s4:dsdb: add dsdb_notification module

This adds a simple implementation of LDB_CONTROL_NOTIFICATION_OID.
It requires caller (the ldap server task) to retry the request peridically,
using the same ldb_control structure in order to get some progress and
the never ending search behaviour an LDAP client expects.

For now we remember the known_usn in a cookie stored
in the otherwise unused ldb_control->data fielf
and we do a simple search using (uSNChanged>=${known_usn}+1).

In future we may do things based on the uSNChanged value.

for (i = old_highest + 1; i <= current_highest; i) {
	search for (uSNChanged=i)
}

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Garming Sam <garming@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

source4/dsdb/samdb/ldb_modules/dsdb_notification.c

@@ -0,0 +1,262 @@
+/*
+   notification control module
+
+   Copyright (C) Stefan Metzmacher 2015
+
+   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/>.
+*/
+
+
+#include "includes.h"
+#include "ldb/include/ldb.h"
+#include "ldb/include/ldb_errors.h"
+#include "ldb/include/ldb_module.h"
+#include "dsdb/samdb/samdb.h"
+#include "dsdb/samdb/ldb_modules/util.h"
+
+struct dsdb_notification_cookie {
+	uint64_t known_usn;
+};
+
+static int dsdb_notification_verify_tree(struct ldb_parse_tree *tree)
+{
+	unsigned int i;
+	int ret;
+	unsigned int num_ok = 0;
+	/*
+	 * these attributes are present on every object
+	 * and windows accepts them.
+	 *
+	 * While [MS-ADTS] says only '(objectClass=*)'
+	 * would be allowed.
+	 */
+	static const char * const attrs_ok[] = {
+		"objectClass",
+		"objectGUID",
+		"distinguishedName",
+		"name",
+		NULL,
+	};
+
+	switch (tree->operation) {
+	case LDB_OP_AND:
+		for (i = 0; i < tree->u.list.num_elements; i++) {
+			/*
+			 * all elements need to be valid
+			 */
+			ret = dsdb_notification_verify_tree(tree->u.list.elements[i]);
+			if (ret != LDB_SUCCESS) {
+				return ret;
+			}
+			num_ok++;
+		}
+		break;
+	case LDB_OP_OR:
+		for (i = 0; i < tree->u.list.num_elements; i++) {
+			/*
+			 * at least one element needs to be valid
+			 */
+			ret = dsdb_notification_verify_tree(tree->u.list.elements[i]);
+			if (ret == LDB_SUCCESS) {
+				num_ok++;
+				break;
+			}
+		}
+		break;
+	case LDB_OP_NOT:
+	case LDB_OP_EQUALITY:
+	case LDB_OP_GREATER:
+	case LDB_OP_LESS:
+	case LDB_OP_APPROX:
+	case LDB_OP_SUBSTRING:
+	case LDB_OP_EXTENDED:
+		break;
+
+	case LDB_OP_PRESENT:
+		ret = ldb_attr_in_list(attrs_ok, tree->u.present.attr);
+		if (ret == 1) {
+			num_ok++;
+		}
+		break;
+	}
+
+	if (num_ok != 0) {
+		return LDB_SUCCESS;
+	}
+
+	return LDB_ERR_UNWILLING_TO_PERFORM;
+}
+
+static int dsdb_notification_filter_search(struct ldb_module *module,
+					  struct ldb_request *req,
+					  struct ldb_control *control)
+{
+	struct ldb_context *ldb = ldb_module_get_ctx(module);
+	char *filter_usn = NULL;
+	struct ldb_parse_tree *down_tree = NULL;
+	struct ldb_request *down_req = NULL;
+	struct dsdb_notification_cookie *cookie = NULL;
+	int ret;
+
+	if (req->op.search.tree == NULL) {
+		return dsdb_module_werror(module, LDB_ERR_OTHER,
+					  WERR_DS_NOTIFY_FILTER_TOO_COMPLEX,
+					  "Search filter missing.");
+	}
+
+	ret = dsdb_notification_verify_tree(req->op.search.tree);
+	if (ret != LDB_SUCCESS) {
+		return dsdb_module_werror(module, ret,
+					  WERR_DS_NOTIFY_FILTER_TOO_COMPLEX,
+					  "Search filter too complex.");
+	}
+
+	/*
+	 * For now we use a very simple design:
+	 *
+	 * - We don't do fully async ldb_requests,
+	 *   the caller needs to retry periodically!
+	 * - The only useful caller is the LDAP server, which is a long
+	 *   running task that can do periodic retries.
+	 * - We use a cookie in order to transfer state between the
+	 *   retries.
+	 * - We just search the available new objects each time we're
+	 *   called.
+	 *
+	 * As the only valid search filter is '(objectClass=*)' or
+	 * something similar that matches every object, we simply
+	 * replace it with (uSNChanged >= ) filter.
+	 * We could improve this later if required...
+	 */
+
+	/*
+	 * The ldap_control_handler() decode_flag_request for
+	 * LDB_CONTROL_NOTIFICATION_OID. This makes sure
+	 * notification_control->data is NULL when comming from
+	 * the client.
+	 */
+	if (control->data == NULL) {
+		cookie = talloc_zero(control, struct dsdb_notification_cookie);
+		if (cookie == NULL) {
+			return ldb_module_oom(module);
+		}
+		control->data = (uint8_t *)cookie;
+
+		/* mark the control as done */
+		control->critical = 0;
+	}
+
+	cookie = talloc_get_type_abort(control->data,
+				       struct dsdb_notification_cookie);
+
+	if (cookie->known_usn != 0) {
+		filter_usn = talloc_asprintf(req, "%llu",
+				(unsigned long long)(cookie->known_usn)+1);
+		if (filter_usn == NULL) {
+			return ldb_module_oom(module);
+		}
+	}
+
+	ret = ldb_sequence_number(ldb, LDB_SEQ_HIGHEST_SEQ,
+				  &cookie->known_usn);
+	if (ret != LDB_SUCCESS) {
+		return ret;
+	}
+
+	if (filter_usn == NULL) {
+		/*
+		 * It's the first time, let the caller comeback later
+		 * as we won't find any new objects.
+		 */
+		return ldb_request_done(req, LDB_SUCCESS);
+	}
+
+	down_tree = talloc_zero(req, struct ldb_parse_tree);
+	if (down_tree == NULL) {
+		return ldb_module_oom(module);
+	}
+	down_tree->operation = LDB_OP_GREATER;
+	down_tree->u.equality.attr = "uSNChanged";
+	down_tree->u.equality.value = data_blob_string_const(filter_usn);
+	talloc_move(down_req, &filter_usn);
+
+	ret = ldb_build_search_req_ex(&down_req, ldb, req,
+				      req->op.search.base,
+				      req->op.search.scope,
+				      down_tree,
+				      req->op.search.attrs,
+				      req->controls,
+				      req, dsdb_next_callback,
+				      req);
+	LDB_REQ_SET_LOCATION(down_req);
+	if (ret != LDB_SUCCESS) {
+		return ret;
+	}
+
+	/* perform the search */
+	return ldb_next_request(module, down_req);
+}
+
+static int dsdb_notification_search(struct ldb_module *module, struct ldb_request *req)
+{
+	struct ldb_control *control = NULL;
+
+	if (ldb_dn_is_special(req->op.search.base)) {
+		return ldb_next_request(module, req);
+	}
+
+	/*
+	 * check if there's an extended dn control
+	 */
+	control = ldb_request_get_control(req, LDB_CONTROL_NOTIFICATION_OID);
+	if (control == NULL) {
+		/* not found go on */
+		return ldb_next_request(module, req);
+	}
+
+	return dsdb_notification_filter_search(module, req, control);
+}
+
+static int dsdb_notification_init(struct ldb_module *module)
+{
+	int ret;
+
+	ret = ldb_mod_register_control(module, LDB_CONTROL_NOTIFICATION_OID);
+	if (ret != LDB_SUCCESS) {
+		struct ldb_context *ldb = ldb_module_get_ctx(module);
+
+		ldb_debug(ldb, LDB_DEBUG_ERROR,
+			"notification: Unable to register control with rootdse!\n");
+		return ldb_module_operr(module);
+	}
+
+	return ldb_next_init(module);
+}
+
+static const struct ldb_module_ops ldb_dsdb_notification_module_ops = {
+	.name		   = "dsdb_notification",
+	.search            = dsdb_notification_search,
+	.init_context	   = dsdb_notification_init,
+};
+
+/*
+  initialise the module
+ */
+_PUBLIC_ int ldb_dsdb_notification_module_init(const char *version)
+{
+	int ret;
+	LDB_MODULE_CHECK_VERSION(version);
+	ret = ldb_register_module(&ldb_dsdb_notification_module_ops);
+	return ret;
+}

source4/dsdb/samdb/ldb_modules/wscript_build_server

@@ -365,6 +365,15 @@ bld.SAMBA_MODULE('ldb_dirsync',
 	deps='talloc samba-security samdb DSDB_MODULE_HELPERS'
 	)
 
+bld.SAMBA_MODULE('ldb_dsdb_notification',
+	source='dsdb_notification.c',
+	subsystem='ldb',
+	init_function='ldb_dsdb_notification_module_init',
+	module_init_name='ldb_init_module',
+	internal_module=False,
+	deps='talloc samba-security samdb DSDB_MODULE_HELPERS'
+	)
+
 bld.SAMBA_MODULE('ldb_dns_notify',
 	source='dns_notify.c',
 	subsystem='ldb',