So I ran into a rather strange problem. I’ve setup my new servers running Linux (2.4.25). My family-in-law living in Kuwait was having problems contacting my new servers. A router somewhere in Kuwait would drop the connections with “Destination net unreachable”. I also had a similar problem pinging my servers from my parents dial-up Telus account where a router along the way would just kill the connection. I mentioned this problem to a coworker and he said to look into the TCP/IP ECN setting in Linux.
ECN is some feature for congestion control that looks like was/is not in common use. Linux started using this feature by default. Unfortunately it sounds like older IOS versions from Cisco would reset connections when they encountered a packet with this ECN field set. This made certain Linux hosts appear unreachable if ECN was enabled. Interesting.
A quick look shows that all of my Linux servers have ECN enabled by default and the router returning the “Destination net unreachable” was a CISCO of some sort (not that most of the routers are not).
In order to turn off this ECN feature and increase chances of really old firewalls not killing connections to your machine you can do the following:
$ echo "0" >/proc/sys/net/ipv4/tcp_ecn
or add the following to /etc/sysctl.conf:
net/ipv4/tcp_ecn=0
Hopefully this is the cause of the problem. I’m waiting for confirmation from our family in Kuwait that the server is now reachable. In any case this seemed strange enough to make a journal entry about. If anyone else has ideas let me know.
Update: It seems that the problem was simply they were using an older version of Putty/PLink which was incompatible with the OpenSSH server on my machine. No idea why that was crashing. Also the firewall was dropping ICMP packets and returning dest/net unavailable which complicated things.
Everyone else has themes. Now jclement.ca does to. CSS makes this fairly simple in that I can dynamically change the style-sheet the pages reference. What a complete waste of time 
Anji, Kailey and I went to Heritage Park again on Saturday and I took several pictures I’m quite happy with. The color pictures all turned out rather nice with the leaves turning on the trees and the Black and Whites of the train turned out nice as well. I might have to try getting large prints of some of these.
I really like this photo I took this weekend. It was a B&W with yellow filter and I fogged the filter with my breath right before taking the photo. Looks really old fashioned to me.
No not that crazy modelling language that’s all the rage with the OOP programmers these days but User-Mode-Linux. I finally setup a machine and set of admin tools that basically allows me to create virtual machines as I need them and attach them to the Internet. Since I have 16 IPs through Nucleus this means I can have 15 or so hosts on the net without having nearly that much hardware in the basement. This site, jclement.ca, is now entirely hosted in a UML instance on a P2-400 w/ 128M of ram. Not bad.
Instructions and software available here.
A coworker gave me an invite to Google Mail. I signed up and started playing with it and so far I think I’m in love. Their interface is incredibly snappy and nice looking (unfortunately not very browser friendly but I can live with that). Google Mail, for those who don’t know, basically gives you a 1GB mailbox where instead of organizing your mail in folders you just keep it all and search it using some Google like mail searching. So far I’ve been diverting all my e-mail through gmail and been loving it. I hated always trying to pick an appropriate folder for my mail so that on the off chance I needed it in the future I might be able to find it. If you get a chance to sign-up for gmail you really ought to take a look! They also offer top notch spam filtering. As far as contacting me you can still use all the old addresses. They just forward to gmail.
This morning I started up Anji’s ’91 Escort and just pulled away from her house and it stalled. I tried to restart it but to no avail. The dash indicated the fuel cutoff had tripped so I tried resetting that but that didn’t help. Anji called AMA and they came out and towed our car to the local Minute Tune. Our guess was that something to do with the fuel cutoff had worked it’s way free. Unfortunately this wasn’t the case. It seems our timing belt broke which is expensive enough to fix. To make it worse this car has an interference engine which means the in all likelihood the engine is damaged too. Given the age and condition of the car sinking $1000+ into repairs doesn’t seem to worthwhile so I guess that leaves us in the market for a new vehicle. Talk about bad timing. We’ve been spending enough with the new house we really didn’t need this.
