s4:dsdb Don't segfault with ldb_transaction_prepare_commit() without begin()

[Samba/cd1.git] / source4 / dsdb / samdb / ldb_modules / linked_attributes.c

/* 
   ldb database library

   Copyright (C) Andrew Bartlett <abartlet@samba.org> 2007
   Copyright (C) Simo Sorce <idra@samba.org> 2008

   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 linked_attributes module
 *
 *  Description: Module to ensure linked attribute pairs remain in sync
 *
 *  Author: Andrew Bartlett
 */

#include "includes.h"
#include "ldb_module.h"
#include "dlinklist.h"
#include "dsdb/samdb/samdb.h"
#include "librpc/gen_ndr/ndr_misc.h"

struct la_private {
        struct la_context *la_list;
};

struct la_op_store {
        struct la_op_store *next;
        struct la_op_store *prev;
        enum la_op {LA_OP_ADD, LA_OP_DEL} op;
        struct GUID guid;
        char *name;
        char *value;
};

struct replace_context {
        struct la_context *ac;
        unsigned int num_elements;
        struct ldb_message_element *el;
};

struct la_context {
        struct la_context *next, *prev;
        const struct dsdb_schema *schema;
        struct ldb_module *module;
        struct ldb_request *req;
        struct ldb_dn *partition_dn;
        struct ldb_dn *add_dn;
        struct ldb_dn *del_dn;
        struct replace_context *rc;
        struct la_op_store *ops;
        struct ldb_extended *op_response;
        struct ldb_control **op_controls;
};

static struct la_context *linked_attributes_init(struct ldb_module *module,
                                                 struct ldb_request *req)
{
        struct ldb_context *ldb;
        struct la_context *ac;
        const struct ldb_control *partition_ctrl;

        ldb = ldb_module_get_ctx(module);

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

        ac->schema = dsdb_get_schema(ldb);
        ac->module = module;
        ac->req = req;

        /* remember the partition DN that came in, if given */
        partition_ctrl = ldb_request_get_control(req, DSDB_CONTROL_CURRENT_PARTITION_OID);
        if (partition_ctrl) {
                const struct dsdb_control_current_partition *partition;
                partition = talloc_get_type(partition_ctrl->data,
                                            struct dsdb_control_current_partition);
                SMB_ASSERT(partition && partition->version == DSDB_CONTROL_CURRENT_PARTITION_VERSION);
        
                ac->partition_dn = ldb_dn_copy(ac, partition->dn);
        }

        return ac;
}

/*
  turn a DN into a GUID
 */
static int la_guid_from_dn(struct la_context *ac, struct ldb_dn *dn, struct GUID *guid)
{
        const struct ldb_val *guid_val;
        int ret;

        guid_val = ldb_dn_get_extended_component(dn, "GUID");
        if (guid_val) {
                /* there is a GUID embedded in the DN */
                enum ndr_err_code ndr_err;
                ndr_err = ndr_pull_struct_blob(guid_val, ac, NULL, guid,
                                               (ndr_pull_flags_fn_t)ndr_pull_GUID);
                if (ndr_err != NDR_ERR_SUCCESS) {
                        DEBUG(0,(__location__ ": Failed to parse GUID\n"));
                        return LDB_ERR_OPERATIONS_ERROR;
                }
        } else {
                ret = dsdb_find_guid_by_dn(ldb_module_get_ctx(ac->module), dn, guid);
                if (ret != LDB_SUCCESS) {
                        DEBUG(4,(__location__ ": Failed to find GUID for dn %s\n",
                                 ldb_dn_get_linearized(dn)));
                        return ret;
                }
        }
        return LDB_SUCCESS;
}


/* Common routine to handle reading the attributes and creating a
 * series of modify requests */
static int la_store_op(struct la_context *ac,
                       enum la_op op, struct ldb_val *dn,
                       const char *name)
{
        struct ldb_context *ldb;
        struct la_op_store *os;
        struct ldb_dn *op_dn;
        int ret;

        ldb = ldb_module_get_ctx(ac->module);

        op_dn = ldb_dn_from_ldb_val(ac, ldb, dn);
        if (!op_dn) {
                ldb_asprintf_errstring(ldb, 
                                       "could not parse attribute as a DN");
                return LDB_ERR_INVALID_DN_SYNTAX;
        }

        os = talloc_zero(ac, struct la_op_store);
        if (!os) {
                ldb_oom(ldb);
                return LDB_ERR_OPERATIONS_ERROR;
        }

        os->op = op;

        ret = la_guid_from_dn(ac, op_dn, &os->guid);
        if (ret == LDB_ERR_NO_SUCH_OBJECT && ac->req->operation == LDB_DELETE) {
                /* we are deleting an object, and we've found it has a
                 * forward link to a target that no longer
                 * exists. This is not an error in the delete, and we
                 * should just not do the deferred delete of the
                 * target attribute
                 */
                talloc_free(os);
                return LDB_SUCCESS;
        }
        if (ret != LDB_SUCCESS) {
                return ret;
        }

        os->name = talloc_strdup(os, name);
        if (!os->name) {
                ldb_oom(ldb);
                return LDB_ERR_OPERATIONS_ERROR;
        }

        /* Do deletes before adds */
        if (op == LA_OP_ADD) {
                DLIST_ADD_END(ac->ops, os, struct la_op_store *);
        } else {
                /* By adding to the head of the list, we do deletes before
                 * adds when processing a replace */
                DLIST_ADD(ac->ops, os);
        }

        return LDB_SUCCESS;
}

static int la_op_search_callback(struct ldb_request *req,
                                 struct ldb_reply *ares);
static int la_queue_mod_request(struct la_context *ac);
static int la_down_req(struct la_context *ac);



/* add */
static int linked_attributes_add(struct ldb_module *module, struct ldb_request *req)
{
        struct ldb_context *ldb;
        const struct dsdb_attribute *target_attr;
        struct la_context *ac;
        const char *attr_name;
        int ret;
        int i, j;

        ldb = ldb_module_get_ctx(module);

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

        ac = linked_attributes_init(module, req);
        if (!ac) {
                return LDB_ERR_OPERATIONS_ERROR;
        }

        if (!ac->schema) {
                /* without schema, this doesn't make any sense */
                talloc_free(ac);
                return ldb_next_request(module, req);
        }

        /* Need to ensure we only have forward links being specified */
        for (i=0; i < req->op.add.message->num_elements; i++) {
                const struct ldb_message_element *el = &req->op.add.message->elements[i];
                const struct dsdb_attribute *schema_attr
                        = dsdb_attribute_by_lDAPDisplayName(ac->schema, el->name);
                if (!schema_attr) {
                        ldb_asprintf_errstring(ldb, 
                                               "attribute %s is not a valid attribute in schema", el->name);
                        return LDB_ERR_OBJECT_CLASS_VIOLATION;                  
                }
                /* We have a valid attribute, now find out if it is linked */
                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;
                }
                
                /* Even link IDs are for the originating attribute */
                target_attr = dsdb_attribute_by_linkID(ac->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
                         */
                        continue;
                }

                attr_name = target_attr->lDAPDisplayName;

                for (j = 0; j < el->num_values; j++) {
                        ret = la_store_op(ac, LA_OP_ADD,
                                          &el->values[j],
                                          attr_name);
                        if (ret != LDB_SUCCESS) {
                                return ret;
                        }
                }
        }

        /* if no linked attributes are present continue */
        if (ac->ops == NULL) {
                /* nothing to do for this module, proceed */
                talloc_free(ac);
                return ldb_next_request(module, req);
        }

        /* start with the original request */
        return la_down_req(ac);
}

/* For a delete or rename, we need to find out what linked attributes
 * are currently on this DN, and then deal with them.  This is the
 * callback to the base search */

static int la_mod_search_callback(struct ldb_request *req, struct ldb_reply *ares)
{
        struct ldb_context *ldb;
        const struct dsdb_attribute *schema_attr;
        const struct dsdb_attribute *target_attr;
        struct ldb_message_element *search_el;
        struct replace_context *rc;
        struct la_context *ac;
        const char *attr_name;
        int i, j;
        int ret = LDB_SUCCESS;

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

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

        /* Only entries are interesting, and we only want the olddn */
        switch (ares->type) {
        case LDB_REPLY_ENTRY:

                if (ldb_dn_compare(ares->message->dn, ac->req->op.mod.message->dn) != 0) {
                        ldb_asprintf_errstring(ldb, 
                                               "linked_attributes: %s is not the DN we were looking for", ldb_dn_get_linearized(ares->message->dn));
                        /* Guh?  We only asked for this DN */
                        talloc_free(ares);
                        return ldb_module_done(ac->req, NULL, NULL,
                                                LDB_ERR_OPERATIONS_ERROR);
                }

                ac->add_dn = ac->del_dn = talloc_steal(ac, ares->message->dn);

                /* We don't populate 'rc' for ADD - it can't be deleting elements anyway */
                for (i = 0; rc && i < rc->num_elements; i++) {

                        schema_attr = dsdb_attribute_by_lDAPDisplayName(ac->schema, rc->el[i].name);
                        if (!schema_attr) {
                                ldb_asprintf_errstring(ldb,
                                        "attribute %s is not a valid attribute in schema",
                                        rc->el[i].name);
                                talloc_free(ares);
                                return ldb_module_done(ac->req, NULL, NULL,
                                                LDB_ERR_OBJECT_CLASS_VIOLATION);
                        }

                        search_el = ldb_msg_find_element(ares->message,
                                                         rc->el[i].name);

                        /* See if this element already exists */
                        /* otherwise just ignore as
                         * the add has already been scheduled */
                        if ( ! search_el) {
                                continue;
                        }

                        target_attr = dsdb_attribute_by_linkID(ac->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
                                 */
                                continue;
                        }
                        attr_name = target_attr->lDAPDisplayName;

                        /* Now we know what was there, we can remove it for the re-add */
                        for (j = 0; j < search_el->num_values; j++) {
                                ret = la_store_op(ac, LA_OP_DEL,
                                                  &search_el->values[j],
                                                  attr_name);
                                if (ret != LDB_SUCCESS) {
                                        talloc_free(ares);
                                        return ldb_module_done(ac->req,
                                                               NULL, NULL, ret);
                                }
                        }
                }

                break;

        case LDB_REPLY_REFERRAL:
                /* ignore */
                break;

        case LDB_REPLY_DONE:

                talloc_free(ares);

                if (ac->req->operation == LDB_ADD) {
                        /* Start the modifies to the backlinks */
                        ret = la_queue_mod_request(ac);

                        if (ret != LDB_SUCCESS) {
                                return ldb_module_done(ac->req, NULL, NULL,
                                                       ret);
                        }
                } else {
                        /* Start with the original request */
                        ret = la_down_req(ac);
                        if (ret != LDB_SUCCESS) {
                                return ldb_module_done(ac->req, NULL, NULL, ret);
                        }
                }
                return LDB_SUCCESS;
        }

        talloc_free(ares);
        return ret;
}


/* modify */
static int linked_attributes_modify(struct ldb_module *module, struct ldb_request *req)
{
        /* Look over list of modifications */
        /* Find if any are for linked attributes */
        /* Determine the effect of the modification */
        /* Apply the modify to the linked entry */

        struct ldb_context *ldb;
        int i, j;
        struct la_context *ac;
        struct ldb_request *search_req;
        const char **attrs;

        int ret;

        ldb = ldb_module_get_ctx(module);

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

        ac = linked_attributes_init(module, req);
        if (!ac) {
                return LDB_ERR_OPERATIONS_ERROR;
        }

        if (!ac->schema) {
                /* without schema, this doesn't make any sense */
                return ldb_next_request(module, req);
        }

        ac->rc = talloc_zero(ac, struct replace_context);
        if (!ac->rc) {
                ldb_oom(ldb);
                return LDB_ERR_OPERATIONS_ERROR;
        }

        for (i=0; i < req->op.mod.message->num_elements; i++) {
                bool store_el = false;
                const char *attr_name;
                const struct dsdb_attribute *target_attr;
                const struct ldb_message_element *el = &req->op.mod.message->elements[i];
                const struct dsdb_attribute *schema_attr
                        = dsdb_attribute_by_lDAPDisplayName(ac->schema, el->name);
                if (!schema_attr) {
                        ldb_asprintf_errstring(ldb, 
                                               "attribute %s is not a valid attribute in schema", el->name);
                        return LDB_ERR_OBJECT_CLASS_VIOLATION;                  
                }
                /* We have a valid attribute, now find out if it is linked */
                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;
                }
                
                /* Even link IDs are for the originating attribute */
                
                /* Now find the target attribute */
                target_attr = dsdb_attribute_by_linkID(ac->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
                         */
                        continue;
                }

                attr_name = target_attr->lDAPDisplayName;
        
                switch (el->flags & LDB_FLAG_MOD_MASK) {
                case LDB_FLAG_MOD_REPLACE:
                        /* treat as just a normal add the delete part is handled by the callback */
                        store_el = true;

                        /* break intentionally missing */

                case LDB_FLAG_MOD_ADD:

                        /* For each value being added, we need to setup the adds */
                        for (j = 0; j < el->num_values; j++) {
                                ret = la_store_op(ac, LA_OP_ADD,
                                                  &el->values[j],
                                                  attr_name);
                                if (ret != LDB_SUCCESS) {
                                        return ret;
                                }
                        }
                        break;

                case LDB_FLAG_MOD_DELETE:

                        if (el->num_values) {
                                /* For each value being deleted, we need to setup the delete */
                                for (j = 0; j < el->num_values; j++) {
                                        ret = la_store_op(ac, LA_OP_DEL,
                                                          &el->values[j],
                                                          attr_name);
                                        if (ret != LDB_SUCCESS) {
                                                return ret;
                                        }
                                }
                        } else {
                                /* Flag that there was a DELETE
                                 * without a value specified, so we
                                 * need to look for the old value */
                                store_el = true;
                        }

                        break;
                }

                if (store_el) {
                        struct ldb_message_element *search_el;

                        search_el = talloc_realloc(ac->rc, ac->rc->el,
                                                   struct ldb_message_element,
                                                   ac->rc->num_elements +1);
                        if (!search_el) {
                                ldb_oom(ldb);
                                return LDB_ERR_OPERATIONS_ERROR;
                        }
                        ac->rc->el = search_el;

                        ac->rc->el[ac->rc->num_elements] = *el;
                        ac->rc->num_elements++;
                }
        }
        
        if (ac->ops || ac->rc->el) {
                /* both replace and delete without values are handled in the callback
                 * after the search on the entry to be modified is performed */
                
                attrs = talloc_array(ac->rc, const char *, ac->rc->num_elements + 1);
                if (!attrs) {
                        ldb_oom(ldb);
                        return LDB_ERR_OPERATIONS_ERROR;
                }
                for (i = 0; ac->rc && i < ac->rc->num_elements; i++) {
                        attrs[i] = ac->rc->el[i].name;
                }
                attrs[i] = NULL;
                
                /* The callback does all the hard work here */
                ret = ldb_build_search_req(&search_req, ldb, ac,
                                           req->op.mod.message->dn,
                                           LDB_SCOPE_BASE,
                                           "(objectClass=*)", attrs,
                                           NULL,
                                           ac, la_mod_search_callback,
                                           req);

                /* We need to figure out our own extended DN, to fill in as the backlink target */
                if (ret == LDB_SUCCESS) {
                        ret = ldb_request_add_control(search_req,
                                                      LDB_CONTROL_EXTENDED_DN_OID,
                                                      false, NULL);
                }
                if (ret == LDB_SUCCESS) {
                        talloc_steal(search_req, attrs);
                        
                        ret = ldb_next_request(module, search_req);
                }

        } else {
                /* nothing to do for this module, proceed */
                talloc_free(ac);
                ret = ldb_next_request(module, req);
        }

        return ret;
}

/* delete */
static int linked_attributes_del(struct ldb_module *module, struct ldb_request *req)
{
        struct ldb_context *ldb;
        struct ldb_request *search_req;
        struct la_context *ac;
        const char **attrs;
        WERROR werr;
        int ret;

        /* This gets complex:  We need to:
           - Do a search for the entry
           - Wait for these result to appear
           - In the callback for the result, issue a modify
                request based on the linked attributes found
           - Wait for each modify result
           - Regain our sainity
        */

        ldb = ldb_module_get_ctx(module);

        ac = linked_attributes_init(module, req);
        if (!ac) {
                return LDB_ERR_OPERATIONS_ERROR;
        }

        if (!ac->schema) {
                /* without schema, this doesn't make any sense */
                return ldb_next_request(module, req);
        }

        werr = dsdb_linked_attribute_lDAPDisplayName_list(ac->schema, ac, &attrs);
        if (!W_ERROR_IS_OK(werr)) {
                return LDB_ERR_OPERATIONS_ERROR;
        }

        ret = ldb_build_search_req(&search_req, ldb, req,
                                   req->op.del.dn, LDB_SCOPE_BASE,
                                   "(objectClass=*)", attrs,
                                   NULL,
                                   ac, la_op_search_callback,
                                   req);

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

        talloc_steal(search_req, attrs);

        return ldb_next_request(module, search_req);
}

/* rename */
static int linked_attributes_rename(struct ldb_module *module, struct ldb_request *req)
{
        struct la_context *ac;

        /* This gets complex:  We need to:
           - Do a search for the entry
           - Wait for these result to appear
           - In the callback for the result, issue a modify
                request based on the linked attributes found
           - Wait for each modify result
           - Regain our sainity
        */

        ac = linked_attributes_init(module, req);
        if (!ac) {
                return LDB_ERR_OPERATIONS_ERROR;
        }

        if (!ac->schema) {
                /* without schema, this doesn't make any sense */
                return ldb_next_request(module, req);
        }

        /* start with the original request */
        return la_down_req(ac);
}


static int la_op_search_callback(struct ldb_request *req,
                                 struct ldb_reply *ares)
{
        struct ldb_context *ldb;
        struct la_context *ac;
        const struct dsdb_attribute *schema_attr;
        const struct dsdb_attribute *target_attr;
        const struct ldb_message_element *el;
        const char *attr_name;
        int i, j;
        int ret;

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

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

        /* Only entries are interesting, and we only want the olddn */
        switch (ares->type) {
        case LDB_REPLY_ENTRY:
                ret = ldb_dn_compare(ares->message->dn, req->op.search.base);
                if (ret != 0) {
                        /* Guh?  We only asked for this DN */
                        talloc_free(ares);
                        return ldb_module_done(ac->req, NULL, NULL,
                                                LDB_ERR_OPERATIONS_ERROR);
                }
                if (ares->message->num_elements == 0) {
                        /* only bother at all if there were some
                         * linked attributes found */
                        talloc_free(ares);
                        return LDB_SUCCESS;
                }

                switch (ac->req->operation) {
                case LDB_DELETE:
                        ac->del_dn = talloc_steal(ac, ares->message->dn);
                        break;
                case LDB_RENAME:
                        ac->add_dn = talloc_steal(ac, ares->message->dn); 
                        ac->del_dn = talloc_steal(ac, ac->req->op.rename.olddn);
                        break;
                default:
                        talloc_free(ares);
                        ldb_set_errstring(ldb,
                                          "operations must be delete or rename");
                        return ldb_module_done(ac->req, NULL, NULL,
                                                LDB_ERR_OPERATIONS_ERROR);
                }

                for (i = 0; i < ares->message->num_elements; i++) {
                        el = &ares->message->elements[i];

                        schema_attr = dsdb_attribute_by_lDAPDisplayName(ac->schema, el->name);
                        if (!schema_attr) {
                                ldb_asprintf_errstring(ldb,
                                        "attribute %s is not a valid attribute"
                                        " in schema", el->name);
                                talloc_free(ares);
                                return ldb_module_done(ac->req, NULL, NULL,
                                                LDB_ERR_OBJECT_CLASS_VIOLATION);
                        }

                        /* Valid attribute, now find out if it is linked */
                        if (schema_attr->linkID == 0) {
                                /* Not a linked attribute, skip */
                                continue;
                        }

                        if ((schema_attr->linkID & 1) == 0) {
                                /* Odd is for the target. */
                                target_attr = dsdb_attribute_by_linkID(ac->schema, schema_attr->linkID + 1);
                                if (!target_attr) {
                                        continue;
                                }
                                attr_name = target_attr->lDAPDisplayName;
                        } else {
                                target_attr = dsdb_attribute_by_linkID(ac->schema, schema_attr->linkID - 1);
                                if (!target_attr) {
                                        continue;
                                }
                                attr_name = target_attr->lDAPDisplayName;
                        }
                        for (j = 0; j < el->num_values; j++) {
                                ret = la_store_op(ac, LA_OP_DEL,
                                                  &el->values[j],
                                                  attr_name);

                                /* for renames, ensure we add it back */
                                if (ret == LDB_SUCCESS
                                    && ac->req->operation == LDB_RENAME) {
                                        ret = la_store_op(ac, LA_OP_ADD,
                                                          &el->values[j],
                                                          attr_name);
                                }
                                if (ret != LDB_SUCCESS) {
                                        talloc_free(ares);
                                        return ldb_module_done(ac->req,
                                                               NULL, NULL, ret);
                                }
                        }
                }

                break;

        case LDB_REPLY_REFERRAL:
                /* ignore */
                break;

        case LDB_REPLY_DONE:

                talloc_free(ares);


                switch (ac->req->operation) {
                case LDB_DELETE:
                        /* start the mod requests chain */
                        ret = la_down_req(ac);
                        if (ret != LDB_SUCCESS) {
                                return ldb_module_done(ac->req, NULL, NULL, ret);
                        }
                        return ret;

                case LDB_RENAME:        
                        /* start the mod requests chain */
                        ret = la_queue_mod_request(ac);
                        if (ret != LDB_SUCCESS) {
                                return ldb_module_done(ac->req, NULL, NULL,
                                                       ret);
                        }       
                        return ret;
                        
                default:
                        talloc_free(ares);
                        ldb_set_errstring(ldb,
                                          "operations must be delete or rename");
                        return ldb_module_done(ac->req, NULL, NULL,
                                                LDB_ERR_OPERATIONS_ERROR);
                }
        }

        talloc_free(ares);
        return LDB_SUCCESS;
}

/* queue a linked attributes modify request in the la_private
   structure */
static int la_queue_mod_request(struct la_context *ac)
{
        struct la_private *la_private = 
                talloc_get_type(ldb_module_get_private(ac->module), struct la_private);

        if (la_private == NULL) {
                ldb_debug(ldb_module_get_ctx(ac->module), LDB_DEBUG_ERROR, __location__ ": No la_private transaction setup\n");
                return LDB_ERR_OPERATIONS_ERROR;
        }

        talloc_steal(la_private, ac);
        DLIST_ADD(la_private->la_list, ac);

        return ldb_module_done(ac->req, ac->op_controls,
                               ac->op_response, LDB_SUCCESS);
}

/* Having done the original operation, then try to fix up all the linked attributes for modify and delete */
static int la_mod_del_callback(struct ldb_request *req, struct ldb_reply *ares)
{
        int ret;
        struct la_context *ac;
        struct ldb_context *ldb;

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

        if (!ares) {
                return ldb_module_done(ac->req, NULL, NULL,
                                        LDB_ERR_OPERATIONS_ERROR);
        }
        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);
        }
        
        ac->op_controls = talloc_steal(ac, ares->controls);
        ac->op_response = talloc_steal(ac, ares->response);

        /* If we have modfies to make, this is the time to do them for modify and delete */
        ret = la_queue_mod_request(ac);
        
        if (ret != LDB_SUCCESS) {
                return ldb_module_done(ac->req, NULL, NULL, ret);
        }
        talloc_free(ares);

        /* la_queue_mod_request has already sent the callbacks */
        return LDB_SUCCESS;

}

/* Having done the original rename try to fix up all the linked attributes */
static int la_rename_callback(struct ldb_request *req, struct ldb_reply *ares)
{
        int ret;
        struct la_context *ac;
        struct ldb_request *search_req;
        const char **attrs;
        WERROR werr;
        struct ldb_context *ldb;

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

        if (!ares) {
                return ldb_module_done(ac->req, NULL, NULL,
                                        LDB_ERR_OPERATIONS_ERROR);
        }
        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);
        }
        
        werr = dsdb_linked_attribute_lDAPDisplayName_list(ac->schema, ac, &attrs);
        if (!W_ERROR_IS_OK(werr)) {
                return LDB_ERR_OPERATIONS_ERROR;
        }
        
        ret = ldb_build_search_req(&search_req, ldb, req,
                                   ac->req->op.rename.newdn, LDB_SCOPE_BASE,
                                   "(objectClass=*)", attrs,
                                   NULL,
                                   ac, la_op_search_callback,
                                   req);
        
        if (ret != LDB_SUCCESS) {
                return ret;
        }
                
        talloc_steal(search_req, attrs);

        if (ret == LDB_SUCCESS) {
                ret = ldb_request_add_control(search_req,
                                              LDB_CONTROL_EXTENDED_DN_OID,
                                              false, NULL);
        }
        if (ret != LDB_SUCCESS) {
                return ldb_module_done(ac->req, NULL, NULL,
                                       ret);
        }
        
        ac->op_controls = talloc_steal(ac, ares->controls);
        ac->op_response = talloc_steal(ac, ares->response);

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

/* Having done the original add, then try to fix up all the linked attributes

  This is done after the add so the links can get the extended DNs correctly.
 */
static int la_add_callback(struct ldb_request *req, struct ldb_reply *ares)
{
        int ret;
        struct la_context *ac;
        struct ldb_context *ldb;

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

        if (!ares) {
                return ldb_module_done(ac->req, NULL, NULL,
                                        LDB_ERR_OPERATIONS_ERROR);
        }
        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);
        }
        
        if (ac->ops) {
                struct ldb_request *search_req;
                static const char *attrs[] = { NULL };
                
                /* The callback does all the hard work here - we need
                 * the objectGUID and SID of the added record */
                ret = ldb_build_search_req(&search_req, ldb, ac,
                                           ac->req->op.add.message->dn,
                                           LDB_SCOPE_BASE,
                                           "(objectClass=*)", attrs,
                                           NULL,
                                           ac, la_mod_search_callback,
                                           ac->req);
                
                if (ret == LDB_SUCCESS) {
                        ret = ldb_request_add_control(search_req,
                                                      LDB_CONTROL_EXTENDED_DN_OID,
                                                      false, NULL);
                }
                if (ret != LDB_SUCCESS) {
                        return ldb_module_done(ac->req, NULL, NULL,
                                               ret);
                }

                ac->op_controls = talloc_steal(ac, ares->controls);
                ac->op_response = talloc_steal(ac, ares->response);

                return ldb_next_request(ac->module, search_req);
                
        } else {
                return ldb_module_done(ac->req, ares->controls,
                                       ares->response, ares->error);
        }
}

/* Reconstruct the original request, but pointing at our local callback to finish things off */
static int la_down_req(struct la_context *ac)
{
        struct ldb_request *down_req;
        int ret;
        struct ldb_context *ldb;

        ldb = ldb_module_get_ctx(ac->module);

        switch (ac->req->operation) {
        case LDB_ADD:
                ret = ldb_build_add_req(&down_req, ldb, ac,
                                        ac->req->op.add.message,
                                        ac->req->controls,
                                        ac, la_add_callback,
                                        ac->req);
                break;
        case LDB_MODIFY:
                ret = ldb_build_mod_req(&down_req, ldb, ac,
                                        ac->req->op.mod.message,
                                        ac->req->controls,
                                        ac, la_mod_del_callback,
                                        ac->req);
                break;
        case LDB_DELETE:
                ret = ldb_build_del_req(&down_req, ldb, ac,
                                        ac->req->op.del.dn,
                                        ac->req->controls,
                                        ac, la_mod_del_callback,
                                        ac->req);
                break;
        case LDB_RENAME:
                ret = ldb_build_rename_req(&down_req, ldb, ac,
                                           ac->req->op.rename.olddn,
                                           ac->req->op.rename.newdn,
                                           ac->req->controls,
                                           ac, la_rename_callback,
                                           ac->req);
                break;
        default:
                ret = LDB_ERR_OPERATIONS_ERROR;
        }
        if (ret != LDB_SUCCESS) {
                return ret;
        }

        return ldb_next_request(ac->module, down_req);
}

/*
  use the GUID part of an extended DN to find the target DN, in case
  it has moved
 */
static int la_find_dn_target(struct ldb_module *module, struct la_context *ac, 
                             struct GUID *guid, struct ldb_dn **dn)
{
        return dsdb_find_dn_by_guid(ldb_module_get_ctx(ac->module), ac, GUID_string(ac, guid), dn);
}

/* apply one la_context op change */
static int la_do_op_request(struct ldb_module *module, struct la_context *ac, struct la_op_store *op)
{
        struct ldb_message_element *ret_el;
        struct ldb_request *mod_req;
        struct ldb_message *new_msg;
        struct ldb_context *ldb;
        int ret;

        ldb = ldb_module_get_ctx(ac->module);

        /* Create the modify request */
        new_msg = ldb_msg_new(ac);
        if (!new_msg) {
                ldb_oom(ldb);
                return LDB_ERR_OPERATIONS_ERROR;
        }

        ret = la_find_dn_target(module, ac, &op->guid, &new_msg->dn);
        if (ret != LDB_SUCCESS) {
                return ret;
        }

        if (op->op == LA_OP_ADD) {
                ret = ldb_msg_add_empty(new_msg, op->name,
                                        LDB_FLAG_MOD_ADD, &ret_el);
        } else {
                ret = ldb_msg_add_empty(new_msg, op->name,
                                        LDB_FLAG_MOD_DELETE, &ret_el);
        }
        if (ret != LDB_SUCCESS) {
                return ret;
        }
        ret_el->values = talloc_array(new_msg, struct ldb_val, 1);
        if (!ret_el->values) {
                ldb_oom(ldb);
                return LDB_ERR_OPERATIONS_ERROR;
        }
        ret_el->num_values = 1;
        if (op->op == LA_OP_ADD) {
                ret_el->values[0] = data_blob_string_const(ldb_dn_get_extended_linearized(new_msg, ac->add_dn, 1));
        } else {
                ret_el->values[0] = data_blob_string_const(ldb_dn_get_extended_linearized(new_msg, ac->del_dn, 1));
        }

#if 0
        ldb_debug(ldb, LDB_DEBUG_WARNING,
                  "link on %s %s: %s %s\n", 
                  ldb_dn_get_linearized(new_msg->dn), ret_el->name, 
                  ret_el->values[0].data, ac->ops->op == LA_OP_ADD ? "added" : "deleted");
#endif  

        ret = ldb_build_mod_req(&mod_req, ldb, op,
                                new_msg,
                                NULL,
                                NULL, 
                                ldb_op_default_callback,
                                NULL);
        if (ret != LDB_SUCCESS) {
                return ret;
        }
        talloc_steal(mod_req, new_msg);

        if (DEBUGLVL(4)) {
                DEBUG(4,("Applying linked attribute change:\n%s\n",
                         ldb_ldif_message_string(ldb, op, LDB_CHANGETYPE_MODIFY, new_msg)));
        }

        /* Run the new request */
        ret = ldb_next_request(module, mod_req);

        /* we need to wait for this to finish, as we are being called
           from the synchronous end_transaction hook of this module */
        if (ret == LDB_SUCCESS) {
                ret = ldb_wait(mod_req->handle, LDB_WAIT_ALL);
        }

        if (ret != LDB_SUCCESS) {
                ldb_debug(ldb, LDB_DEBUG_WARNING, "Failed to apply linked attribute change '%s' %s\n",
                          ldb_errstring(ldb),
                          ldb_ldif_message_string(ldb, op, LDB_CHANGETYPE_MODIFY, new_msg));
        }

        return ret;
}

/* apply one set of la_context changes */
static int la_do_mod_request(struct ldb_module *module, struct la_context *ac)
{
        struct la_op_store *op;

        for (op = ac->ops; op; op=op->next) {
                int ret = la_do_op_request(module, ac, op);
                if (ret != LDB_SUCCESS) {
                        if (ret != LDB_ERR_NO_SUCH_OBJECT) {
                                return ret;
                        }
                }
        }

        return LDB_SUCCESS;
}


/*
  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 target is created, as long as the target is created
  in the same transaction
 */
static int linked_attributes_start_transaction(struct ldb_module *module)
{
        /* create our private structure for this transaction */
        struct la_private *la_private = talloc_get_type(ldb_module_get_private(module),
                                                        struct la_private);
        talloc_free(la_private);
        la_private = talloc(module, struct la_private);
        if (la_private == NULL) {
                return LDB_ERR_OPERATIONS_ERROR;
        }
        la_private->la_list = NULL;
        ldb_module_set_private(module, la_private);
        return ldb_next_start_trans(module);
}

/*
  on prepare commit we loop over our queued la_context structures
  and apply each of them
 */
static int linked_attributes_prepare_commit(struct ldb_module *module)
{
        struct la_private *la_private = 
                talloc_get_type(ldb_module_get_private(module), struct la_private);
        struct la_context *ac;

        if (!la_private) {
                /* prepare commit without begin_transaction - let someone else return the error, just don't segfault */
                return ldb_next_prepare_commit(module);
        }
        /* 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 (ac = la_private->la_list; ac && ac->next; ac=ac->next) ;

        for (; ac; ac=ac->prev) {
                int ret;
                ac->req = NULL;
                ret = la_do_mod_request(module, ac);
                if (ret != LDB_SUCCESS) {
                        DEBUG(0,(__location__ ": Failed mod request ret=%d\n", ret));
                        talloc_free(la_private);
                        ldb_module_set_private(module, NULL);   
                        return ret;
                }
        }

        talloc_free(la_private);
        ldb_module_set_private(module, NULL);   

        return ldb_next_prepare_commit(module);
}

static int linked_attributes_del_transaction(struct ldb_module *module)
{
        struct la_private *la_private = 
                talloc_get_type(ldb_module_get_private(module), struct la_private);
        talloc_free(la_private);
        ldb_module_set_private(module, NULL);
        return ldb_next_del_trans(module);
}


_PUBLIC_ const struct ldb_module_ops ldb_linked_attributes_module_ops = {
        .name              = "linked_attributes",
        .add               = linked_attributes_add,
        .modify            = linked_attributes_modify,
        .del               = linked_attributes_del,
        .rename            = linked_attributes_rename,
        .start_transaction = linked_attributes_start_transaction,
        .prepare_commit    = linked_attributes_prepare_commit,
        .del_transaction   = linked_attributes_del_transaction,
};