Dropping packet from invalid source address

Peter Lithner plithner at yahoo.com
Wed Oct 5 09:46:59 UTC 2016


Hi

I'm trying out openGGSN, currently running it on an Ubuntu 16.04 VM in Amazon. The reason I'm doing this is part of an evaluation I'm helping out with for a customer in the Telco-industry.

I have been able to install, and run ggsn and sgsnemu to the point of sending the ECHO and creating the PDP-C (see attachment). 

However, I can't see that a network interface is created after the PDP-C has been accepted. According to the README on https://github.com/osmobuntu/openggsn that should happen:
"After this it will attempt to establish a pdp
context. If successful it will create a local interface and set up
routing."

Anyway, I have probably missed something in the setup. If you have any suggestions, that would be highly appreciated!

What I did so far is:

Install
sudo apt-get update
sudo apt-get install openggsn

Create "virtual" interfaces (since I'm running everything on the same machine. Not sure if this is the right way to do it though)
ifconfig eth0:0 192.168.1.2 netmask 255.255.255.0 up
ifconfig eth0:1 192.168.1.3 netmask 255.255.255.0 up


I also did the following steps, but I'm not sure exactly what they do... pardon my ignorance!
1. Add the following line to /etc/modules.conf: alias char-major-10-200 tun 
2. depmod -a

Start GGSN
ggsn -c ggsn.conf --fg -l 192.168.1.2 --net 192.168.0.0/24 --dynip 192.168.0.0/24

After this I can see the new tun0
tun0: flags=81<UP,POINTOPOINT,RUNNING>  mtu 1500 inet 192.168.0.1  netmask 255.255.255.0  destination 192.168.0.1 inet6 fe80::9ea3:6876:c4ce:fc96  prefixlen 64  scopeid 0x20<link> unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen 500  (UNSPEC) RX packets 0  bytes 0 (0.0 B) RX errors 0  dropped 0  overruns 0  frame 0 TX packets 7  bytes 448 (448.0 B) TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0


send ECHO (successfully)
sgsnemu --listen 192.168.1.3 --remote 192.168.1.2 --dns 10.20.38.51 --timelimit 10 --contexts 0


Send ECHO + Create PDP-C
sgsnemu --listen 192.168.1.3 --remote 192.168.1.2 --dns 10.20.38.51 --timelimit 10 --contexts 1 --apn internet --imsi 240011234567890 --msisdn 46702123456 --createif --defaultroute


Which outputs the following:
Using DNS server:      10.20.38.51 (10.20.38.51)
Local IP address is:   192.168.1.3 (192.168.1.3)
Remote IP address is:  192.168.1.2 (192.168.1.2)
IMSI is:               240011234567890 (0xf098765432110042)
Using NSAPI:           0
Using GTP version:     1
Using APN:             internet
Using selection mode:  1
Using MSISDN:          46702123456

Initialising GTP library
<000c> gtp.c:700 GTP: gtp_newgsn() started


After printing this line, sgsnemu stays very silent for 30-ish seconds, after which it prints (all in one go):

Setting up interface
Done initialising GTP library

Sending off echo request
Setting up PDP context #0
Waiting for response from ggsn........

Received echo response
Received create PDP context response. IP address: 192.168.0.2
Dropping packet from invalid source address: 0.0.0.0
Dropping packet from invalid source address: 0.0.0.0
Dropping packet from invalid source address: 0.0.0.0
Dropping packet from invalid source address: 10.7.0.240
Dropping packet from invalid source address: 10.7.0.240
Dropping packet from invalid source address: 0.0.0.0
Dropping packet from invalid source address: 10.7.0.240
Dropping packet from invalid source address: 0.0.0.0
Dropping packet from invalid source address: 10.7.0.240
Dropping packet from invalid source address: 10.7.0.240
Dropping packet from invalid source address: 0.0.0.0
Dropping packet from invalid source address: 10.7.0.240
Dropping packet from invalid source address: 0.0.0.0
Dropping packet from invalid source address: 10.7.0.240
Disconnecting PDP context #0
Received delete PDP context response. Cause value: 128

Where 10.7.0.240 is the ip address of eth0

Once again, if you have any suggestions, I'm all ears! Thanks in advance!

/peter
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