Hacking on tollgate

Tasks that I’ve got in mind at the moment:

IPv6 support

I’ve started implementing IPv6 support in the backend of tollgate in a seperate branch. At the moment it’s got some basic backend support but I haven’t implemented the frontend code just yet (or the scanning module for ipv6). There’s some stuff to consider though:

  • Done, implemented in IPv4 -t nat -j REDIRECT doesn’t work in ip6tables at all. They have -t mangle -j TPROXY instead, which requires setting some “interesting” socket options (ie: I don’t think Apache will work any more for the first stage of the captivity landing).
  • IPv6 privacy extensions will mean you have a lot of constantly changing IPs. We can handle this pretty easily though (at least for the outgoing connections) by having a browser window open that updates the IP address periodically (treating it similar to an IPv4 change).
  • Incoming connections I want to have a flag on to say whether a host may be accessible from the outside world, defaulting to no. As part of this getting the “permanent” IPv6 RA address may be important. This can be done by a multicasted ping for most operating systems, or sniffing router advertisements.

Improve the documentation

This is a fairly general task, anyone can pick this up. Particularly a step-by-step installation guide would be helpful, or some sort of bootstrap script so you can put that on a system, it pulls deps and then the git repo.

This has been now started in the form of the tollgatebuilder project: https://github.com/micolous/tollgatebuilder

Testing framework

There’s no test cases, we probably should have some.

Internationalisation / localisation

Started an Esperanto translation of the project a while ago, haven’t really touched it since. Many strings aren’t in the translation files, and the setup of where the strings actually are could be improved a lot, because it’s a mess.

Porting to non-Linux systems

I’d like to see this software ported to non-Linux systems. I’ve done some preliminary research that’s come up empty as yet as to operating systems with firewalls that meet all of the following requirements for tollgate’s backend to work properly.

The majority of the work you’d need to do in porting the software is in the backend. There’s a little bit of Linux-specific frontend code to print out the contents of the ARP table. All the backend is setup in a way that it calls from the frontend are abstracted away from iptables.

Before you start work porting it to a new operating system, please consider the following list of requirements. If you can’t get it to do everything in this list, then tollgate won’t work.

  • Ability to filter traffic by IP and MAC address.
  • Port redirection, so captivity can work. (ie: When you have no quota it redirects HTTP requests to a web server, resets all connections)
  • Ability to filter based on quota remaining.
  • Ability to do both positive and negative accounting. Positive accounting is where you count upwards continuously the amount you’ve used, and negative accounting is where you decrement the amount you’ve used. Many firewalls I’ve looked at only do positive accounting.
  • Ability to have shared/named accounting labels. So I can say “decrement counter X”, and multiple rules can share that counter.
  • Expose the counters via some procfs or sysfs-like interface. For example, xt_quota2 (the module we use in iptables for quota) exposes it’s counters in /proc/net/xt_quota/LABEL_NAME. With that you can read and write counters like files.
  • Ability to access the ARP table.
  • Doing all of the above stuff in kernel space. Running an extra daemon isn’t really an acceptable solution to me.

Flow diagram (Linux)

TODO: Finish writing this.

This is how a packet is handled inside tollgate when running on Linux.

  1. If it’s a new connection, it hits the NAT table rules.

Submitting Patches / Coding Style Manual

All the patch management for the project is handled via the GitHub project. Please file a pull request using the GitHub interface.

As for coding “style”, we use mostly follow PEP-8, with the exception that we use tabs instead of spaces. Anything that is thrown as an error by the pep8 tool should be fixed.

We target Python 2.6 and 2.7, and Django 1.2 - 1.4.

Please make sure that any platform-specific (Linux) code you write has a fallback for development on non-Linux systems. There’s a platform support module in frontend for this. backend doesn’t matter – that should only ever work on platforms that actually are supported.

Never include any project files in the source tree, or any editor-specific garbage in the headers of files.

Known Issues

  • xt_quota2 doesn’t always show current quota data in iptables command. It should not be relied on for accurate display of quota information via iptables command, use /proc/net/xt_quota/ instead because that is accurate. This effects all SMP systems. The actual accounting process is accurate however.
  • Port forwarding doesn’t work correctly when the internal and external ports are different.

  • There’s no way to deregister a console from an account that hasn’t signed in to the current event. (ie: Previous event the console is marked as being owned by user X, next event user Y can’t sign it in because user X hasn’t attended)

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