jumphost_required.sh

#!/bin/bash
# we're testing to see if we need to use the jumphost.  we don't need the jumphost when the target IP address starts with 10.
# this script is called by ssh config, so that script is checking to see if it needs the jumphost.
# if this script exits successfully, then it means that input was provided, and that the ip address did not start with 10
# in the second case we're forcing the "false" value "1" if the "starts with a 10" condition is met
# if the 10 is found, we exit with 1 and that tells ssh we didn't need the jump
# if the value turns out to not be a 10, then this script exits successfully, and ssh invokes the jump condiion. 
#
# If there were no arguments provided, exit.  You really don't want to wait for nslookup to timeout over nothing, do you?

if [ -z $1 ]; then 
	#echo "No input given."
	exit 1

# If they did provide an arguement, let's see if it was a 10 or something else, then exit.

else
	hostTest=`nslookup $1 | tail -2 | head -1 | cut -d ' ' -f 2 | cut -d '.' -f 1`
	#echo "hostTest is now:  $hostTest"

# first test if "hostTest" has letters, if the nslookup doesn't find a digit,
# we usually see "server" or "Can't" so this should quit if we didn't get the first octet of the ip address

	if [[ "$hostTest" =~ [a-zA-Z] ]] ; then
		#echo "$hostTest is not a number!"
		exit 1

# next test to see if "hostTest" is a 10, which means we don't need to use the jumphost and can go directly

	elif [[ "$hostTest" -eq "10" ]] ; then
		#echo "$hostTest is a 10, take the express!" 
		exit 1

# the result should be a number, maybe we can put some more logic here,
# but should be fine to exit and use the jump

	else
		#echo "$hostTest is not a 10, you need a jump!"
		exit 0
	fi
fi