network_stats() - 返回网络连接相关数据统计

mapping network_stats();

返回网络相关数据统计的映射，内容如下：

- incoming packets total : int
- incoming volume total : int
- outgoing packets total : int
- outgoing volume total : int

- incoming packets port X : int
- incoming volume port X : int
- outgoing packets port X : int
- outgoing volume port X : int

如果驱动编译时定义了 PACKAGE_SOCKETS，还会有以下内容：

- incoming packets sockets : int
- incoming volume sockets : int
- outgoing packets sockets : int
- outgoing volume sockets : int

雪风(i@mud.ren)