Re: Detecting link up

Baruch Even
2005-05-18T22:26:07Z

Stephen Hemminger wrote:
> 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.

And libnl is a very good library to get just that information without
the need to manually parse netlink messages.

Baruch