ssh-and-tmux: part two

Many of the hosts I wish to use my ssh-and-tmux script to connect to are behind firewalls so I can't connect to them directly. I find that it is more reliable to just ssh through a gateway host rather than using any VPN that might be available. This can easily be bolted on to the ssh-and-tmux script provided a good guess can be made as to which network you're actually on:

#!/bin/sh
if [ -n "$TMUX" ]; then
    echo Already in tmux
    exit 1
fi

if [ -n "$STY" ]; then
    echo Already in screen
    exit 1
fi

while true; do
    # First work out where we are based on our IP address.
    # We do this every time round the loop in case we've 
    # moved network since last time.
    addrs=`ip --family inet --oneline addr`

    work_via=gateway.example.com
    home_via=gateway.randombitsofuselessinformation.blogspot.com

    case "$addrs" in
 *192.168.1.*)
     # We're on the home network
     home_via=
     ;;
 *172.16.*)
     # We're on the work network
     work_via=
     ;;
    esac

    extra=
    via=
    case "$1" in
 work-host1)
     via=$work_via
     # Add a port forward for this host too
     extra=-L8080:work-host1:8080
     dest=work-host1
     ;;
 home-host1)
     via=$home_via
     dest=home-host1
     ;;
 home-host2)
     via=$home_via
     dest=home-host2
     ;;
 *.*)
     # Hosts with dots are assumed to be on the
            # Internet at large
     via=
     dest="$1"
     ;;
 *)
     # All other hosts are assumed to be on the work
            # network
     via=$work_via
     dest="$1"
     ;;
    esac
    
    if [ -n "$via" ]; then
 ssh $extra -A -t "$via" \
            ssh -t "$dest" "tmux -2 -L netbook attach \
            || tmux -2 -L netbook"
    else
 ssh $extra -t "$dest" "tmux -2 -L netbook attach \
            || tmux -2 -L netbook"
    fi
    
    stty sane
    echo "Dropped, press Enter to reconnect."
    if read x; then
 echo "Reconnecting..."
    else
 # Something bad happened to our tty. We'd better exit.
 exit 1
    fi
done

So now I can connect to work-host1 from home via the gateway, shut the laptop, travel to work, open it again, hit Enter and reconnect directly to work-host1 without losing any state. What's not to like? Well, there's still some more things we can do.