This applications allows to set some options for the IPv6 stack that is part
of the main Linux kernel and also used on Android devices. Most importantly,
it allows to automatically enable the "Privacy Extensions for Stateless 
Address Autoconfiguration in IPv6" as specified in IETF RFC4941 and implemented
by the standard Linux kernel.

Why address privacy?
--------------------
With IPv6 as the next Internet Protocol, the default behavior on current
Android systems is to derive IPv6 addresses from a so-called prefix that is
automatically announced (broadcast) in a network that has been IPv6-enabled and
the so-called suffix that includes the MAC address of the network card.

Including the MAC address in this automatically generated IPv6 addressing 
scheme means that, independently of the network a specific device connects to,
the last 64 Bits of its IPv6 address will always remain the same. Even when 
moving between different networks, each device using this scheme is therefore
uniquely identifiable by its suffix. This allows to easily track devices as 
they connect to different networks and whenever they use any network resources.

What does address privacy do?
-----------------------------
When enabled, the RFC4941 extensions cause a device to generate dynamic IPv6
address with random suffixes and change these addresses randomly. This prevents
tracking a device, as it is unlikely that it will use the same address again
(and if so, then only by chance).

What does this application do?
------------------------------
This android application can be set to start at device bootup and automatically
set the appropriate Linux kernel configuration option on all known network 
interfaces (WiFi and GPRS/UMTS, mostly) so that they will use randomly 
generated addresses instead of those derived from the device MAC address.

What are the requirements?
--------------------------
This is only possible on rooted Android devices, because the kernel 
configuration options are only writable by the root user.

Tested devices and rooting applications/methods:
------------------------------------------------
This application has been tested successfully on:

 * Google Nexus S GT-i9023 with Android 2.3.3 (rooted with Clockwork Recovery 
   3.0.0.0-crespo, then busybox installed with Busybox Installer app)  
 * HTC Desire with Android 2.2 (unrevoked)
 * Samsung Galaxy S2 rooted with modified kernel (flashed with Odin)
 * HTC Desire HD with Android 2.3 (Visionary+ r14)
 * Motorola Milestone with Cyanogenmod 7 rc3

IPv6Config will not currently work on:

 * Motorola Milestone with stock Android 2.1 (ip binary missing)
 * Samsung Galaxy Tab GT-P1000 (z4root) because the Samsung kernel has not been
   compiled with IPv6 address privacy extensions. (busybox also doesn't link to
   the ip binary, but that could be worked around by calling "busybox ip" 
   instead of "ip".) 

Isn't rooting unsafe? What does this application really do?
-----------------------------------------------------------
Don't just trust me. Please check the source code. It is online at
http://gitorious.org/android-ipv6config/android-ipv6config.git

Why should I pay for this application if it is open source?
-----------------------------------------------------------
You don't have to. There are two versions available in the Android Market that
I compile: one that can be installed for free and one version that will donate
a small amount. Both versions are completely the same, and the free version 
is not restricted in any way. In fact, anybody can take the source code and
compile and install the APK and even redistribute it as long as they conform
to the terms of the GNU GPL version 3 (that is, the modified source code is
redistributed as well) and use different application icons.

The donate version is in the market if you would like to donate to the further
development of this and other applications. Luckily, I do not have to make a 
living with my applications, and therefore release all of them as open source.
However, I do have infrastructure costs for my own server, which I use as a 
development resource and e.g. to support determining the globally visible IPv6
address in this application. If you wish to contribute towards these 
development costs, then please buy the donate version. If not, then just take 
the free one.

==============================================================================
Copyright (C) René Mayrhofer, 2011-2014