session recovery on change of IP

[David Woodhouse]

On Fri, 2003-04-11 at 14:32, John Sutton wrote:
> I can't see how using screen gets me any further?  Surely screen just
> allows multiple sessions multiplexed into one tty stream (badly put but
> I think I know what I mean ;-).  End result will be that *all* the
> sessions get broken on a change of IP?  

I think someone answered this already.

> This is an intriguing notion... Markus Friedl (see other post) has
> suggested the same.  I have limited experience with tunnelling protocols
> (I messed around with pptp bewteen linux and windoze boxes some years ago)
> but I can't immediately see how this could work.  Surely to set up an IP
> tunnel of any sort you have got to have two "fixed" endpoints?

Well you want your peer to be fixed obviously since that's the whole
point in the exercise, but as long as they can find each other there's
no fundamental requirement for tunnel endpoints to be fixed.

> OTOH, I can see how you *might* have a "lightweight, non-encrypted"
> tunnelling protocol which *is* impervious to change of IP.  Then you could
> run an ssh session through this tunnel.  Quite how the server end of the
> tunnel would recognise that this "new" connection was actually an existing
> connection which had changed it's IP and therefore be able to tie the 2
> ends back together, I don't know...

You just need to connect your ssh's proxycommand to a 'sshd -i'
somewhere, or to a fixed-ip box from which you use netcat. Variations on
the theme of...

ssh -o "proxycommand sshd -i" localhost
ssh -o "proxycommand my-magic-rsh %h exec sshd -i" anywhere
ssh -o "proxycommand my-magic-rsh-to-fixed-ip-box netcat %h %p" anywhere

> How expensive is that?  The minimum I've found is £51+vat per month (for
> 300 hours per month) single channel ISDN.  I consider this *too* expensive
> so I've gone back to using a dynamic dialup for £11+vat ;-(

Demon 'Premier Connect Plus' and BT SurfTime Anytime -- £20 to each
party, giving permanent dialup at a static IP address for £40. (That's
~$60 USD for the benefit of the peanut gallery who just want to laugh at
how expensive Internet connectivity is in the UK :)

-- 
dwmw2