December 2005
Intermediate to advanced
1066 pages
33h 38m
English
Content preview from Understanding Linux Network InternalsBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Chapter 32. Routing: Li nux Implementation
Chapter 30 provided an overview of the main tasks of the routing subsystem, and Chapter 31 introduced the features such as Policy Routing and Multipath that IP implements on top of the basic routing functionality. In this chapter, I introduce the main data structures used by the routing code. I then show:
How scopes are defined for routes and IP addresses
How the routing subsystem is initialized
What kind of external events the routing subsystem needs to be notified of to keep its routing information updated
Later chapters will go into detail on the routing cache, routing tables, and routing lookups.
Kernel Options
As we will see in the rest of this chapter, routing does not involve just receiving a packet on one interface, consulting the routing table, and forwarding the packet out of the right outgoing interface. There are a number of additional tasks to take care of at the same time. Quite a few interesting routing-related features have been implemented in the Linux kernel. In addition to those we will see later in this chapter, many others are waiting for the green light from Linus or owners of other subsystems to be integrated into the kernel.
Here I briefly introduce the features of the Linux kernel that influence the behavior of the routing code so that you will not suffer confusion when you peruse the source code. Each feature is further described in dedicated sections in this and later chapters.
Routing options can be classified into two ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.