ldb: Add read_lock and read_unlock to ldb_module_ops

[Samba.git] / lib / ldb / common / ldb_modules.c

/*
   ldb database library

   Copyright (C) Simo Sorce  2004-2008

     ** NOTE! The following LGPL license applies to the ldb
     ** library. This does NOT imply that all of Samba is released
     ** under the LGPL

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

   This library 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
   Lesser General Public License for more details.

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

/*
 *  Name: ldb
 *
 *  Component: ldb modules core
 *
 *  Description: core modules routines
 *
 *  Author: Simo Sorce
 */

#include "ldb_private.h"
#include "dlinklist.h"
#include "system/dir.h"

static char *ldb_modules_strdup_no_spaces(TALLOC_CTX *mem_ctx, const char *string)
{
        size_t i, len;
        char *trimmed;

        trimmed = talloc_strdup(mem_ctx, string);
        if (!trimmed) {
                return NULL;
        }

        len = strlen(trimmed);
        for (i = 0; trimmed[i] != '\0'; i++) {
                switch (trimmed[i]) {
                case ' ':
                case '\t':
                case '\n':
                        memmove(&trimmed[i], &trimmed[i + 1], len -i -1);
                        break;
                }
        }

        return trimmed;
}


/* modules are called in inverse order on the stack.
   Lets place them as an admin would think the right order is.
   Modules order is important */
const char **ldb_modules_list_from_string(struct ldb_context *ldb, TALLOC_CTX *mem_ctx, const char *string)
{
        char **modules = NULL;
        const char **m;
        char *modstr, *p;
        unsigned int i;

        /* spaces not admitted */
        modstr = ldb_modules_strdup_no_spaces(mem_ctx, string);
        if ( ! modstr) {
                ldb_debug(ldb, LDB_DEBUG_FATAL, "Out of Memory in ldb_modules_strdup_no_spaces()");
                return NULL;
        }

        modules = talloc_realloc(mem_ctx, modules, char *, 2);
        if ( ! modules ) {
                ldb_debug(ldb, LDB_DEBUG_FATAL, "Out of Memory in ldb_modules_list_from_string()");
                talloc_free(modstr);
                return NULL;
        }
        talloc_steal(modules, modstr);

        if (modstr[0] == '\0') {
                modules[0] = NULL;
                m = discard_const_p(const char *, modules);
                return m;
        }

        i = 0;
        /* The str*r*chr walks backwards:  This is how we get the inverse order mentioned above */
        while ((p = strrchr(modstr, ',')) != NULL) {
                *p = '\0';
                p++;
                modules[i] = p;

                i++;
                modules = talloc_realloc(mem_ctx, modules, char *, i + 2);
                if ( ! modules ) {
                        ldb_debug(ldb, LDB_DEBUG_FATAL, "Out of Memory in ldb_modules_list_from_string()");
                        return NULL;
                }

        }
        modules[i] = modstr;

        modules[i + 1] = NULL;

        m = discard_const_p(const char *, modules);

        return m;
}

static struct backends_list_entry {
        struct ldb_backend_ops *ops;
        struct backends_list_entry *prev, *next;
} *ldb_backends = NULL;

static struct ops_list_entry {
        const struct ldb_module_ops *ops;
        struct ops_list_entry *next;
} *registered_modules = NULL;

static struct backends_list_entry *ldb_find_backend(const char *url_prefix)
{
        struct backends_list_entry *backend;

        for (backend = ldb_backends; backend; backend = backend->next) {
                if (strcmp(backend->ops->name, url_prefix) == 0) {
                        return backend;
                }
        }

        return NULL;
}

/*
  register a new ldb backend

  if override is true, then override any existing backend for this prefix
*/
int ldb_register_backend(const char *url_prefix, ldb_connect_fn connectfn, bool override)
{
        struct backends_list_entry *be;

        be = ldb_find_backend(url_prefix);
        if (be) {
                if (!override) {
                        return LDB_SUCCESS;
                }
        } else {
                be = talloc_zero(ldb_backends, struct backends_list_entry);
                if (!be) {
                        return LDB_ERR_OPERATIONS_ERROR;
                }
                be->ops = talloc_zero(be, struct ldb_backend_ops);
                if (!be->ops) {
                        talloc_free(be);
                        return LDB_ERR_OPERATIONS_ERROR;
                }
                DLIST_ADD_END(ldb_backends, be);
        }

        be->ops->name = url_prefix;
        be->ops->connect_fn = connectfn;

        return LDB_SUCCESS;
}

/*
   Return the ldb module form of a database.
   The URL can either be one of the following forms
   ldb://path
   ldapi://path

   flags is made up of LDB_FLG_*

   the options are passed uninterpreted to the backend, and are
   backend specific.

   This allows modules to get at only the backend module, for example where a
   module may wish to direct certain requests at a particular backend.
*/
int ldb_module_connect_backend(struct ldb_context *ldb,
                               const char *url,
                               const char *options[],
                               struct ldb_module **backend_module)
{
        int ret;
        char *backend;
        struct backends_list_entry *be;

        if (strchr(url, ':') != NULL) {
                backend = talloc_strndup(ldb, url, strchr(url, ':')-url);
        } else {
                /* Default to tdb */
                backend = talloc_strdup(ldb, "tdb");
        }
        if (backend == NULL) {
                return ldb_oom(ldb);
        }

        be = ldb_find_backend(backend);

        talloc_free(backend);

        if (be == NULL) {
                ldb_debug(ldb, LDB_DEBUG_FATAL,
                          "Unable to find backend for '%s' - do you need to set LDB_MODULES_PATH?", url);
                return LDB_ERR_OTHER;
        }

        ret = be->ops->connect_fn(ldb, url, ldb->flags, options, backend_module);

        if (ret != LDB_SUCCESS) {
                ldb_debug(ldb, LDB_DEBUG_ERROR,
                          "Failed to connect to '%s' with backend '%s': %s", url, be->ops->name, ldb_errstring(ldb));
                return ret;
        }
        return ret;
}

static struct ldb_hooks {
        struct ldb_hooks *next, *prev;
        ldb_hook_fn hook_fn;
} *ldb_hooks;

/*
  register a ldb hook function
 */
int ldb_register_hook(ldb_hook_fn hook_fn)
{
        struct ldb_hooks *lc;
        lc = talloc_zero(ldb_hooks, struct ldb_hooks);
        if (lc == NULL) {
                return LDB_ERR_OPERATIONS_ERROR;
        }
        lc->hook_fn = hook_fn;
        DLIST_ADD_END(ldb_hooks, lc);
        return LDB_SUCCESS;
}

/*
  call ldb hooks of a given type
 */
int ldb_modules_hook(struct ldb_context *ldb, enum ldb_module_hook_type t)
{
        struct ldb_hooks *lc;
        for (lc = ldb_hooks; lc; lc=lc->next) {
                int ret = lc->hook_fn(ldb, t);
                if (ret != LDB_SUCCESS) {
                        return ret;
                }
        }
        return LDB_SUCCESS;
}


static const struct ldb_module_ops *ldb_find_module_ops(const char *name)
{
        struct ops_list_entry *e;

        for (e = registered_modules; e; e = e->next) {
                if (strcmp(e->ops->name, name) == 0)
                        return e->ops;
        }

        return NULL;
}


int ldb_register_module(const struct ldb_module_ops *ops)
{
        struct ops_list_entry *entry;

        if (ldb_find_module_ops(ops->name) != NULL)
                return LDB_ERR_ENTRY_ALREADY_EXISTS;

        entry = talloc(talloc_autofree_context(), struct ops_list_entry);
        if (entry == NULL) {
                return LDB_ERR_OPERATIONS_ERROR;
        }

        entry->ops = ops;
        entry->next = registered_modules;
        registered_modules = entry;

        return LDB_SUCCESS;
}

/*
  load a list of modules
 */
int ldb_module_load_list(struct ldb_context *ldb, const char **module_list,
                         struct ldb_module *backend, struct ldb_module **out)
{
        struct ldb_module *module;
        unsigned int i;

        module = backend;

        for (i = 0; module_list && module_list[i] != NULL; i++) {
                struct ldb_module *current;
                const struct ldb_module_ops *ops;

                if (strcmp(module_list[i], "") == 0) {
                        continue;
                }

                ops = ldb_find_module_ops(module_list[i]);

                if (ops == NULL) {
                        ldb_debug(ldb, LDB_DEBUG_FATAL, "WARNING: Module [%s] not found - do you need to set LDB_MODULES_PATH?",
                                  module_list[i]);
                        return LDB_ERR_OPERATIONS_ERROR;
                }

                current = talloc_zero(ldb, struct ldb_module);
                if (current == NULL) {
                        return LDB_ERR_OPERATIONS_ERROR;
                }
                talloc_set_name(current, "ldb_module: %s", module_list[i]);

                current->ldb = ldb;
                current->ops = ops;

                DLIST_ADD(module, current);
        }
        *out = module;
        return LDB_SUCCESS;
}

/*
  initialise a chain of modules
 */
int ldb_module_init_chain(struct ldb_context *ldb, struct ldb_module *module)
{
        while (module && module->ops->init_context == NULL)
                module = module->next;

        /* init is different in that it is not an error if modules
         * do not require initialization */

        if (module) {
                int ret = module->ops->init_context(module);
                if (ret != LDB_SUCCESS) {
                        ldb_debug(ldb, LDB_DEBUG_FATAL, "module %s initialization failed : %s",
                                  module->ops->name, ldb_strerror(ret));
                        return ret;
                }
        }

        return LDB_SUCCESS;
}

int ldb_load_modules(struct ldb_context *ldb, const char *options[])
{
        const char *modules_string;
        const char **modules = NULL;
        int ret;
        TALLOC_CTX *mem_ctx = talloc_new(ldb);
        if (!mem_ctx) {
                return ldb_oom(ldb);
        }

        /* find out which modules we are requested to activate */

        /* check if we have a custom module list passd as ldb option */
        if (options) {
                modules_string = ldb_options_find(ldb, options, "modules");
                if (modules_string) {
                        modules = ldb_modules_list_from_string(ldb, mem_ctx, modules_string);
                }
        }

        /* if not overloaded by options and the backend is not ldap try to load the modules list from ldb */
        if ((modules == NULL) && (strcmp("ldap", ldb->modules->ops->name) != 0)) {
                const char * const attrs[] = { "@LIST" , NULL};
                struct ldb_result *res = NULL;
                struct ldb_dn *mods_dn;

                mods_dn = ldb_dn_new(mem_ctx, ldb, "@MODULES");
                if (mods_dn == NULL) {
                        talloc_free(mem_ctx);
                        return ldb_oom(ldb);
                }

                ret = ldb_search(ldb, mods_dn, &res, mods_dn, LDB_SCOPE_BASE, attrs, "@LIST=*");

                if (ret == LDB_ERR_NO_SUCH_OBJECT) {
                        ldb_debug(ldb, LDB_DEBUG_TRACE, "no modules required by the db");
                } else if (ret != LDB_SUCCESS) {
                        ldb_debug(ldb, LDB_DEBUG_FATAL, "ldb error (%s) occurred searching for modules, bailing out", ldb_errstring(ldb));
                        talloc_free(mem_ctx);
                        return ret;
                } else {
                        const char *module_list;
                        if (res->count == 0) {
                                ldb_debug(ldb, LDB_DEBUG_TRACE, "no modules required by the db");
                        } else if (res->count > 1) {
                                ldb_debug(ldb, LDB_DEBUG_FATAL, "Too many records found (%u), bailing out", res->count);
                                talloc_free(mem_ctx);
                                return LDB_ERR_OPERATIONS_ERROR;
                        } else {
                                module_list = ldb_msg_find_attr_as_string(res->msgs[0], "@LIST", NULL);
                                if (!module_list) {
                                        ldb_debug(ldb, LDB_DEBUG_TRACE, "no modules required by the db");
                                }
                                modules = ldb_modules_list_from_string(ldb, mem_ctx,
                                                               module_list);
                        }
                }

                talloc_free(mods_dn);
        }

        if (modules != NULL) {
                ret = ldb_module_load_list(ldb, modules, ldb->modules, &ldb->modules);
                if (ret != LDB_SUCCESS) {
                        talloc_free(mem_ctx);
                        return ret;
                }
        } else {
                ldb_debug(ldb, LDB_DEBUG_TRACE, "No modules specified for this database");
        }

        ret = ldb_module_init_chain(ldb, ldb->modules);
        talloc_free(mem_ctx);
        return ret;
}

/*
  by using this we allow ldb modules to only implement the functions they care about,
  which makes writing a module simpler, and makes it more likely to keep working
  when ldb is extended
*/
#define FIND_OP_NOERR(module, op) do { \
        module = module->next; \
        while (module && module->ops->op == NULL) module = module->next; \
        if ((module && module->ldb->flags & LDB_FLG_ENABLE_TRACING)) { \
                ldb_debug(module->ldb, LDB_DEBUG_TRACE, "ldb_trace_next_request: (%s)->" #op, \
                          module->ops->name);                           \
        }                                                               \
} while (0)

#define FIND_OP(module, op) do { \
        struct ldb_context *ldb = module->ldb; \
        FIND_OP_NOERR(module, op); \
        if (module == NULL) { \
                ldb_asprintf_errstring(ldb, "Unable to find backend operation for " #op ); \
                return LDB_ERR_OPERATIONS_ERROR;        \
        }                                               \
} while (0)


struct ldb_module *ldb_module_new(TALLOC_CTX *memctx,
                                  struct ldb_context *ldb,
                                  const char *module_name,
                                  const struct ldb_module_ops *ops)
{
        struct ldb_module *module;

        module = talloc(memctx, struct ldb_module);
        if (!module) {
                ldb_oom(ldb);
                return NULL;
        }
        talloc_set_name_const(module, module_name);
        module->ldb = ldb;
        module->prev = module->next = NULL;
        module->ops = ops;

        return module;
}

const char * ldb_module_get_name(struct ldb_module *module)
{
        return module->ops->name;
}

struct ldb_context *ldb_module_get_ctx(struct ldb_module *module)
{
        return module->ldb;
}

const struct ldb_module_ops *ldb_module_get_ops(struct ldb_module *module)
{
        return module->ops;
}

void *ldb_module_get_private(struct ldb_module *module)
{
        return module->private_data;
}

void ldb_module_set_private(struct ldb_module *module, void *private_data)
{
        module->private_data = private_data;
}

/*
   helper functions to call the next module in chain
*/

int ldb_next_request(struct ldb_module *module, struct ldb_request *request)
{
        int ret;

        if (request->callback == NULL) {
                ldb_set_errstring(module->ldb, "Requests MUST define callbacks");
                return LDB_ERR_UNWILLING_TO_PERFORM;
        }

        request->handle->nesting++;

        switch (request->operation) {
        case LDB_SEARCH:
                FIND_OP(module, search);
                ret = module->ops->search(module, request);
                break;
        case LDB_ADD:
                FIND_OP(module, add);
                ret = module->ops->add(module, request);
                break;
        case LDB_MODIFY:
                FIND_OP(module, modify);
                ret = module->ops->modify(module, request);
                break;
        case LDB_DELETE:
                FIND_OP(module, del);
                ret = module->ops->del(module, request);
                break;
        case LDB_RENAME:
                FIND_OP(module, rename);
                ret = module->ops->rename(module, request);
                break;
        case LDB_EXTENDED:
                FIND_OP(module, extended);
                ret = module->ops->extended(module, request);
                break;
        default:
                FIND_OP(module, request);
                ret = module->ops->request(module, request);
                break;
        }

        request->handle->nesting--;

        if (ret == LDB_SUCCESS) {
                return ret;
        }
        if (!ldb_errstring(module->ldb)) {
                const char *op;
                switch (request->operation) {
                case LDB_SEARCH:
                        op = "LDB_SEARCH";
                        break;
                case LDB_ADD:
                        op = "LDB_ADD";
                        break;
                case LDB_MODIFY:
                        op = "LDB_MODIFY";
                        break;
                case LDB_DELETE:
                        op = "LDB_DELETE";
                        break;
                case LDB_RENAME:
                        op = "LDB_RENAME";
                        break;
                case LDB_EXTENDED:
                        op = "LDB_EXTENDED";
                        break;
                default:
                        op = "request";
                        break;
                }

                /* Set a default error string, to place the blame somewhere */
                ldb_asprintf_errstring(module->ldb, "error in module %s: %s during %s (%d)", module->ops->name, ldb_strerror(ret), op, ret);
        }

        if (!(request->handle->flags & LDB_HANDLE_FLAG_DONE_CALLED)) {
                /* It is _extremely_ common that a module returns a
                 * failure without calling ldb_module_done(), but that
                 * guarantees we will end up hanging in
                 * ldb_wait(). This fixes it without having to rewrite
                 * all our modules, and leaves us one less sharp
                 * corner for module developers to cut themselves on
                 */
                ret = ldb_module_done(request, NULL, NULL, ret);
        }
        return ret;
}

int ldb_next_init(struct ldb_module *module)
{
        module = module->next;

        return ldb_module_init_chain(module->ldb, module);
}

int ldb_next_start_trans(struct ldb_module *module)
{
        int ret;
        FIND_OP(module, start_transaction);
        ret = module->ops->start_transaction(module);
        if (ret == LDB_SUCCESS) {
                return ret;
        }
        if (!ldb_errstring(module->ldb)) {
                /* Set a default error string, to place the blame somewhere */
                ldb_asprintf_errstring(module->ldb, "start_trans error in module %s: %s (%d)", module->ops->name, ldb_strerror(ret), ret);
        }
        if ((module && module->ldb->flags & LDB_FLG_ENABLE_TRACING)) { 
                ldb_debug(module->ldb, LDB_DEBUG_TRACE, "ldb_next_start_trans error: %s", 
                          ldb_errstring(module->ldb));                          
        }
        return ret;
}

int ldb_next_end_trans(struct ldb_module *module)
{
        int ret;
        FIND_OP(module, end_transaction);
        ret = module->ops->end_transaction(module);
        if (ret == LDB_SUCCESS) {
                return ret;
        }
        if (!ldb_errstring(module->ldb)) {
                /* Set a default error string, to place the blame somewhere */
                ldb_asprintf_errstring(module->ldb, "end_trans error in module %s: %s (%d)", module->ops->name, ldb_strerror(ret), ret);
        }
        if ((module && module->ldb->flags & LDB_FLG_ENABLE_TRACING)) { 
                ldb_debug(module->ldb, LDB_DEBUG_TRACE, "ldb_next_end_trans error: %s", 
                          ldb_errstring(module->ldb));                          
        }
        return ret;
}

int ldb_next_read_lock(struct ldb_module *module)
{
        int ret;
        FIND_OP(module, read_lock);
        ret = module->ops->read_lock(module);
        if (ret == LDB_SUCCESS) {
                return ret;
        }
        if (!ldb_errstring(module->ldb)) {
                /* Set a default error string, to place the blame somewhere */
                ldb_asprintf_errstring(module->ldb,
                                       "read_lock error in module %s: %s (%d)",
                                       module->ops->name, ldb_strerror(ret),
                                       ret);
        }
        if ((module && module->ldb->flags & LDB_FLG_ENABLE_TRACING)) {
                ldb_debug(module->ldb, LDB_DEBUG_TRACE,
                          "ldb_next_read_lock error: %s",
                          ldb_errstring(module->ldb));
        }
        return ret;
}

int ldb_next_read_unlock(struct ldb_module *module)
{
        int ret;
        FIND_OP(module, read_unlock);
        ret = module->ops->read_unlock(module);
        if (ret == LDB_SUCCESS) {
                return ret;
        }
        if (!ldb_errstring(module->ldb)) {
                /* Set a default error string, to place the blame somewhere */
                ldb_asprintf_errstring(module->ldb,
                                       "read_unlock error in module %s: %s (%d)",
                                       module->ops->name, ldb_strerror(ret),
                                       ret);
        }
        if ((module && module->ldb->flags & LDB_FLG_ENABLE_TRACING)) {
                ldb_debug(module->ldb, LDB_DEBUG_TRACE,
                          "ldb_next_read_unlock error: %s",
                          ldb_errstring(module->ldb));
        }
        return ret;
}

int ldb_next_prepare_commit(struct ldb_module *module)
{
        int ret;
        FIND_OP_NOERR(module, prepare_commit);
        if (module == NULL) {
                /* we are allowed to have no prepare commit in
                   backends */
                return LDB_SUCCESS;
        }
        ret = module->ops->prepare_commit(module);
        if (ret == LDB_SUCCESS) {
                return ret;
        }
        if (!ldb_errstring(module->ldb)) {
                /* Set a default error string, to place the blame somewhere */
                ldb_asprintf_errstring(module->ldb, "prepare_commit error in module %s: %s (%d)", module->ops->name, ldb_strerror(ret), ret);
        }
        if ((module && module->ldb->flags & LDB_FLG_ENABLE_TRACING)) { 
                ldb_debug(module->ldb, LDB_DEBUG_TRACE, "ldb_next_prepare_commit error: %s", 
                          ldb_errstring(module->ldb));                          
        }
        return ret;
}

int ldb_next_del_trans(struct ldb_module *module)
{
        int ret;
        FIND_OP(module, del_transaction);
        ret = module->ops->del_transaction(module);
        if (ret == LDB_SUCCESS) {
                return ret;
        }
        if (!ldb_errstring(module->ldb)) {
                /* Set a default error string, to place the blame somewhere */
                ldb_asprintf_errstring(module->ldb, "del_trans error in module %s: %s (%d)", module->ops->name, ldb_strerror(ret), ret);
        }
        if ((module && module->ldb->flags & LDB_FLG_ENABLE_TRACING)) { 
                ldb_debug(module->ldb, LDB_DEBUG_TRACE, "ldb_next_del_trans error: %s", 
                          ldb_errstring(module->ldb));                          
        }
        return ret;
}

/* calls the request callback to send an entry
 *
 * params:
 *      req: the original request passed to your module
 *      msg: reply message (must be a talloc pointer, and it will be stolen
 *           on the ldb_reply that is sent to the callback)
 *      ctrls: controls to send in the reply  (must be a talloc pointer, and it will be stolen
 *           on the ldb_reply that is sent to the callback)
 */

int ldb_module_send_entry(struct ldb_request *req,
                          struct ldb_message *msg,
                          struct ldb_control **ctrls)
{
        struct ldb_reply *ares;

        ares = talloc_zero(req, struct ldb_reply);
        if (!ares) {
                ldb_oom(req->handle->ldb);
                req->callback(req, NULL);
                return LDB_ERR_OPERATIONS_ERROR;
        }
        ares->type = LDB_REPLY_ENTRY;
        ares->message = talloc_steal(ares, msg);
        ares->controls = talloc_steal(ares, ctrls);
        ares->error = LDB_SUCCESS;

        if ((req->handle->ldb->flags & LDB_FLG_ENABLE_TRACING) &&
            req->handle->nesting == 0) {
                char *s;
                struct ldb_ldif ldif;
                
                ldif.changetype = LDB_CHANGETYPE_NONE;
                ldif.msg = discard_const_p(struct ldb_message, msg);

                ldb_debug_add(req->handle->ldb, "ldb_trace_response: ENTRY\n");

                /* 
                 * The choice to call
                 * ldb_ldif_write_redacted_trace_string() is CRITICAL
                 * for security.  It ensures that we do not output
                 * passwords into debug logs 
                 */

                s = ldb_ldif_write_redacted_trace_string(req->handle->ldb, msg, &ldif);
                ldb_debug_add(req->handle->ldb, "%s\n", s);
                talloc_free(s);
                ldb_debug_end(req->handle->ldb, LDB_DEBUG_TRACE);
        }

        return req->callback(req, ares);
}

/* calls the request callback to send an referrals
 *
 * params:
 *      req: the original request passed to your module
 *      ref: referral string (must be a talloc pointer, steal)
 */

int ldb_module_send_referral(struct ldb_request *req,
                                           char *ref)
{
        struct ldb_reply *ares;

        ares = talloc_zero(req, struct ldb_reply);
        if (!ares) {
                ldb_oom(req->handle->ldb);
                req->callback(req, NULL);
                return LDB_ERR_OPERATIONS_ERROR;
        }
        ares->type = LDB_REPLY_REFERRAL;
        ares->referral = talloc_steal(ares, ref);
        ares->error = LDB_SUCCESS;

        if ((req->handle->ldb->flags & LDB_FLG_ENABLE_TRACING) &&
            req->handle->nesting == 0) {
                ldb_debug_add(req->handle->ldb, "ldb_trace_response: REFERRAL\n");
                ldb_debug_add(req->handle->ldb, "ref: %s\n", ref);
                ldb_debug_end(req->handle->ldb, LDB_DEBUG_TRACE);
        }

        return req->callback(req, ares);
}

/* calls the original request callback
 *
 * params:
 *      req:   the original request passed to your module
 *      ctrls: controls to send in the reply (must be a talloc pointer, steal)
 *      response: results for extended request (steal)
 *      error: LDB_SUCCESS for a successful return
 *             any other ldb error otherwise
 */
int ldb_module_done(struct ldb_request *req,
                    struct ldb_control **ctrls,
                    struct ldb_extended *response,
                    int error)
{
        struct ldb_reply *ares;

        ares = talloc_zero(req, struct ldb_reply);
        if (!ares) {
                ldb_oom(req->handle->ldb);
                req->callback(req, NULL);
                return LDB_ERR_OPERATIONS_ERROR;
        }
        ares->type = LDB_REPLY_DONE;
        ares->controls = talloc_steal(ares, ctrls);
        ares->response = talloc_steal(ares, response);
        ares->error = error;

        req->handle->flags |= LDB_HANDLE_FLAG_DONE_CALLED;

        if ((req->handle->ldb->flags & LDB_FLG_ENABLE_TRACING) &&
            req->handle->nesting == 0) {
                ldb_debug_add(req->handle->ldb, "ldb_trace_response: DONE\n");
                ldb_debug_add(req->handle->ldb, "error: %d\n", error);
                if (ldb_errstring(req->handle->ldb)) {
                        ldb_debug_add(req->handle->ldb, "msg: %s\n",
                                  ldb_errstring(req->handle->ldb));
                }
                ldb_debug_end(req->handle->ldb, LDB_DEBUG_TRACE);
        }

        return req->callback(req, ares);
}

/* to be used *only* in modules init functions.
 * this function is synchronous and will register
 * the requested OID in the rootdse module if present
 * otherwise it will return an error */
int ldb_mod_register_control(struct ldb_module *module, const char *oid)
{
        struct ldb_request *req;
        int ret;

        req = talloc_zero(module, struct ldb_request);
        if (req == NULL) {
                return LDB_ERR_OPERATIONS_ERROR;
        }

        req->operation = LDB_REQ_REGISTER_CONTROL;
        req->op.reg_control.oid = oid;
        req->callback = ldb_op_default_callback;

        ldb_set_timeout(module->ldb, req, 0);

        req->handle = ldb_handle_new(req, module->ldb);
        if (req->handle == NULL) {
                return LDB_ERR_OPERATIONS_ERROR;
        }

        ret = ldb_request(module->ldb, req);
        if (ret == LDB_SUCCESS) {
                ret = ldb_wait(req->handle, LDB_WAIT_ALL);
        }
        talloc_free(req);

        return ret;
}

static int ldb_modules_load_dir(const char *modules_dir, const char *version);


/*
  load one module. A static list of loaded module inode numbers is
  used to prevent a module being loaded twice

  dlopen() is used on the module, and dlsym() is then used to look for
  a ldb_init_module() function. If present, that function is called
  with the ldb version number as an argument.

  The ldb_init_module() function will typically call
  ldb_register_module() and ldb_register_backend() to register a
  module or backend, but it may also be used to register command line
  handling functions, ldif handlers or any other local
  modififications.

  The ldb_init_module() function does not get a ldb_context passed in,
  as modules will be used for multiple ldb context handles. The call
  from the first ldb_init() is just a convenient way to ensure it is
  called early enough.
 */
static int ldb_modules_load_path(const char *path, const char *version)
{
        void *handle;
        int (*init_fn)(const char *);
        int ret;
        struct stat st;
        static struct loaded {
                struct loaded *next, *prev;
                ino_t st_ino;
                dev_t st_dev;
        } *loaded;
        struct loaded *le;
        int dlopen_flags;

#ifdef RTLD_DEEPBIND
        bool deepbind_enabled = (getenv("LDB_MODULES_DISABLE_DEEPBIND") == NULL);
#endif

        ret = stat(path, &st);
        if (ret != 0) {
                fprintf(stderr, "ldb: unable to stat module %s : %s\n", path, strerror(errno));
                return LDB_ERR_UNAVAILABLE;
        }

        for (le=loaded; le; le=le->next) {
                if (le->st_ino == st.st_ino &&
                    le->st_dev == st.st_dev) {
                        /* its already loaded */
                        return LDB_SUCCESS;
                }
        }

        le = talloc(loaded, struct loaded);
        if (le == NULL) {
                fprintf(stderr, "ldb: unable to allocated loaded entry\n");
                return LDB_ERR_UNAVAILABLE;
        }

        le->st_ino = st.st_ino;
        le->st_dev = st.st_dev;

        DLIST_ADD_END(loaded, le);

        /* if it is a directory, recurse */
        if (S_ISDIR(st.st_mode)) {
                return ldb_modules_load_dir(path, version);
        }

        dlopen_flags = RTLD_NOW;
#ifdef RTLD_DEEPBIND
        /*
         * use deepbind if possible, to avoid issues with different
         * system library variants, for example ldb modules may be linked
         * against Heimdal while the application may use MIT kerberos.
         *
         * See the dlopen manpage for details.
         *
         * One typical user is the bind_dlz module of Samba,
         * but symbol versioning might be enough...
         *
         * We need a way to disable this in order to allow the
         * ldb_*ldap modules to work with a preloaded socket wrapper.
         *
         * So in future we may remove this completely
         * or at least invert the default behavior.
        */
        if (deepbind_enabled) {
                dlopen_flags |= RTLD_DEEPBIND;
        }
#endif

        handle = dlopen(path, dlopen_flags);
        if (handle == NULL) {
                fprintf(stderr, "ldb: unable to dlopen %s : %s\n", path, dlerror());
                return LDB_SUCCESS;
        }

        init_fn = dlsym(handle, "ldb_init_module");
        if (init_fn == NULL) {
                /* ignore it, it could be an old-style
                 * module. Once we've converted all modules we
                 * could consider this an error */
                dlclose(handle);
                return LDB_SUCCESS;
        }

        ret = init_fn(version);
        if (ret == LDB_ERR_ENTRY_ALREADY_EXISTS) {
                /* the module is already registered - ignore this, as
                 * it can happen if LDB_MODULES_PATH points at both
                 * the build and install directory
                 */
                ret = LDB_SUCCESS;
        }
        return ret;
}

static int qsort_string(const char **s1, const char **s2)
{
        return strcmp(*s1, *s2);
}


/*
  load all modules from the given ldb modules directory. This is run once
  during the first ldb_init() call.

  Modules are loaded in alphabetical order to ensure that any module
  load ordering dependencies are reproducible. Modules should avoid
  relying on load order
 */
static int ldb_modules_load_dir(const char *modules_dir, const char *version)
{
        DIR *dir;
        struct dirent *de;
        const char **modlist = NULL;
        TALLOC_CTX *tmp_ctx = talloc_new(NULL);
        unsigned i, num_modules = 0;

        dir = opendir(modules_dir);
        if (dir == NULL) {
                if (errno == ENOENT) {
                        talloc_free(tmp_ctx);
                        /* we don't have any modules */
                        return LDB_SUCCESS;
                }
                talloc_free(tmp_ctx);
                fprintf(stderr, "ldb: unable to open modules directory '%s' - %s\n",
                        modules_dir, strerror(errno));
                return LDB_ERR_UNAVAILABLE;
        }


        while ((de = readdir(dir))) {
                if (ISDOT(de->d_name) || ISDOTDOT(de->d_name))
                        continue;

                modlist = talloc_realloc(tmp_ctx, modlist, const char *, num_modules+1);
                if (modlist == NULL) {
                        talloc_free(tmp_ctx);
                        closedir(dir);
                        fprintf(stderr, "ldb: unable to allocate modules list\n");
                        return LDB_ERR_UNAVAILABLE;
                }
                modlist[num_modules] = talloc_asprintf(modlist, "%s/%s", modules_dir, de->d_name);
                if (modlist[num_modules] == NULL) {
                        talloc_free(tmp_ctx);
                        closedir(dir);
                        fprintf(stderr, "ldb: unable to allocate module list entry\n");
                        return LDB_ERR_UNAVAILABLE;
                }
                num_modules++;
        }

        closedir(dir);

        /* sort the directory, so we get consistent load ordering */
        TYPESAFE_QSORT(modlist, num_modules, qsort_string);

        for (i=0; i<num_modules; i++) {
                int ret = ldb_modules_load_path(modlist[i], version);
                if (ret != LDB_SUCCESS) {
                        fprintf(stderr, "ldb: failed to initialise module %s : %s\n",
                                modlist[i], ldb_strerror(ret));
                        talloc_free(tmp_ctx);
                        return ret;
                }
        }

        talloc_free(tmp_ctx);

        return LDB_SUCCESS;
}

/* 
   load any additional modules from the given directory 
*/
void ldb_set_modules_dir(struct ldb_context *ldb, const char *path)
{
        int ret = ldb_modules_load_path(path, LDB_VERSION);
        if (ret != LDB_SUCCESS) {
                ldb_asprintf_errstring(ldb, "Failed to load modules from: %s\n", path);
        }
}


/*
  load all modules static (builtin) modules
 */
static int ldb_modules_load_static(const char *version)
{
        static bool initialised;
#define _MODULE_PROTO(init) extern int init(const char *);
        STATIC_ldb_MODULES_PROTO;
        const ldb_module_init_fn static_init_functions[] = { STATIC_ldb_MODULES };
        unsigned i;

        if (initialised) {
                return LDB_SUCCESS;
        }
        initialised = true;

        for (i=0; static_init_functions[i]; i++) {
                int ret = static_init_functions[i](version);
                if (ret != LDB_SUCCESS) {
                        return ret;
                }
        }
        return LDB_SUCCESS;
}

/*
  load all modules from the given ldb modules path, colon
  separated.

  modules are loaded recursively for all subdirectories in the paths
 */
int ldb_modules_load(const char *modules_path, const char *version)
{
        char *tok, *path, *tok_ptr=NULL;
        int ret;

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

        path = talloc_strdup(NULL, modules_path);
        if (path == NULL) {
                fprintf(stderr, "ldb: failed to allocate modules_path\n");
                return LDB_ERR_UNAVAILABLE;
        }

        for (tok=strtok_r(path, ":", &tok_ptr);
             tok;
             tok=strtok_r(NULL, ":", &tok_ptr)) {
                ret = ldb_modules_load_path(tok, version);
                if (ret != LDB_SUCCESS) {
                        talloc_free(path);
                        return ret;
                }
        }
        talloc_free(path);

        return LDB_SUCCESS;
}


/*
  return a string representation of the calling chain for the given
  ldb request
 */
char *ldb_module_call_chain(struct ldb_request *req, TALLOC_CTX *mem_ctx)
{
        char *ret;
        unsigned int i = 0;

        ret = talloc_strdup(mem_ctx, "");
        if (ret == NULL) {
                return NULL;
        }

        while (req && req->handle) {
                char *s = talloc_asprintf_append_buffer(ret, "req[%u] %p  : %s\n",
                                                        i++, req, ldb_req_location(req));
                if (s == NULL) {
                        talloc_free(ret);
                        return NULL;
                }
                ret = s;
                req = req->handle->parent;
        }
        return ret;
}


/*
  return the next module in the chain
 */
struct ldb_module *ldb_module_next(struct ldb_module *module)
{
        return module->next;
}

/*
  set the next module in the module chain
 */
void ldb_module_set_next(struct ldb_module *module, struct ldb_module *next)
{
        module->next = next;
}


/*
  get the popt_options pointer in the ldb structure. This allows a ldb
  module to change the command line parsing
 */
struct poptOption **ldb_module_popt_options(struct ldb_context *ldb)
{
        return &ldb->popt_options;
}


/*
  return the current ldb flags LDB_FLG_*
 */
uint32_t ldb_module_flags(struct ldb_context *ldb)
{
        return ldb->flags;
}