database: Add support for serializable transactions

src/libstrongswan/database/database.h

@@ -115,6 +115,10 @@ struct database_t {
 	/**
 	 * Start a transaction.
 	 *
+	 * A serializable transaction forces a strict separation between other
+	 * transactions.  Due to the performance overhead they should only be used
+	 * in certain situations (e.g. SELECT->INSERT|UPDATE).
+	 *
 	 * @note Either commit() or rollback() has to be called to end the
 	 * transaction.
 	 * @note Transactions are thread-specific. So commit()/rollbak() has to be
@@ -124,9 +128,10 @@ struct database_t {
 	 * not supported.  So if any if the "inner" transactions are rolled back
 	 * the outer most transaction is rolled back.
 	 *
-	 * @return			TRUE on success
+	 * @param serializable	TRUE to create a serializable transaction
+	 * @return				TRUE on success
 	 */
-	bool (*transaction)(database_t *this);
+	bool (*transaction)(database_t *this, bool serializable);
 
 	/**
 	 * Commit all changes made during the current transaction.

src/libstrongswan/plugins/mysql/mysql_database.c

@@ -652,7 +652,7 @@ METHOD(database_t, execute, int,
 }
 
 METHOD(database_t, transaction, bool,
-	private_mysql_database_t *this)
+	private_mysql_database_t *this, bool serializable)
 {
 	transaction_t *trans = NULL;
 	conn_t *conn;
@@ -669,6 +669,17 @@ METHOD(database_t, transaction, bool,
 	}
 	/* these statements are not supported in prepared statements that are used
 	 * by the execute() method */
+	if (serializable)
+	{
+		if (mysql_query(conn->mysql,
+						"SET TRANSACTION ISOLATION LEVEL SERIALIZABLE") != 0)
+		{
+			DBG1(DBG_LIB, "starting transaction failed: %s",
+				 mysql_error(conn->mysql));
+			conn_release(this, conn);
+			return FALSE;
+		}
+	}
 	if (mysql_query(conn->mysql, "START TRANSACTION") != 0)
 	{
 		DBG1(DBG_LIB, "starting transaction failed: %s",

src/libstrongswan/plugins/sqlite/sqlite_database.c

@@ -305,9 +305,11 @@ METHOD(database_t, execute, int,
 }
 
 METHOD(database_t, transaction, bool,
-	private_sqlite_database_t *this)
+	private_sqlite_database_t *this, bool serializable)
 {
 	transaction_t *trans;
+	char *cmd = serializable ? "BEGIN EXCLUSIVE TRANSACTION"
+							 : "BEGIN TRANSACTION";
 
 	trans = this->transaction->get(this->transaction);
 	if (trans)
@@ -315,7 +317,7 @@ METHOD(database_t, transaction, bool,
 		ref_get(&trans->refs);
 		return TRUE;
 	}
-	if (execute(this, NULL, "BEGIN EXCLUSIVE TRANSACTION") == -1)
+	if (execute(this, NULL, cmd) == -1)
 	{
 		return FALSE;
 	}