);
	if (ac == NULL) {
		ldb_oom(ldb);
		return NULL;
	}

	ac->module = module;
	ac->req	= req;

	ac->schema = dsdb_get_schema(ldb, ac);
	if (!ac->schema) {
		ldb_debug_set(ldb, LDB_DEBUG_FATAL,
			      "replmd_modify: no dsdb_schema loaded");
		DEBUG(0,(__location__ ": %s\n", ldb_errstring(ldb)));
		return NULL;
	}

	return ac;
}

/*
  add a time element to a record
*/
static int add_time_element(struct ldb_message *msg, const char *attr, time_t t)
{
	struct ldb_message_element *el;
	char *s;
	int ret;

	if (ldb_msg_find_element(msg, attr) != NULL) {
		return LDB_SUCCESS;
	}

	s = ldb_timestring(msg, t);
	if (s == NULL) {
		return LDB_ERR_OPERATIONS_ERROR;
	}

	ret = ldb_msg_add_string(msg, attr, s);
	if (ret != LDB_SUCCESS) {
		return ret;
	}

	el = ldb_msg_find_element(msg, attr);
	/* always set as replace. This works because on add ops, the flag
	   is ignored */
	el->flags = LDB_FLAG_MOD_REPLACE;

	return LDB_SUCCESS;
}

/*
  add a uint64_t element to a record
*/
static int add_uint64_element(struct ldb_context *ldb, struct ldb_message *msg,
			      const char *attr, uint64_t v)
{
	struct ldb_message_element *el;
	int ret;

	if (ldb_msg_find_element(msg, attr) != NULL) {
		return LDB_SUCCESS;
	}

	ret = samdb_msg_add_uint64(ldb, msg, msg, attr, v);
	if (ret != LDB_SUCCESS) {
		return ret;
	}

	el = ldb_msg_find_element(msg, attr);
	/* always set as replace. This works because on add ops, the flag
	   is ignored */
	el->flags = LDB_FLAG_MOD_REPLACE;

	return LDB_SUCCESS;
}

static int replmd_replPropertyMetaData1_attid_sort(const struct replPropertyMetaData1 *m1,
						   const struct replPropertyMetaData1 *m2,
						   const uint32_t *rdn_attid)
{
	if (m1->attid == m2->attid) {
		return 0;
	}

	/*
	 * the rdn attribute should be at the end!
	 * so we need to return a value greater than zero
	 * which means m1 is greater than m2
	 */
	if (m1->attid == *rdn_attid) {
		return 1;
	}

	/*
	 * the rdn attribute should be at the end!
	 * so we need to return a value less than zero
	 * which means m2 is greater than m1
	 */
	if (m2->attid == *rdn_attid) {
		return -1;
	}

	return m1->attid > m2->attid ? 1 : -1;
}

static int replmd_replPropertyMetaDataCtr1_sort(struct replPropertyMetaDataCtr1 *ctr1,
						const struct dsdb_schema *schema,
						struct ldb_dn *dn)
{
	const char *rdn_name;
	const struct dsdb_attribute *rdn_sa;

	rdn_name = ldb_dn_get_rdn_name(dn);
	if (!rdn_name) {
		DEBUG(0,(__location__ ": No rDN for %s?\n", ldb_dn_get_linearized(dn)));
		return LDB_ERR_OPERATIONS_ERROR;
	}

	rdn_sa = dsdb_attribute_by_lDAPDisplayName(schema, rdn_name);
	if (rdn_sa == NULL) {
		DEBUG(0,(__location__ ": No sa found for rDN %s for %s\n", rdn_name, ldb_dn_get_linearized(dn)));
		return LDB_ERR_OPERATIONS_ERROR;
	}

	DEBUG(6,("Sorting rpmd with attid exception %u rDN=%s DN=%s\n",
		 rdn_sa->attributeID_id, rdn_name, ldb_dn_get_linearized(dn)));

	LDB_TYPESAFE_QSORT(ctr1->array, ctr1->count, &rdn_sa->attributeID_id, replmd_replPropertyMetaData1_attid_sort);

	return LDB_SUCCESS;
}

static int replmd_ldb_message_element_attid_sort(const struct ldb_message_element *e1,
						 const struct ldb_message_element *e2,
						 const struct dsdb_schema *schema)
{
	const struct dsdb_attribute *a1;
	const struct dsdb_attribute *a2;

	/*
	 * TODO: make this faster by caching the dsdb_attribute pointer
	 *       on the ldb_messag_element
	 */

	a1 = dsdb_attribute_by_lDAPDisplayName(schema, e1->name);
	a2 = dsdb_attribute_by_lDAPDisplayName(schema, e2->name);

	/*
	 * TODO: remove this check, we should rely on e1 and e2 having valid attribute names
	 *       in the schema
	 */
	if (!a1 || !a2) {
		return strcasecmp(e1->name, e2->name);
	}
	if (a1->attributeID_id == a2->attributeID_id) {
		return 0;
	}
	return a1->attributeID_id > a2->attributeID_id ? 1 : -1;
}

static void replmd_ldb_message_sort(struct ldb_message *msg,
				    const struct dsdb_schema *schema)
{
	LDB_TYPESAFE_QSORT(msg->elements, msg->num_elements, schema, replmd_ldb_message_element_attid_sort);
}

static int replmd_build_la_val(TALLOC_CTX *mem_ctx, struct ldb_val *v, struct dsdb_dn *dsdb_dn,
			       const struct GUID *invocation_id, uint64_t seq_num,
			       uint64_t local_usn, NTTIME nttime, uint32_t version, bool deleted);


/*
  fix up linked attributes in replmd_add.
  This involves setting up the right meta-data in extended DN
  components, and creating backlinks to the object
 */
static int replmd_add_fix_la(struct ldb_module *module, struct ldb_message_element *el,
			     uint64_t seq_num, const struct GUID *invocationId, time_t t,
			     struct GUID *guid, const struct dsdb_attribute *sa, struct ldb_request *parent)
{
	unsigned int i;
	TALLOC_CTX *tmp_ctx = talloc_new(el->values);
	struct ldb_context *ldb = ldb_module_get_ctx(module);

	/* We will take a reference to the schema in replmd_add_backlink */
	const struct dsdb_schema *schema = dsdb_get_schema(ldb, NULL);
	NTTIME now;

	unix_to_nt_time(&now, t);

	for (i=0; i<el->num_values; i++) {
		struct ldb_val *v = &el->values[i];
		struct dsdb_dn *dsdb_dn = dsdb_dn_parse(tmp_ctx, ldb, v, sa->syntax->ldap_oid);
		struct GUID target_guid;
		NTSTATUS status;
		int ret;

		/* note that the DN already has the extended
		   components from the extended_dn_store module */
		status = dsdb_get_extended_dn_guid(dsdb_dn->dn, &target_guid, "GUID");
		if (!NT_STATUS_IS_OK(status) || GUID_all_zero(&target_guid)) {
			ret = dsdb_module_guid_by_dn(module, dsdb_dn->dn, &target_guid, parent);
			if (ret != LDB_SUCCESS) {
				talloc_free(tmp_ctx);
				return ret;
			}
			ret = dsdb_set_extended_dn_guid(dsdb_dn->dn, &target_guid, "GUID");
			if (ret != LDB_SUCCESS) {
				talloc_free(tmp_ctx);
				return ret;
			}
		}

		ret = replmd_build_la_val(el->values, v, dsdb_dn, invocationId,
					  seq_num, seq_num, now, 0, false);
		if (ret != LDB_SUCCESS) {
			talloc_free(tmp_ctx);
			return ret;
		}

		ret = replmd_add_backlink(module, schema, guid, &target_guid, true, sa, false);
		if (ret != LDB_SUCCESS) {
			talloc_free(tmp_ctx);
			return ret;
		}
	}

	talloc_free(tmp_ctx);
	return LDB_SUCCESS;
}


/*
  intercept add requests
 */
static int replmd_add(struct ldb_module *module, struct ldb_request *req)
{
	struct ldb_context *ldb;
        struct ldb_control *control;
	struct replmd_replicated_request *ac;
	enum ndr_err_code ndr_err;
	struct ldb_request *down_req;
	struct ldb_message *msg;
        const DATA_BLOB *guid_blob;
	struct GUID guid;
	struct replPropertyMetaDataBlob nmd;
	struct ldb_val nmd_value;
	const struct GUID *our_invocation_id;
	time_t t = time(NULL);
	NTTIME now;
	char *time_str;
	int ret;
	unsigned int i;
	unsigned int functional_level;
	uint32_t ni=0;
	bool allow_add_guid = false;
	bool remove_current_guid = false;
	bool is_urgent = false;
	struct ldb_message_element *objectclass_el;

        /* check if there's a show relax control (used by provision to say 'I know what I'm doing') */
        control = ldb_request_get_control(req, LDB_CONTROL_RELAX_OID);
	if (control) {
		allow_add_guid = true;
	}

	/* do not manipulate our control entries */
	if (ldb_dn_is_special(req->op.add.message->dn)) {
		return ldb_next_request(module, req);
	}

	ldb = ldb_module_get_ctx(module);

	ldb_debug(ldb, LDB_DEBUG_TRACE, "replmd_add\n");

	guid_blob = ldb_msg_find_ldb_val(req->op.add.message, "objectGUID");
	if (guid_blob != NULL) {
		if (!allow_add_guid) {
			ldb_set_errstring(ldb,
					  "replmd_add: it's not allowed to add an object with objectGUID!");
			return LDB_ERR_UNWILLING_TO_PERFORM;
		} else {
			NTSTATUS status = GUID_from_data_blob(guid_blob,&guid);
			if (!NT_STATUS_IS_OK(status)) {
				ldb_set_errstring(ldb,
						  "replmd_add: Unable to parse the 'objectGUID' as a GUID!");
				return LDB_ERR_UNWILLING_TO_PERFORM;
			}
			/* we remove this attribute as it can be a string and
			 * will not be treated correctly and then we will re-add
			 * it later on in the good format */
			remove_current_guid = true;
		}
	} else {
		/* a new GUID */
		guid = GUID_random();
	}

	ac = replmd_ctx_init(module, req);
	if (ac == NULL) {
		return ldb_module_oom(module);
	}

	functional_level = dsdb_functional_level(ldb);

	/* Get a sequence number from the backend */
	ret = ldb_sequence_number(ldb, LDB_SEQ_NEXT, &ac->seq_num);
	if (ret != LDB_SUCCESS) {
		talloc_free(ac);
		return ret;
	}

	/* get our invocationId */
	our_invocation_id = samdb_ntds_invocation_id(ldb);
	if (!our_invocation_id) {
		ldb_debug_set(ldb, LDB_DEBUG_ERROR,
			      "replmd_add: unable to find invocationId\n");
		talloc_free(ac);
		return LDB_ERR_OPERATIONS_ERROR;
	}

	/* we have to copy the message as the caller might have it as a const */
	msg = ldb_msg_copy_shallow(ac, req->op.add.message);
	if (msg == NULL) {
		ldb_oom(ldb);
		talloc_free(ac);
		return LDB_ERR_OPERATIONS_ERROR;
	}

	/* generated times */
	unix_to_nt_time(&now, t);
	time_str = ldb_timestring(msg, t);
	if (!time_str) {
		ldb_oom(ldb);
		talloc_free(ac);
		return LDB_ERR_OPERATIONS_ERROR;
	}
	if (remove_current_guid) {
		ldb_msg_remove_attr(msg,"objectGUID");
	}

	/*
	 * remove autogenerated attributes
	 */
	ldb_msg_remove_attr(msg, "whenCreated");
	ldb_msg_remove_attr(msg, "whenChanged");
	ldb_msg_remove_attr(msg, "uSNCreated");
	ldb_msg_remove_attr(msg, "uSNChanged");
	ldb_msg_remove_attr(msg, "replPropertyMetaData");

	/*
	 * readd replicated attributes
	 */
	ret = ldb_msg_add_string(msg, "whenCreated", time_str);
	if (ret != LDB_SUCCESS) {
		ldb_oom(ldb);
		talloc_free(ac);
		return ret;
	}

	/* build the replication meta_data */
	ZERO_STRUCT(nmd);
	nmd.version		= 1;
	nmd.ctr.ctr1.count	= msg->num_elements;
	nmd.ctr.ctr1.array	= talloc_array(msg,
					       struct replPropertyMetaData1,
					       nmd.ctr.ctr1.count);
	if (!nmd.ctr.ctr1.array) {
		ldb_oom(ldb);
		talloc_free(ac);
		return LDB_ERR_OPERATIONS_ERROR;
	}

	for (i=0; i < msg->num_elements; i++) {
		struct ldb_message_element *e = &msg->elements[i];
		struct replPropertyMetaData1 *m = &nmd.ctr.ctr1.array[ni];
		const struct dsdb_attribute *sa;

		if (e->name[0] == '@') continue;

		sa = dsdb_attribute_by_lDAPDisplayName(ac->schema, e->name);
		if (!sa) {
			ldb_debug_set(ldb, LDB_DEBUG_ERROR,
				      "replmd_add: attribute '%s' not defined in schema\n",
				      e->name);
			talloc_free(ac);
			return LDB_ERR_NO_SUCH_ATTRIBUTE;
		}

		if ((sa->systemFlags & DS_FLAG_ATTR_NOT_REPLICATED) || (sa->systemFlags & DS_FLAG_ATTR_IS_CONSTRUCTED)) {
			/* if the attribute is not replicated (0x00000001)
			 * or constructed (0x00000004) it has no metadata
			 */
			continue;
		}

		if (sa->linkID != 0 && functional_level > DS_DOMAIN_FUNCTION_2000) {
			ret = replmd_add_fix_la(module, e, ac->seq_num, our_invocation_id, t, &guid, sa, req);
			if (ret != LDB_SUCCESS) {
				talloc_free(ac);
				return ret;
			}
			/* linked attributes are not stored in
			   replPropertyMetaData in FL above w2k */
			continue;
		}

		m->attid			= sa->attributeID_id;
		m->version			= 1;
		m->originating_change_time	= now;
		m->originating_invocation_id	= *our_invocation_id;
		m->originating_usn		= ac->seq_num;
		m->local_usn			= ac->seq_num;
		ni++;
	}

	/* fix meta data count */
	nmd.ctr.ctr1.count = ni;

	/*
	 * sort meta data array, and move the rdn attribute entry to the end
	 */
	ret = replmd_replPropertyMetaDataCtr1_sort(&nmd.ctr.ctr1, ac->schema, msg->dn);
	if (ret != LDB_SUCCESS) {
		talloc_free(ac);
		return ret;
	}

	/* generated NDR encoded values */
	ndr_err = ndr_push_struct_blob(&nmd_value, msg,
				       &nmd,
				       (ndr_push_flags_fn_t)ndr_push_replPropertyMetaDataBlob);
	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
		ldb_oom(ldb);
		talloc_free(ac);
		return LDB_ERR_OPERATIONS_ERROR;
	}

	/*
	 * add the autogenerated values
	 */
	ret = dsdb_msg_add_guid(msg, &guid, "objectGUID");
	if (ret != LDB_SUCCESS) {
		ldb_oom(ldb);
		talloc_free(ac);
		return ret;
	}
	ret = ldb_msg_add_string(msg, "whenChanged", time_str);
	if (ret != LDB_SUCCESS) {
		ldb_oom(ldb);
		talloc_free(ac);
		return ret;
	}
	ret = samdb_msg_add_uint64(ldb, msg, msg, "uSNCreated", ac->seq_num);
	if (ret != LDB_SUCCESS) {
		ldb_oom(ldb);
		talloc_free(ac);
		return ret;
	}
	ret = samdb_msg_add_uint64(ldb, msg, msg, "uSNChanged", ac->seq_num);
	if (ret != LDB_SUCCESS) {
		ldb_oom(ldb);
		talloc_free(ac);
		return ret;
	}
	ret = ldb_msg_add_value(msg, "replPropertyMetaData", &nmd_value, NULL);
	if (ret != LDB_SUCCESS) {
		ldb_oom(ldb);
		talloc_free(ac);
		return ret;
	}

	/*
	 * sort the attributes by attid before storing the object
	 */
	replmd_ldb_message_sort(msg, ac->schema);

	objectclass_el = ldb_msg_find_element(msg, "objectClass");
	is_urgent = replmd_check_urgent_objectclass(objectclass_el,
							REPL_URGENT_ON_CREATE);

	ac->is_urgent = is_urgent;
	ret = ldb_build_add_req(&down_req, ldb, ac,
				msg,
				req->controls,
				ac, replmd_op_callback,
				req);

	LDB_REQ_SET_LOCATION(down_req);
	if (ret != LDB_SUCCESS) {
		talloc_free(ac);
		return ret;
	}

	/* current partition control is needed by "replmd_op_callback" */
	if (ldb_request_get_control(req, DSDB_CONTROL_CURRENT_PARTITION_OID) == NULL) {
		ret = ldb_request_add_control(down_req,
					      DSDB_CONTROL_CURRENT_PARTITION_OID,
					      false, NULL);
		if (ret != LDB_SUCCESS) {
			talloc_free(ac);
			return ret;
		}
	}

	if (functional_level == DS_DOMAIN_FUNCTION_2000) {
		ret = ldb_request_add_control(down_req, DSDB_CONTROL_APPLY_LINKS, false, NULL);
		if (ret != LDB_SUCCESS) {
			talloc_free(ac);
			return ret;
		}
	}

	/* mark the control done */
	if (control) {
		control->critical = 0;
	}

	/* go on with the call chain */
	return ldb_next_request(module, down_req);
}


/*
 * update the replPropertyMetaData for one element
 */
static int replmd_update_rpmd_element(struct ldb_context *ldb,
				      struct ldb_message *msg,
				      struct ldb_message_element *el,
				      struct ldb_message_element *old_el,
				      struct replPropertyMetaDataBlob *omd,
				      const struct dsdb_schema *schema,
				      uint64_t *seq_num,
				      const struct GUID *our_invocation_id,
				      NTTIME now,
				      struct ldb_request *req)
{
	uint32_t i;
	const struct dsdb_attribute *a;
	struct replPropertyMetaData1 *md1;

	a = dsdb_attribute_by_lDAPDisplayName(schema, el->name);
	if (a == NULL) {
		if (ldb_request_get_control(req, LDB_CONTROL_RELAX_OID)) {
			/* allow this to make it possible for dbcheck
			   to remove bad attributes */
			return LDB_SUCCESS;
		}

		DEBUG(0,(__location__ ": Unable to find attribute %s in schema\n",
			 el->name));
		return LDB_ERR_OPERATIONS_ERROR;
	}

	if ((a->systemFlags & DS_FLAG_ATTR_NOT_REPLICATED) || (a->systemFlags & DS_FLAG_ATTR_IS_CONSTRUCTED)) {
		return LDB_SUCCESS;
	}

	/* if the attribute's value haven't changed then return LDB_SUCCESS	*/
	if (old_el != NULL && ldb_msg_element_compare(el, old_el) == 0) {
		if (!ldb_request_get_control(req, LDB_CONTROL_PROVISION_OID)) {
			/*
			 * allow this to make it possible for dbcheck
			 * to rebuild broken metadata
			 */
			return LDB_SUCCESS;
		}
	}

	for (i=0; i<omd->ctr.ctr1.count; i++) {
		if (a->attributeID_id == omd->ctr.ctr1.array[i].attid) break;
	}

	if (a->linkID != 0 && dsdb_functional_level(ldb) > DS_DOMAIN_FUNCTION_2000) {
		/* linked attributes are not stored in
		   replPropertyMetaData in FL above w2k, but we do
		   raise the seqnum for the object  */
		if (*seq_num == 0 &&
		    ldb_sequence_number(ldb, LDB_SEQ_NEXT, seq_num) != LDB_SUCCESS) {
			return LDB_ERR_OPERATIONS_ERROR;
		}
		return LDB_SUCCESS;
	}

	if (i == omd->ctr.ctr1.count) {
		/* we need to add a new one */
		omd->ctr.ctr1.array = talloc_realloc(msg, omd->ctr.ctr1.array,
						     struct replPropertyMetaData1, omd->ctr.ctr1.count+1);
		if (omd->ctr.ctr1.array == NULL) {
			ldb_oom(ldb);
			return LDB_ERR_OPERATIONS_ERROR;
		}
		omd->ctr.ctr1.count++;
		ZERO_STRUCT(omd->ctr.ctr1.array[i]);
	}

	/* Get a new sequence number from the backend. We only do this
	 * if we have a change that requires a new
	 * replPropertyMetaData element
	 */
	if (*seq_num == 0) {
		int ret = ldb_sequence_number(ldb, LDB_SEQ_NEXT, seq_num);
		if (ret != LDB_SUCCESS) {
			return LDB_ERR_OPERATIONS_ERROR;
		}
	}

	md1 = &omd->ctr.ctr1.array[i];
	md1->version++;
	md1->attid                     = a->attributeID_id;
	md1->originating_change_time   = now;
	md1->originating_invocation_id = *our_invocation_id;
	md1->originating_usn           = *seq_num;
	md1->local_usn                 = *seq_num;

	return LDB_SUCCESS;
}

static uint64_t find_max_local_usn(struct replPropertyMetaDataBlob omd)
{
	uint32_t count = omd.ctr.ctr1.count;
	uint64_t max = 0;
	uint32_t i;
	for (i=0; i < count; i++) {
		struct replPropertyMetaData1 m = omd.ctr.ctr1.array[i];
		if (max < m.local_usn) {
			max = m.local_usn;
		}
	}
	return max;
}

/*
 * update the replPropertyMetaData object each time we modify an
 * object. This is needed for DRS replication, as the merge on the
 * client is based on this object
 */
static int replmd_update_rpmd(struct ldb_module *module,
			      const struct dsdb_schema *schema,
			      struct ldb_request *req,
			      const char * const *rename_attrs,
			      struct ldb_message *msg, uint64_t *seq_num,
			      time_t t,
			      bool *is_urgent)
{
	const struct ldb_val *omd_value;
	enum ndr_err_code ndr_err;
	struct replPropertyMetaDataBlob omd;
	unsigned int i;
	NTTIME now;
	const struct GUID *our_invocation_id;
	int ret;
	const char * const *attrs = NULL;
	const char * const attrs1[] = { "replPropertyMetaData", "*", NULL };
	const char * const attrs2[] = { "uSNChanged", "objectClass", NULL };
	struct ldb_result *res;
	struct ldb_context *ldb;
	struct ldb_message_element *objectclass_el;
	enum urgent_situation situation;
	bool rodc, rmd_is_provided;

	if (rename_attrs) {
		attrs = rename_attrs;
	} else {
		attrs = attrs1;
	}

	ldb = ldb_module_get_ctx(module);

	our_invocation_id = samdb_ntds_invocation_id(ldb);
	if (!our_invocation_id) {
		/* this happens during an initial vampire while
		   updating the schema */
		DEBUG(5,("No invocationID - skipping replPropertyMetaData update\n"));
		return LDB_SUCCESS;
	}

	unix_to_nt_time(&now, t);

	if (ldb_request_get_control(req, DSDB_CONTROL_CHANGEREPLMETADATA_OID)) {
		rmd_is_provided = true;
	} else {
		rmd_is_provided = false;
	}

	/* if isDeleted is present and is TRUE, then we consider we are deleting,
	 * otherwise we consider we are updating */
	if (ldb_msg_check_string_attribute(msg, "isDeleted", "TRUE")) {
		situation = REPL_URGENT_ON_DELETE;
	} else if (rename_attrs) {
		situation = REPL_URGENT_ON_CREATE | REPL_URGENT_ON_DELETE;
	} else {
		situation = REPL_URGENT_ON_UPDATE;
	}

	if (rmd_is_provided) {
		/* In this case the change_replmetadata control was supplied */
		/* We check that it's the only attribute that is provided
		 * (it's a rare case so it's better to keep the code simplier)
		 * We also check that the highest local_usn is bigger than
		 * uSNChanged. */
		uint64_t db_seq;
		if( msg->num_elements != 1 ||
			strncmp(msg->elements[0].name,
				"replPropertyMetaData", 20) ) {
			DEBUG(0,(__location__ ": changereplmetada control called without "\
				"a specified replPropertyMetaData attribute or with others\n"));
			return LDB_ERR_OPERATIONS_ERROR;
		}
		if (situation != REPL_URGENT_ON_UPDATE) {
			DEBUG(0,(__location__ ": changereplmetada control can't be called when deleting an object\n"));
			return LDB_ERR_OPERATIONS_ERROR;
		}
		omd_value = ldb_msg_find_ldb_val(msg, "replPropertyMetaData");
		if (!omd_value) {
			DEBUG(0,(__location__ ": replPropertyMetaData was not specified for Object %s\n",
				 ldb_dn_get_linearized(msg->dn)));
			return LDB_ERR_OPERATIONS_ERROR;
		}
		ndr_err = ndr_pull_struct_blob(omd_value, msg, &omd,
					       (ndr_pull_flags_fn_t)ndr_pull_replPropertyMetaDataBlob);
		if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
			DEBUG(0,(__location__ ": Failed to parse replPropertyMetaData for %s\n",
				 ldb_dn_get_linearized(msg->dn)));
			return LDB_ERR_OPERATIONS_ERROR;
		}
		*seq_num = find_max_local_usn(omd);

		ret = dsdb_module_search_dn(module, msg, &res, msg->dn, attrs2,
					    DSDB_FLAG_NEXT_MODULE |
					    DSDB_SEARCH_SHOW_RECYCLED |
					    DSDB_SEARCH_SHOW_EXTENDED_DN |
					    DSDB_SEARCH_SHOW_DN_IN_STORAGE_FORMAT |
					    DSDB_SEARCH_REVEAL_INTERNALS, req);

		if (ret != LDB_SUCCESS || res->count != 1) {
			DEBUG(0,(__location__ ": Object %s failed to find uSNChanged\n",
				 ldb_dn_get_linearized(msg->dn)));
			return LDB_ERR_OPERATIONS_ERROR;
		}

		objectclass_el = ldb_msg_find_element(res->msgs[0], "objectClass");
		if (is_urgent && replmd_check_urgent_objectclass(objectclass_el,
								situation)) {
			*is_urgent = true;
		}

		db_seq = ldb_msg_find_attr_as_uint64(res->msgs[0], "uSNChanged", 0);
		if (*seq_num <= db_seq) {
			DEBUG(0,(__location__ ": changereplmetada control provided but max(local_usn)"\
					      " is less or equal to uSNChanged (max = %lld uSNChanged = %lld)\n",
				 (long long)*seq_num, (long long)db_seq));
			return LDB_ERR_OPERATIONS_ERROR;
		}

	} else {
		/* search for the existing replPropertyMetaDataBlob. We need
		 * to use REVEAL and ask for DNs in storage format to support
		 * the check for values being the same in
		 * replmd_update_rpmd_element()
		 */
		ret = dsdb_module_search_dn(module, msg, &res, msg->dn, attrs,
					    DSDB_FLAG_NEXT_MODULE |
					    DSDB_SEARCH_SHOW_RECYCLED |
					    DSDB_SEARCH_SHOW_EXTENDED_DN |
					    DSDB_SEARCH_SHOW_DN_IN_STORAGE_FORMAT |
					    DSDB_SEARCH_REVEAL_INTERNALS, req);
		if (ret != LDB_SUCCESS || res->count != 1) {
			DEBUG(0,(__location__ ": Object %s failed to find replPropertyMetaData\n",
				 ldb_dn_get_linearized(msg->dn)));
			return LDB_ERR_OPERATIONS_ERROR;
		}

		objectclass_el = ldb_msg_find_element(res->msgs[0], "objectClass");
		if (is_urgent && replmd_check_urgent_objectclass(objectclass_el,
								situation)) {
			*is_urgent = true;
		}

		omd_value = ldb_msg_find_ldb_val(res->msgs[0], "replPropertyMetaData");
		if (!omd_value) {
			DEBUG(0,(__location__ ": Object %s does not have a replPropertyMetaData attribute\n",
				 ldb_dn_get_linearized(msg->dn)));
			return LDB_ERR_OPERATIONS_ERROR;
		}

		ndr_err = ndr_pull_struct_blob(omd_value, msg, &omd,
					       (ndr_pull_flags_fn_t)ndr_pull_replPropertyMetaDataBlob);
		if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
			DEBUG(0,(__location__ ": Failed to parse replPropertyMetaData for %s\n",
				 ldb_dn_get_linearized(msg->dn)));
			return LDB_ERR_OPERATIONS_ERROR;
		}

		if (omd.version != 1) {
			DEBUG(0,(__location__ ": bad version %u in replPropertyMetaData for %s\n",
				 omd.version, ldb_dn_get_linearized(msg->dn)));
			return LDB_ERR_OPERATIONS_ERROR;
		}

		for (i=0; i<msg->num_elements; i++) {
			struct ldb_message_element *old_el;
			old_el = ldb_msg_find_element(res->msgs[0], msg->elements[i].name);
			ret = replmd_update_rpmd_element(ldb, msg, &msg->elements[i], old_el, &omd, schema, seq_num,
							 our_invocation_id, now, req);
			if (ret != LDB_SUCCESS) {
				return ret;
			}

			if (is_urgent && !*is_urgent && (situation == REPL_URGENT_ON_UPDATE)) {
				*is_urgent = replmd_check_urgent_attribute(&msg->elements[i]);
			}

		}
	}
	/*
	 * replmd_update_rpmd_element has done an update if the
	 * seq_num is set
	 */
	if (*seq_num != 0) {
		struct ldb_val *md_value;
		struct ldb_message_element *el;

		/*if we are RODC and this is a DRSR update then its ok*/
		if (!ldb_request_get_control(req, DSDB_CONTROL_REPLICATED_UPDATE_OID)) {
			ret = samdb_rodc(ldb, &rodc);
			if (ret != LDB_SUCCESS) {
				DEBUG(4, (__location__ ": unable to tell if we are an RODC\n"));
			} else if (rodc) {
				ldb_asprintf_errstring(ldb, "RODC modify is forbidden\n");
				return LDB_ERR_REFERRAL;
			}
		}

		md_value = talloc(msg, struct ldb_val);
		if (md_value == NULL) {
			ldb_oom(ldb);
			return LDB_ERR_OPERATIONS_ERROR;
		}

		ret = replmd_replPropertyMetaDataCtr1_sort(&omd.ctr.ctr1, schema, msg->dn);
		if (ret != LDB_SUCCESS) {
			return ret;
		}

		ndr_err = ndr_push_struct_blob(md_value, msg, &omd,
					       (ndr_push_flags_fn_t)ndr_push_replPropertyMetaDataBlob);
		if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
			DEBUG(0,(__location__ ": Failed to marshall replPropertyMetaData for %s\n",
				 ldb_dn_get_linearized(msg->dn)));
			return LDB_ERR_OPERATIONS_ERROR;
		}

		ret = ldb_msg_add_empty(msg, "replPropertyMetaData", LDB_FLAG_MOD_REPLACE, &el);
		if (ret != LDB_SUCCESS) {
			DEBUG(0,(__location__ ": Failed to add updated replPropertyMetaData %s\n",
				 ldb_dn_get_linearized(msg->dn)));
			return ret;
		}

		el->num_values = 1;
		el->values = md_value;
	}

	return LDB_SUCCESS;
}

struct parsed_dn {
	struct dsdb_dn *dsdb_dn;
	struct GUID *guid;
	struct ldb_val *v;
};

static int parsed_dn_compare(struct parsed_dn *pdn1, struct parsed_dn *pdn2)
{
	return GUID_compare(pdn1->guid, pdn2->guid);
}

static struct parsed_dn *parsed_dn_find(struct parsed_dn *pdn,
					unsigned int count, struct GUID *guid,
					struct ldb_dn *dn)
{
	struct parsed_dn *ret;
	unsigned int i;
	if (dn && GUID_all_zero(guid)) {
		/* when updating a link using DRS, we sometimes get a
		   NULL GUID. We then need to try and match by DN */
		for (i=0; i<count; i++) {
			if (ldb_dn_compare(pdn[i].dsdb_dn->dn, dn) == 0) {
				dsdb_get_extended_dn_guid(pdn[i].dsdb_dn->dn, guid, "GUID");
				return &pdn[i];
			}
		}
		return NULL;
	}
	BINARY_ARRAY_SEARCH(pdn, count, guid, guid, GUID_compare, ret);
	return ret;
}

/*
  get a series of message element values as an array of DNs and GUIDs
  the result is sorted by GUID
 */
static int get_parsed_dns(struct ldb_module *module, TALLOC_CTX *mem_ctx,
			  struct ldb_message_element *el, struct parsed_dn **pdn,
			  const char *ldap_oid, struct ldb_request *parent)
{
	unsigned int i;
	struct ldb_context *ldb = ldb_module_get_ctx(module);

	if (el == NULL) {
		*pdn = NULL;
		return LDB_SUCCESS;
	}

	(*pdn) = talloc_array(mem_ctx, struct parsed_dn, el->num_values);
	if (!*pdn) {
		ldb_module_oom(module);
		return LDB_ERR_OPERATIONS_ERROR;
	}

	for (i=0; i<el->num_values; i++) {
		struct ldb_val *v = &el->values[i];
		NTSTATUS status;
		struct ldb_dn *dn;
		struct parsed_dn *p;

		p = &(*pdn)[i];

		p->dsdb_dn = dsdb_dn_parse(*pdn, ldb, v, ldap_oid);
		if (p->dsdb_dn == NULL) {
			return LDB_ERR_INVALID_DN_SYNTAX;
		}

		dn = p->dsdb_dn->dn;

		p->guid = talloc(*pdn, struct GUID);
		if (p->guid == NULL) {
			ldb_module_oom(module);
			return LDB_ERR_OPERATIONS_ERROR;
		}

		status = dsdb_get_extended_dn_guid(dn, p->guid, "GUID");
		if (NT_STATUS_EQUAL(status, NT_STATUS_OBJECT_NAME_NOT_FOUND)) {
			/* we got a DN without a GUID - go find the GUID */
			int ret = dsdb_module_guid_by_dn(module, dn, p->guid, parent);
			if (ret != LDB_SUCCESS) {
				ldb_asprintf_errstring(ldb, "Unable to find GUID for DN %s\n",
						       ldb_dn_get_linearized(dn));
				if (ret == LDB_ERR_NO_SUCH_OBJECT &&
				    LDB_FLAG_MOD_TYPE(el->flags) == LDB_FLAG_MOD_DELETE &&
				    ldb_attr_cmp(el->name, "member") == 0) {
					return LDB_ERR_UNWILLING_TO_PERFORM;
				}
				return ret;
			}
			ret = dsdb_set_extended_dn_guid(dn, p->guid, "GUID");
			if (ret != LDB_SUCCESS) {
				return ret;
			}
		} else if (!NT_STATUS_IS_OK(status)) {
			return LDB_ERR_OPERATIONS_ERROR;
		}

		/* keep a pointer to the original ldb_val */
		p->v = v;
	}

	TYPESAFE_QSORT(*pdn, el->num_values, parsed_dn_compare);

	return LDB_SUCCESS;
}

/*
  build a new extended DN, including all meta data fields

  RMD_FLAGS           = DSDB_RMD_FLAG_* bits
  RMD_ADDTIME         = originating_add_time
  RMD_INVOCID         = originating_invocation_id
  RMD_CHANGETIME      = originating_change_time
  RMD_ORIGINATING_USN = originating_usn
  RMD_LOCAL_USN       = local_usn
  RMD_VERSION         = version
 */
static int replmd_build_la_val(TALLOC_CTX *mem_ctx, struct ldb_val *v, struct dsdb_dn *dsdb_dn,
			       const struct GUID *invocation_id, uint64_t seq_num,
			       uint64_t local_usn, NTTIME nttime, uint32_t version, bool deleted)
{
	struct ldb_dn *dn = dsdb_dn->dn;
	const char *tstring, *usn_string, *flags_string;
	struct ldb_val tval;
	struct ldb_val iid;
	struct ldb_val usnv, local_usnv;
	struct ldb_val vers, flagsv;
	NTSTATUS status;
	int ret;
	const char *dnstring;
	char *vstring;
	uint32_t rmd_flags = deleted?DSDB_RMD_FLAG_DELETED:0;

	tstring = talloc_asprintf(mem_ctx, "%llu", (unsigned long long)nttime);
	if (!tstring) {
		return LDB_ERR_OPERATIONS_ERROR;
	}
	tval = data_blob_string_const(tstring);

	usn_string = talloc_asprintf(mem_ctx, "%llu", (unsigned long long)seq_num);
	if (!usn_string) {
		return LDB_ERR_OPERATIONS_ERROR;
	}
	usnv = data_blob_string_const(usn_string);

	usn_string = talloc_asprintf(mem_ctx, "%llu", (unsigned long long)local_usn);
	if (!usn_string) {
		return LDB_ERR_OPERATIONS_ERROR;
	}
	local_usnv = data_blob_string_const(usn_string);

	vstring = talloc_asprintf(mem_ctx, "%lu", (unsigned long)version);
	if (!vstring) {
		return LDB_ERR_OPERATIONS_ERROR;
	}
	vers = data_blob_string_const(vstring);

	status = GUID_to_ndr_blob(invocation_id, dn, &iid);
	if (!NT_STATUS_IS_OK(status)) {
		return LDB_ERR_OPERATIONS_ERROR;
	}

	flags_string = talloc_asprintf(mem_ctx, "%u", rmd_flags);
	if (!flags_string) {
		return LDB_ERR_OPERATIONS_ERROR;
	}
	flagsv = data_blob_string_const(flags_string);

	ret = ldb_dn_set_extended_component(dn, "RMD_FLAGS", &flagsv);
	if (ret != LDB_SUCCESS) return ret;
	ret = ldb_dn_set_extended_component(dn, "RMD_ADDTIME", &tval);
	if (ret != LDB_SUCCESS) return ret;
	ret = ldb_dn_set_extended_component(dn, "RMD_INVOCID", &iid);
	if (ret != LDB_SUCCESS) return ret;
	ret = ldb_dn_set_extended_component(dn, "RMD_CHANGETIME", &tval);
	if (ret != LDB_SUCCESS) return ret;
	ret = ldb_dn_set_extended_component(dn, "RMD_LOCAL_USN", &local_usnv);
	if (ret != LDB_SUCCESS) return ret;
	ret = ldb_dn_set_extended_component(dn, "RMD_ORIGINATING_USN", &usnv);
	if (ret != LDB_SUCCESS) return ret;
	ret = ldb_dn_set_extended_component(dn, "RMD_VERSION", &vers);
	if (ret != LDB_SUCCESS) return ret;

	dnstring = dsdb_dn_get_extended_linearized(mem_ctx, dsdb_dn, 1);
	if (dnstring == NULL) {
		return LDB_ERR_OPERATIONS_ERROR;
	}
	*v = data_blob_string_const(dnstring);

	return LDB_SUCCESS;
}

static int replmd_update_la_val(TALLOC_CTX *mem_ctx, struct ldb_val *v, struct dsdb_dn *dsdb_dn,
				struct dsdb_dn *old_dsdb_dn, const struct GUID *invocation_id,
				uint64_t seq_num, uint64_t local_usn, NTTIME nttime,
				uint32_t version, bool deleted);

/*
  check if any links need upgrading from w2k format

  The parent_ctx is the ldb_message_element which contains the values array that dns[i].v points at, and which should be used for allocating any new value.
 */
static int replmd_check_upgrade_links(struct parsed_dn *dns, uint32_t count, struct ldb_message_element *parent_ctx, const struct GUID *invocation_id)
{
	uint32_t i;
	for (i=0; i<count; i++) {
		NTSTATUS status;
		uint32_t version;
		int ret;

		status = dsdb_get_extended_dn_uint32(dns[i].dsdb_dn->dn, &version, "RMD_VERSION");
		if (!NT_STATUS_EQUAL(status, NT_STATUS_OBJECT_NAME_NOT_FOUND)) {
			continue;
		}

		/* it's an old one that needs upgrading */
		ret = replmd_update_la_val(parent_ctx->values, dns[i].v, dns[i].dsdb_dn, dns[i].dsdb_dn, invocation_id,
					   1, 1, 0, 0, false);
		if (ret != LDB_SUCCESS) {
			return ret;
		}
	}
	return LDB_SUCCESS;
}

/*
  update an extended DN, including all meta data fields

  see replmd_build_la_val for value names
 */
static int replmd_update_la_val(TALLOC_CTX *mem_ctx, struct ldb_val *v, struct dsdb_dn *dsdb_dn,
				struct dsdb_dn *old_dsdb_dn, const struct GUID *invocation_id,
				uint64_t seq_num, uint64_t local_usn, NTTIME nttime,
				uint32_t version, bool deleted)
{
	struct ldb_dn *dn = dsdb_dn->dn;
	const char *tstring, *usn_string, *flags_string;
	struct ldb_val tval;
	struct ldb_val iid;
	struct ldb_val usnv, local_usnv;
	struct ldb_val vers, flagsv;
	const struct ldb_val *old_addtime;
	uint32_t old_version;
	NTSTATUS status;
	int ret;
	const char *dnstring;
	char *vstring;
	uint32_t rmd_flags = deleted?DSDB_RMD_FLAG_DELETED:0;

	tstring = talloc_asprintf(mem_ctx, "%llu", (unsigned long long)nttime);
	if (!tstring) {
		return LDB_ERR_OPERATIONS_ERROR;
	}
	tval = data_blob_string_const(tstring);

	usn_string = talloc_asprintf(mem_ctx, "%llu", (unsigned long long)seq_num);
	if (!usn_string) {
		return LDB_ERR_OPERATIONS_ERROR;
	}
	usnv = data_blob_string_const(usn_string);

	usn_string = talloc_asprintf(mem_ctx, "%llu", (unsigned long long)local_usn);
	if (!usn_string) {
		return LDB_ERR_OPERATIONS_ERROR;
	}
	local_usnv = data_blob_string_const(usn_string);

	status = GUID_to_ndr_blob(invocation_id, dn, &iid);
	if (!NT_STATUS_IS_OK(status)) {
		return LDB_ERR_OPERATIONS_ERROR;
	}

	flags_string = talloc_asprintf(mem_ctx, "%u", rmd_flags);
	if (!flags_string) {
		return LDB_ERR_OPERATIONS_ERROR;
	}
	flagsv = data_blob_string_const(flags_string);

	ret = ldb_dn_set_extended_component(dn, "RMD_FLAGS", &flagsv);
	if (ret != LDB_SUCCESS) return ret;

	/* get the ADDTIME from the original */
	old_addtime = ldb_dn_get_extended_component(old_dsdb_dn->dn, "RMD_ADDTIME");
	if (old_addtime == NULL) {
		old_addtime = &tval;
	}
	if (dsdb_dn != old_dsdb_dn ||
	    ldb_dn_get_extended_component(dn, "RMD_ADDTIME") == NULL) {
		ret = ldb_dn_set_extended_component(dn, "RMD_ADDTIME", old_addtime);
		if (ret != LDB_SUCCESS) return ret;
	}

	/* use our invocation id */
	ret = ldb_dn_set_extended_component(dn, "RMD_INVOCID", &iid);
	if (ret != LDB_SUCCESS) return ret;

	/* changetime is the current time */
	ret = ldb_dn_set_extended_component(dn, "RMD_CHANGETIME", &tval);
	if (ret != LDB_SUCCESS) return ret;

	/* update the USN */
	ret = ldb_dn_set_extended_component(dn, "RMD_ORIGINATING_USN", &usnv);
	if (ret != LDB_SUCCESS) return ret;

	ret = ldb_dn_set_extended_component(dn, "RMD_LOCAL_USN", &local_usnv);
	if (ret != LDB_SUCCESS) return ret;

	/* increase the version by 1 */
	status = dsdb_get_extended_dn_uint32(old_dsdb_dn->dn, &old_version, "RMD_VERSION");
	if (NT_STATUS_IS_OK(status) && old_version >= version) {
		version = old_version+1;
	}
	vstring = talloc_asprintf(dn, "%lu", (unsigned long)version);
	vers = data_blob_string_const(vstring);
	ret = ldb_dn_set_extended_component(dn, "RMD_VERSION", &vers);
	if (ret != LDB_SUCCESS) return ret;

	dnstring = dsdb_dn_get_extended_linearized(mem_ctx, dsdb_dn, 1);
	if (dnstring == NULL) {
		return LDB_ERR_OPERATIONS_ERROR;
	}
	*v = data_blob_string_const(dnstring);

	return LDB_SUCCESS;
}

/*
  handle adding a linked attribute
 */
static int replmd_modify_la_add(struct ldb_module *module,
				const struct dsdb_schema *schema,
				struct ldb_message *msg,
				struct ldb_message_element *el,
				struct ldb_message_element *old_el,
				const struct dsdb_attribute *schema_attr,
				uint64_t seq_num,
				time_t t,
				struct GUID *msg_guid,
				struct ldb_request *parent)
{
	unsigned int i;
	struct parsed_dn *dns, *old_dns;
	TALLOC_CTX *tmp_ctx = talloc_new(msg);
	int ret;
	struct ldb_val *new_values = NULL;
	unsigned int num_new_values = 0;
	unsigned old_num_values = old_el?old_el->num_values:0;
	const struct GUID *invocation_id;
	struct ldb_context *ldb = ldb_module_get_ctx(module);
	NTTIME now;

	unix_to_nt_time(&now, t);

	ret = get_parsed_dns(module, tmp_ctx, el, &dns, schema_attr->syntax->ldap_oid, parent);
	if (ret != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ret;
	}

	ret = get_parsed_dns(module, tmp_ctx, old_el, &old_dns, schema_attr->syntax->ldap_oid, parent);
	if (ret != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ret;
	}

	invocation_id = samdb_ntds_invocation_id(ldb);
	if (!invocation_id) {
		talloc_free(tmp_ctx);
		return LDB_ERR_OPERATIONS_ERROR;
	}

	ret = replmd_check_upgrade_links(old_dns, old_num_values, old_el, invocation_id);
	if (ret != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ret;
	}

	/* for each new value, see if it exists already with the same GUID */
	for (i=0; i<el->num_values; i++) {
		struct parsed_dn *p = parsed_dn_find(old_dns, old_num_values, dns[i].guid, NULL);
		if (p == NULL) {
			/* this is a new linked attribute value */
			new_values = talloc_realloc(tmp_ctx, new_values, struct ldb_val, num_new_values+1);
			if (new_values == NULL) {
				ldb_module_oom(module);
				talloc_free(tmp_ctx);
				return LDB_ERR_OPERATIONS_ERROR;
			}
			ret = replmd_build_la_val(new_values, &new_values[num_new_values], dns[i].dsdb_dn,
						  invocation_id, seq_num, seq_num, now, 0, false);
			if (ret != LDB_SUCCESS) {
				talloc_free(tmp_ctx);
				return ret;
			}
			num_new_values++;
		} else {
			/* this is only allowed if the GUID was
			   previously deleted. */
			uint32_t rmd_flags = dsdb_dn_rmd_flags(p->dsdb_dn->dn);

			if (!(rmd_flags & DSDB_RMD_FLAG_DELETED)) {
				ldb_asprintf_errstring(ldb, "Attribute %s already exists for target GUID %s",
						       el->name, GUID_string(tmp_ctx, p->guid));
				talloc_free(tmp_ctx);
				/* error codes for 'member' need to be
				   special cased */
				if (ldb_attr_cmp(el->name, "member") == 0) {
					return LDB_ERR_ENTRY_ALREADY_EXISTS;
				} else {
					return LDB_ERR_ATTRIBUTE_OR_VALUE_EXISTS;
				}
			}
			ret = replmd_update_la_val(old_el->values, p->v, dns[i].dsdb_dn, p->dsdb_dn,
						   invocation_id, seq_num, seq_num, now, 0, false);
			if (ret != LDB_SUCCESS) {
				talloc_free(tmp_ctx);
				return ret;
			}
		}

		ret = replmd_add_backlink(module, schema, msg_guid, dns[i].guid, true, schema_attr, true);
		if (ret != LDB_SUCCESS) {
			talloc_free(tmp_ctx);
			return ret;
		}
	}

	/* add the new ones on to the end of the old values, constructing a new el->values */
	el->values = talloc_realloc(msg->elements, old_el?old_el->values:NULL,
				    struct ldb_val,
				    old_num_values+num_new_values);
	if (el->values == NULL) {
		ldb_module_oom(module);
		return LDB_ERR_OPERATIONS_ERROR;
	}

	memcpy(&el->values[old_num_values], new_values, num_new_values*sizeof(struct ldb_val));
	el->num_values = old_num_values + num_new_values;

	talloc_steal(msg->elements, el->values);
	talloc_steal(el->values, new_values);

	talloc_free(tmp_ctx);

	/* we now tell the backend to replace all existing values
	   with the one we have constructed */
	el->flags = LDB_FLAG_MOD_REPLACE;

	return LDB_SUCCESS;
}


/*
  handle deleting all active linked attributes
 */
static int replmd_modify_la_delete(struct ldb_module *module,
				   const struct dsdb_schema *schema,
				   struct ldb_message *msg,
				   struct ldb_message_element *el,
				   struct ldb_message_element *old_el,
				   const struct dsdb_attribute *schema_attr,
				   uint64_t seq_num,
				   time_t t,
				   struct GUID *msg_guid,
				   struct ldb_request *parent)
{
	unsigned int i;
	struct parsed_dn *dns, *old_dns;
	TALLOC_CTX *tmp_ctx = talloc_new(msg);
	int ret;
	const struct GUID *invocation_id;
	struct ldb_context *ldb = ldb_module_get_ctx(module);
	NTTIME now;

	unix_to_nt_time(&now, t);

	/* check if there is nothing to delete */
	if ((!old_el || old_el->num_values == 0) &&
	    el->num_values == 0) {
		return LDB_SUCCESS;
	}

	if (!old_el || old_el->num_values == 0) {
		return LDB_ERR_NO_SUCH_ATTRIBUTE;
	}

	ret = get_parsed_dns(module, tmp_ctx, el, &dns, schema_attr->syntax->ldap_oid, parent);
	if (ret != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ret;
	}

	ret = get_parsed_dns(module, tmp_ctx, old_el, &old_dns, schema_attr->syntax->ldap_oid, parent);
	if (ret != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ret;
	}

	invocation_id = samdb_ntds_invocation_id(ldb);
	if (!invocation_id) {
		return LDB_ERR_OPERATIONS_ERROR;
	}

	ret = replmd_check_upgrade_links(old_dns, old_el->num_values, old_el, invocation_id);
	if (ret != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ret;
	}

	el->values = NULL;

	/* see if we are being asked to delete any links that
	   don't exist or are already deleted */
	for (i=0; i<el->num_values; i++) {
		struct parsed_dn *p = &dns[i];
		struct parsed_dn *p2;
		uint32_t rmd_flags;

		p2 = parsed_dn_find(old_dns, old_el->num_values, p->guid, NULL);
		if (!p2) {
			ldb_asprintf_errstring(ldb, "Attribute %s doesn't exist for target GUID %s",
					       el->name, GUID_string(tmp_ctx, p->guid));
			if (ldb_attr_cmp(el->name, "member") == 0) {
				return LDB_ERR_UNWILLING_TO_PERFORM;
			} else {
				return LDB_ERR_NO_SUCH_ATTRIBUTE;
			}
		}
		rmd_flags = dsdb_dn_rmd_flags(p2->dsdb_dn->dn);
		if (rmd_flags & DSDB_RMD_FLAG_DELETED) {
			ldb_asprintf_errstring(ldb, "Attribute %s already deleted for target GUID %s",
					       el->name, GUID_string(tmp_ctx, p->guid));
			if (ldb_attr_cmp(el->name, "member") == 0) {
				return LDB_ERR_UNWILLING_TO_PERFORM;
			} else {
				return LDB_ERR_NO_SUCH_ATTRIBUTE;
			}
		}
	}

	/* for each new value, see if it exists already with the same GUID
	   if it is not already deleted and matches the delete list then delete it
	*/
	for (i=0; i<old_el->num_values; i++) {
		struct parsed_dn *p = &old_dns[i];
		uint32_t rmd_flags;

		if (el->num_values && parsed_dn_find(dns, el->num_values, p->guid, NULL) == NULL) {
			continue;
		}

		rmd_flags = dsdb_dn_rmd_flags(p->dsdb_dn->dn);
		if (rmd_flags & DSDB_RMD_FLAG_DELETED) continue;

		ret = replmd_update_la_val(old_el->values, p->v, p->dsdb_dn, p->dsdb_dn,
					   invocation_id, seq_num, seq_num, now, 0, true);
		if (ret != LDB_SUCCESS) {
			talloc_free(tmp_ctx);
			return ret;
		}

		ret = replmd_add_backlink(module, schema, msg_guid, old_dns[i].guid, false, schema_attr, true);
		if (ret != LDB_SUCCESS) {
			talloc_free(tmp_ctx);
			return ret;
		}
	}

	el->values = talloc_steal(msg->elements, old_el->values);
	el->num_values = old_el->num_values;

	talloc_free(tmp_ctx);

	/* we now tell the backend to replace all existing values
	   with the one we have constructed */
	el->flags = LDB_FLAG_MOD_REPLACE;

	return LDB_SUCCESS;
}

/*
  handle replacing a linked attribute
 */
static int replmd_modify_la_replace(struct ldb_module *module,
				    const struct dsdb_schema *schema,
				    struct ldb_message *msg,
				    struct ldb_message_element *el,
				    struct ldb_message_element *old_el,
				    const struct dsdb_attribute *schema_attr,
				    uint64_t seq_num,
				    time_t t,
				    struct GUID *msg_guid,
				    struct ldb_request *parent)
{
	unsigned int i;
	struct parsed_dn *dns, *old_dns;
	TALLOC_CTX *tmp_ctx = talloc_new(msg);
	int ret;
	const struct GUID *invocation_id;
	struct ldb_context *ldb = ldb_module_get_ctx(module);
	struct ldb_val *new_values = NULL;
	unsigned int num_new_values = 0;
	unsigned int old_num_values = old_el?old_el->num_values:0;
	NTTIME now;

	unix_to_nt_time(&now, t);

	/* check if there is nothing to replace */
	if ((!old_el || old_el->num_values == 0) &&
	    el->num_values == 0) {
		return LDB_SUCCESS;
	}

	ret = get_parsed_dns(module, tmp_ctx, el, &dns, schema_attr->syntax->ldap_oid, parent);
	if (ret != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ret;
	}

	ret = get_parsed_dns(module, tmp_ctx, old_el, &old_dns, schema_attr->syntax->ldap_oid, parent);
	if (ret != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ret;
	}

	invocation_id = samdb_ntds_invocation_id(ldb);
	if (!invocation_id) {
		return LDB_ERR_OPERATIONS_ERROR;
	}

	ret = replmd_check_upgrade_links(old_dns, old_num_values, old_el, invocation_id);
	if (ret != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ret;
	}

	/* mark all the old ones as deleted */
	for (i=0; i<old_num_values; i++) {
		struct parsed_dn *old_p = &old_dns[i];
		struct parsed_dn *p;
		uint32_t rmd_flags = dsdb_dn_rmd_flags(old_p->dsdb_dn->dn);

		if (rmd_flags & DSDB_RMD_FLAG_DELETED) continue;

		ret = replmd_add_backlink(module, schema, msg_guid, old_dns[i].guid, false, schema_attr, false);
		if (ret != LDB_SUCCESS) {
			talloc_free(tmp_ctx);
			return ret;
		}

		p = parsed_dn_find(dns, el->num_values, old_p->guid, NULL);
		if (p) {
			/* we don't delete it if we are re-adding it */
			continue;
		}

		ret = replmd_update_la_val(old_el->values, old_p->v, old_p->dsdb_dn, old_p->dsdb_dn,
					   invocation_id, seq_num, seq_num, now, 0, true);
		if (ret != LDB_SUCCESS) {
			talloc_free(tmp_ctx);
			return ret;
		}
	}

	/* for each new value, either update its meta-data, or add it
	 * to old_el
	*/
	for (i=0; i<el->num_values; i++) {
		struct parsed_dn *p = &dns[i], *old_p;

		if (old_dns &&
		    (old_p = parsed_dn_find(old_dns,
					    old_num_values, p->guid, NULL)) != NULL) {
			/* update in place */
			ret = replmd_update_la_val(old_el->values, old_p->v, p->dsdb_dn,
						   old_p->dsdb_dn, invocation_id,
						   seq_num, seq_num, now, 0, false);
			if (ret != LDB_SUCCESS) {
				talloc_free(tmp_ctx);
				return ret;
			}
		} else {
			/* add a new one */
			new_values = talloc_realloc(tmp_ctx, new_values, struct ldb_val,
						    num_new_values+1);
			if (new_values == NULL) {
				ldb_module_oom(module);
				talloc_free(tmp_ctx);
				return LDB_ERR_OPERATIONS_ERROR;
			}
			ret = replmd_build_la_val(new_values, &new_values[num_new_values], dns[i].dsdb_dn,
						  invocation_id, seq_num, seq_num, now, 0, false);
			if (ret != LDB_SUCCESS) {
				talloc_free(tmp_ctx);
				return ret;
			}
			num_new_values++;
		}

		ret = replmd_add_backlink(module, schema, msg_guid, dns[i].guid, true, schema_attr, false);
		if (ret != LDB_SUCCESS) {
			talloc_free(tmp_ctx);
			return ret;
		}
	}

	/* add the new values to the end of old_el */
	if (num_new_values != 0) {
		el->values = talloc_realloc(msg->elements, old_el?old_el->values:NULL,
					    struct ldb_val, old_num_values+num_new_values);
		if (el->values == NULL) {
			ldb_module_oom(module);
			return LDB_ERR_OPERATIONS_ERROR;
		}
		memcpy(&el->values[old_num_values], &new_values[0],
		       sizeof(struct ldb_val)*num_new_values);
		el->num_values = old_num_values + num_new_values;
		talloc_steal(msg->elements, new_values);
	} else {
		el->values = old_el->values;
		el->num_values = old_el->num_values;
		talloc_steal(msg->elements, el->values);
	}

	talloc_free(tmp_ctx);

	/* we now tell the backend to replace all existing values
	   with the one we have constructed */
	el->flags = LDB_FLAG_MOD_REPLACE;

	return LDB_SUCCESS;
}


/*
  handle linked attributes in modify requests
 */
static int replmd_modify_handle_linked_attribs(struct ldb_module *module,
					       struct ldb_message *msg,
					       uint64_t seq_num, time_t t,
					       struct ldb_request *parent)
{
	struct ldb_result *res;
	unsigned int i;
	int ret;
	struct ldb_context *ldb = ldb_module_get_ctx(module);
	struct ldb_message *old_msg;

	const struct dsdb_schema *schema;
	struct GUID old_guid;

	if (seq_num == 0) {
		/* there the replmd_update_rpmd code has already
		 * checked and saw that there are no linked
		 * attributes */
		return LDB_SUCCESS;
	}

	if (dsdb_functional_level(ldb) == DS_DOMAIN_FUNCTION_2000) {
		/* don't do anything special for linked attributes */
		return LDB_SUCCESS;
	}

	ret = dsdb_module_search_dn(module, msg, &res, msg->dn, NULL,
	                            DSDB_FLAG_NEXT_MODULE |
	                            DSDB_SEARCH_SHOW_RECYCLED |
				    DSDB_SEARCH_REVEAL_INTERNALS |
				    DSDB_SEARCH_SHOW_DN_IN_STORAGE_FORMAT,
				    parent);
	if (ret != LDB_SUCCESS) {
		return ret;
	}
	schema = dsdb_get_schema(ldb, res);
	if (!schema) {
		return LDB_ERR_OPERATIONS_ERROR;
	}

	old_msg = res->msgs[0];

	old_guid = samdb_result_guid(old_msg, "objectGUID");

	for (i=0; i<msg->num_elements; i++) {
		struct ldb_message_element *el = &msg->elements[i];
		struct ldb_message_element *old_el, *new_el;
		const struct dsdb_attribute *schema_attr
			= dsdb_attribute_by_lDAPDisplayName(schema, el->name);
		if (!schema_attr) {
			ldb_asprintf_errstring(ldb,
					       "%s: attribute %s is not a valid attribute in schema",
					       __FUNCTION__, el->name);
			return LDB_ERR_OBJECT_CLASS_VIOLATION;
		}
		if (schema_attr->linkID == 0) {
			continue;
		}
		if ((schema_attr->linkID & 1) == 1) {
			/* Odd is for the target.  Illegal to modify */
			ldb_asprintf_errstring(ldb,
					       "attribute %s must not be modified directly, it is a linked attribute", el->name);
			return LDB_ERR_UNWILLING_TO_PERFORM;
		}
		old_el = ldb_msg_find_element(old_msg, el->name);
		switch (el->flags & LDB_FLAG_MOD_MASK) {
		case LDB_FLAG_MOD_REPLACE:
			ret = replmd_modify_la_replace(module, schema, msg, el, old_el, schema_attr, seq_num, t, &old_guid, parent);
			break;
		case LDB_FLAG_MOD_DELETE:
			ret = replmd_modify_la_delete(module, schema, msg, el, old_el, schema_attr, seq_num, t, &old_guid, parent);
			break;
		case LDB_FLAG_MOD_ADD:
			ret = replmd_modify_la_add(module, schema, msg, el, old_el, schema_attr, seq_num, t, &old_guid, parent);
			break;
		default:
			ldb_asprintf_errstring(ldb,
					       "invalid flags 0x%x for %s linked attribute",
					       el->flags, el->name);
			return LDB_ERR_UNWILLING_TO_PERFORM;
		}
		if (dsdb_check_single_valued_link(schema_attr, el) != LDB_SUCCESS) {
			ldb_asprintf_errstring(ldb,
					       "Attribute %s is single valued but more than one value has been supplied",
					       el->name);
			return LDB_ERR_ATTRIBUTE_OR_VALUE_EXISTS;
		} else {
			el->flags |= LDB_FLAG_INTERNAL_DISABLE_SINGLE_VALUE_CHECK;
		}



		if (ret != LDB_SUCCESS) {
			return ret;
		}
		if (old_el) {
			ldb_msg_remove_attr(old_msg, el->name);
		}
		ldb_msg_add_empty(old_msg, el->name, 0, &new_el);
		new_el->num_values = el->num_values;
		new_el->values = talloc_steal(msg->elements, el->values);

		/* TODO: this relises a bit too heavily on the exact
		   behaviour of ldb_msg_find_element and
		   ldb_msg_remove_element */
		old_el = ldb_msg_find_element(msg, el->name);
		if (old_el != el) {
			ldb_msg_remove_element(msg, old_el);
			i--;
		}
	}

	talloc_free(res);
	return ret;
}



static int replmd_modify(struct ldb_module *module, struct ldb_request *req)
{
	struct ldb_context *ldb;
	struct replmd_replicated_request *ac;
	struct ldb_request *down_req;
	struct ldb_message *msg;
	time_t t = time(NULL);
	int ret;
	bool is_urgent = false;
	struct loadparm_context *lp_ctx;
	char *referral;
	unsigned int functional_level;
	const DATA_BLOB *guid_blob;

	/* do not manipulate our control entries */
	if (ldb_dn_is_special(req->op.mod.message->dn)) {
		return ldb_next_request(module, req);
	}

	ldb = ldb_module_get_ctx(module);

	ldb_debug(ldb, LDB_DEBUG_TRACE, "replmd_modify\n");

	guid_blob = ldb_msg_find_ldb_val(req->op.mod.message, "objectGUID");
	if ( guid_blob != NULL ) {
		ldb_set_errstring(ldb,
				  "replmd_modify: it's not allowed to change the objectGUID!");
		return LDB_ERR_CONSTRAINT_VIOLATION;
	}

	ac = replmd_ctx_init(module, req);
	if (ac == NULL) {
		return ldb_module_oom(module);
	}

	functional_level = dsdb_functional_level(ldb);

	lp_ctx = talloc_get_type(ldb_get_opaque(ldb, "loadparm"),
				 struct loadparm_context);

	/* we have to copy the message as the caller might have it as a const */
	msg = ldb_msg_copy_shallow(ac, req->op.mod.message);
	if (msg == NULL) {
		ldb_oom(ldb);
		talloc_free(ac);
		return LDB_ERR_OPERATIONS_ERROR;
	}

	ldb_msg_remove_attr(msg, "whenChanged");
	ldb_msg_remove_attr(msg, "uSNChanged");

	ret = replmd_update_rpmd(module, ac->schema, req, NULL,
				 msg, &ac->seq_num, t, &is_urgent);
	if (ret == LDB_ERR_REFERRAL) {
		referral = talloc_asprintf(req,
					   "ldap://%s/%s",
					   lpcfg_dnsdomain(lp_ctx),
					   ldb_dn_get_linearized(msg->dn));
		ret = ldb_module_send_referral(req, referral);
		talloc_free(ac);
		return ldb_module_done(req, NULL, NULL, ret);
	}

	if (ret != LDB_SUCCESS) {
		talloc_free(ac);
		return ret;
	}

	ret = replmd_modify_handle_linked_attribs(module, msg, ac->seq_num, t, req);
	if (ret != LDB_SUCCESS) {
		talloc_free(ac);
		return ret;
	}

	/* TODO:
	 * - replace the old object with the newly constructed one
	 */

	ac->is_urgent = is_urgent;

	ret = ldb_build_mod_req(&down_req, ldb, ac,
				msg,
				req->controls,
				ac, replmd_op_callback,
				req);
	LDB_REQ_SET_LOCATION(down_req);
	if (ret != LDB_SUCCESS) {
		talloc_free(ac);
		return ret;
	}

	/* current partition control is needed by "replmd_op_callback" */
	if (ldb_request_get_control(req, DSDB_CONTROL_CURRENT_PARTITION_OID) == NULL) {
		ret = ldb_request_add_control(down_req,
					      DSDB_CONTROL_CURRENT_PARTITION_OID,
					      false, NULL);
		if (ret != LDB_SUCCESS) {
			talloc_free(ac);
			return ret;
		}
	}

	/* If we are in functional level 2000, then
	 * replmd_modify_handle_linked_attribs will have done
	 * nothing */
	if (functional_level == DS_DOMAIN_FUNCTION_2000) {
		ret = ldb_request_add_control(down_req, DSDB_CONTROL_APPLY_LINKS, false, NULL);
		if (ret != LDB_SUCCESS) {
			talloc_free(ac);
			return ret;
		}
	}

	talloc_steal(down_req, msg);

	/* we only change whenChanged and uSNChanged if the seq_num
	   has changed */
	if (ac->seq_num != 0) {
		ret = add_time_element(msg, "whenChanged", t);
		if (ret != LDB_SUCCESS) {
			talloc_free(ac);
			return ret;
		}

		ret = add_uint64_element(ldb, msg, "uSNChanged", ac->seq_num);
		if (ret != LDB_SUCCESS) {
			talloc_free(ac);
			return ret;
		}
	}

	/* go on with the call chain */
	return ldb_next_request(module, down_req);
}

static int replmd_rename_callback(struct ldb_request *req, struct ldb_reply *ares);

/*
  handle a rename request

  On a rename we need to do an extra ldb_modify which sets the
  whenChanged and uSNChanged attributes.  We do this in a callback after the success.
 */
static int replmd_rename(struct ldb_module *module, struct ldb_request *req)
{
	struct ldb_context *ldb;
	struct replmd_replicated_request *ac;
	int ret;
	struct ldb_request *down_req;

	/* do not manipulate our control entries */
	if (ldb_dn_is_special(req->op.mod.message->dn)) {
		return ldb_next_request(module, req);
	}

	ldb = ldb_module_get_ctx(module);

	ldb_debug(ldb, LDB_DEBUG_TRACE, "replmd_rename\n");

	ac = replmd_ctx_init(module, req);
	if (ac == NULL) {
		return ldb_module_oom(module);
	}

	ret = ldb_build_rename_req(&down_req, ldb, ac,
				   ac->req->op.rename.olddn,
				   ac->req->op.rename.newdn,
				   ac->req->controls,
				   ac, replmd_rename_callback,
				   ac->req);
	LDB_REQ_SET_LOCATION(down_req);
	if (ret != LDB_SUCCESS) {
		talloc_free(ac);
		return ret;
	}

	/* go on with the call chain */
	return ldb_next_request(module, down_req);
}

/* After the rename is compleated, update the whenchanged etc */
static int replmd_rename_callback(struct ldb_request *req, struct ldb_reply *ares)
{
	struct ldb_context *ldb;
	struct replmd_replicated_request *ac;
	struct ldb_request *down_req;
	struct ldb_message *msg;
	const struct dsdb_attribute *rdn_attr;
	const char *rdn_name;
	const struct ldb_val *rdn_val;
	const char *attrs[4] = { NULL, };
	time_t t = time(NULL);
	int ret;
	bool is_urgent = false;

	ac = talloc_get_type(req->context, struct replmd_replicated_request);
	ldb = ldb_module_get_ctx(ac->module);

	if (ares->error != LDB_SUCCESS) {
		return ldb_module_done(ac->req, ares->controls,
					ares->response, ares->error);
	}

	if (ares->type != LDB_REPLY_DONE) {
		ldb_set_errstring(ldb,
				  "invalid ldb_reply_type in callback");
		talloc_free(ares);
		return ldb_module_done(ac->req, NULL, NULL,
					LDB_ERR_OPERATIONS_ERROR);
	}

	/* TODO:
	 * - replace the old object with the newly constructed one
	 */

	msg = ldb_msg_new(ac);
	if (msg == NULL) {
		ldb_oom(ldb);
		return LDB_ERR_OPERATIONS_ERROR;
	}

	msg->dn = ac->req->op.rename.newdn;

	rdn_name = ldb_dn_get_rdn_name(msg->dn);
	if (rdn_name == NULL) {
		talloc_free(ares);
		return ldb_module_done(ac->req, NULL, NULL,
				       ldb_operr(ldb));
	}

	/* normalize the rdn attribute name */
	rdn_attr = dsdb_attribute_by_lDAPDisplayName(ac->schema, rdn_name);
	if (rdn_attr == NULL) {
		talloc_free(ares);
		return ldb_module_done(ac->req, NULL, NULL,
				       ldb_operr(ldb));
	}
	rdn_name = rdn_attr->lDAPDisplayName;

	rdn_val = ldb_dn_get_rdn_val(msg->dn);
	if (rdn_val == NULL) {
		talloc_free(ares);
		return ldb_module_done(ac->req, NULL, NULL,
				       ldb_operr(ldb));
	}

	if (ldb_msg_add_empty(msg, rdn_name, LDB_FLAG_MOD_REPLACE, NULL) != 0) {
		talloc_free(ares);
		return ldb_module_done(ac->req, NULL, NULL,
				       ldb_oom(ldb));
	}
	if (ldb_msg_add_value(msg, rdn_name, rdn_val, NULL) != 0) {
		talloc_free(ares);
		return ldb_module_done(ac->req, NULL, NULL,
				       ldb_oom(ldb));
	}
	if (ldb_msg_add_empty(msg, "name", LDB_FLAG_MOD_REPLACE, NULL) != 0) {
		talloc_free(ares);
		return ldb_module_done(ac->req, NULL, NULL,
				       ldb_oom(ldb));
	}
	if (ldb_msg_add_value(msg, "name", rdn_val, NULL) != 0) {
		talloc_free(ares);
		return ldb_module_done(ac->req, NULL, NULL,
				       ldb_oom(ldb));
	}

	/*
	 * here we let replmd_update_rpmd() only search for
	 * the existing "replPropertyMetaData" and rdn_name attributes.
	 *
	 * We do not want the existing "name" attribute as
	 * the "name" attribute needs to get the version
	 * updated on rename even if the rdn value hasn't changed.
	 *
	 * This is the diff of the meta data, for a moved user
	 * on a w2k8r2 server:
	 *
	 * # record 1
	 * -dn: CN=sdf df,CN=Users,DC=bla,DC=base
	 * +dn: CN=sdf df,OU=TestOU,DC=bla,DC=base
	 *  replPropertyMetaData:     NDR: struct replPropertyMetaDataBlob
	 *         version                  : 0x00000001 (1)
	 *         reserved                 : 0x00000000 (0)
	 * @@ -66,11 +66,11 @@ replPropertyMetaData:     NDR: struct re
	 *                      local_usn                : 0x00000000000037a5 (14245)
	 *                 array: struct replPropertyMetaData1
	 *                      attid                    : DRSUAPI_ATTID_name (0x90001)
	 * -                    version                  : 0x00000001 (1)
	 * -                    originating_change_time  : Wed Feb  9 17:20:49 2011 CET
	 * +                    version                  : 0x00000002 (2)
	 * +                    originating_change_time  : Wed Apr  6 15:21:01 2011 CEST
	 *                      originating_invocation_id: 0d36ca05-5507-4e62-aca3-354bab0d39e1
	 * -                    originating_usn          : 0x00000000000037a5 (14245)
	 * -                    local_usn                : 0x00000000000037a5 (14245)
	 * +                    originating_usn          : 0x0000000000003834 (14388)
	 * +                    local_usn                : 0x0000000000003834 (14388)
	 *                 array: struct replPropertyMetaData1
	 *                      attid                    : DRSUAPI_ATTID_userAccountControl (0x90008)
	 *                      version                  : 0x00000004 (4)
	 */
	attrs[0] = "replPropertyMetaData";
	attrs[1] = "objectClass";
	attrs[2] = rdn_name;
	attrs[3] = NULL;

	ret = replmd_update_rpmd(ac->module, ac->schema, req, attrs,
				 msg, &ac->seq_num, t, &is_urgent);
	if (ret == LDB_ERR_REFERRAL) {
		struct ldb_dn *olddn = ac->req->op.rename.olddn;
		struct loadparm_context *lp_ctx;
		char *referral;

		lp_ctx = talloc_get_type(ldb_get_opaque(ldb, "loadparm"),
					 struct loadparm_context);

		referral = talloc_asprintf(req,
					   "ldap://%s/%s",
					   lpcfg_dnsdomain(lp_ctx),
					   ldb_dn_get_linearized(olddn));
		ret = ldb_module_send_referral(req, referral);
		talloc_free(ac);
		return ldb_module_done(req, NULL, NULL, ret);
	}

	if (ret != LDB_SUCCESS) {
		talloc_free(ares);
		return ldb_module_done(ac->req, NULL, NULL,
				       ldb_error(ldb, ret,
					"failed to call replmd_update_rpmd()"));
	}

	if (ac->seq_num == 0) {
		talloc_free(ares);
		return ldb_module_done(ac->req, NULL, NULL,
				       ldb_error(ldb, ret,
					"internal error seq_num == 0"));
	}
	ac->is_urgent = is_urgent;

	ret = ldb_build_mod_req(&down_req, ldb, ac,
				msg,
				req->controls,
				ac, replmd_op_callback,
				req);
	LDB_REQ_SET_LOCATION(down_req);
	if (ret != LDB_SUCCESS) {
		talloc_free(ac);
		return ret;
	}

	/* current partition control is needed by "replmd_op_callback" */
	if (ldb_request_get_control(req, DSDB_CONTROL_CURRENT_PARTITION_OID) == NULL) {
		ret = ldb_request_add_control(down_req,
					      DSDB_CONTROL_CURRENT_PARTITION_OID,
					      false, NULL);
		if (ret != LDB_SUCCESS) {
			talloc_free(ac);
			return ret;
		}
	}

	talloc_steal(down_req, msg);

	ret = add_time_element(msg, "whenChanged", t);
	if (ret != LDB_SUCCESS) {
		talloc_free(ac);
		return ret;
	}

	ret = add_uint64_element(ldb, msg, "uSNChanged", ac->seq_num);
	if (ret != LDB_SUCCESS) {
		talloc_free(ac);
		return ret;
	}

	/* go on with the call chain - do the modify after the rename */
	return ldb_next_request(ac->module, down_req);
}

/*
   remove links from objects that point at this object when an object
   is deleted
 */
static int replmd_delete_remove_link(struct ldb_module *module,
				     const struct dsdb_schema *schema,
				     struct ldb_dn *dn,
				     struct ldb_message_element *el,
				     const struct dsdb_attribute *sa,
				     struct ldb_request *parent)
{
	unsigned int i;
	TALLOC_CTX *tmp_ctx = talloc_new(module);
	struct ldb_context *ldb = ldb_module_get_ctx(module);

	for (i=0; i<el->num_values; i++) {
		struct dsdb_dn *dsdb_dn;
		NTSTATUS status;
		int ret;
		struct GUID guid2;
		struct ldb_message *msg;
		const struct dsdb_attribute *target_attr;
		struct ldb_message_element *el2;
		struct ldb_val dn_val;

		if (dsdb_dn_is_deleted_val(&el->values[i])) {
			continue;
		}

		dsdb_dn = dsdb_dn_parse(tmp_ctx, ldb, &el->values[i], sa->syntax->ldap_oid);
		if (!dsdb_dn) {
			talloc_free(tmp_ctx);
			return LDB_ERR_OPERATIONS_ERROR;
		}

		status = dsdb_get_extended_dn_guid(dsdb_dn->dn, &guid2, "GUID");
		if (!NT_STATUS_IS_OK(status)) {
			talloc_free(tmp_ctx);
			return LDB_ERR_OPERATIONS_ERROR;
		}

		/* remove the link */
		msg = ldb_msg_new(tmp_ctx);
		if (!msg) {
			ldb_module_oom(module);
			talloc_free(tmp_ctx);
			return LDB_ERR_OPERATIONS_ERROR;
		}


		msg->dn = dsdb_dn->dn;

		target_attr = dsdb_attribute_by_linkID(schema, sa->linkID ^ 1);
		if (target_attr == NULL) {
			continue;
		}

		ret = ldb_msg_add_empty(msg, target_attr->lDAPDisplayName, LDB_FLAG_MOD_DELETE, &el2);
		if (ret != LDB_SUCCESS) {
			ldb_module_oom(module);
			talloc_free(tmp_ctx);
			return LDB_ERR_OPERATIONS_ERROR;
		}
		dn_val = data_blob_string_const(ldb_dn_get_linearized(dn));
		el2->values = &dn_val;
		el2->num_values = 1;

		ret = dsdb_module_modify(module, msg, DSDB_FLAG_OWN_MODULE, parent);
		if (ret != LDB_SUCCESS) {
			talloc_free(tmp_ctx);
			return ret;
		}
	}
	talloc_free(tmp_ctx);
	return LDB_SUCCESS;
}


/*
  handle update of replication meta data for deletion of objects

  This also handles the mapping of delete to a rename operation
  to allow deletes to be replicated.
 */
static int replmd_delete(struct ldb_module *module, struct ldb_request *req)
{
	int ret = LDB_ERR_OTHER;
	bool retb, disallow_move_on_delete;
	struct ldb_dn *old_dn, *new_dn;
	const char *rdn_name;
	const struct ldb_val *rdn_value, *new_rdn_value;
	struct GUID guid;
	struct ldb_context *ldb = ldb_module_get_ctx(module);
	const struct dsdb_schema *schema;
	struct ldb_message *msg, *old_msg;
	struct ldb_message_element *el;
	TALLOC_CTX *tmp_ctx;
	struct ldb_result *res, *parent_res;
	const char *preserved_attrs[] = {
		/* yes, this really is a hard coded list. See MS-ADTS
		   section 3.1.1.5.5.1.1 */
		"nTSecurityDescriptor", "attributeID", "attributeSyntax", "dNReferenceUpdate", "dNSHostName",
		"flatName", "governsID", "groupType", "instanceType", "lDAPDisplayName", "legacyExchangeDN",
		"isDeleted", "isRecycled", "lastKnownParent", "msDS-LastKnownRDN", "mS-DS-CreatorSID",
		"mSMQOwnerID", "nCName", "objectClass", "distinguishedName", "objectGUID", "objectSid",
		"oMSyntax", "proxiedObjectName", "name", "replPropertyMetaData", "sAMAccountName",
		"securityIdentifier", "sIDHistory", "subClassOf", "systemFlags", "trustPartner", "trustDirection",
		"trustType", "trustAttributes", "userAccountControl", "uSNChanged", "uSNCreated", "whenCreated",
		"whenChanged", NULL};
	unsigned int i, el_count = 0;
	enum deletion_state { OBJECT_NOT_DELETED=1, OBJECT_DELETED=2, OBJECT_RECYCLED=3,
						OBJECT_TOMBSTONE=4, OBJECT_REMOVED=5 };
	enum deletion_state deletion_state, next_deletion_state;
	bool enabled;

	if (ldb_dn_is_special(req->op.del.dn)) {
		return ldb_next_request(module, req);
	}

	tmp_ctx = talloc_new(ldb);
	if (!tmp_ctx) {
		ldb_oom(ldb);
		return LDB_ERR_OPERATIONS_ERROR;
	}

	schema = dsdb_get_schema(ldb, tmp_ctx);
	if (!schema) {
		return LDB_ERR_OPERATIONS_ERROR;
	}

	old_dn = ldb_dn_copy(tmp_ctx, req->op.del.dn);

	/* we need the complete msg off disk, so we can work out which
	   attributes need to be removed */
	ret = dsdb_module_search_dn(module, tmp_ctx, &res, old_dn, NULL,
	                            DSDB_FLAG_NEXT_MODULE |
	                            DSDB_SEARCH_SHOW_RECYCLED |
				    DSDB_SEARCH_REVEAL_INTERNALS |
				    DSDB_SEARCH_SHOW_DN_IN_STORAGE_FORMAT, req);
	if (ret != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ret;
	}
	old_msg = res->msgs[0];


	ret = dsdb_recyclebin_enabled(module, &enabled);
	if (ret != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ret;
	}

	if (ldb_msg_check_string_attribute(old_msg, "isDeleted", "TRUE")) {
		if (!enabled) {
			deletion_state = OBJECT_TOMBSTONE;
			next_deletion_state = OBJECT_REMOVED;
		} else if (ldb_msg_check_string_attribute(old_msg, "isRecycled", "TRUE")) {
			deletion_state = OBJECT_RECYCLED;
			next_deletion_state = OBJECT_REMOVED;
		} else {
			deletion_state = OBJECT_DELETED;
			next_deletion_state = OBJECT_RECYCLED;
		}
	} else {
		deletion_state = OBJECT_NOT_DELETED;
		if (enabled) {
			next_deletion_state = OBJECT_DELETED;
		} else {
			next_deletion_state = OBJECT_TOMBSTONE;
		}
	}

	if (next_deletion_state == OBJECT_REMOVED) {
		struct auth_session_info *session_info =
				(struct auth_session_info *)ldb_get_opaque(ldb, "sessionInfo");
		if (security_session_user_level(session_info, NULL) != SECURITY_SYSTEM) {
			ldb_asprintf_errstring(ldb, "Refusing to delete deleted object %s",
					ldb_dn_get_linearized(old_msg->dn));
			return LDB_ERR_UNWILLING_TO_PERFORM;
		}

		/* it is already deleted - really remove it this time */
		talloc_free(tmp_ctx);
		return ldb_next_request(module, req);
	}

	rdn_name = ldb_dn_get_rdn_name(old_dn);
	rdn_value = ldb_dn_get_rdn_val(old_dn);
	if ((rdn_name == NULL) || (rdn_value == NULL)) {
		talloc_free(tmp_ctx);
		return ldb_operr(ldb);
	}

	msg = ldb_msg_new(tmp_ctx);
	if (msg == NULL) {
		ldb_module_oom(module);
		talloc_free(tmp_ctx);
		return LDB_ERR_OPERATIONS_ERROR;
	}

	msg->dn = old_dn;

	if (deletion_state == OBJECT_NOT_DELETED){
		/* consider the SYSTEM_FLAG_DISALLOW_MOVE_ON_DELETE flag */
		disallow_move_on_delete =
			(ldb_msg_find_attr_as_int(old_msg, "systemFlags", 0)
				& SYSTEM_FLAG_DISALLOW_MOVE_ON_DELETE);

		/* work out where we will be renaming this object to */
		if (!disallow_move_on_delete) {
			ret = dsdb_get_deleted_objects_dn(ldb, tmp_ctx, old_dn,
							  &new_dn);
			if (ret != LDB_SUCCESS) {
				/* this is probably an attempted delete on a partition
				 * that doesn't allow delete operations, such as the
				 * schema partition */
				ldb_asprintf_errstring(ldb, "No Deleted Objects container for DN %s",
							   ldb_dn_get_linearized(old_dn));
				talloc_free(tmp_ctx);
				return LDB_ERR_UNWILLING_TO_PERFORM;
			}
		} else {
			new_dn = ldb_dn_get_parent(tmp_ctx, old_dn);
			if (new_dn == NULL) {
				ldb_module_oom(module);
				talloc_free(tmp_ctx);
				return LDB_ERR_OPERATIONS_ERROR;
			}
		}

		/* get the objects GUID from the search we just did */
		guid = samdb_result_guid(old_msg, "objectGUID");

		/* Add a formatted child */
		retb = ldb_dn_add_child_fmt(new_dn, "%s=%s\\0ADEL:%s",
						rdn_name,
						ldb_dn_escape_value(tmp_ctx, *rdn_value),
						GUID_string(tmp_ctx, &guid));
		if (!retb) {
			DEBUG(0,(__location__ ": Unable to add a formatted child to dn: %s",
					ldb_dn_get_linearized(new_dn)));
			talloc_free(tmp_ctx);
			return LDB_ERR_OPERATIONS_ERROR;
		}

		ret = ldb_msg_add_string(msg, "isDeleted", "TRUE");
		if (ret != LDB_SUCCESS) {
			DEBUG(0,(__location__ ": Failed to add isDeleted string to the msg\n"));
			ldb_module_oom(module);
			talloc_free(tmp_ctx);
			return ret;
		}
		msg->elements[el_count++].flags = LDB_FLAG_MOD_REPLACE;
	}

	/*
	  now we need to modify the object in the following ways:

	  - add isDeleted=TRUE
	  - update rDN and name, with new rDN
	  - remove linked attributes
	  - remove objectCategory and sAMAccountType
	  - remove attribs not on the preserved list
	     - preserved if in above list, or is rDN
	  - remove all linked attribs from this object
	  - remove all links from other objects to this object
	  - add lastKnownParent
	  - update replPropertyMetaData?

	  see MS-ADTS "Tombstone Requirements" section 3.1.1.5.5.1.1
	 */

	/* we need the storage form of the parent GUID */
	ret = dsdb_module_search_dn(module, tmp_ctx, &parent_res,
				    ldb_dn_get_parent(tmp_ctx, old_dn), NULL,
				    DSDB_FLAG_NEXT_MODULE |
				    DSDB_SEARCH_SHOW_DN_IN_STORAGE_FORMAT |
				    DSDB_SEARCH_REVEAL_INTERNALS|
				    DSDB_SEARCH_SHOW_RECYCLED, req);
	if (ret != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ret;
	}

	if (deletion_state == OBJECT_NOT_DELETED){
		ret = ldb_msg_add_steal_string(msg, "lastKnownParent",
						   ldb_dn_get_extended_linearized(tmp_ctx, parent_res->msgs[0]->dn, 1));
		if (ret != LDB_SUCCESS) {
			DEBUG(0,(__location__ ": Failed to add lastKnownParent string to the msg\n"));
			ldb_module_oom(module);
			talloc_free(tmp_ctx);
			return ret;
		}
		msg->elements[el_count++].flags = LDB_FLAG_MOD_ADD;
	}

	switch (next_deletion_state){

	case OBJECT_DELETED:

		ret = ldb_msg_add_value(msg, "msDS-LastKnownRDN", rdn_value, NULL);
		if (ret != LDB_SUCCESS) {
			DEBUG(0,(__location__ ": Failed to add msDS-LastKnownRDN string to the msg\n"));
			ldb_module_oom(module);
			talloc_free(tmp_ctx);
			return ret;
		}
		msg->elements[el_count++].flags = LDB_FLAG_MOD_ADD;

		ret = ldb_msg_add_empty(msg, "objectCategory", LDB_FLAG_MOD_DELETE, NULL);
		if (ret != LDB_SUCCESS) {
			talloc_free(tmp_ctx);
			ldb_module_oom(module);
			return ret;
		}

		ret = ldb_msg_add_empty(msg, "sAMAccountType", LDB_FLAG_MOD_DELETE, NULL);
		if (ret != LDB_SUCCESS) {
			talloc_free(tmp_ctx);
			ldb_module_oom(module);
			return ret;
		}

		break;

	case OBJECT_RECYCLED:
	case OBJECT_TOMBSTONE:

		/* we also mark it as recycled, meaning this object can't be
		   recovered (we are stripping its attributes) */
		if (dsdb_functional_level(ldb) >= DS_DOMAIN_FUNCTION_2008_R2) {
			ret = ldb_msg_add_string(msg, "isRecycled", "TRUE");
			if (ret != LDB_SUCCESS) {
				DEBUG(0,(__location__ ": Failed to add isRecycled string to the msg\n"));
				ldb_module_oom(module);
				talloc_free(tmp_ctx);
				return ret;
			}
			msg->elements[el_count++].flags = LDB_FLAG_MOD_ADD;
		}

		/* work out which of the old attributes we will be removing */
		for (i=0; i<old_msg->num_elements; i++) {
			const struct dsdb_attribute *sa;
			el = &old_msg->elements[i];
			sa = dsdb_attribute_by_lDAPDisplayName(schema, el->name);
			if (!sa) {
				talloc_free(tmp_ctx);
				return LDB_ERR_OPERATIONS_ERROR;
			}
			if (ldb_attr_cmp(el->name, rdn_name) == 0) {
				/* don't remove the rDN */
				continue;
			}
			if (sa->linkID && sa->linkID & 1) {
				ret = replmd_delete_remove_link(module, schema, old_dn, el, sa, req);
				if (ret != LDB_SUCCESS) {
					talloc_free(tmp_ctx);
					return LDB_ERR_OPERATIONS_ERROR;
				}
				continue;
			}
			if (!sa->linkID && ldb_attr_in_list(preserved_attrs, el->name)) {
				continue;
			}
			ret = ldb_msg_add_empty(msg, el->name, LDB_FLAG_MOD_DELETE, &el);
			if (ret != LDB_SUCCESS) {
				talloc_free(tmp_ctx);
				ldb_module_oom(module);
				return ret;
			}
		}
		break;

	default:
		break;
	}

	if (deletion_state == OBJECT_NOT_DELETED) {
		const struct dsdb_attribute *sa;

		/* work out what the new rdn value is, for updating the
		   rDN and name fields */
		new_rdn_value = ldb_dn_get_rdn_val(new_dn);
		if (new_rdn_value == NULL) {
			talloc_free(tmp_ctx);
			return ldb_operr(ldb);
		}

		sa = dsdb_attribute_by_lDAPDisplayName(schema, rdn_name);
		if (!sa) {
			talloc_free(tmp_ctx);
			return LDB_ERR_OPERATIONS_ERROR;
		}

		ret = ldb_msg_add_value(msg, sa->lDAPDisplayName, new_rdn_value,
					&el);
		if (ret != LDB_SUCCESS) {
			talloc_free(tmp_ctx);
			return ret;
		}
		el->flags = LDB_FLAG_MOD_REPLACE;

		el = ldb_msg_find_element(old_msg, "name");
		if (el) {
			ret = ldb_msg_add_value(msg, "name", new_rdn_value, &el);
			if (ret != LDB_SUCCESS) {
				talloc_free(tmp_ctx);
				return ret;
			}
			el->flags = LDB_FLAG_MOD_REPLACE;
		}
	}

	ret = dsdb_module_modify(module, msg, DSDB_FLAG_OWN_MODULE, req);
	if (ret != LDB_SUCCESS) {
		ldb_asprintf_errstring(ldb, "replmd_delete: Failed to modify object %s in delete - %s",
				       ldb_dn_get_linearized(old_dn), ldb_errstring(ldb));
		talloc_free(tmp_ctx);
		return ret;
	}

	if (deletion_state == OBJECT_NOT_DELETED) {
		/* now rename onto the new DN */
		ret = dsdb_module_rename(module, old_dn, new_dn, DSDB_FLAG_NEXT_MODULE, req);
		if (ret != LDB_SUCCESS){
			DEBUG(0,(__location__ ": Failed to rename object from '%s' to '%s' - %s\n",
				 ldb_dn_get_linearized(old_dn),
				 ldb_dn_get_linearized(new_dn),
				 ldb_errstring(ldb)));
			talloc_free(tmp_ctx);
			return ret;
		}
	}

	talloc_free(tmp_ctx);

	return ldb_module_done(req, NULL, NULL, LDB_SUCCESS);
}



static int replmd_replicated_request_error(struct replmd_replicated_request *ar, int ret)
{
	return ret;
}

static int replmd_replicated_request_werror(struct replmd_replicated_request *ar, WERROR status)
{
	int ret = LDB_ERR_OTHER;
	/* TODO: do some error mapping */
	return ret;
}


static struct replPropertyMetaData1 *
replmd_replPropertyMetaData1_find_attid(struct replPropertyMetaDataBlob *md_blob,
                                        enum drsuapi_DsAttributeId attid)
{
	uint32_t i;
	struct replPropertyMetaDataCtr1 *rpmd_ctr = &md_blob->ctr.ctr1;

	for (i = 0; i < rpmd_ctr->count; i++) {
		if (rpmd_ctr->array[i].attid == attid) {
			return &rpmd_ctr->array[i];
		}
	}
	return NULL;
}


/*
   return true if an update is newer than an existing entry
   see section 5.11 of MS-ADTS
*/
static bool replmd_update_is_newer(const struct GUID *current_invocation_id,
				   const struct GUID *update_invocation_id,
				   uint32_t current_version,
				   uint32_t update_version,
				   NTTIME current_change_time,
				   NTTIME update_change_time)
{
	if (update_version != current_version) {
		return update_version > current_version;
	}
	if (update_change_time != current_change_time) {
		return update_change_time > current_change_time;
	}
	return GUID_compare(update_invocation_id, current_invocation_id) > 0;
}

static bool replmd_replPropertyMetaData1_is_newer(struct replPropertyMetaData1 *cur_m,
						  struct replPropertyMetaData1 *new_m)
{
	return replmd_update_is_newer(&cur_m->originating_invocation_id,
				      &new_m->originating_invocation_id,
				      cur_m->version,
				      new_m->version,
				      cur_m->originating_change_time,
				      new_m->originating_change_time);
}


/*
  form a conflict DN
 */
static struct ldb_dn *replmd_conflict_dn(TALLOC_CTX *mem_ctx, struct ldb_dn *dn, struct GUID *guid)
{
	const struct ldb_val *rdn_val;
	const char *rdn_name;
	struct ldb_dn *new_dn;

	rdn_val = ldb_dn_get_rdn_val(dn);
	rdn_name = ldb_dn_get_rdn_name(dn);
	if (!rdn_val || !rdn_name) {
		return NULL;
	}

	new_dn = ldb_dn_copy(mem_ctx, dn);
	if (!new_dn) {
		return NULL;
	}

	if (!ldb_dn_remove_child_components(new_dn, 1)) {
		return NULL;
	}

	if (!ldb_dn_add_child_fmt(new_dn, "%s=%s\\0ACNF:%s",
				  rdn_name,
				  ldb_dn_escape_value(new_dn, *rdn_val),
				  GUID_string(new_dn, guid))) {
		return NULL;
	}

	return new_dn;
}


/*
  perform a modify operation which sets the rDN and name attributes to
  their current values. This has the effect of changing these
  attributes to have been last updated by the current DC. This is
  needed to ensure that renames performed as part of conflict
  resolution are propogated to other DCs
 */
static int replmd_name_modify(struct replmd_replicated_request *ar,
			      struct ldb_request *req, struct ldb_dn *dn)
{
	struct ldb_message *msg;
	const char *rdn_name;
	const struct ldb_val *rdn_val;
	const struct dsdb_attribute *rdn_attr;
	int ret;

	msg = ldb_msg_new(req);
	if (msg == NULL) {
		goto failed;
	}
	msg->dn = dn;

	rdn_name = ldb_dn_get_rdn_name(dn);
	if (rdn_name == NULL) {
		goto failed;
	}

	/* normalize the rdn attribute name */
	rdn_attr = dsdb_attribute_by_lDAPDisplayName(ar->schema, rdn_name);
	if (rdn_attr == NULL) {
		goto failed;
	}
	rdn_name = rdn_attr->lDAPDisplayName;

	rdn_val = ldb_dn_get_rdn_val(dn);
	if (rdn_val == NULL) {
		goto failed;
	}

	if (ldb_msg_add_empty(msg, rdn_name, LDB_FLAG_MOD_REPLACE, NULL) != 0) {
		goto failed;
	}
	if (ldb_msg_add_value(msg, rdn_name, rdn_val, NULL) != 0) {
		goto failed;
	}
	if (ldb_msg_add_empty(msg, "name", LDB_FLAG_MOD_REPLACE, NULL) != 0) {
		goto failed;
	}
	if (ldb_msg_add_value(msg, "name", rdn_val, NULL) != 0) {
		goto failed;
	}

	ret = dsdb_module_modify(ar->module, msg, DSDB_FLAG_OWN_MODULE, req);
	if (ret != LDB_SUCCESS) {
		DEBUG(0,(__location__ ": Failed to modify rDN/name of conflict DN '%s' - %s",
			 ldb_dn_get_linearized(dn),
			 ldb_errstring(ldb_module_get_ctx(ar->module))));
		return ret;
	}

	talloc_free(msg);

	return LDB_SUCCESS;

failed:
	talloc_free(msg);
	DEBUG(0,(__location__ ": Failed to setup modify rDN/name of conflict DN '%s'",
		 ldb_dn_get_linearized(dn)));
	return LDB_ERR_OPERATIONS_ERROR;
}


/*
  callback for conflict DN handling where we have renamed the incoming
  record. After renaming it, we need to ensure the change of name and
  rDN for the incoming record is seen as an originating update by this DC.
 */
static int replmd_op_name_modify_callback(struct ldb_request *req, struct ldb_reply *ares)
{
	struct replmd_replicated_request *ar =
		talloc_get_type_abort(req->context, struct replmd_replicated_request);
	int ret;

	if (ares->error != LDB_SUCCESS) {
		/* call the normal callback for everything except success */
		return replmd_op_callback(req, ares);
	}

	/* perform a modify of the rDN and name of the record */
	ret = replmd_name_modify(ar, req, req->op.add.message->dn);
	if (ret != LDB_SUCCESS) {
		ares->error = ret;
		return replmd_op_callback(req, ares);
	}

	return replmd_op_callback(req, ares);
}

/*
  callback for replmd_replicated_apply_add()
  This copes with the creation of conflict records in the case where
  the DN exists, but with a different objectGUID
 */
static int replmd_op_add_callback(struct ldb_request *req, struct ldb_reply *ares)
{
	struct ldb_dn *conflict_dn;
	struct replmd_replicated_request *ar =
		talloc_get_type_abort(req->context, struct replmd_replicated_request);
	struct ldb_result *res;
	const char *attrs[] = { "replPropertyMetaData", "objectGUID", NULL };
	int ret;
	const struct ldb_val *rmd_value, *omd_value;
	struct replPropertyMetaDataBlob omd, rmd;
	enum ndr_err_code ndr_err;
	bool rename_incoming_record;
	struct replPropertyMetaData1 *rmd_name, *omd_name;

	if (ares->error != LDB_ERR_ENTRY_ALREADY_EXISTS) {
		/* call the normal callback for everything except
		   conflicts */
		return replmd_op_callback(req, ares);
	}

	/*
	 * we have a conflict, and need to decide if we will keep the
	 * new record or the old record
	 */
	conflict_dn = req->op.add.message->dn;

	/*
	 * first we need the replPropertyMetaData attribute from the
	 * old record
	 */
	ret = dsdb_module_search_dn(ar->module, req, &res, conflict_dn,
				    attrs,
				    DSDB_FLAG_NEXT_MODULE |
				    DSDB_SEARCH_SHOW_DELETED |
				    DSDB_SEARCH_SHOW_RECYCLED, req);
	if (ret != LDB_SUCCESS) {
		DEBUG(0,(__location__ ": Unable to find object for conflicting record '%s'\n",
			 ldb_dn_get_linearized(conflict_dn)));
		goto failed;
	}

	omd_value = ldb_msg_find_ldb_val(res->msgs[0], "replPropertyMetaData");
	if (omd_value == NULL) {
		DEBUG(0,(__location__ ": Unable to find replPropertyMetaData for conflicting record '%s'\n",
			 ldb_dn_get_linearized(conflict_dn)));
		goto failed;
	}

	ndr_err = ndr_pull_struct_blob(omd_value, res->msgs[0], &omd,
				       (ndr_pull_flags_fn_t)ndr_pull_replPropertyMetaDataBlob);
	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
		DEBUG(0,(__location__ ": Failed to parse old replPropertyMetaData for %s\n",
			 ldb_dn_get_linearized(conflict_dn)));
		goto failed;
	}

	/*
	 * and the replPropertyMetaData attribute from the
	 * new record
	 */
	rmd_value = ldb_msg_find_ldb_val(req->op.add.message, "replPropertyMetaData");
	if (rmd_value == NULL) {
		DEBUG(0,(__location__ ": Unable to find replPropertyMetaData for new record '%s'\n",
			 ldb_dn_get_linearized(conflict_dn)));
		goto failed;
	}

	ndr_err = ndr_pull_struct_blob(rmd_value, req, &rmd,
				       (ndr_pull_flags_fn_t)ndr_pull_replPropertyMetaDataBlob);
	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
		DEBUG(0,(__location__ ": Failed to parse new replPropertyMetaData for %s\n",
			 ldb_dn_get_linearized(conflict_dn)));
		goto failed;
	}

	/* we decide which is newer based on the RPMD on the name
	   attribute.  See [MS-DRSR] ResolveNameConflict */
	rmd_name = replmd_replPropertyMetaData1_find_attid(&rmd, DRSUAPI_ATTID_name);
	omd_name = replmd_replPropertyMetaData1_find_attid(&omd, DRSUAPI_ATTID_name);
	if (!rmd_name || !omd_name) {
		DEBUG(0,(__location__ ": Failed to find name attribute in replPropertyMetaData for %s\n",
			 ldb_dn_get_linearized(conflict_dn)));
		goto failed;
	}

	rename_incoming_record = !replmd_replPropertyMetaData1_is_newer(omd_name, rmd_name);

	if (rename_incoming_record) {
		struct GUID guid;
		struct ldb_dn *new_dn;
		struct ldb_message *new_msg;

		guid = samdb_result_guid(req->op.add.message, "objectGUID");
		if (GUID_all_zero(&guid)) {
			DEBUG(0,(__location__ ": Failed to find objectGUID for conflicting incoming record %s\n",
				 ldb_dn_get_linearized(conflict_dn)));
			goto failed;
		}
		new_dn = replmd_conflict_dn(req, conflict_dn, &guid);
		if (new_dn == NULL) {
			DEBUG(0,(__location__ ": Failed to form conflict DN for %s\n",
				 ldb_dn_get_linearized(conflict_dn)));
			goto failed;
		}

		DEBUG(1,(__location__ ": Resolving conflict record via incoming rename '%s' -> '%s'\n",
			 ldb_dn_get_linearized(conflict_dn), ldb_dn_get_linearized(new_dn)));

		/* re-submit the request, but with a different
		   callback, so we don't loop forever. */
		new_msg = ldb_msg_copy_shallow(req, req->op.add.message);
		if (!new_msg) {
			goto failed;
			DEBUG(0,(__location__ ": Failed to copy conflict DN message for %s\n",
				 ldb_dn_get_linearized(conflict_dn)));
		}
		new_msg->dn = new_dn;
		req->op.add.message = new_msg;
		req->callback = replmd_op_name_modify_callback;

		return ldb_next_request(ar->module, req);
	} else {
		/* we are renaming the existing record */
		struct GUID guid;
		struct ldb_dn *new_dn;

		guid = samdb_result_guid(res->msgs[0], "objectGUID");
		if (GUID_all_zero(&guid)) {
			DEBUG(0,(__location__ ": Failed to find objectGUID for existing conflict record %s\n",
				 ldb_dn_get_linearized(conflict_dn)));
			goto failed;
		}

		new_dn = replmd_conflict_dn(req, conflict_dn, &guid);
		if (new_dn == NULL) {
			DEBUG(0,(__location__ ": Failed to form conflict DN for %s\n",
				 ldb_dn_get_linearized(conflict_dn)));
			goto failed;
		}

		DEBUG(1,(__location__ ": Resolving conflict record via existing rename '%s' -> '%s'\n",
			 ldb_dn_get_linearized(conflict_dn), ldb_dn_get_linearized(new_dn)));

		ret = dsdb_module_rename(ar->module, conflict_dn, new_dn,
					 DSDB_FLAG_OWN_MODULE, req);
		if (ret != LDB_SUCCESS) {
			DEBUG(0,(__location__ ": Failed to rename conflict dn '%s' to '%s' - %s\n",
				 ldb_dn_get_linearized(conflict_dn),
				 ldb_dn_get_linearized(new_dn),
				 ldb_errstring(ldb_module_get_ctx(ar->module))));
			goto failed;
		}

		/*
		 * now we need to ensure that the rename is seen as an
		 * originating update. We do that with a modify.
		 */
		ret = replmd_name_modify(ar, req, new_dn);
		if (ret != LDB_SUCCESS) {
			goto failed;
		}

		req->callback = replmd_op_callback;

		return ldb_next_request(ar->module, req);
	}

failed:
	/* on failure do the original callback. This means replication
	 * will stop with an error, but there is not much else we can
	 * do
	 */
	return replmd_op_callback(req, ares);
}

/*
  this is called when a new object comes in over DRS
 */
static int replmd_replicated_apply_add(struct replmd_replicated_request *ar)
{
	struct ldb_context *ldb;
	struct ldb_request *change_req;
	enum ndr_err_code ndr_err;
	struct ldb_message *msg;
	struct replPropertyMetaDataBlob *md;
	struct ldb_val md_value;
	unsigned int i;
	int ret;

	/*
	 * TODO: check if the parent object exist
	 */

	/*
	 * TODO: handle the conflict case where an object with the
	 *       same name exist
	 */

	ldb = ldb_module_get_ctx(ar->module);
	msg = ar->objs->objects[ar->index_current].msg;
	md = ar->objs->objects[ar->index_current].meta_data;

	ret = ldb_sequence_number(ldb, LDB_SEQ_NEXT, &ar->seq_num);
	if (ret != LDB_SUCCESS) {
		return replmd_replicated_request_error(ar, ret);
	}

	ret = ldb_msg_add_value(msg, "objectGUID", &ar->objs->objects[ar->index_current].guid_value, NULL);
	if (ret != LDB_SUCCESS) {
		return replmd_replicated_request_error(ar, ret);
	}

	ret = ldb_msg_add_string(msg, "whenChanged", ar->objs->objects[ar->index_current].when_changed);
	if (ret != LDB_SUCCESS) {
		return replmd_replicated_request_error(ar, ret);
	}

	ret = samdb_msg_add_uint64(ldb, msg, msg, "uSNCreated", ar->seq_num);
	if (ret != LDB_SUCCESS) {
		return replmd_replicated_request_error(ar, ret);
	}

	ret = samdb_msg_add_uint64(ldb, msg, msg, "uSNChanged", ar->seq_num);
	if (ret != LDB_SUCCESS) {
		return replmd_replicated_request_error(ar, ret);
	}

	/* remove any message elements that have zero values */
	for (i=0; i<msg->num_elements; i++) {
		struct ldb_message_element *el = &msg->elements[i];

		if (el->num_values == 0) {
			DEBUG(4,(__location__ ": Removing attribute %s with num_values==0\n",
				 el->name));
			memmove(el, el+1, sizeof(*el)*(msg->num_elements - (i+1)));
			msg->num_elements--;
			i--;
			continue;
		}
	}

	/*
	 * the meta data array is already sorted by the caller
	 */
	for (i=0; i < md->ctr.ctr1.count; i++) {
		md->ctr.ctr1.array[i].local_usn = ar->seq_num;
	}
	ndr_err = ndr_push_struct_blob(&md_value, msg, md,
				       (ndr_push_flags_fn_t)ndr_push_replPropertyMetaDataBlob);
	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
		NTSTATUS nt_status = ndr_map_error2ntstatus(ndr_err);
		return replmd_replicated_request_werror(ar, ntstatus_to_werror(nt_status));
	}
	ret = ldb_msg_add_value(msg, "replPropertyMetaData", &md_value, NULL);
	if (ret != LDB_SUCCESS) {
		return replmd_replicated_request_error(ar, ret);
	}

	replmd_ldb_message_sort(msg, ar->schema);

	if (DEBUGLVL(4)) {
		char *s = ldb_ldif_message_string(ldb, ar, LDB_CHANGETYPE_ADD, msg);
		DEBUG(4, ("DRS replication add message:\n%s\n", s));
		talloc_free(s);
	}

	ret = ldb_build_add_req(&change_req,
				ldb,
				ar,
				msg,
				ar->controls,
				ar,
				replmd_op_add_callback,
				ar->req);
	LDB_REQ_SET_LOCATION(change_req);
	if (ret != LDB_SUCCESS) return replmd_replicated_request_error(ar, ret);

	/* current partition control needed by "repmd_op_callback" */
	ret = ldb_request_add_control(change_req,
				      DSDB_CONTROL_CURRENT_PARTITION_OID,
				      false, NULL);
	if (ret != LDB_SUCCESS) return replmd_replicated_request_error(ar, ret);

	return ldb_next_request(ar->module, change_req);
}

/*
  handle renames that come in over DRS replication
 */
static int replmd_replicated_handle_rename(struct replmd_replicated_request *ar,
					   struct ldb_message *msg,
					   struct replPropertyMetaDataBlob *rmd,
					   struct replPropertyMetaDataBlob *omd,
					   struct ldb_request *parent)
{
	struct replPropertyMetaData1 *md_remote;
	struct replPropertyMetaData1 *md_local;

	if (ldb_dn_compare(msg->dn, ar->search_msg->dn) == 0) {
		/* no rename */
		return LDB_SUCCESS;
	}

	/* now we need to check for double renames. We could have a
	 * local rename pending which our replication partner hasn't
	 * received yet. We choose which one wins by looking at the
	 * attribute stamps on the two objects, the newer one wins
	 */
	md_remote = replmd_replPropertyMetaData1_find_attid(rmd, DRSUAPI_ATTID_name);
	md_local  = replmd_replPropertyMetaData1_find_attid(omd, DRSUAPI_ATTID_name);
	/* if there is no name attribute then we have to assume the
	   object we've received is in fact newer */
	if (!md_remote || !md_local ||
	    replmd_replPropertyMetaData1_is_newer(md_local, md_remote)) {
		DEBUG(4,("replmd_replicated_request rename %s => %s\n",
			 ldb_dn_get_linearized(ar->search_msg->dn),
			 ldb_dn_get_linearized(msg->dn)));
		/* pass rename to the next module
		 * so it doesn't appear as an originating update */
		return dsdb_module_rename(ar->module,
					  ar->search_msg->dn, msg->dn,
					  DSDB_FLAG_NEXT_MODULE | DSDB_MODIFY_RELAX, parent);
	}

	/* we're going to keep our old object */
	DEBUG(4,(__location__ ": Keeping object %s and rejecting older rename to %s\n",
		 ldb_dn_get_linearized(ar->search_msg->dn),
		 ldb_dn_get_linearized(msg->dn)));
	return LDB_SUCCESS;
}


static int replmd_replicated_apply_merge(struct replmd_replicated_request *ar)
{
	struct ldb_context *ldb;
	struct ldb_request *change_req;
	enum ndr_err_code ndr_err;
	struct ldb_message *msg;
	struct replPropertyMetaDataBlob *rmd;
	struct replPropertyMetaDataBlob omd;
	const struct ldb_val *omd_value;
	struct replPropertyMetaDataBlob nmd;
	struct ldb_val nmd_value;
	unsigned int i;
	uint32_t j,ni=0;
	unsigned int removed_attrs = 0;
	int ret;

	ldb = ldb_module_get_ctx(ar->module);
	msg = ar->objs->objects[ar->index_current].msg;
	rmd = ar->objs->objects[ar->index_current].meta_data;
	ZERO_STRUCT(omd);
	omd.version = 1;

	/* find existing meta data */
	omd_value = ldb_msg_find_ldb_val(ar->search_msg, "replPropertyMetaData");
	if (omd_value) {
		ndr_err = ndr_pull_struct_blob(omd_value, ar, &omd,
					       (ndr_pull_flags_fn_t)ndr_pull_replPropertyMetaDataBlob);
		if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
			NTSTATUS nt_status = ndr_map_error2ntstatus(ndr_err);
			return replmd_replicated_request_werror(ar, ntstatus_to_werror(nt_status));
		}

		if (omd.version != 1) {
			return replmd_replicated_request_werror(ar, WERR_DS_DRA_INTERNAL_ERROR);
		}
	}

	/* handle renames that come in over DRS */
	ret = replmd_replicated_handle_rename(ar, msg, rmd, &omd, ar->req);
	if (ret != LDB_SUCCESS) {
		ldb_debug(ldb, LDB_DEBUG_FATAL,
			  "replmd_replicated_request rename %s => %s failed - %s\n",
			  ldb_dn_get_linearized(ar->search_msg->dn),
			  ldb_dn_get_linearized(msg->dn),
			  ldb_errstring(ldb));
		return replmd_replicated_request_werror(ar, WERR_DS_DRA_DB_ERROR);
	}

	ZERO_STRUCT(nmd);
	nmd.version = 1;
	nmd.ctr.ctr1.count = omd.ctr.ctr1.count + rmd->ctr.ctr1.count;
	nmd.ctr.ctr1.array = talloc_array(ar,
					  struct replPropertyMetaData1,
					  nmd.ctr.ctr1.count);
	if (!nmd.ctr.ctr1.array) return replmd_replicated_request_werror(ar, WERR_NOMEM);

	/* first copy the old meta data */
	for (i=0; i < omd.ctr.ctr1.count; i++) {
		nmd.ctr.ctr1.array[ni]	= omd.ctr.ctr1.array[i];
		ni++;
	}

	ar->seq_num = 0;
	/* now merge in the new meta data */
	for (i=0; i < rmd->ctr.ctr1.count; i++) {
		bool found = false;

		for (j=0; j < ni; j++) {
			bool cmp;

			if (rmd->ctr.ctr1.array[i].attid != nmd.ctr.ctr1.array[j].attid) {
				continue;
			}

			cmp = replmd_replPropertyMetaData1_is_newer(&nmd.ctr.ctr1.array[j],
								    &rmd->ctr.ctr1.array[i]);
			if (cmp) {
				/* replace the entry */
				nmd.ctr.ctr1.array[j] = rmd->ctr.ctr1.array[i];
				if (ar->seq_num == 0) {
					ret = ldb_sequence_number(ldb, LDB_SEQ_NEXT, &ar->seq_num);
					if (ret != LDB_SUCCESS) {
						return replmd_replicated_request_error(ar, ret);
					}
				}
				nmd.ctr.ctr1.array[j].local_usn = ar->seq_num;
				found = true;
				break;
			}

			if (rmd->ctr.ctr1.array[i].attid != DRSUAPI_ATTID_instanceType) {
				DEBUG(3,("Discarding older DRS attribute update to %s on %s from %s\n",
					 msg->elements[i-removed_attrs].name,
					 ldb_dn_get_linearized(msg->dn),
					 GUID_string(ar, &rmd->ctr.ctr1.array[i].originating_invocation_id)));
			}

			/* we don't want to apply this change so remove the attribute */
			ldb_msg_remove_element(msg, &msg->elements[i-removed_attrs]);
			removed_attrs++;

			found = true;
			break;
		}

		if (found) continue;

		nmd.ctr.ctr1.array[ni] = rmd->ctr.ctr1.array[i];
		if (ar->seq_num == 0) {
			ret = ldb_sequence_number(ldb, LDB_SEQ_NEXT, &ar->seq_num);
			if (ret != LDB_SUCCESS) {
				return replmd_replicated_request_error(ar, ret);
			}
		}
		nmd.ctr.ctr1.array[ni].local_usn = ar->seq_num;
		ni++;
	}

	/*
	 * finally correct the size of the meta_data array
	 */
	nmd.ctr.ctr1.count = ni;

	/*
	 * the rdn attribute (the alias for the name attribute),
	 * 'cn' for most objects is the last entry in the meta data array
	 * we have stored
	 *
	 * sort the new meta data array
	 */
	ret = replmd_replPropertyMetaDataCtr1_sort(&nmd.ctr.ctr1, ar->schema, msg->dn);
	if (ret != LDB_SUCCESS) {
		return ret;
	}

	/*
	 * check if some replicated attributes left, otherwise skip the ldb_modify() call
	 */
	if (msg->num_elements == 0) {
		ldb_debug(ldb, LDB_DEBUG_TRACE, "replmd_replicated_apply_merge[%u]: skip replace\n",
			  ar->index_current);

		ar->index_current++;
		return replmd_replicated_apply_next(ar);
	}

	ldb_debug(ldb, LDB_DEBUG_TRACE, "replmd_replicated_apply_merge[%u]: replace %u attributes\n",
		  ar->index_current, msg->num_elements);

	/* create the meta data value */
	ndr_err = ndr_push_struct_blob(&nmd_value, msg, &nmd,
				       (ndr_push_flags_fn_t)ndr_push_replPropertyMetaDataBlob);
	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
		NTSTATUS nt_status = ndr_map_error2ntstatus(ndr_err);
		return replmd_replicated_request_werror(ar, ntstatus_to_werror(nt_status));
	}

	/*
	 * when we know that we'll modify the record, add the whenChanged, uSNChanged
	 * and replPopertyMetaData attributes
	 */
	ret = ldb_msg_add_string(msg, "whenChanged", ar->objs->objects[ar->index_current].when_changed);
	if (ret != LDB_SUCCESS) {
		return replmd_replicated_request_error(ar, ret);
	}
	ret = samdb_msg_add_uint64(ldb, msg, msg, "uSNChanged", ar->seq_num);
	if (ret != LDB_SUCCESS) {
		return replmd_replicated_request_error(ar, ret);
	}
	ret = ldb_msg_add_value(msg, "replPropertyMetaData", &nmd_value, NULL);
	if (ret != LDB_SUCCESS) {
		return replmd_replicated_request_error(ar, ret);
	}

	replmd_ldb_message_sort(msg, ar->schema);

	/* we want to replace the old values */
	for (i=0; i < msg->num_elements; i++) {
		msg->elements[i].flags = LDB_FLAG_MOD_REPLACE;
	}

	if (DEBUGLVL(4)) {
		char *s = ldb_ldif_message_string(ldb, ar, LDB_CHANGETYPE_MODIFY, msg);
		DEBUG(4, ("DRS replication modify message:\n%s\n", s));
		talloc_free(s);
	}

	ret = ldb_build_mod_req(&change_req,
				ldb,
				ar,
				msg,
				ar->controls,
				ar,
				replmd_op_callback,
				ar->req);
	LDB_REQ_SET_LOCATION(change_req);
	if (ret != LDB_SUCCESS) return replmd_replicated_request_error(ar, ret);

	/* current partition control needed by "repmd_op_callback" */
	ret = ldb_request_add_control(change_req,
				      DSDB_CONTROL_CURRENT_PARTITION_OID,
				      false, NULL);
	if (ret != LDB_SUCCESS) return replmd_replicated_request_error(ar, ret);

	return ldb_next_request(ar->module, change_req);
}

static int replmd_replicated_apply_search_callback(struct ldb_request *req,
						   struct ldb_reply *ares)
{
	struct replmd_replicated_request *ar = talloc_get_type(req->context,
					       struct replmd_replicated_request);
	int ret;

	if (!ares) {
		return ldb_module_done(ar->req, NULL, NULL,
					LDB_ERR_OPERATIONS_ERROR);
	}
	if (ares->error != LDB_SUCCESS &&
	    ares->error != LDB_ERR_NO_SUCH_OBJECT) {
		return ldb_module_done(ar->req, ares->controls,
					ares->response, ares->error);
	}

	switch (ares->type) {
	case LDB_REPLY_ENTRY:
		ar->search_msg = talloc_steal(ar, ares->message);
		break;

	case LDB_REPLY_REFERRAL:
		/* we ignore referrals */
		break;

	case LDB_REPLY_DONE:
		if (ar->search_msg != NULL) {
			ret = replmd_replicated_apply_merge(ar);
		} else {
			ret = replmd_replicated_apply_add(ar);
		}
		if (ret != LDB_SUCCESS) {
			return ldb_module_done(ar->req, NULL, NULL, ret);
		}
	}

	talloc_free(ares);
	return LDB_SUCCESS;
}

static int replmd_replicated_uptodate_vector(struct replmd_replicated_request *ar);

static int replmd_replicated_apply_next(struct replmd_replicated_request *ar)
{
	struct ldb_context *ldb;
	int ret;
	char *tmp_str;
	char *filter;
	struct ldb_request *search_req;
	struct ldb_search_options_control *options;

	if (ar->index_current >= ar->objs->num_objects) {
		/* done with it, go to next stage */
		return replmd_replicated_uptodate_vector(ar);
	}

	ldb = ldb_module_get_ctx(ar->module);
	ar->search_msg = NULL;

	tmp_str = ldb_binary_encode(ar, ar->objs->objects[ar->index_current].guid_value);
	if (!tmp_str) return replmd_replicated_request_werror(ar, WERR_NOMEM);

	filter = talloc_asprintf(ar, "(objectGUID=%s)", tmp_str);
	if (!filter) return replmd_replicated_request_werror(ar, WERR_NOMEM);
	talloc_free(tmp_str);

	ret = ldb_build_search_req(&search_req,
				   ldb,
				   ar,
				   NULL,
				   LDB_SCOPE_SUBTREE,
				   filter,
				   NULL,
				   NULL,
				   ar,
				   replmd_replicated_apply_search_callback,
				   ar->req);
	LDB_REQ_SET_LOCATION(search_req);

	ret = ldb_request_add_control(search_req, LDB_CONTROL_SHOW_RECYCLED_OID,
				      true, NULL);
	if (ret != LDB_SUCCESS) {
		return ret;
	}

	/* we need to cope with cross-partition links, so search for
	   the GUID over all partitions */
	options = talloc(search_req, struct ldb_search_options_control);
	if (options == NULL) {
		DEBUG(0, (__location__ ": out of memory\n"));
		return LDB_ERR_OPERATIONS_ERROR;
	}
	options->search_options = LDB_SEARCH_OPTION_PHANTOM_ROOT;

	ret = ldb_request_add_control(search_req,
				      LDB_CONTROL_SEARCH_OPTIONS_OID,
				      true, options);
	if (ret != LDB_SUCCESS) {
		return ret;
	}

	return ldb_next_request(ar->module, search_req);
}

static int replmd_replicated_uptodate_modify_callback(struct ldb_request *req,
						      struct ldb_reply *ares)
{
	struct ldb_context *ldb;
	struct replmd_replicated_request *ar = talloc_get_type(req->context,
					       struct replmd_replicated_request);
	ldb = ldb_module_get_ctx(ar->module);

	if (!ares) {
		return ldb_module_done(ar->req, NULL, NULL,
					LDB_ERR_OPERATIONS_ERROR);
	}
	if (ares->error != LDB_SUCCESS) {
		return ldb_module_done(ar->req, ares->controls,
					ares->response, ares->error);
	}

	if (ares->type != LDB_REPLY_DONE) {
		ldb_set_errstring(ldb, "Invalid reply type\n!");
		return ldb_module_done(ar->req, NULL, NULL,
					LDB_ERR_OPERATIONS_ERROR);
	}

	talloc_free(ares);

	return ldb_module_done(ar->req, NULL, NULL, LDB_SUCCESS);
}

static int replmd_replicated_uptodate_modify(struct replmd_replicated_request *ar)
{
	struct ldb_context *ldb;
	struct ldb_request *change_req;
	enum ndr_err_code ndr_err;
	struct ldb_message *msg;
	struct replUpToDateVectorBlob ouv;
	const struct ldb_val *ouv_value;
	const struct drsuapi_DsReplicaCursor2CtrEx *ruv;
	struct replUpToDateVectorBlob nuv;
	struct ldb_val nuv_value;
	struct ldb_message_element *nuv_el = NULL;
	const struct GUID *our_invocation_id;
	struct ldb_message_element *orf_el = NULL;
	struct repsFromToBlob nrf;
	struct ldb_val *nrf_value = NULL;
	struct ldb_message_element *nrf_el = NULL;
	unsigned int i;
	uint32_t j,ni=0;
	bool found = false;
	time_t t = time(NULL);
	NTTIME now;
	int ret;
	uint32_t instanceType;

	ldb = ldb_module_get_ctx(ar->module);
	ruv = ar->objs->uptodateness_vector;
	ZERO_STRUCT(ouv);
	ouv.version = 2;
	ZERO_STRUCT(nuv);
	nuv.version = 2;

	unix_to_nt_time(&now, t);

	instanceType = ldb_msg_find_attr_as_uint(ar->search_msg, "instanceType", 0);
	if (! (instanceType & INSTANCE_TYPE_IS_NC_HEAD)) {
		DEBUG(4,(__location__ ": Skipping UDV and repsFrom update as not NC root: %s\n",
			 ldb_dn_get_linearized(ar->search_msg->dn)));
		return ldb_module_done(ar->req, NULL, NULL, LDB_SUCCESS);
	}

	/*
	 * first create the new replUpToDateVector
	 */
	ouv_value = ldb_msg_find_ldb_val(ar->search_msg, "replUpToDateVector");
	if (ouv_value) {
		ndr_err = ndr_pull_struct_blob(ouv_value, ar, &ouv,
					       (ndr_pull_flags_fn_t)ndr_pull_replUpToDateVectorBlob);
		if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
			NTSTATUS nt_status = ndr_map_error2ntstatus(ndr_err);
			return replmd_replicated_request_werror(ar, ntstatus_to_werror(nt_status));
		}

		if (ouv.version != 2) {
			return replmd_replicated_request_werror(ar, WERR_DS_DRA_INTERNAL_ERROR);
		}
	}

	/*
	 * the new uptodateness vector will at least
	 * contain 1 entry, one for the source_dsa
	 *
	 * plus optional values from our old vector and the one from the source_dsa
	 */
	nuv.ctr.ctr2.count = 1 + ouv.ctr.ctr2.count;
	if (ruv) nuv.ctr.ctr2.count += ruv->count;
	nuv.ctr.ctr2.cursors = talloc_array(ar,
					    struct drsuapi_DsReplicaCursor2,
					    nuv.ctr.ctr2.count);
	if (!nuv.ctr.ctr2.cursors) return replmd_replicated_request_werror(ar, WERR_NOMEM);

	/* first copy the old vector */
	for (i=0; i < ouv.ctr.ctr2.count; i++) {
		nuv.ctr.ctr2.cursors[ni] = ouv.ctr.ctr2.cursors[i];
		ni++;
	}

	/* get our invocation_id if we have one already attached to the ldb */
	our_invocation_id = samdb_ntds_invocation_id(ldb);

	/* merge in the source_dsa vector is available */
	for (i=0; (ruv && i < ruv->count); i++) {
		found = false;

		if (our_invocation_id &&
		    GUID_equal(&ruv->cursors[i].source_dsa_invocation_id,
			       our_invocation_id)) {
			continue;
		}

		for (j=0; j < ni; j++) {
			if (!GUID_equal(&ruv->cursors[i].source_dsa_invocation_id,
					&nuv.ctr.ctr2.cursors[j].source_dsa_invocation_id)) {
				continue;
			}

			found = true;

			/*
			 * we update only the highest_usn and not the latest_sync_success time,
			 * because the last success stands for direct replication
			 */
			if (ruv->cursors[i].highest_usn > nuv.ctr.ctr2.cursors[j].highest_usn) {
				nuv.ctr.ctr2.cursors[j].highest_usn = ruv->cursors[i].highest_usn;
			}
			break;
		}

		if (found) continue;

		/* if it's not there yet, add it */
		nuv.ctr.ctr2.cursors[ni] = ruv->cursors[i];
		ni++;
	}

	/*
	 * merge in the current highwatermark for the source_dsa
	 */
	found = false;
	for (j=0; j < ni; j++) {
		if (!GUID_equal(&ar->objs->source_dsa->source_dsa_invocation_id,
				&nuv.ctr.ctr2.cursors[j].source_dsa_invocation_id)) {
			continue;
		}

		found = true;

		/*
		 * here we update the highest_usn and last_sync_success time
		 * because we're directly replicating from the source_dsa
		 *
		 * and use the tmp_highest_usn because this is what we have just applied
		 * to our ldb
		 */
		nuv.ctr.ctr2.cursors[j].highest_usn		= ar->objs->source_dsa->highwatermark.tmp_highest_usn;
		nuv.ctr.ctr2.cursors[j].last_sync_success	= now;
		break;
	}
	if (!found) {
		/*
		 * here we update the highest_usn and last_sync_success time
		 * because we're directly replicating from the source_dsa
		 *
		 * and use the tmp_highest_usn because this is what we have just applied
		 * to our ldb
		 */
		nuv.ctr.ctr2.cursors[ni].source_dsa_invocation_id= ar->objs->source_dsa->source_dsa_invocation_id;
		nuv.ctr.ctr2.cursors[ni].highest_usn		= ar->objs->source_dsa->highwatermark.tmp_highest_usn;
		nuv.ctr.ctr2.cursors[ni].last_sync_success	= now;
		ni++;
	}

	/*
	 * finally correct the size of the cursors array
	 */
	nuv.ctr.ctr2.count = ni;

	/*
	 * sort the cursors
	 */
	TYPESAFE_QSORT(nuv.ctr.ctr2.cursors, nuv.ctr.ctr2.count, drsuapi_DsReplicaCursor2_compare);

	/*
	 * create the change ldb_message
	 */
	msg = ldb_msg_new(ar);
	if (!msg) return replmd_replicated_request_werror(ar, WERR_NOMEM);
	msg->dn = ar->search_msg->dn;

	ndr_err = ndr_push_struct_blob(&nuv_value, msg, &nuv,
				       (ndr_push_flags_fn_t)ndr_push_replUpToDateVectorBlob);
	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
		NTSTATUS nt_status = ndr_map_error2ntstatus(ndr_err);
		return replmd_replicated_request_werror(ar, ntstatus_to_werror(nt_status));
	}
	ret = ldb_msg_add_value(msg, "replUpToDateVector", &nuv_value, &nuv_el);
	if (ret != LDB_SUCCESS) {
		return replmd_replicated_request_error(ar, ret);
	}
	nuv_el->flags = LDB_FLAG_MOD_REPLACE;

	/*
	 * now create the new repsFrom value from the given repsFromTo1 structure
	 */
	ZERO_STRUCT(nrf);
	nrf.version					= 1;
	nrf.ctr.ctr1					= *ar->objs->source_dsa;
	nrf.ctr.ctr1.highwatermark.highest_usn		= nrf.ctr.ctr1.highwatermark.tmp_highest_usn;

	/*
	 * first see if we already have a repsFrom value for the current source dsa
	 * if so we'll later replace this value
	 */
	orf_el = ldb_msg_find_element(ar->search_msg, "repsFrom");
	if (orf_el) {
		for (i=0; i < orf_el->num_values; i++) {
			struct repsFromToBlob *trf;

			trf = talloc(ar, struct repsFromToBlob);
			if (!trf) return replmd_replicated_request_werror(ar, WERR_NOMEM);

			ndr_err = ndr_pull_struct_blob(&orf_el->values[i], trf, trf,
						       (ndr_pull_flags_fn_t)ndr_pull_repsFromToBlob);
			if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
				NTSTATUS nt_status = ndr_map_error2ntstatus(ndr_err);
				return replmd_replicated_request_werror(ar, ntstatus_to_werror(nt_status));
			}

			if (trf->version != 1) {
				return replmd_replicated_request_werror(ar, WERR_DS_DRA_INTERNAL_ERROR);
			}

			/*
			 * we compare the source dsa objectGUID not the invocation_id
			 * because we want only one repsFrom value per source dsa
			 * and when the invocation_id of the source dsa has changed we don't need
			 * the old repsFrom with the old invocation_id
			 */
			if (!GUID_equal(&trf->ctr.ctr1.source_dsa_obj_guid,
					&ar->objs->source_dsa->source_dsa_obj_guid)) {
				talloc_free(trf);
				continue;
			}

			talloc_free(trf);
			nrf_value = &orf_el->values[i];
			break;
		}

		/*
		 * copy over all old values to the new ldb_message
		 */
		ret = ldb_msg_add_empty(msg, "repsFrom", 0, &nrf_el);
		if (ret != LDB_SUCCESS) return replmd_replicated_request_error(ar, ret);
		*nrf_el = *orf_el;
	}

	/*
	 * if we haven't found an old repsFrom value for the current source dsa
	 * we'll add a new value
	 */
	if (!nrf_value) {
		struct ldb_val zero_value;
		ZERO_STRUCT(zero_value);
		ret = ldb_msg_add_value(msg, "repsFrom", &zero_value, &nrf_el);
		if (ret != LDB_SUCCESS) return replmd_replicated_request_error(ar, ret);

		nrf_value = &nrf_el->values[nrf_el->num_values - 1];
	}

	/* we now fill the value which is already attached to ldb_message */
	ndr_err = ndr_push_struct_blob(nrf_value, msg,
				       &nrf,
				       (ndr_push_flags_fn_t)ndr_push_repsFromToBlob);
	if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
		NTSTATUS nt_status = ndr_map_error2ntstatus(ndr_err);
		return replmd_replicated_request_werror(ar, ntstatus_to_werror(nt_status));
	}

	/*
	 * the ldb_message_element for the attribute, has all the old values and the new one
	 * so we'll replace the whole attribute with all values
	 */
	nrf_el->flags = LDB_FLAG_MOD_REPLACE;

	if (DEBUGLVL(4)) {
		char *s = ldb_ldif_message_string(ldb, ar, LDB_CHANGETYPE_MODIFY, msg);
		DEBUG(4, ("DRS replication uptodate modify message:\n%s\n", s));
		talloc_free(s);
	}

	/* prepare the ldb_modify() request */
	ret = ldb_build_mod_req(&change_req,
				ldb,
				ar,
				msg,
				ar->controls,
				ar,
				replmd_replicated_uptodate_modify_callback,
				ar->req);
	LDB_REQ_SET_LOCATION(change_req);
	if (ret != LDB_SUCCESS) return replmd_replicated_request_error(ar, ret);

	return ldb_next_request(ar->module, change_req);
}

static int replmd_replicated_uptodate_search_callback(struct ldb_request *req,
						      struct ldb_reply *ares)
{
	struct replmd_replicated_request *ar = talloc_get_type(req->context,
					       struct replmd_replicated_request);
	int ret;

	if (!ares) {
		return ldb_module_done(ar->req, NULL, NULL,
					LDB_ERR_OPERATIONS_ERROR);
	}
	if (ares->error != LDB_SUCCESS &&
	    ares->error != LDB_ERR_NO_SUCH_OBJECT) {
		return ldb_module_done(ar->req, ares->controls,
					ares->response, ares->error);
	}

	switch (ares->type) {
	case LDB_REPLY_ENTRY:
		ar->search_msg = talloc_steal(ar, ares->message);
		break;

	case LDB_REPLY_REFERRAL:
		/* we ignore referrals */
		break;

	case LDB_REPLY_DONE:
		if (ar->search_msg == NULL) {
			ret = replmd_replicated_request_werror(ar, WERR_DS_DRA_INTERNAL_ERROR);
		} else {
			ret = replmd_replicated_uptodate_modify(ar);
		}
		if (ret != LDB_SUCCESS) {
			return ldb_module_done(ar->req, NULL, NULL, ret);
		}
	}

	talloc_free(ares);
	return LDB_SUCCESS;
}


static int replmd_replicated_uptodate_vector(struct replmd_replicated_request *ar)
{
	struct ldb_context *ldb;
	int ret;
	static const char *attrs[] = {
		"replUpToDateVector",
		"repsFrom",
		"instanceType",
		NULL
	};
	struct ldb_request *search_req;

	ldb = ldb_module_get_ctx(ar->module);
	ar->search_msg = NULL;

	ret = ldb_build_search_req(&search_req,
				   ldb,
				   ar,
				   ar->objs->partition_dn,
				   LDB_SCOPE_BASE,
				   "(objectClass=*)",
				   attrs,
				   NULL,
				   ar,
				   replmd_replicated_uptodate_search_callback,
				   ar->req);
	LDB_REQ_SET_LOCATION(search_req);
	if (ret != LDB_SUCCESS) return replmd_replicated_request_error(ar, ret);

	return ldb_next_request(ar->module, search_req);
}



static int replmd_extended_replicated_objects(struct ldb_module *module, struct ldb_request *req)
{
	struct ldb_context *ldb;
	struct dsdb_extended_replicated_objects *objs;
	struct replmd_replicated_request *ar;
	struct ldb_control **ctrls;
	int ret;
	uint32_t i;
	struct replmd_private *replmd_private =
		talloc_get_type(ldb_module_get_private(module), struct replmd_private);

	ldb = ldb_module_get_ctx(module);

	ldb_debug(ldb, LDB_DEBUG_TRACE, "replmd_extended_replicated_objects\n");

	objs = talloc_get_type(req->op.extended.data, struct dsdb_extended_replicated_objects);
	if (!objs) {
		ldb_debug(ldb, LDB_DEBUG_FATAL, "replmd_extended_replicated_objects: invalid extended data\n");
		return LDB_ERR_PROTOCOL_ERROR;
	}

	if (objs->version != DSDB_EXTENDED_REPLICATED_OBJECTS_VERSION) {
		ldb_debug(ldb, LDB_DEBUG_FATAL, "replmd_extended_replicated_objects: extended data invalid version [%u != %u]\n",
			  objs->version, DSDB_EXTENDED_REPLICATED_OBJECTS_VERSION);
		return LDB_ERR_PROTOCOL_ERROR;
	}

	ar = replmd_ctx_init(module, req);
	if (!ar)
		return LDB_ERR_OPERATIONS_ERROR;

	/* Set the flags to have the replmd_op_callback run over the full set of objects */
	ar->apply_mode = true;
	ar->objs = objs;
	ar->schema = dsdb_get_schema(ldb, ar);
	if (!ar->schema) {
		ldb_debug_set(ldb, LDB_DEBUG_FATAL, "replmd_ctx_init: no loaded schema found\n");
		talloc_free(ar);
		DEBUG(0,(__location__ ": %s\n", ldb_errstring(ldb)));
		return LDB_ERR_CONSTRAINT_VIOLATION;
	}

	ctrls = req->controls;

	if (req->controls) {
		req->controls = talloc_memdup(ar, req->controls,
					      talloc_get_size(req->controls));
		if (!req->controls) return replmd_replicated_request_werror(ar, WERR_NOMEM);
	}

	/* This allows layers further down to know if a change came in over replication */
	ret = ldb_request_add_control(req, DSDB_CONTROL_REPLICATED_UPDATE_OID, false, NULL);
	if (ret != LDB_SUCCESS) {
		return ret;
	}

	/* If this change contained linked attributes in the body
	 * (rather than in the links section) we need to update
	 * backlinks in linked_attributes */
	ret = ldb_request_add_control(req, DSDB_CONTROL_APPLY_LINKS, false, NULL);
	if (ret != LDB_SUCCESS) {
		return ret;
	}

	ar->controls = req->controls;
	req->controls = ctrls;

	DEBUG(4,("linked_attributes_count=%u\n", objs->linked_attributes_count));

	/* save away the linked attributes for the end of the
	   transaction */
	for (i=0; i<ar->objs->linked_attributes_count; i++) {
		struct la_entry *la_entry;

		if (replmd_private->la_ctx == NULL) {
			replmd_private->la_ctx = talloc_new(replmd_private);
		}
		la_entry = talloc(replmd_private->la_ctx, struct la_entry);
		if (la_entry == NULL) {
			ldb_oom(ldb);
			return LDB_ERR_OPERATIONS_ERROR;
		}
		la_entry->la = talloc(la_entry, struct drsuapi_DsReplicaLinkedAttribute);
		if (la_entry->la == NULL) {
			talloc_free(la_entry);
			ldb_oom(ldb);
			return LDB_ERR_OPERATIONS_ERROR;
		}
		*la_entry->la = ar->objs->linked_attributes[i];

		/* we need to steal the non-scalars so they stay
		   around until the end of the transaction */
		talloc_steal(la_entry->la, la_entry->la->identifier);
		talloc_steal(la_entry->la, la_entry->la->value.blob);

		DLIST_ADD(replmd_private->la_list, la_entry);
	}

	return replmd_replicated_apply_next(ar);
}

/*
  process one linked attribute structure
 */
static int replmd_process_linked_attribute(struct ldb_module *module,
					   struct la_entry *la_entry,
					   struct ldb_request *parent)
{
	struct drsuapi_DsReplicaLinkedAttribute *la = la_entry->la;
	struct ldb_context *ldb = ldb_module_get_ctx(module);
	struct ldb_message *msg;
	TALLOC_CTX *tmp_ctx = talloc_new(la_entry);
	const struct dsdb_schema *schema = dsdb_get_schema(ldb, tmp_ctx);
	int ret;
	const struct dsdb_attribute *attr;
	struct dsdb_dn *dsdb_dn;
	uint64_t seq_num = 0;
	struct ldb_message_element *old_el;
	WERROR status;
	time_t t = time(NULL);
	struct ldb_result *res;
	const char *attrs[2];
	struct parsed_dn *pdn_list, *pdn;
	struct GUID guid = GUID_zero();
	NTSTATUS ntstatus;
	bool active = (la->flags & DRSUAPI_DS_LINKED_ATTRIBUTE_FLAG_ACTIVE)?true:false;
	const struct GUID *our_invocation_id;

/*
linked_attributes[0]:
     &objs->linked_attributes[i]: struct drsuapi_DsReplicaLinkedAttribute
        identifier               : *
            identifier: struct drsuapi_DsReplicaObjectIdentifier
                __ndr_size               : 0x0000003a (58)
                __ndr_size_sid           : 0x00000000 (0)
                guid                     : 8e95b6a9-13dd-4158-89db-3220a5be5cc7
                sid                      : S-0-0
                __ndr_size_dn            : 0x00000000 (0)
                dn                       : ''
        attid                    : DRSUAPI_ATTID_member (0x1F)
        value: struct drsuapi_DsAttributeValue
            __ndr_size               : 0x0000007e (126)
            blob                     : *
                blob                     : DATA_BLOB length=126
        flags                    : 0x00000001 (1)
               1: DRSUAPI_DS_LINKED_ATTRIBUTE_FLAG_ACTIVE
        originating_add_time     : Wed Sep  2 22:20:01 2009 EST
        meta_data: struct drsuapi_DsReplicaMetaData
            version                  : 0x00000015 (21)
            originating_change_time  : Wed Sep  2 23:39:07 2009 EST
            originating_invocation_id: 794640f3-18cf-40ee-a211-a93992b67a64
            originating_usn          : 0x000000000001e19c (123292)

(for cases where the link is to a normal DN)
     &target: struct drsuapi_DsReplicaObjectIdentifier3
        __ndr_size               : 0x0000007e (126)
        __ndr_size_sid           : 0x0000001c (28)
        guid                     : 7639e594-db75-4086-b0d4-67890ae46031
        sid                      : S-1-5-21-2848215498-2472035911-1947525656-19924
        __ndr_size_dn            : 0x00000022 (34)
        dn                       : 'CN=UOne,OU=TestOU,DC=vsofs8,DC=com'
 */

	/* find the attribute being modified */
	attr = dsdb_attribute_by_attributeID_id(schema, la->attid);
	if (attr == NULL) {
		DEBUG(0, (__location__ ": Unable to find attributeID 0x%x\n", la->attid));
		talloc_free(tmp_ctx);
		return LDB_ERR_OPERATIONS_ERROR;
	}

	attrs[0] = attr->lDAPDisplayName;
	attrs[1] = NULL;

	/* get the existing message from the db for the object with
	   this GUID, returning attribute being modified. We will then
	   use this msg as the basis for a modify call */
	ret = dsdb_module_search(module, tmp_ctx, &res, NULL, LDB_SCOPE_SUBTREE, attrs,
	                         DSDB_FLAG_NEXT_MODULE |
				 DSDB_SEARCH_SEARCH_ALL_PARTITIONS |
				 DSDB_SEARCH_SHOW_RECYCLED |
				 DSDB_SEARCH_SHOW_DN_IN_STORAGE_FORMAT |
				 DSDB_SEARCH_REVEAL_INTERNALS,
				 parent,
				 "objectGUID=%s", GUID_string(tmp_ctx, &la->identifier->guid));
	if (ret != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ret;
	}
	if (res->count != 1) {
		ldb_asprintf_errstring(ldb, "DRS linked attribute for GUID %s - DN not found",
				       GUID_string(tmp_ctx, &la->identifier->guid));
		talloc_free(tmp_ctx);
		return LDB_ERR_NO_SUCH_OBJECT;
	}
	msg = res->msgs[0];

	if (msg->num_elements == 0) {
		ret = ldb_msg_add_empty(msg, attr->lDAPDisplayName, LDB_FLAG_MOD_REPLACE, &old_el);
		if (ret != LDB_SUCCESS) {
			ldb_module_oom(module);
			talloc_free(tmp_ctx);
			return LDB_ERR_OPERATIONS_ERROR;
		}
	} else {
		old_el = &msg->elements[0];
		old_el->flags = LDB_FLAG_MOD_REPLACE;
	}

	/* parse the existing links */
	ret = get_parsed_dns(module, tmp_ctx, old_el, &pdn_list, attr->syntax->ldap_oid, parent);
	if (ret != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ret;
	}

	/* get our invocationId */
	our_invocation_id = samdb_ntds_invocation_id(ldb);
	if (!our_invocation_id) {
		ldb_debug_set(ldb, LDB_DEBUG_ERROR, __location__ ": unable to find invocationId\n");
		talloc_free(tmp_ctx);
		return LDB_ERR_OPERATIONS_ERROR;
	}

	ret = replmd_check_upgrade_links(pdn_list, old_el->num_values, old_el, our_invocation_id);
	if (ret != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ret;
	}

	status = dsdb_dn_la_from_blob(ldb, attr, schema, tmp_ctx, la->value.blob, &dsdb_dn);
	if (!W_ERROR_IS_OK(status)) {
		ldb_asprintf_errstring(ldb, "Failed to parsed linked attribute blob for %s on %s - %s\n",
				       old_el->name, ldb_dn_get_linearized(msg->dn), win_errstr(status));
		return LDB_ERR_OPERATIONS_ERROR;
	}

	ntstatus = dsdb_get_extended_dn_guid(dsdb_dn->dn, &guid, "GUID");
	if (!NT_STATUS_IS_OK(ntstatus) && active) {
		ldb_asprintf_errstring(ldb, "Failed to find GUID in linked attribute blob for %s on %s from %s",
				       old_el->name,
				       ldb_dn_get_linearized(dsdb_dn->dn),
				       ldb_dn_get_linearized(msg->dn));
		return LDB_ERR_OPERATIONS_ERROR;
	}

	/* re-resolve the DN by GUID, as the DRS server may give us an
	   old DN value */
	ret = dsdb_module_dn_by_guid(module, dsdb_dn, &guid, &dsdb_dn->dn, parent);
	if (ret != LDB_SUCCESS) {
		DEBUG(2,(__location__ ": WARNING: Failed to re-resolve GUID %s - using %s",
			 GUID_string(tmp_ctx, &guid),
			 ldb_dn_get_linearized(dsdb_dn->dn)));
	}

	/* see if this link already exists */
	pdn = parsed_dn_find(pdn_list, old_el->num_values, &guid, dsdb_dn->dn);
	if (pdn != NULL) {
		/* see if this update is newer than what we have already */
		struct GUID invocation_id = GUID_zero();
		uint32_t version = 0;
		uint32_t originating_usn = 0;
		NTTIME change_time = 0;
		uint32_t rmd_flags = dsdb_dn_rmd_flags(pdn->dsdb_dn->dn);

		dsdb_get_extended_dn_guid(pdn->dsdb_dn->dn, &invocation_id, "RMD_INVOCID");
		dsdb_get_extended_dn_uint32(pdn->dsdb_dn->dn, &version, "RMD_VERSION");
		dsdb_get_extended_dn_uint32(pdn->dsdb_dn->dn, &originating_usn, "RMD_ORIGINATING_USN");
		dsdb_get_extended_dn_nttime(pdn->dsdb_dn->dn, &change_time, "RMD_CHANGETIME");

		if (!replmd_update_is_newer(&invocation_id,
					    &la->meta_data.originating_invocation_id,
					    version,
					    la->meta_data.version,
					    change_time,
					    la->meta_data.originating_change_time)) {
			DEBUG(3,("Discarding older DRS linked attribute update to %s on %s from %s\n",
				 old_el->name, ldb_dn_get_linearized(msg->dn),
				 GUID_string(tmp_ctx, &la->meta_data.originating_invocation_id)));
			talloc_free(tmp_ctx);
			return LDB_SUCCESS;
		}

		/* get a seq_num for this change */
		ret = ldb_sequence_number(ldb, LDB_SEQ_NEXT, &seq_num);
		if (ret != LDB_SUCCESS) {
			talloc_free(tmp_ctx);
			return ret;
		}

		if (!(rmd_flags & DSDB_RMD_FLAG_DELETED)) {
			/* remove the existing backlink */
			ret = replmd_add_backlink(module, schema, &la->identifier->guid, &guid, false, attr, false);
			if (ret != LDB_SUCCESS) {
				talloc_free(tmp_ctx);
				return ret;
			}
		}

		ret = replmd_update_la_val(tmp_ctx, pdn->v, dsdb_dn, pdn->dsdb_dn,
					   &la->meta_data.originating_invocation_id,
					   la->meta_data.originating_usn, seq_num,
					   la->meta_data.originating_change_time,
					   la->meta_data.version,
					   !active);
		if (ret != LDB_SUCCESS) {
			talloc_free(tmp_ctx);
			return ret;
		}

		if (active) {
			/* add the new backlink */
			ret = replmd_add_backlink(module, schema, &la->identifier->guid, &guid, true, attr, false);
			if (ret != LDB_SUCCESS) {
				talloc_free(tmp_ctx);
				return ret;
			}
		}
	} else {
		/* get a seq_num for this change */
		ret = ldb_sequence_number(ldb, LDB_SEQ_NEXT, &seq_num);
		if (ret != LDB_SUCCESS) {
			talloc_free(tmp_ctx);
			return ret;
		}

		old_el->values = talloc_realloc(msg->elements, old_el->values,
						struct ldb_val, old_el->num_values+1);
		if (!old_el->values) {
			ldb_module_oom(module);
			return LDB_ERR_OPERATIONS_ERROR;
		}
		old_el->num_values++;

		ret = replmd_build_la_val(tmp_ctx, &old_el->values[old_el->num_values-1], dsdb_dn,
					  &la->meta_data.originating_invocation_id,
					  la->meta_data.originating_usn, seq_num,
					  la->meta_data.originating_change_time,
					  la->meta_data.version,
					  (la->flags & DRSUAPI_DS_LINKED_ATTRIBUTE_FLAG_ACTIVE)?false:true);
		if (ret != LDB_SUCCESS) {
			talloc_free(tmp_ctx);
			return ret;
		}

		if (active) {
			ret = replmd_add_backlink(module, schema, &la->identifier->guid, &guid,
						  true, attr, false);
			if (ret != LDB_SUCCESS) {
				talloc_free(tmp_ctx);
				return ret;
			}
		}
	}

	/* we only change whenChanged and uSNChanged if the seq_num
	   has changed */
	if (add_time_element(msg, "whenChanged", t) != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ldb_operr(ldb);
	}

	if (add_uint64_element(ldb, msg, "uSNChanged",
			       seq_num) != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ldb_operr(ldb);
	}

	old_el = ldb_msg_find_element(msg, attr->lDAPDisplayName);
	if (old_el == NULL) {
		talloc_free(tmp_ctx);
		return ldb_operr(ldb);
	}

	ret = dsdb_check_single_valued_link(attr, old_el);
	if (ret != LDB_SUCCESS) {
		talloc_free(tmp_ctx);
		return ret;
	}

	old_el->flags |= LDB_FLAG_INTERNAL_DISABLE_SINGLE_VALUE_CHECK;

	ret = dsdb_module_modify(module, msg, DSDB_FLAG_NEXT_MODULE, parent);
	if (ret != LDB_SUCCESS) {
		ldb_debug(ldb, LDB_DEBUG_WARNING, "Failed to apply linked attribute change '%s'\n%s\n",
			  ldb_errstring(ldb),
			  ldb_ldif_message_string(ldb, tmp_ctx, LDB_CHANGETYPE_MODIFY, msg));
		talloc_free(tmp_ctx);
		return ret;
	}

	talloc_free(tmp_ctx);

	return ret;
}

static int replmd_extended(struct ldb_module *module, struct ldb_request *req)
{
	if (strcmp(req->op.extended.oid, DSDB_EXTENDED_REPLICATED_OBJECTS_OID) == 0) {
		return replmd_extended_replicated_objects(module, req);
	}

	return ldb_next_request(module, req);
}


/*
  we hook into the transaction operations to allow us to
  perform the linked attribute updates at the end of the whole
  transaction. This allows a forward linked attribute to be created
  before the object is created. During a vampire, w2k8 sends us linked
  attributes before the objects they are part of.
 */
static int replmd_start_transaction(struct ldb_module *module)
{
	/* create our private structure for this transaction */
	struct replmd_private *replmd_private = talloc_get_type(ldb_module_get_private(module),
								struct replmd_private);
	replmd_txn_cleanup(replmd_private);

	/* free any leftover mod_usn records from cancelled
	   transactions */
	while (replmd_private->ncs) {
		struct nc_entry *e = replmd_private->ncs;
		DLIST_REMOVE(replmd_private->ncs, e);
		talloc_free(e);
	}

	return ldb_next_start_trans(module);
}

/*
  on prepare commit we loop over our queued la_context structures and
  apply each of them
 */
static int replmd_prepare_commit(struct ldb_module *module)
{
	struct replmd_private *replmd_private =
		talloc_get_type(ldb_module_get_private(module), struct replmd_private);
	struct la_entry *la, *prev;
	struct la_backlink *bl;
	int ret;

	/* walk the list backwards, to do the first entry first, as we
	 * added the entries with DLIST_ADD() which puts them at the
	 * start of the list */
	for (la = DLIST_TAIL(replmd_private->la_list); la; la=prev) {
		prev = DLIST_PREV(la);
		DLIST_REMOVE(replmd_private->la_list, la);
		ret = replmd_process_linked_attribute(module, la, NULL);
		if (ret != LDB_SUCCESS) {
			replmd_txn_cleanup(replmd_private);
			return ret;
		}
	}

	/* process our backlink list, creating and deleting backlinks
	   as necessary */
	for (bl=replmd_private->la_backlinks; bl; bl=bl->next) {
		ret = replmd_process_backlink(module, bl, NULL);
		if (ret != LDB_SUCCESS) {
			replmd_txn_cleanup(replmd_private);
			return ret;
		}
	}

	replmd_txn_cleanup(replmd_private);

	/* possibly change @REPLCHANGED */
	ret = replmd_notify_store(module, NULL);
	if (ret != LDB_SUCCESS) {
		return ret;
	}

	return ldb_next_prepare_commit(module);
}

static int replmd_del_transaction(struct ldb_module *module)
{
	struct replmd_private *replmd_private =
		talloc_get_type(ldb_module_get_private(module), struct replmd_private);
	replmd_txn_cleanup(replmd_private);

	return ldb_next_del_trans(module);
}


static const struct ldb_module_ops ldb_repl_meta_data_module_ops = {
	.name          = "repl_meta_data",
	.init_context	   = replmd_init,
	.add               = replmd_add,
	.modify            = replmd_modify,
	.rename            = replmd_rename,
	.del	           = replmd_delete,
	.extended          = replmd_extended,
	.start_transaction = replmd_start_transaction,
	.prepare_commit    = replmd_prepare_commit,
	.del_transaction   = replmd_del_transaction,
};

int ldb_repl_meta_data_module_init(const char *version)
{
	LDB_MODULE_CHECK_VERSION(version);
	return ldb_register_module(&ldb_repl_meta_data_module_ops);
}