在linux上获取NIC /以太网卡链接状态的事件

Question

Is there any API(or special file) on Linux that provides an event on the change in link status of an ethernet card without polling ? ie when you plug in/out the cable ?

Answer 1

如果此文件/sys/class/net/eth0/carrier为1，则接口eth0具有carrier。

Answer 2

You can get link up/down events via netlink. You would create a PF_NETLINK socket, bind to the RTMGRP_LINK group, and wait for RTM_NEWLINK / RTM_DELLINK messages. Link up events have IFF_RUNNING and IFF_LOWER_UP set in ifinfomsg.flags , while link down events have both flags cleared (funnily enough, I'm getting RTM_NEWLINK messages for both type of events).