> At least earlier versions of ergw had support for the kernel GTP-U plane, why > not simply use that code?
My experience with erlang is very limited so far, that's why I was attracted with libgtpnl, because I was able to create a GTP tunnel by invoking only 2 lines
# ./gtp-link add
# ./gtp-tunnel add
> They created
https://github.com/travelping/gen_netlink to talk netlink from > erlang, including gtpnl support.
Yes, I saw it. but even trying to build it from tetrapak, I have made some search but I'm struggling:
# tetrapak build check (don't even know what is tetrapak :-) )
The creators of these libraries already answer some questions from me in the public erlang mailing list, but about general erlang related questions. I didn't find any public mailing list to these libraries, so I gave up.
> You cannot do that, sorry.
> This will obviously not work.
> You need to manage the socket from your program.
> You are asking for the impossible.
I totally agree with you but I've got some idea this afternoon as a workaround.
I think I can forward the echo-request that I received on my network interface (owned by gtpnl at GTP-U) to my Erlang program by using some Linux helper like
# tcpdump
# replay the traffic by tcpreplay to another interface owned by my Erlang program
# or I can Write them to a Linux named pipe fifo, and get it from Erlang
By this way, I would be able to craft an echo-response for GTP-U I think.
Those steps are not related to libgtpnl anymore, so would be off-topic.
But Clarifications regarding libgtpnl is very clear for me now.
Thank you,
P.S: I will update here if this echo-response at GTP-U side from my erlang works for me. Have a nice day.
On Fri, Aug 21, 2020 at 09:53:34AM +0300, Papa Tana wrote:
> But for GTP-U, I was trying to listen in port 2152 several times, and it
> yields an error that I cannot listen on it, port 2152 is already used.
You cannot do that, sorry.
> > You manage all your UDP sockets.
> > your application is responsible for receiving and responding to any GTP-U
> packets there.
> As I said, I am using Erlang as a userspace program.
> And when I create a tunnel, I "just" send a basic command exec to the Linux
> by open_port like this:
This will obviously not work. You need to manage the socket from your program.
IF it's erlang, you either have to speak netlink directly from within Erlang,
or you need to add some native functions for calling libgtpnl.
> So I don't have any idea on how to listen to 2152 as my Erlang program is
> forbidden to listen on it when libgtpnl is invoked.
You are asking for the impossible. You need to open the socket from within your
program. You cannot crate a second socket for what you are trying to do.
At least earlier versions of ergw had support for the kernel GTP-U plane,
why not simply use that code?
They created https://github.com/travelping/gen_netlink
to talk netlink from erlang, including gtpnl support.
--
- Harald Welte <laforge@gnumonks.org> http://laforge.gnumonks.org/
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