Detecting ethernet gadget connections

Helge Hafting helge.hafting at hist.no
Fri Mar 6 11:04:40 CET 2009


Daniel Benoy wrote:
> I'm working on a script that will detect which network interfaces are connected and mess with the routing accordingly, but I'm having trouble detecting whether my USB ethernet gadget connection is up or down.
> 
> ----
> ethtool when it's up:
> lisa:~# ethtool usb0
> Settings for usb0:
> 	Link detected: yes
> 
> ethtool when it's down:
> lisa:~# ethtool usb0
> Settings for usb0:
> 	Link detected: yes
> ----
> 
> Unlike on the host side, the usb0 interface doesn't appear and disappear, allowing udev scripts to bring up/down the interface.
> 
> Anyone know if there's a way to detect that a network connection has actually been established?
> 

Is this necessary?
Just set a higher metric on usb0, then routes thorough eth0 will be 
preferred when available. The default route through usb0 will only be 
used as a last resort when there is no other way.

Such a setup works very well on my laptop. It doesn't on the freerunner 
yet, because the "ip" utility in busybox currently can't set metrics. 
But port that (or use debian with its binary ip utility) and you'll be 
fine.

Helge Hafting




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