Decapsulate GTP-U payload and forward to a Router

Papa Tana papa.tana101@REDACTED
Mon Jul 6 08:48:22 CEST 2020

Yes! I already saw it, it's a really interested one.

Someone else seems to manage to do it very well, and I'm still on the
ongoing process of exploring this huge source code as well:

But actually, I don't need to create or manipulate, I need to
decapsulate the user-data inside GTP-u (this I can do) and forward
these data packets to external Router, "without changing any

I am kind of the "default router" for some client equipment who is
sending me packets in GTP-u format, I receive and decapsulate them,
forward and don't have to look what are inside.

I should have changed the title as "Erlang used as a  Router", but I
wanted to illustrate my real scenario.

2020-07-06 4:13 UTC+03:00, Matthew Evans <mattevans123@REDACTED>:
> Have you looked at the procket library? Lots of low-level socket
> manipulation tools..
> Sent from my iPhone
> On Jul 5, 2020, at 8:56 PM, Papa Tana <papa.tana101@REDACTED> wrote:
> Hi All,
> I am a node built in Erlang, and I receive lots of GTP-U packets:
> ---> GTP-U packets ---------> My Node as a Relay ----> Router [using
> NAT]----> Internet
> As shown above, the Erlang node task is to decapsulate the user data
> (GTP-U Message Type is T-PDU (0xff)) and forward them to the Router,
> without changing any information, just forward it, that's all.
> I was used to send application message in binary as a Client, just
> using gen_udp and gen_tcp, but now, I am not the Client. And not the
> server because those messages are not for me neither.
> => Then, after I decapsulate these messages from GTP-U, I would like
> to relay these layer messages to the Router with which I am connected.
> The Router should connect with me with one network interface, using
> the same netmask, let's say a small /30 netmask, it's obvious.
> The IP addresses (src and dst) in the payload are not "from" me and
> not "for" me.
> Any tips please?
> Thank you,
> Best Regards,

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