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Linux NETFILTER-HOWTO

Rusty Russell, `netfilter@rustcorp.com`

v0, Fri Apr 23 01:07:54 CST 1999

This document describes the netfilter architecture for Linux, and some of the major systems which sit on top of it, such as packet filtering and Network Address Translation.

1. Introduction

1.1 What is netfilter?
1.2 What's wrong with what we had in 2.0 and 2.2?
1.3 Who are you?
1.4 Why does it crash?

2. Netfilter Architecture

2.1 Netfilter Base
2.2 Packet Filtering
2.3 NAT and Masquerading
2.4 Reverse NAT (load-sharing), Port Forwarding, and Transparent
2.5 Other Additions

3. Information For Users

3.1 Packet Filtering with iptables
3.2 Packet Filtering with ipfwadm or ipchains
3.3 Network Address Translation with ipnatctl
3.4 Masquerading/REDIRECT With ipfwadm or ipchains
3.5 Mixing iptables and ipnatctl

4. Information for Programmers

4.1 Understanding iptables
4.2 Extending iptables
4.3 Understanding NAT
4.4 Extending NAT
4.5 Understanding Netfilter
4.6 Writing New Netfilter Modules
4.7 Packet Handling in Userspace
4.8 Translating 2.0 and 2.2 Packet Filter Modules
4.9 Motivation