Cellular Network Infrastructure » Core Network (CN) » OsmoGGSN (former OpenGGSN)

please try to find a linux distribution/version that already has the kernel support for GTP-U included, i.e. let's avoid you having to re-build the linux kernel for this task. Once you have the required kernel, you will need to compile libgtpnl, and rebuild openggsn to link against the libgtpnl for supporting the GTP-u in the kernel plane.

Please also make sure that the process of building + using OpenGGSN with kernel-gtp is properly documented in the OpenGGSN project wiki here on osmocom.org.

Looking for a linux distribution/version, which already has the kernel support for GTP-U included.
Installing of kernel 4.8.

After installation of Ubuntu 16.10 (4.8.0-30-generic) on a virtual machine, libgtpnl libsomsocore were compiled and OpenGGSN was rebuild.

wiki page of building + using OpenGGSN with kernel-gtp is drafted and it is under construction.

Starting OpenGGSN with option --gtp-linux leads to following:

from OpenGGSN the following messages are to be seen:

gtp.c:701 GTP: gtp_newgsn() started
gtp-kernel.c:156 GTP kernel configured

length: 12 content: 32 1a 00 04 00 00 00 00 00 00 00 00 : Unknown PDP context

from SGSN : length: 52 content: 38 ff 00 2c 00 00 00 00 45 00 00 2c 03 bb 00 00 6c 06 ad 69 0c 9b d0 61 c0 a8 00 03 52 08 04 05 f5 19 a2 62 04 40 61 02 60 12 20 00 87 f2 00 00 02 04 05 64 : Unknown PDP context.

Having that circumstance, it is not possible to run PS traffic and to load web site on the test mobile station.

Addinng to wiki site command for starting OpenGGSN
sudo ggsn --gtp-linux -c ggsn.conf -f

laforge wrote:

Hi,

On Tue, Dec 13, 2016 at 06:02:20PM +0000, wirelesss [REDMINE] wrote:

Starting OpenGGSN with option --gtp-linux leads to following:

[...]

from SGSN : length: 52 content: 38 ff 00 2c 00 00 00 00 45 00 00 2c 03
bb 00 00 6c 06 ad 69 0c 9b d0 61 c0 a8 00 03 52 08 04 05 f5 19 a2 62
04 40 61 02 60 12 20 00 87 f2 00 00 02 04 05 64 : Unknown PDP context.

Having that circumstance, it is not possible to run PS traffic and to
load web site on the test mobile station.

so you have discovered a problem. But where is the comprehensive bug
report? Where are the protocol traces (pcap files) of the Gb and
Gp interface while the above log lines of OpenGGSN where observed.

As somebody who receives bug reports from others, you should understand
how important it is to first collect all the relevant information and
then post it together. This is very important in terms of efifciency.

It might even make sense to raise all this ina separate bug ticket and
mark that related to this ticket on whcih you are working on.

--
- Harald Welte <laforge@gnumonks.org> http://laforge.gnumonks.org/ ============================================================================
"Privacy in residential applications is a desirable marketing option."
(ETSI EN 300 175-7 Ch. A6)

Hi,

Yes. I agree. I have sent this post / note a bit earlier without complete troubleshooting information.
I thought it would be valuable just as a progress of this Ticket. I do understand that in this case it was just useless.

After building and compiling of openbsc, libgtpnl and OpenGGSN on a virtual machine running Ubuntu 16.10 with kernel 4.8.0-30-generic following was observed:

from SGSN console (time stamps:08:55:23 - 08:56:57) it is to be seen that GPRS attach is accepted and PDP CONTEXT activation is acknowledged. Please refer to sgsn.log file

at time stamp: 08:57:05 following message is present:

gtp.c:2619 Packet from 127.0.0.1:2152, length: 82 content: 38 ff 00 4a 00 00 00 00 45 00 00 4a 51 d5 00 00 2b 
11 6d 14 08 08 08 08 c0 a8 00 02 00 35 40 01 00 36 74 a4 0d ce 81 80 00 01 00 01 00 00 00 00 03 77 77 77 04 7a 
6f 63 6b 03 63 6f 6d 00 00 01 00 01 c0 0c 00 01 00 01 00 00 17 64 00 04 55 0d 93 d7 : Unknown PDP context
Wed Dec 14 08:57:05 2016
<0025> gtp.c:213 Unknown packet flag: 56

Output from the GGSN console is:

  gtp.c:2581 Packet from 127.0.0.2:2152, length: 12 content: 32 1a 00 04 00 00 00 00 00 00 00 00 : Unknown PDP context

The pcap file from Gb interface to be attached.

It was found that communication between SGSN and GGSN is running, but at certain point GGSN switches Reserved bit to 1. This can be seen from the GGSN standard query response. In the attach Gp_trace.pcapng file we can see that in the frame no: 1082, 1889 etc.

Test that relates to OpenGGSN with osmo-gtp-kernel code has been executed.
As conclusion: so-called "reserved" bit in the flags octet of the GTPv1 header is set to value '1'. This is done in the existing Linux Kernel GTP code. This operation is incorrect. As per 3GPP TS 129.060 (ETSI TS 129 060 V13.5.0), Chapter 6, bit 4 in octet 1, should be equal to value '0'.

TEID for GTP-C has been compared. SonyEricsson K790i mobile has been used.

In file lo_trace.pcapng next information can be seen.

In message "create PDP context request" (MS to Network direction - Uplinik), TEIDs have the following values:
Frame No.: 2569
TEID:0x00000000
TEID Data I: 0x00000001
TEID Control Plane: 0x00000001

In message "create PDP context response message" (Network to MS direction - Downlink) shows next TEIDs:
Frame No.: 2570
TEID:0x00000001
TEID Data I: 0x00000001
TEID Control Plane: 0x00000001

Message Standard query 0x0dce A wap.sonyericsson.com, includes TEIDs as presented below:
Frame No.: 2579
TEID:0x00000001

Frame No.: 2584 which is Standart query response message to frame no. 2579.
TEID:0x00000000

The output from gtp-tunnel list command is:

version 1 tei 1/0 ms_addr 192.168.0.2 sgsn_addr 127.0.0.2

OpenGGSN log shows: teid 1. Part of this log is presented in the next lines:

<000c> gtp.c:701 GTP: gtp_newgsn() started
<0002> gtp-kernel.c:123 Using the GTP kernel mode (genl ID is 27)

<0002> gtp-kernel.c:156 GTP kernel configured

<000b> control_if.c:693 CTRL at 127.0.0.1 4257
version 1
teid 1
address (6)
f1 21 c0 a8 0 2 
sgsn-addr (4)
7f 0 0 2 
<000c> gtp.c:2581 Packet from 127.0.0.2:2152, length: 12 content: 32 1a 00 04 00 00 00 00 00 00 00 00 : Unknown PDP context
<000c> gtp.c:2581 Packet from 127.0.0.2:2152, length: 12 content: 32 1a 00 04 00 00 00 00 00 00 00 00 : Unknown PDP context
<000c> gtp.c:2581 Packet from 127.0.0.2:2152, length: 12 content: 32 1a 00 04 00 00 00 00 00 00 00 00 : Unknown PDP context
version 1
teid 1
address (6)
f1 21 c0 a8 0 2 
sgsn-addr (4)
7f 0 0 2 

TEIDs are different or non-synchronized.

TEID in Frame No.: 2584 or Standard query response message shall be equal to 1.

laforge wrote:

I just requested Debian to enable CONFIG_GTP in Debian bug report
846913: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=846913

FYI, Debian has just activated the kernel GTP module in their latest experimental build "linux 4.9.1-1~exp1"

From the change log:

* net: Enable GTP as module (Closes: #846913)

Would be good to collect all the information here about which distribution has kernel GTP and which not to a wiki page in the OpenGGSN project.

Information about which distribution has GTP kernel is collected and added in wiki site.

with the recent patches merged ahead of the openggsn 0.93 release, the kernel-gtp integration with GTPv1 is finally working in OpenGGSN. I could establish PDP contexts between sgsnemu and openggsn and route bi-directional IP packets through them.

I've also been playing around with using different TEI values on both side of the tunnels, to make sure there are no mistakes in the local/remote TEI value handling.

I'll be documenting the test setup shortly and put it on an OpenGGSN wiki page.

the setup is documented (and has been verified) in the wiki. see Basic_Testing and Kernel_GTP