[Contrib] Captive Portal like lock for internet bound connection on an offline node (#229)

contrib/offline/redirect-port-80.sh

@@ -0,0 +1,17 @@
+#!/bin/sh
+
+# Backup file
+if ! [ -f "/etc/hostapd/nat.sh.bak" ]; then
+  sudo cp /etc/hostapd/nat.sh /etc/hostapd/nat.sh.bak
+fi
+
+# Redirect all IPv4 80 traffic to the pi
+echo iptables -t nat -I PREROUTING -i wlan-ap -p tcp --dport 80 -j DNAT --to-destination 10.0.0.1:80 | sudo tee --append  /etc/hostapd/nat.sh > /dev/null 
+
+# Prevent masquerading out IPv4
+# This is to prevent IPTUNNEL and routing to the internet (Exit node)
+sudo sed -i "/iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE/d" /etc/hostapd/nat.sh 
+
+# Set nginx to redirect any 404 errors to /
+sed -i '$i    error_page 404 =200 /index.html;' /etc/nginx/sites-enabled/main.conf
+sudo systemctl restart hostapd