How to Write a Linux Firewall in Less than 1000 Lines of Code

Searching_ _ _ · Nov 25, 2011

This article is based on a project in my master course about computer system security at 2010. I’m writing this article to recall the knowledge I’ve learned through the project and also hoping someone else can benefit from it.

The firewall can BLOCK or UNBLOCK packets according to a set of rules. The rules are set by a user space configuraiton utility program.
The firewall configuration utility can add, delete and print rules. And the kernel module will manipulate the network packets according to these rules.

The firewall implementation is done as a Linux kernel module. If you don’t have experience in kernel programming, don’t worry, I’ll try to be as detailed as necessary.

The implementation also has a simple configuration program for users to configure the firewall in user space. And procfs virtual file system is used to pass information between user space and kernel space.

All programming is done in C, and the computing knowledge covered includes command line parsing API in GNU libc, how to write a linux kernel module, knowledge about Linux proc file system, and understanding of netfilter.
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How to Write a Linux Firewall in Less than 1000 Lines of Code - Roman10 Blog

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How to Write a Linux Firewall in Less than 1000 Lines of Code

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How to Write a Linux Firewall in Less than 1000 Lines of Code

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