This is some experiments with IP tunneling and Python. I have intentions to implement IP over DNS, HTTP, ICMP, etc.

                       +---------+
                       | Routing |
                       |  table  |
                       +---------+
                           ^
                           | consults
+--------+            +---------+
|   IP   |  goes into | Network | forwards    +------+
| packet | ---------> |  stack  | --------->  | tun0 |
+--------+            +---------+             +------+
                        |     ^   encapsulated   |
                        |     +------------------+
                        V           packet
                    +------+
                    | eth0 |
                    +------+
                       |
client                 |
------------------------------------------------------------------------
server                 |
                       V
 +--------+         +------+  client  +--------+
 | Server | <------ | eth0 | -------> | Target |
 | daemon |         +------+  packet  | server |
 +--------+            ^              +--------+
    | decapsulated     |
    |   IP packet      |
    V                  |
+------+ client    +---------+           +---------+
| tun0 | --------> | Network | consults  | Routing |
+------+ packet    |  stack  | --------> |  table  |
                   +---------+           +---------+

Where tun0 is virtual network device.

First of all the server must be started:

$ make pyenv
$ sudo pyenv/bin/python -m iptun.server

Currently it's accepting packets over UDP port 3000.

Once the server is ready to relay packets, we can start the client:

$ make pyenv
$ sudo pyenv/bin/python -m iptun.client

By default no routes are configured, they should be added manually. E.g. to route all traffic through our tunnel, execute:

$ sudo ip route add default via 10.1.0.1

To route traffic to specific destination, execute:

$ sudo ip route add 1.2.3.4 via 10.1.0.1