Reconnect possibilities (was Re: telnet and SIGHUP)

[Jay R. Ashworth]

On Thu, Jun 17, 2004 at 04:15:23PM -0700, Bob Rasmussen wrote:
> This topic brings to mind an idea I have kicked around for some time.
> Suppose I have telnetted or SSH'd into a Linux/Unix server over a wireless
> access point from my laptop. I move around the office complex, and lose my
> connection.
> 
> At some point later I link up with a new WAP, maybe get a new IP address,
> and then connect back in to the same server. What I WANT is to be able to
> reconnect to my previous session, which has been carefully suspended at
> the point of the disconnect. Of course, authentication would have to take
> place.
> 
> I believe I could create a protocol for doing this, and modify the SSHD
> program from, say, OpenSSH.

You don't need to: if you're VPN'd in, then the session should pick
back up, as long as you are *not* using keepalives, and the host didn't
try to talk to you (nor the other way around) while the session's
transport was invalid.

Invalid transport is invisible to a TCP session as long as 1) the
session remains completely idle while the transport is broken, and 2)
the endpoint IP addresses are the same after reconnection.  Clearly, a
static address (whether VPN/1918 or public) makes this possible; DHCP,
it's iffy.

Cheers,
-- jra
-- 
Jay R. Ashworth                                                jra at baylink.com
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