db_flatstore: Fix another race condition around MI 'flat_rotate'

This race condition was related to invoking 'flat_rotate' 2+ times
during the same second (UNIX timestamp).  Due to the way the
timestamping logic was implemented, this could lead to files NOT being
rotated at all on the 2nd 'flat_rotate', which falls in the same second.

Although very rare, this race condition could lead to massive CDR loss,
since all CDRs between 2nd and 3rd 'flat_rotate' commands have a great
chance of being fully lost (unread and discarded).

(cherry picked from commit e180b15)

modules/db_flatstore/flat_mi.c

@@ -30,10 +30,8 @@ rw_lock_t *rotate_lock;
 mi_response_t *mi_flat_rotate_cmd(const mi_params_t *params,
 								struct mi_handler *async_hdl)
 {
-	time_t now = time(NULL);
-
 	lock_start_write(rotate_lock);
-	*flat_rotate = now;
+	(*flat_rotate)++;
 	lock_stop_write(rotate_lock);
 
 	return init_mi_result_ok();

modules/db_flatstore/flatstore.c

@@ -339,9 +339,9 @@ int flat_db_insert(const db_con_t* h, const db_key_t* k, const db_val_t* v,
 
 	lock_start_read(rotate_lock);
 
-	if (local_timestamp < *flat_rotate) {
+	if (my_rotate < *flat_rotate) {
 		flat_rotate_logs();
-		local_timestamp = *flat_rotate;
+		my_rotate = *flat_rotate;
 	}
 
 	if ( !h || !CON_TAIL(h) || (f=CON_FILE(h))==NULL ) {

modules/db_flatstore/flatstore_mod.c

@@ -73,12 +73,10 @@ str flat_prefix_s = {0,0};
 pv_elem_t *flat_prefix = NULL;
 
 /*
- * Timestamp of the last log rotation request from
- * the FIFO interface
+ * Counter for the last log rotation request from the MI interface
  */
-time_t* flat_rotate;
-
-time_t local_timestamp;
+unsigned long long *flat_rotate;
+unsigned long long my_rotate;
 
 /*
  * Flatstore database module interface
@@ -141,14 +139,12 @@ static int mod_init(void)
 		return -1;
 	}
 
-	flat_rotate = (time_t*)shm_malloc(sizeof(time_t));
+	flat_rotate = shm_malloc(sizeof *flat_rotate);
 	if (!flat_rotate) {
 		LM_ERR("no shared memory left\n");
 		return -1;
 	}
-
-	*flat_rotate = time(0);
-	local_timestamp = *flat_rotate;
+	*flat_rotate = 0;
 
 	if (!(rotate_lock = lock_init_rw())) {
 		LM_ERR("oom\n");
@@ -176,7 +172,7 @@ static int mod_init(void)
 
 static void mod_destroy(void)
 {
-	if (flat_rotate) shm_free(flat_rotate);
+	shm_free(flat_rotate);
 }
 
 

modules/db_flatstore/flatstore_mod.h

@@ -51,17 +51,16 @@ extern char* flat_delimiter;
 
 
 /*
- * The timestamp of log rotation request from
- * the FIFO interface
+ * Counter for the last log rotation request from the MI interface
  */
-extern time_t* flat_rotate;
+extern unsigned long long *flat_rotate;
 
 
 /*
- * Local timestamp marking the time of the
+ * Local counter marking the time of the
  * last log rotation in the process
  */
-extern time_t local_timestamp;
+extern unsigned long long my_rotate;
 
 
 /*