Raw Sockets - IP-Encapsulation

[Matthias Guentert]

Hello list members

I would like to create an IP tunnel using the IP protocol type 4
(socket.IPPROTO_IPIP) on a Linux host. (I also would be happy if I
could create a GRE tunnel)

The thing is, I just don't understand how I such a socket could be
created and then later on handled.

Regarding to help(socket.socke()) the constructor looks like this:

 | socket([family[, type[, proto]]]) -> socket object
 |
 |  Open a socket of the given type.  The family argument specifies the
 |  address family; it defaults to AF_INET.  The type argument specifies
 |  whether this is a stream (SOCK_STREAM, this is the default)
 |  or datagram (SOCK_DGRAM) socket.  The protocol argument defaults to 0,
 |  specifying the default protocol.  Keyword arguments are accepted.

This means to create a simple UDP socket I can do the following where
the last argument is optional.

s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_IP)

So to create an IP-Encapsulation socket I would have to do this:

s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_IPIP)

or for GRE this.

s = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.IPPROTO_GRE)

But how can I now set the fields? How do I really encapsulate other
data (=sockets?)? Do I need a Raw socket at all? Or should this work
somehow like the following to encapsulate UDP payload?

s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_IPIP)

I really would be happy if someone could help me with this and even
better could provide some examples on the usage.

Thanks in advance, Matthias