Visualize your firewall by graphing its rules. (See the example graph if this doesn't make sense yet.)

• Graphviz
• iptables

If compiling from source:

• GHC (>= 6.8.2)
• lhs2TeX (>= 1.11)
• GNU Make

For Ubuntu Server 16.04 run the following to install prerequisites

$ sudo apt install iptables graphviz make lhs2tex ghc libghc-parsec3-dev

$ iptables -L -vx | gressgraph > iptables.twopi
$ twopi -Tsvg iptables.twopi > iptables.svg

See the source for more detailed documentation, including a description of how the program was written.

Note: There are no commandline options. Also, I've only tested the program on my own simple iptables ruleset. It's likely that it will fail to parse your rules.

$ make
$ make test

If you didn't receive gressgraph.pdf:

$ make doc

gressgraph is waiting for input. Make sure you've sent it something on its stdin (it does not take a file as a commandline argument).

I build gressgraph with Nix to try to ensure reproducible builds:

nix-build dev.nix

default.nix is for inclusion in a top-level file (such as all-packages.nix). dev.nix builds gressgraph with a fixed version of nixpkgs, providing stability at the cost of inflating the nix store.