rtlink消息内存布局如下：

RTM_NEWLINK, RTM_DELLINK, RTM_GETLINK消息示例:
(规则: 每个 "|" 都需要4字节对齐)

+-----------------------------------------------------------------------------------------+
| struct nlmsghdr |  struct ifinfomsg | struct rtattr | data | struct rtattr | data | ... |
+-----------------------------------------------------------------------------------------+


+----------------------------------------------+
|     netlink socket 数据报(原始数据)            |
+----------------------------------------------+
|           netlink msg                        |
+-----------------+----------------------------+
| struct nlmsghdr |  netlink data              |
+-----------------+----------------------------+
                  |                            |
          +--> 对齐                     +--> 对齐

+----------------------------------------------+
|             netlink data                     |
+----------------------------------------------+
|             rtnetlink msg                    |
+------------------+---------------------------+
| struct ifinfomsg | rtnetlink data            |
+------------------+---------------------------+
                   |                           |
                   +--> 对齐                    +-->对齐


+---------------------------------------------------+
|             rtnetlink data                        |
+---------------+------+---------------+------+-----+
| struct rtattr | data | struct rtattr | data | ... |
+---------------+------+---------------+------+-----+
                |      |               |      |     |
                |      |               |      |     +-->对齐
                |      |               |      +--> 对齐
                |      |               +-->对齐     
                |      +--> 对齐
                +--> 对齐

图片格式防止乱码

rtnetlink消息和netlink消息关系_rtnetlink