detecting network change.

[Tim Woodall <debianuser@woodall.me.uk>]

Is there a portable (not specific to how networking is configured) way 
of detecting a network change and forcing ssh to close.

At work I have an ubuntu laptop, when at my desk I'm using wired 
connection, when I go to a meeting it switches to wifi.

All my ssh sessions hang when this happens. Obviously, I can close them 
with <cr>~. and then reconnect, but I'm wondering if there's a neat way 
to automate the disconnect? Sometimes I'm waiting for a job to finish 
and the terminal never updates because nothing tries to transmit. It 
might be hours before I notice because I'm missing that flicker when 
something happens.

(I'm using screen to reestablish the session, that part is all working, 
it's just the explicit disconnect I want to automate)