Re: Detecting link up

Stephen Hemminger
2005-05-18T18:21:27Z

Filipe Abrantes wrote:
> Hi all,
>
> I need to detect when an interface (wired ethernet) has link up/down. Is
> there a system signal which is sent when this happens? What is the best
> way to this programatically?
>
> Best Regards
>
> Filipe
>
>

The best way is to open a netlink socket and look for the mesaages about
link up/down there. Read iproute2 http://developer.osdl.org/dev/iproute2
source for ip command (ipmonitor.c).

This works for almost all devices unlike ethtool and mii which only
work on a small subset of devices.