I wanted to always be able to shell to a machine within the Uni network. The Uni network has a firewall that stops incoming requests to most machines. There’s a machine that all undergrads can shell to, which I normally use netcat combined with the ssh ProxyCommand setting. However, it’s a little silly to divert all traffic through another machine when I’m in the network. So, meet the new script I use in the ProxyCommand:

#!/bin/bash
HOST=$1

got=`ifconfig eth1 | egrep -o "inet addr:152.78.[0-9]{1,3}\\.[0-9]{1,3}"`
got+=`ifconfig eth0 | egrep -o "inet addr:152.78.[0-9]{1,3}\\.[0-9]{1,3}"`

if [[ "$got" == "" ]]
then
    ssh uglogin.ecs.soton.ac.uk nc $HOST 22
else
    nc $HOST 22
fi

Tags: linux, ssh