Sat 05 November 2011 | tags: backwards ip, belkin, reverse ip, rtkit, -- (permalink)

While attempting to remotely debug a linux machine today, I was first encountering a strange problem. Any process that took more than about 1/2 second to complete, would freeze. top, ps, lsmod, tail -f, the list goes on. For example, trying to run dmesg and display it's output would freeze, but dmesg into a file, and it would complete!

After much digging, I eventually found that rtkit (rtkit-daemon) is constantly trying to make pulseaudio operate at realtime. In reality, we don't need our audio to operate in realtime as most modern computers can keep up with video playback just fine. For the few people we actually want near real time audio (say, people recording multitrack stuff), then they can enable it themselves. Disabling rtkit (actually, uninstalling it as it appears to be started in dbus stuff), seems to have solved that problem.

The next problem was a strange DNS response. A dns request through the Belkin modem, to this server (purewhite.id.au) would return 10.45.41.175 instead of 175.41.45.10. I know what reverse DNS is, but this is reverse IP! Belkin is returning the ip in reverse!! (Or backwards if you desire). A quick check reveals that this relatively new modem, hasn't got any new firmware for it (and it's firmware is over 1 year old). Apparently, someone else had this problem and belkin told them to just hard code the ip's in your hosts file for the hosts that are being returned wrong! I believe it was also a Belkin modem that would return strange results when you did an AAAA request (ipv6).
So if you have a Belkin, maybe force your computer to use your ISP's DNS servers directly, rather than the routers. (Or take it back to the shop, because after all, it is faulty)