iptables_extensions

Contains custom iptables extensions (matches/targets) used in DNOS.

Prerequisites

1. sudo apt install iptables-dev
2. Make sure the machine you're compiling at is running the same kernel and iptables version as what DNOS is running (5.4.0-73-generic and 1.8.4 respectively, as of the time of this writing).

Building

• Build all extensions: make all
• Clean all extensions: make clean

These iterate and build/clean all the extensions under the extensions/ directory.

The output of each extension is:

1. A .ko file - The kernel module responsible for the heavy lifting of the extension (registers to netfilter, processes skbs etc).
2. A .so file - A userspace plugin for the iptables program. Mostly responsible for argument parsing.

Tree structure

1. extensions/
   • Contains all the extensions, each in its own directory.
2. out/
   • The build process will place here the .so and .ko files, each in the matching extensions' directory.
3. help/
   • Contains helpful tutorials.

Installing new extensions

1. Copy the .so files into /usr/lib/x86_64-linux-gnu/xtables
2. insmod the .ko files

But Lahav Senpai, how do I write a new extension myself?

Check the help/ directory. help/Netfilter_Modules.pdf is a pretty good one.