Present any network "logon page" with network connect.

inet_test.sh

#!/bin/bash

# I have both the interface and external ip echoed to conky, so I had a version of this script already.
# This version is for autolaunch, so it presents a nice popup browser if it can't resolve its own IP
# address (such as for places that have public wifi and "click here".

# This version is designed to start up with the GUI interface, not as a system 
# service! So if you use it with WICD, do not do it as an ifup command, otherwise
# you will have issues because it can't launch the browser.

function getextip {
	ext_ip=$(wget -q -O - checkip.dyndns.org |grep "Current IP Check"| sed -e 's/[^[:digit:]|.]//g')
	len_ext_ip=${#ext_ip}
	# Yes, I am only testing IPv4 here.
	status=0
	if [ $len_ext_ip -lt 16 ]; then
		if [ $len_ext_ip -gt 7 ]; then
			status=1
		fi
	fi
}

#main function

ext_ip=$(echo "0.0.0.0")

interface=$(netstat -nr | grep -m 1 ^0.0.0.0 | awk -F " " '{print $8}')
# Response should be tun[0-9], wlan[0-9], eth[0-9]
# You can use a more complex case statement here if you like
if [ "$interface" != "" ]; then
	getextip
	if [ $status = 0 ]; then
		# I use midori here because it's the lightest weight browser that can handle
		# all the different forms and such that I've encountered for public wifi login
		# otherwise I'd use elinks.  Ah well.
		midori http://stevesaus.com &
		sleep 60
		# Alternately, get rid of the ampersand and have the script wait for you to close the browser.
		getextip
		if [ "$status" = "0" ]; then
			ext_ip=$(echo "0.0.0.0")
		fi
	fi
fi

# This could also be where you insert a command to bring up your VPN if $ext_ip != 0.0.0.0 :)

echo "$interface"
echo "$ext_ip"