Raw Sockets - IP-Encapsulation

[Alexander Gattin]

Hello,

On Fri, Sep 24, 2010 at 04:51:01PM +0100, Nobody
wrote:
> On Thu, 23 Sep 2010 21:41:19 +0200, Matthias
> Guentert wrote:
> > 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.
> 
> You don't create sockets for IPPROTO_IPIP or
> IPPROTO_GRE.  Outside of the kernel, those
> identifiers are only likely to be used for
> specifying protocols when e.g. configuring
> packet filtering.
> 
> Tunnelling only involves user-space for
> configuration.

For GRE/IPIP this is true, but with /dev/tun
and /dev/tap tunnels it isn't -- userspace
program actually reads from/writes to tun/tap
device file descriptor.

-- 
With best regards,
xrgtn