Asterisk, and other worldly endeavours.

A blog by Leif Madsen

Archive for 2009

Why NDAs are Useless

Here is a post I came across from my twitter feed discussing why NDAs are essentially useless and unenforceable in the digital age. Many good points are made, and for the most part I agree with them. I’m not quite so vehemently opposed to them as the author is as I know they aren’t enforceable. The reason I sign them is a good faith gesture to my clients. I think we both know they aren’t useful, but it gives the client a nice litmus test to determine whether I’m just looking to steal ideas, or at least to say, “Hey, it’d be great if you didn’t twitter or blog about anything you learn while looking at our system.” — at least not directly of course, you can’t ask me to forget something I may have learned while working on a project for you 🙂

Written by Leif Madsen

2009/12/09 at 6:01 pm

Update: Asterisk TFoT v3 Progressing Nicely

Jim and I have been working feverishly for the past few days, and the only thing that can cure it is more cowbell! Or probably more accurately, more writing!

We’ve been making some good progress on rewriting a couple of chapters so far, and tweaking a few other ones. We’re in the process of finishing up the first drafts of the new installation chapter and the initial configuration chapter, and I’ve started work on a chapter about queues. I hope to have about 50% of the queue chapter done by the end of today.

Last night Jim and myself went out to have a pint and to talk about the book, and we both realized how much our consulting experience is going to impact the quality of the book, and the ability to better define a set of best practices. I certainly think this edition of the book will surmount the quality of the first two editions, and the entire community will benefit from it. I’m really excited about it.

Hopefully we can make some good pushes over the next couple of months and get a draft of the book done early in the new year, which should set us up for a release in the spring. It’s amazing how much work and time goes into creating books; the people who do this for a living are certainly a special kind of people.

Since our plan is to more openly develop the book and get the community more actively involved in the testing and proofreading of the book, I’ll be sure to post an update here as soon as we have something available for reading.

Written by Leif Madsen

2009/11/27 at 8:27 am

Posted in Asterisk

Tagged with , , ,

Cisco VPN Client on Ubuntu Karmic 9.10

I have a client who I need to connect to via a Cisco VPN, and since I use Ubuntu as my primary OS on my MacBook Pro, I’ve often needed to find some information about how to get the client working.

I had previously found some information about patching on Ubuntu 9.04 and it worked great, but since updating to 9.10 I had the same compile time issues I had before, which makes sense since the kernel is different now.

I found this site: which had some good instructions for getting it going, but there almost appeared to be a patch missing, at least for my platform. The patch I needed was found on this site here:

All the patches for the VPN client appear to have come from the forums:

Hopefully that gets you all the information you need to get your Cisco VPN client working on Ubuntu Karmic 9.10!

Update: June 15, 2010

So I’ve been having some problems trying to get the Cisco VPN client working past a certain kernel version update (I think it’s something like 2.6.19-something). I’m currently running 2.6.31-22-generic x86_64. I spent a bit of time trying to figure out why I couldn’t get past that older kernel (and to avoid rebooting). On some kernels it would lock up the system entirely, on other kernels the CPN client just wouldn’t connect.

After some web searching, I came across this blog post dated September 2009: It seems to have the patch I needed to get around a compile time option that is described on that blog post. The error I was getting when compiling was:

CC [M]  /usr/src/vpnclient/interceptor.o
/usr/src/vpnclient/interceptor.c: In function ‘add_netdev’:
/usr/src/vpnclient/interceptor.c:284: error: assignment of read-only location ‘*dev->netdev_ops’
/usr/src/vpnclient/interceptor.c: In function ‘remove_netdev’:
/usr/src/vpnclient/interceptor.c:311: error: assignment of read-only location ‘*dev->netdev_ops’
make[2]: *** [/usr/src/vpnclient/interceptor.o] Error 1
make[1]: *** [_module_/usr/src/vpnclient] Error 2
make[1]: Leaving directory `/usr/src/linux-headers-2.6.31-22-generic'
make: *** [default] Error 2

After the patch provided on that blog post I was still getting an error like so:

Making module
make -C /lib/modules/2.6.31-22-generic/build SUBDIRS=/usr/src/vpnclient- modules
make[1]: Entering directory `/usr/src/linux-headers-2.6.31-22-generic'
scripts/ *** CFLAGS was changed in "/usr/src/vpnclient-". Fix it to use EXTRA_CFLAGS.  Stop.
make[1]: *** [_module_/usr/src/vpnclient-] Error 2
make[1]: Leaving directory `/usr/src/linux-headers-2.6.31-22-generic'
make: *** [default] Error 2
Failed to make module "cisco_ipsec.ko".

Oh I’ve seen that error before. I used a patch from a site I mentioned earlier:

Note that I’ve not actually checked to see if I only needed the latter patch, but with a combination of patch with the first site I mentioned in this update followed by the above mentioned sites patch, I was able to get onto my VPN connection for the client I require this for. Hope it helps!

Written by Leif Madsen

2009/11/27 at 8:19 am

Posted in Technology

Tagged with , , , , ,

Starting work on Asterisk: TFoT 3rd edition

As many of you know, I’m a co-author of Asterisk: The Future of Telephony. While my girlfriend is away in Mexico for a week with the girls, I’m going to try and focus a bunch of attention on getting A:TFoT 3rd edition started (which is much overdue).

If you have any ideas for topics you would like covered in the new edition, or something that wasn’t covered as heavily as you wanted in the 1st and 2nd editions, feel free to let me know, and your ideas will be considered! I hope to get the installation chapter written today, and as things progress, we’ll get them posted up on the web (likely somewhere on for review by the community.

We’re going to try and write mostly in the open as we have things ready to go, so a more thorough community review can be done this time around rather than the closed review we’ve used in the past and the “get it when it’s done” approach.

More information to follow in the coming week(s)!

Written by Leif Madsen

2009/11/23 at 9:03 am

Posted in Asterisk

Tagged with , , ,

Jim van Meggelen, Open Source Telephony Renaissance Man

In case you missed it, Suzanne Bowen of DIDX recently interviewed co-author of Asterisk: The Future of Telephony and good friend of mine, Jim van Meggelen. If you’ve never had a chance to see Jim speak at a conference, do yourself a favour and try to attend one of his sessions. He is extremely entertaining and informative, and is always a joy to speak to.

Jim also talks about the much anticipated 3rd edition of Asterisk: The Future of Telephony.

Check out the interview of Jim van Meggelen by Suzanne Bowen here:

Written by Leif Madsen

2009/11/21 at 10:04 am