ping: unknown host www.google.com (wireless problem)
 

The subject problem often happens (wireless, ifup method), and then I open a konsole, and run:

/etc/rc.d/network restart

and dns resolution works again.

Why does not it work this way (being called from a desktop shortcut)?:
xdg-su -c "/etc/rc.d/network restart"

If I run network restart by xdg-su, then dns resolution only works in the xdg-su window, and nowhere else. Should I export some environment variables, maybe? Which ones?

P.S.
Why do I have to restart the network from time to time to keep it alive?
If the network is idle for some time, or a single, big file is downloaded, the wireless link tends to break after some minutes. But, when I download a hundred thousand small files for days, the network stays alive for days. Why?

Are you connected to a router that has a choice for smart connect or something like that?

Maybe cause of this?

xdg-su provides a graphical dialog that prompts the user for a password to run command as user or as root if no user was specified.

xdg-su is for use inside a desktop session only.

"If I run network restart by xdg-su, then dns resolution only works in the xdg-su window, and nowhere else."

The above is the main problem.
It means that if xdg-su starts "network restart", followed by a ping, then that ping will be OK; name resolution works.

But: if I ping in other konsole windows simultaneously, or subsequently, those pings will not work: "unknown hostname". Why?