Friday, 3 September 2010


As a follow-on from my last post I'll discuss the networking on my Fedora 11 machine. I'm not a massive networking geek; I know quite a bit, but mostly through trial-and-error as a step to getting something else working. For this reason I've never introduced something unnecessary into the mix for its own sake, and thus all I knew about SOCKS was that there's version 4 and 5 in the wild, and it's used by The Onion Router. Since I've always used TOR for HTTP, and used a privacy-filtering-type proxy like Privoxy to handle the HTTP<->SOCKS tunneling, I've never bothered learning more about it.

Now, my office machine is set up to route through a SOCKS proxy on a different machine on the ethernetwork. Web browsing is simply a matter of Firefox's Edit->Settings->Advanced->Network->Settings. However, Thunderbird (which has exactly the same connection changing interface as Firefox) can't connect through IMAP this way. This is due to IMAP not going over HTTP. The same applies to SVN, ping, etc. There is a solution though, which is to use connect-tunnel to run a local server for redirecting calls to any port through a HTTP proxy. Running a connect-tunnel command like "./connect-tunnel -P -T" will allow us to run a command like "svn co svn://localhost:10234" which will think it's checking out a subversion repository from the current machine on port 10234, when in fact it is being routed through a HTTP proxy on port 1080 of to the remote machine at on port 3690.

This is great, but the proxy isn't HTTP, it's SOCKS, so we need some way of tunneling this HTTP connection through SOCKS (so, in this example, we'd have a SOCKS proxy redirecting HTTP traffic which is encapsulating an SVN connection). This was fine for Firefox, which has built-in facilities to redirect over a SOCKS proxy, but not all applications do (especially if they don't even know they're being tunneled through HTTP in the first place!). This is where we use a "socksify" program, which intercepts HTTP requests and redirects them without the application which made them knowing about it. There are a few of these, for example Dante contains such functionality and is in Debian, but unfortunately it isn't in Fedora and I was after something I wouldn't have to compile (due to dependency hell). Fedora does contain tsocks which is pretty simple to set up and use, and worked for some applications. It could be used either via "tsocks my_application_name" (eg. "tsocks evolution" to run the Evolution mail reader through SOCKS), or via adding its library to the LD_PRELOAD environment variable, which affects all subsequently executed applications (eg. put it in your .bash_profile). However I found it didn't work for some programs. I then tried proxychains, which I'm pretty happy with. It is called in a similar way to tsocks, eg. "proxychains evolution", and works in some cases where tsocks doesn't.

Aside from this I also recommend setting environment variables, such as "http_proxy" (which, once again, can be done via .bash_profile) and your desktop's settings (I found Gnome's to be useless here, since I didn't come across any application which actually paid attention to it, but KDE applications consistently adhere to this setting, even if not all of them wind up working properly). For Subversion the /etc/subversion/servers file is a good place to put HTTP proxy settings, and try using http:// for the repository address, as this may be configured to work as well as svn://.

Basically, try everything you can find, try them in combination and try layering/tunneling them. Even if you don't seem to need one method now, the next application you try may need it ;)

Freedom to Work

I've been messing with my new work computer, on which I had the option of running Windows Vista or Fedora 11, and thought I'd give a run-down of how I've been finding it, the issues I've come across, how I've fixed them and future tinkering opportunities. Needless to say, if you're looking for any information about fixing issues with Windows Vista then you're in the right place. As a first step you'll need to wipe over it with Fedora 11, then your computer will be usable and under your control so that you can follow the advice below if you'd like to.

The graphics card is Nvidia, but isn't supported by the nv driver :( I tried nouveau, which starts up OK with the right resolution and a working cursor, but everything else looks like someone's taken a dump in the framebuffer. I've kept clear of Nvidia cards for years because they're anti-Freedom, but a consequence of this is that I'm not familiar with nouveau settings like I am with Intel, AMD and VIA. Rather than spend too long trying to grok nouveau I had to do the unthinkable: install Nvidia's binary blob :( Gives output at the native resolution of the widescreen monitor, unlike VESA, but obviously I'd like to purge this proprietary contaminant from the machine at some point. I think I'll do some research into nouveau driver options in my own time, then spend a few minutes each morning testing them at work, since it obviously requires restarting X over and over. If I can get it working I'll post the results here and maybe on some Wikis. It certainly can't be as awkward as getting my XO's screen to play nicely under Debian ;)

There were only (supposedly) patent-free Free Software codecs installed on the machine, since that's how Fedora has to ship as it's from the "land of the the free", but for those of us in less backwards jurisdictions this isn't particularly brilliant for testing videos and things. I'm not overly familiar with Fedora's package naming conventions so I installed Gstreamer's good, bad and ugly meta-packages, but a lot of guides don't make a distinction between non-Free codecs and patent-encumbered Free Software codecs, so I might've unwittingly pulled in some evilware. I'll take a closer look through at some point, but for now I'm sticking to MPlayer, since it's a far more powerful application than, eg. Totem, and is more useful from the commandline.

Previously-installed Malware
When I took over the machine it was full of proprietary junk. It's got some scarily dangerous repositories enabled like one from Adobe, one from Dropbox and, less evil (or so they say), one from Google. It's got some crappy Flash plugin installed from Adobe, but thankfully SWFDec overrides it. I'm not sure how this proprietary player's installed itself, so I haven't looked into how to undo it utterly. When I do I think I may have to keep an equivalent in some sort of sandbox anyway (eg. a UnionFS overlay) since I may have to test some sites which are infected with Flash (although, of course, I don't know how anyone could debug something for which they don't have full, irrevocable access to the source). As well as this it's also got Skype, which is a program that does a limited form of SIP/Jingle-style VoIP. However, not only is the client proprietary, the whole network it uses is a black box too! I'd like to purge this from existence, but unfortunately work does some communication via this obfuscated mess, so I can't for the moment because there's no interoperable replacement (did someone say "vendor lockin" AKA "the exact reason why this crock should never be used by anyone"?). Once again I think a sandbox might be required to stop it playing havoc with the system, or whatever it's meant to do (I don't know since I've not seen the code). As well as this is Dropbox, which I've never had the misfortune to use directly, but heard many horror stories from the Computer Science department about how prevalent the myth is that Dropbox is somehow a version control system. What it really is seems to be is some sort of UPnP-aware WebDAV-esque remote filesystem, which appears to attempt peer-to-peer synchronisation and causes unending conflicts if it's used for anything more elaborate than the equivalent of an email conversation. I can't really see the point of it, since it's just a poor man's Git, but once again I don't know of any compatible alternative (LOCKIN ALERT! LOCKIN ALERT!) so I think I'll sandbox it too, at least the daemon.

It seems a shame to me that so much infrastructure has been build on such untrustworthy foundations, for a company which is apparently "Proud to be Open Source". Of course, the gatekeepers of these secret services will die at some point, and their code will either be freed or become useless, but hopefully we won't have to wait that long for someone to kill it. Who knows, maybe I could play a role in this now that I'm trying my hand at Web technologies?

Next post will cover networking, which is occasionally cropping up problems as I do new things, but is worth sharing what I tried nonetheless.