- Added generic flood control mechanism to throttle certain operations per hostname (eg. posting comments, requesting passwords, sending e-mails).  See flood_register_event() and flood_is_allowed() for details.

CHANGELOG.txt

@@ -9,8 +9,11 @@ Drupal x.x.x, xxxx-xx-xx
     * improved search output.
 - syndication:
     * added support for RSS ping-notifications of http://technorati.com/.
+- flood control mechanism:
+    * added a mechanism to throttle certain operations.
 - usability:
     * refactored the throttle module configuration.
+    * added a 'add child page' link to book pages.
 - performance:
     * improved performance of the tracker module.
 

includes/common.inc

@@ -669,6 +669,33 @@ function valid_input_data($data) {
  * @} End of "defgroup validation".
  */
 
+/**
+ * Register an event for the current visitor (hostname/IP) to the flood control mechanism.
+ *
+ * @param $name
+ *   The name of the event.
+ */
+function flood_register_event($name) {
+  db_query("INSERT INTO {flood} (event, hostname, timestamp) VALUES ('%s', '%s', %d)", $name, $_SERVER['REMOTE_ADDR'], time());
+}
+
+/**
+ * Check if the current visitor (hostname/IP) is allowed to proceed with the specified event.
+ * The user is allowed to proceed if he did not trigger the specified event more than
+ * $threshold times per hour.
+ *
+ * @param $name
+ *   The name of the event.
+ * @param $number
+ *   The maximum number of the specified event per hour (per visitor).
+ * @return
+ *   True if the user did not exceed the hourly threshold.  False otherwise.
+ */
+function flood_is_allowed($name, $threshold) {
+  $number = db_num_rows(db_query("SELECT event FROM {flood} WHERE event = '%s' AND hostname = '%s' AND timestamp > %d", $name, $_SERVER['REMOTE_ADDR'], time() - 3600));
+  return ($number < $threshold ? TRUE : FALSE);
+}
+
 function check_form($text) {
   return drupal_specialchars($text, ENT_QUOTES);
 }

modules/watchdog.module

@@ -71,10 +71,11 @@ function watchdog_perm() {
 /**
  * Implementation of hook_cron().
  *
- * Remove expired log messages.
+ * Remove expired log messages and flood control events.
  */
 function watchdog_cron() {
   db_query('DELETE FROM {watchdog} WHERE timestamp < %d', time() - variable_get('watchdog_clear', 604800));
+  db_query('DELETE FROM {flood} WHERE timestamp < %d', time() - 3600);
 }
 
 /**

modules/watchdog/watchdog.module

@@ -71,10 +71,11 @@ function watchdog_perm() {
 /**
  * Implementation of hook_cron().
  *
- * Remove expired log messages.
+ * Remove expired log messages and flood control events.
  */
 function watchdog_cron() {
   db_query('DELETE FROM {watchdog} WHERE timestamp < %d', time() - variable_get('watchdog_clear', 604800));
+  db_query('DELETE FROM {flood} WHERE timestamp < %d', time() - 3600);
 }
 
 /**