Understanding Linux Network Internals

Chapter 1. Introduction

To do research in the source code of a large project is to enter a strange, new land with its own customs and unspoken expectations. It is useful to learn some of the major conventions up front, and to try interacting with the inhabitants instead of merely standing back and observing.

The bulk of this chapter is devoted to introducing you to a few of the common programming patterns and tricks that you'll often meet in the networking code.

I encourage you, when possible, to try interacting with a given part of the kernel networking code by means of user-space tools. So in this chapter, I'll give you a few pointers as to where you can download those tools if they're not already installed on your preferred Linux distribution, or if you simply want to upgrade them to the latest versions.

I'll also describe some tools that let you find your way gracefully through the enormous kernel code. Finally, I'll explain briefly why a kernel feature may not be integrated into the official kernel releases, even if it is widely used in the Linux community.

Basic Terminology

In this section, I'll introduce terms and abbreviations that are going to be used extensively in this book.

Eight-bit quantities are normally called octets in the networking literature. In this book, however, I use the more familiar term byte. After all, the book describes the behavior of the kernel rather than some network abstraction, and kernel developers are used to thinking in terms of bytes .

The terms ...