After two years of hibernation, my efforts at implementing simple TR-069 server in perl is alive again. General motivation was to try out few new ADSL modems from ZTE with my server. And it wasn't easy...

General idea of my server is to do implementation which is easy to try and hopefully works with all quirks in existing implementations. And there are A LOT of quirks.

CWMP is basically a sick idea of twisting SOAP into something which will provide persistent connection to client which can be used to introspect device options and set them up. Back in 2007 when I started implementation, current version of TR-069 was 1.0. In meantime, DSL forum (which changed it's name to Broadband forum) decided to push out new TR-069 version 1.1, which I still haven't seen on any devices.

I have anticipated different implementations, so in first round of implementation I decided to parse XML using XML::Rules. This allowed me to use DSL-like language to implement extraction of interesting element from XML responses sent by CPE devices (CPEs are ADSL devices sitting in our homes). And that worked fairly well (at least it was tested with Thompson and Zyxel devices). Until, I got hold of ZTE device that is. It decided to return binary date inside one of XML tags (without CDATA around it) making XML::Parser on which XML::Rules depend bark.

So, I had to change XML parser. I opted for XML::Bare which doesn't have problems with invalid XML, but I had to implement rules part on my own. Which wasn't huge problem because I used only subset of functionality.

But then I tried to setup some data using SetParameterValues. And noticed that it doesn't work. This was strange, and after a two days of trials and errors I found out that ZTE devices require ParameterKey field in XML. Strange thing is that this parameter is defined as optional in TR-069 specification, and it isn't really used: it's enough to have just empty tag in generated XML to make ZTE device happy.

This is not only protocol violation which I found. Specification clearly defined that SOAPAction header is mandatory in all requests, but, ZTE decided not to send it at all. After all this you might wonder why would I like to put so much effort in implementing semi-defined protocol which is really useful only to IPSs. My initial motivation was to provide first free implementation of TR-069, but nowadays there are few TR-069 alternatives: OpenACS is probably best known, but it requires Java, JBOSS and MySQL just to get started.

And I didn't really care about user interface at all. I wanted to be able to write a small snippet of perl code which would allow easy customization of CPE configuration without going through user interface.

To do that, I decided to implement on-disk queue using IPC::DirQueue in which specific commands for clients are inserted and then sent one-by-one until queue for this client is empty. In current version all CPE parameters are first introspected (getting current values and writable status) and stored in simple YAML file on disk, allowing easy review or import into another system.

If you have fixed configuration which you want to push to all client, you can just create vendor.yaml file by copy/paste from file generated by CPE introspection and all CPEs pick up setting from it.

If you wanted to do something more complex (make a lookup into legacy database and deduce configuration from it, for example) you can always extend CWMP::Vendor with new perl function will implement something like this.

To make this even easier, I decided to move project to git (so perl-cwmp is now available on github) and setup publicly visible ACS server which you can use to check weather your CPE implementation of TR-069 will work with my server. This requires you to have administrative privileges on your CPE device, and probably isn't good idea if your provider is already managing your modem using TR-069. But, in that case, you won't be able to change it's setting anyway :-)

However, this would mean that you would have to send full passwords to me also (because TR-069 doesn't encrypts them) so basically you are forced to install version locally to try it out if you have any passwords in your configuration which you don't want to share with everyone.

After nine months of playing with Thompson ADSL modems I have two projects which I wrote in perl, both of which is, as far as I know, first Open Source GPL implementation of those protocols.

MDAP

MDAP is protocol used by Thompson CPE devices to issue commands to CPEs (called ants) using multicast address 224.0.0.103 and port 3235 registered by IANA.

It's very cool idea, since you can connect as many devices as you have network ports or bandwidth, and allthough they all will boot with same IP address (and this create conflicts on IP network), you can still sand commands to each individual device using multicast.

Originally I developed it to flash multiple modems at once, but since I also added simple rules to change IP addresses and issue commands to devices. This essentially enables you to flash devices to some version of firmware and then change configuration a bit and have you test lab ready in few moments.

This project doesn't have a real project page yet, but you can take a look at source if you are interested...

This project also include (but doesn't use yet) simple perl BOOTP and TFTP servers, so in the end it will probably have perl-only solution for MDAP. If you just use included scripts and documentation for setup, it will use binary bootp and tftp server since this configuration was in use for at least half of the year, and I consider it stable.

CWMP

Perl CWMP server is essentially a low-level support for broken idea to communicate with devices using persistent connection SOAP with invalid XML (name spaces in some responses are just invalid) known as TR-069.

This is work-in-progress, and right now it's stable enough to work with multiple devices at once. In essence, it's protocol-violating SOAP server implementing persistent connection handling as described in TR-069 documentation (empty post, even without headers as first request, ehhh....).

Idea is to enable you, the user, to write perl rules against CPE devices.

It's half-way there: It does have disk-based command queue for each device (which is also NFS save, which is nice if you want to have multiple servers) and persistent storage for each CPE internal data tree implemented using DBM::Deep or YAML. When used with YAML, it great way to understand protocol. However, not all methods are implemented, but I hope to have full implementation by end of January 2008.