Tag Archives: Debug

Module debug in Kamailio

Kamailio, VoIP, , ,

Sometimes Kamailio modules don’t behave how you expect them to, and you want to dive a little deeper into what’s going on.

If we load the debugger.so module in our kamailio.cfg file, we can get a bit more of an insight.

For example, if we wanted to deep dive into what RTPengine was thinking we’d include:

loadmodule "debugger"
modparam("debugger", "mod_level_mode", 1)
modparam("debugger", "mod_level", "rtpengine=3")

And bam, now when we run Kamailio we’ll get all the logic that rtpengine exposes when being called.

By setting cfgtrace we can enable a config trace as well, and as we step through our Kamailio config file for a SIP message, we can see what’s going on at every step.

So if you’re like me, you can use the debugger module, combined with reading through the source code, to prove every single time that the issue is with my not understanding the function properly, and never the logic of the Kamailio module!

Samsung-Sysdump-IMS-Debug-DM-View_Cropped

VoLTE/IMS Debugging on Samsung Handsets using Sysdump & Samsung IMS Logger

EPC, EUTRAN, IMS / VoLTE, LTE, Mobile Networks, Security, Software, VoIP, , , , , , , ,

Samsung handsets have a feature built in to allow debugging from the handset, called Sysdump.

Entering *#9900# from the Dialing Screen will bring up the Sysdump App, from here you can dump logs from the device, and run a variety of debugging procedures.

Samsung share information about this app publicly on their website,

Sysdump App in Samsung handsets used for debugging the device

But for private LTE operators, the two most interesting options are by far the TCPDUMP START option and IMS Logger, but both are grayed out.

Tapping on them asks for a one-time password and has a challenge key.

OTP Authentication required to unlock IMS Debugging and TCPDUMP on Samsung Sysdump tool

These options are not available in the commercial version of the OS and need to be unlocked with a one time key generated by a tool Samsung for unlocking engineering firmware on handsets.

Luckily this authentication happens client side, which means we can work out the password it’s expecting.

For those interested I’ve done a write up of how I reversed the password validation algorithm to take the key given in the OTP challenge and generate a valid response.

For those who just want to unlock these features you can click here to run the tool that generates the response.

Once you’ve entered the code and successfully unlocked the IMS Debugging tool there’s a few really cool features in the hamburger menu in the top right.

DM View

This shows the SIP / IMS Messaging and the current signal strength parameters (used to determine which RAN type to use (Ie falling back from VoLTE to UMTS / Circuit Switched when the LTE signal strength drops).

Screenshot of Samsung Sysdump tool in the IMS Debug - DM View section

Tapping on the SIP messages expands them and allows you to see the contents of the SIP messages.

Viewing SIP Messaging directly from the handset

Interesting the actual nitty-gritty parameters in the SIP headers are missing, replaced with X for anything “private” or identifiable.

Luckily all this info can be found in the Pcap.

The DM View is great for getting a quick look at what’s going on, on the mobile device itself, without needing a PC.

Logging

The real power comes in the logging functions,

There’s a lot of logging options, including screen recording, TCPdump (as in Packet Captures) and Syslog logging.

From the hamburger menu we can select the logging parameters we want to change.

Settings for Samsung IMS Logger

From the Filter Options menu we can set what info we’re going to log,

Filter options used in Dump output of Samsung IMS Logger application

If you’re leaning about VoLTE & IMS networks, or building your own, I’d suggest checking out my other posts on the topic.