Tony's ramblings on Open Source Software, Life and Photography

IPTables Trickery

I've had a bit of a strange situation on my network - Googling never did come up with anything for me.

I have a private network. All my servers sit behind the firewall on the private LAN. A few of those servers provide services to the Internet on specific ports.

Sharing those ports to the outside using iptables is trivial. The problem arises when you are trying to access the internal server using the external DNS / IP from inside the network. What would happen is that iptables would redirect your packets to the correct server, but the return address would be your local internal IP, so the packets return to you as if coming from the private address instead of the public address, and your local computer won't know what to do with them.

There's actually a very simple solution, assuming you have static IP's on the Internet and on the internal server. Using a combination of source and destination masquerading, you can rewrite those IP addresses to match. The downside is you double the traffic on your internal network, but it enables you to provide services that are harder to NAT such as SIP traffic.

Read more for an example fix:


Why Bother With Second Life?

I've been playing with an open source software called "OpenSim." It's compatible with the Second Life client software and implements about 80% of the Second Life features and scripting language.

It's just over 2 years old as a project, and it's amazing how usable it is for how big it is. There's even multiple open "grids" that link various servers together and handle a central login and authentication system for avatars. Other than the lack of in game currency, it's very near to a Second Life experience.

Oh, and did I mention it's open source and free? I'm currently running a test server in "standalone" mode - meaning I'm handling all my own authentication, asset and user databases and all the world zones. I can't decide if I want to apply for region coordinates in the largest open grid "OSGrid" and integrate my zones into the overall metaverse, or if I want to keep it separate for now. I've figured out how to manage users from a PHP website, so I could even integrate the authentication system with GamerzCrib.

The downside is that the physics engine is still under heavy development. Actually they offer four separate physics engines depending on what you want your world to be, but none of them are quite ready for primetime when it comes to vehicles. The other problem I'm having is that as soon as I figure out something cool I want to script I learn that one or more functions I'd need to use to accomplish it are not yet implemented.

But, it's free, and it's cool. The picture is of my avatar and the custom sword I designed. I added my own animation to the sword that when I wield it, my avatar steps into a combat pose, snarls and grabs the hilt with both hands. Cool stuff. And, you can even get graphics clients for Linux. With Linden Labs best skill being the ability to anger their customers, having an option like OpenSim is a lifesaver.


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How to Fold a Botero Portable Background

The hardest part of editing my video for use on Flickr was getting Flickr to recognize it with a 16:9 aspect ratio. I was reducing the resolution to make a smaller file, and every time I did, Flickr would squish it into a 4:3 aspect ration.

Finally I found that using a resolution of 640x360 would result in a nice widescreen video on Flickr.

This was captured from a Canon HV20 HD camcorder with a wireless mic and loaded into Linux using dvgrab. Editing was done in Cinelerra and the final resize and conversion for upload to Flickr was done with ffmpeg.

Ubuntu Jaunty 64 bit Flash Video Performance

Ever since upgrading to Jaunty I've been hating the fact that I made the switch. Early on I had overall video performance problems but shortly after the initial release of Jaunty an update fixed those.

Yet still I had horrible full-screen video performance from Macromedia Flash - especially on sites like Hulu.

Well today I found the solution. It seems that the power-saving "ondemand" features in Jaunty was never coming out of power save mode to handle the increased CPU usage of full screen Flash video. Simply adding the "CPU Frequency Scaling Monitor" to the taskbar and setting the CPU to "Performance" - or manually setting it at a higher speed - solved the issue.


Getting CallerID Working With Asterisk

As you may have guessed from yesterday's post, I've just finished a complete reinstall of our PBX system. The old system was running on Mandrake (yeah, Mandrake NOT Mandriva) and had done a great job. Unfortunately we were having a phone port lock up periodically that would require rebooting the server.

Since another "event" left me with a spare motherboard and rack mounted case I went ahead and ordered a Digium PCI-Express analog card to handle our four phone lines.

I've configured four Asterisk servers before and expected things to go smoothly. My first problem was that my last server was a version 1.2 and the newer version of Asterisk made several config file changes, causing very strange problems in my dialplan.

The next problem was that no matter what, caller-id service almost never reported the incoming number. After banging my head against the wall over and over trying to get the Ubuntu Hardy Asterisk packages to work with various configs, I finally took a stab in the dark and downloaded the latest zaptel sources from Digium and compiled them. A quick reboot and all the incoming caller-id worked beautifully.


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One of The (Few) Ways That OSS Sucks

I love open source software so much that nearly our entire enterprise is running on it. Our internally developed software is all either written for LAMP, or some recently in Mono.

I fully understand that open source projects will sometimes become inactive, in fact I have a few I've developed myself that have fallen by the wayside yet at one time had great potential.

What I don't understand is when a commercially backed open-source solution like Openfire from Ignite Realtime has a known issue for years that goes unresolved and requires a simple workaround. Then again, who here hasn't heard of Internet Explorer?

Integrating the Openfire instant messaging system with an Asterisk phone server is relatively easy, but when you first attempt to connect it to the Asterisk server, it just does nothing. It turns out the setup script for the Asterisk-IM plugin is wrong... and has been since 2007.

Here's the solution.

I will say though, I still love Openfire with it's LDAP directory integration and my (now working) Asterisk phone system integration. The ability to know the phone status of any user by glancing at my contact list is such a small thing, but it really does make a difference.


Mounting Windows Shares with "credentials"

I had a hard time using the following line in my fstab until I finally realized the problem:

//winserver/incoming /home/outgoing cifs uid=me,credentials=/etc/smbpassfile,noauto,user 0 0

The mount would fail, and my DMESG would report:

[2492180.882826]  CIFS VFS: No username specified
[2492180.882857]  CIFS VFS: cifs_mount failed w/return code = -22

Doing a mount passing the username and password directly would work just fine. Turns out I was missing the following package:

sudo apt-get install smbfs

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Guess what OS this is running in

Take a guess what OS this is running in:



If you guess Ubuntu 8.10 64 bit with no emulators, you'd be correct! That's a screenshot from Regnum Online, a free to play MMORPG that just happens to offer a Linux client. I took that screenshot from a cliff overlooking the battle before I stupidly jumped into the fray and swiftly died.

Here I am shooting my wimpy magic missile at the beast just before he killed me in one blow:


Regnum has been around for just over two years. It's not quite as in depth or polished as some of the games out there like Knights Online or Silkroad, but it's certainly an enjoyable game. They also have announced that they will be releasing a new upgraded version with better graphics and dynamic shadows in the very near future and that they do plan to continue to support Linux.

Kudos to them - they just go to show that there's no technical reason you can't develop awesome games for Linux. It's mostly political (and market driven,) but we knew that already.


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PHP Sessions can't handle SimpleXML data

I've been banging my head against the wall over an error reported in some PHP code I've been writing. For some reason the session would be trashed on the server and on next page load I'd get "Node no longer exists" when I tried to open the session.

It turns out that you can't take a response from a SimpleXML object and store it in a session. You'd think that if you could type "echo $myxml->thisnode" and get a string that it's really a string, but PHP automatically typecasts and converts as needed - except in the case of storing in a session variable.

There's an easy solution. Use explicit typecasting when trying to store an XML result string in a $_SESSION[] variable:

$_SESSION['myinteger'] = (int)$myxml->myinteger;
$_SESSION['mystring'] = (string)$myxml->mystring;

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DRBD Defaults Too Slow For Today's Servers

I was just setting up a new install of two Ubuntu servers with a TB mirrored between them in realtime using DRBD. It occurred to me while I was configuring DRBD that the default settings are way too slow for current hardware.

For instance, if you're going to set up a high-availability cluster no doubt you're going to have a minimum of a Gigabit network connection between the servers and at least use SATA 300 hard drives - probably in a RAID array to get even more throughput.

The default sync speed in DRBD is only 10 Megabytes / second. It's in your best interests, especially on the initial sync, to increase this considerably. At initial setup time you can safely configure this to be as high as your hardware will allow. Check out this article that describes how to go about calculating it.

For instance, initially my setup used 22 MB as the sync speed, but for the initial sync of 1 TB across a Gigabit crossover using SATA 300 drives was going to take almost 10 hours to complete. My hardware config actually lets me push this as high as 68 MB / second, reducing my initial sync time to about 3 3/4 hours, and that's on two systems with no RAID - simply a 1 TB hard drive synced over a crossover cable.


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