How can I use iptables in an Android application? I need this for a firewall-like functionality i.e. packet filtering, blocking sites etc.
I'm also not sure whether iptables are available in the Android kernel.
I previously heard that I'd have to create cross-compiled binaries of iptables – but how can I do that? And how can I use them in the application?
It's definitely possible. You might consider looking at the source code of Droidwall.
DroidWall - Android Firewall is a front-end application for the powerful iptables Linux firewall. It allows you to restrict which applications are permitted to access your data networks (2G/3G and/or Wi-Fi).
Check out the iptables API from Droidwall for specific examples.
Note that when using iptables you need root access to your phone.
