Network link detection

["Nico Schümann" <dev@nico22.de>]

Dear kernel developers,

currently I'm looking for a way to find out whether a network link went 
down or up. Of course there is mii-tool, which can watch devices, too.

So for now, I created a small program that polls the MII_LINK_OK
flag with the SIOCGMIIREG ioctl - the same thing that mii-tools does. 
But polling that often for a link change that occurs maybe once in a 
month sounds like waste of energy.

Unfortunately, I was not able to find out a way to be notified about 
link status changes asynchronously. Is there a way? I'm looking for 
something like "inotify for link states".

There are some debug outputs as in drivers/net/natsemi.c:1672
                        printk(KERN_NOTICE "%s: link up.\n", dev->name);
so it would be quite easy to insert a notification.

If there is no way yet to get these notifications asynchronosly, would 
there be real use for it or am I just missing something?

Thanks,

Nico