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

h1. OsmoGGSN and Linux Kernel accelerated GTP-U

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OsmoGGSN has support to use the Linux kernel GTP-U code to accelerate the data/user plane while still implementing the control plane (GTP-C) in userspace in OsmoGGSN.

For more information about the Linux kernel GTP-U code, please see [[linux-kernel-gtp-u:]]

h2. Building OsmoGGSN with kernel which has GTP-U support

At the time of writing (2018-04-26) of this wiki, below listed distributions have support of GTP kernels :

* Debian

** Debian 9 "stretch" (kernel 4.9.0-6) 

** Debian 10 "buster"

** Debian "unstable"

* Ubuntu

** Ubuntu 16.04 "xenial" (kernel 4.8, 4.10, 4.13)

** Ubuntu 17.10 "artful" (kernel 4.13)

* OpenSUSE

** OpenSUSE Tumbleweed (kernel "stable" 4.8, 4.12)

* Fedora

** Fedora 25 (kernel 4.13 "kconfig":https://git.kernel.org/pub/scm/linux/kernel/git/jwboyer/fedora.git/diff/fedora/configs/kernel-4.13.16-x86_64.config?h=f25&id=c7f8c6df25a148b887515787667c75e18fa9790d)

** Fedora 26 (kernel 4.15 "kconfig":https://git.kernel.org/pub/scm/linux/kernel/git/jwboyer/fedora.git/diff/fedora/configs/kernel-4.15.18-x86_64.config?h=f26&id=7b0ed3e9a5d6773dddcc904c1d4e67c1307f02dd)

** Fedora 27 (kernel 4.16 "kconfig":https://git.kernel.org/pub/scm/linux/kernel/git/jwboyer/fedora.git/tree/fedora/configs/kernel-4.16.4-x86_64.config?h=f27&id=d06904e7457b50b9cfc108667b5b65777a43cc75)

If you're using any other distribution, or are building your own kernels, please verify that @CONFIG_GTP@ is set to either @m@ or @y@.

*If @CONFIG_GTP@ is not enabled, you cannot use kernel GTP-U!*

Check if package @libc-ares-dev@ is installed and if not please add it.

h3. Installing dependencies and build library @libosmocore@

You can install required dependency packages with:

<pre>

$ sudo apt install libtalloc-dev libpcsclite-dev

</pre>

Please follow instructions provided at [[cellular-infrastructure:Build from source]] in order to install libosmocore

h3.  Installing dependencies and build library @libgtpnl@

You can install dependencies with:

<pre>

$ sudo apt install libmnl-dev

</pre>

Then build libgtpnl like this

<pre>

$ git clone git://git.osmocom.org/libgtpnl.git

$ cd libgtpnl

$ autoreconf -fi

$ ./configure

$ make

$ sudo make install

$ sudo ldconfig

</pre>

h3. osmo-ggsn

Build OsmoGGSN like this:

<pre>

$ git clone git://git.osmocom.org/osmo-ggsn.git

$ cd osmo-ggsn

$ ./configure --enable-gtp-linux

$ make

$ sudo make install

$ sudo ldconfig

</pre>

Following message is shown at end of the command: @ ./configure --enable-gtp-linux@ 

<pre>

OsmoGGSN Configuration:

  GTP Linux kernel support:			yes

</pre>

This means that appropriate header files are available.

h2. Using OsmoGGSN with kernel which has GTP-U support

In order to find out whether gtp.ko module is available we can enter following command:

<pre>

$ find /lib/modules/$(uname -r) -name gtp.ko

</pre>

Output below shows that gtp.ko module is present:

<pre>

/lib/modules/4.8.0-30-generic/kernel/drivers/net/gtp.ko

</pre>

We are loading module gtp from kernel issuing command: <pre>sudo modprobe gtp</pre> 

when you enter: 

<pre>

$ lsmod | grep gtp

</pre>

then more information about gtp and related udp tunnel can be obtained:

<pre>

gtp                    28672  0

udp_tunnel             16384  1 gtp

</pre>

Some helpful tools are available in: @libgtpnl/tools@

you can get more details about gtp-tunnel, entering command from the OsmoGGSN shell:

<pre>

$ sudo ./gtp-tunnel list

</pre>

Output will be similar to:

<pre>

version 1 tei 1/0 ms_addr 192.168.0.2 sgsn_addr 127.0.0.2

</pre>

Note: OsmoGGSN is started by: 

<pre>

$ sudo osmo-ggsn -c osmo-ggsn.cfg

</pre>

Related output should be similar to the one shown below: 

<pre>

<0002> ggsn.c:186 APN(internet): Starting

<0002> ggsn.c:204 APN(internet): Opening Kernel GTP device tun4

<0002> ggsn.c:215 APN(internet): Skipping APN start

<0002> ggsn.c:794 GGSN(ggsn0): Starting GGSN

<000d> gtp.c:902 GTP: gtp_newgsn() started at 127.0.0.2

<0002> ggsn.c:830 GGSN(ggsn0): Successfully started

<0002> ggsn.c:186 APN(internet): Starting

<0002> ggsn.c:204 APN(internet): Opening Kernel GTP device tun4

<0002> gtp-kernel.c:79 Initialized GTP kernel mode (genl ID is 25)

<0001> tun.c:217 GTP kernel configured

<0002> ggsn.c:236 APN(internet): Setting tun IP address 172.16.222.0/24

<0002> ggsn.c:294 APN(internet): Creating IPv4 pool 172.16.222.0/24

<0002> ggsn.c:168 APN(internet): Blacklist tun IP 172.16.222.0/24

<0002> ggsn.c:325 APN(internet): Successfully started

<0005> telnet_interface.c:104 Available via telnet 127.0.0.1 4260

<000c> control_if.c:916 CTRL at 127.0.0.1 4257

</pre>

You can now start to establish PDP contexts to your new osmo-ggsn instance, from [[OsmoSGSN:]], @sgsnemu@ or third-party SGSNs

h2. Automatic Testing

See [[linux-kernel-gtp-u:Automatic_Testing]] for the automatic continuous integration test setup.