使用netlink之前，先参考一下资料：http://www.ibm.com/developerworks/cn/linux/l-connector/
netlink通信机制介绍：资料来源 linux-4.8.13/Documentation/connector/connector.txt 2016-12-10 21:31:04
/*****************************************/
Kernel Connector.
/*****************************************/
Kernel connector - new netlink based userspace <-> kernel space easy
to use communication module.
The Connector driver makes it easy to connect various agents using a
netlink based network. One must register a callback and an identifier.
When the driver receives a special netlink message with the appropriate
identifier, the appropriate callback will be called.
From the userspace point of view it's quite straightforward:
socket();
bind();
send();
recv();
