ether2any/tunnel/ircvpn

IrcVPN - Irc Virtual Public Network
===================================
This is an ethernet tunnel providing basic hubbed or switchet networks via irc.

Warning: If you use this software on a "real" (read: not your own) network:
          1. You might run into various flood protections
		  2. Your IRC-OP might kill you for that

Furthermore: All of your data will go kind-of plaintext over an Irc-channel.
             While this is a rather uncommon way of ip transit, everybody who
			 is able to join the channel might be able to eavesdrop.


Installation and requirements
=============================
 * python-irclib
 * ether2any

For configuration take a look at conf.py, it has some comments to give you a
hint of what this switch will do. Some of the security settings are rather
untested, keep that in mind. After configuration, start the tunnel with
python ircvpn.py. A tap-device will open and the tunnel should be ready to run.


What it does and how it works
=============================
IrcVPN uses an ircchannel as its transport medium. When starting this tunnel,
it makes a connection to the configured irc-server, joins a channel and starts
pushing all outgoing network traffic (base64 encoded with a small header) to
that channel. The nick will be a combination of the configured prefix and
the TAP interfaces mac-address.

There are two network-modes available:

.Hubbed Network
In a hubbed network topology all the clients share one broadcast medium, the
irc channel.

.Switchet Network
In a switched network topology still all the clients join the irc channel and
use it for broadcast messages but unicast traffic goes directly to the user
it is intended for, as it is sent to the nickprefix-macaddress combination.
Wether the user with the specific mac actually IS in the network is not
checked.

Flood protection is kind of the biggest issue for irc as ether: After a
configured amount of messages most irc-servers queue the incoming messages
and send them out as one per second. If the send-queue is overflowed the user
gets kicked from the server. So this tunnel is not going to perform very well
on normal servers out there. Setting up an own server, the flood protection CAN
be turned off but irc-server with configurable flood protections tend to allow
flooding only in channels and only if the user is either voiced, half-op or op.
This is where voicebot.py comes in: The voicebot voices everyone who joins the
channel and utters a certain phrase. Therefore it is kind of ensured that every
bot has the right to flood the ether as much as it wants with network packets.

Ircs right management can always be used to mute, rate-limit or remove spamming
or otherwise unwanted clients. 


Header Format
=============
<fragmentation flag><packet id> <base64 encoded message>

The *fragmentation flag* can be either of o, b, c, e. *o* stands for oneliner,
which means that afterwards there is a complete ethernet frame (no
fragmentation). *b*, *c*, *e* stand for begin, continue, end and mark packets
which are broken into several pieces (as of irc does not support infinit line
length). 

The packet id is just a randon generated number between 0, 99999 (incl.).


What could be done
==================
 * replace base64 with something more fitting for Irc
 * test security settings
 * find static linkable irc server, patch flood protection out of it
 * VVLAN - a Virtual VLAN between irc-channels/servers