Years ago Yahoo got some proxy software from an acquisition, a few years later they made it open source as Apache Traffic Server (http://trafficserver.apache.org/), and today its the backbone of Yahoo's infrastructure. They have a number of full time engineers that work on it full time, they use it in production, and they are implementing cutting edge features like IPv6, SPDY, and HTTP/2 support.

SOCKS is was one of the legacy features of Apache Traffic Server. However, it hasn't been maintained. If you build from git right now you'll find SOCKS support completely broken at least four ways (a couple bad asserts, wrong byte order, and an uninitialized field). They took the documentation on the SOCKS feature out a while ago but never got around to removing the code.

Since it was there I spent some time over the weekend and fixed it. There are still some issues around SOCKS still but it works well enough that you can surf though tor with it. If there is interest in it here I'd be happy to put together a how-to for Linux and MacOS to get it built and configured.

I'd also like to encourage people to make some noise - Yahoo does have SOCKS servers internally but they don't test using Traffic Server with them because they don't think anyone uses the feature (and they are right, there is no way the code works for anyone in the present state). But if there was interest then maybe they'd keep the code fresh going forward.

I'm including a copy of the patch with this e-mail just to get it out. You can pull their git repository (https://github.com/apache/trafficserver) and apply it to the master master branch.