Re: network status change issue...

[Marcel Holtmann <marcel holtmann org>]

Hi Dan,

> > I am currently having issues with Network Manager. Whenever I unplug
> > the ethernet cable Network Manager picks up on the fact it is
> > disconnected. Then it tries to connect to whatever wifi connections I
> > have setup. This works properly. The issue I am running into is
> > whenever I plug back in the active network cable Network Manager
> > continues to see the ethernet card as disconnected. I have to either
> > restart Network Manager or at least uncheck Enable Networking and
> > recheck it in the Network Manager menu. Only after I do that does
> 
> This says that the carrier detection logic with netlink may not be
> working properly.  Can you check /sys/class/net/<interface>/carrier
> after you plug it back in, and what that says?  If it's '1', then
> proceed to the next step here.  If it's '0', then it's a driver problem
> in the kernel.
> 
> If carrier is '1', then it could be a problem with netlink carrier
> events being delivered to NM.  You'll want to poke around in the NM
> source in src/nm-netlink-monitor.c, in the
> netlink_object_message_handler() function, and put some debugging prints
> in there to see what's going on.  We're especially interested in the
> 'flags' variable is at this point, and whether it's IFF_UP or
> IFF_LOWER_UP or what.

actually just calling "ip link" after plugging in that cable would be
enough. It shows the proper flags.

Jonathan, you might be running an old version of NM that uses IFF_UP for
carrier detection and that is wrong (not an obvious bug, but neverless a
bug). For detecting carrier changes via interface flags, IFF_LOWER_UP
should be used.

Regards

Marcel