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,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.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.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.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.
Chapter 33. Routing: The Routing Cache
The routing cache is used to reduce the lookup time on the routing tables. The center of the routing cache is the Protocol Independent Destination Cache, which is simply called DST . Even if policy routing is in effect—creating multiple routing tables—a single routing cache is always shared by all the routing tables.
The main job of the cache is to store information that allows the routing subsystem to find destinations for packets, and to offer this information through a set of functions to higher layers. The cache also offers some functions to manage cleanup. The cache stores the information about the routing table cache entries that applies to all L3 protocols and can therefore be included in any data structure used to represent a routing table cache entry.
In this chapter, we will see:
How the cache is implemented
How new elements are inserted and existing ones are deleted
How ingress and egress lookups are implemented, and where they differ
How external subsystems can interact with the cache via an interface provided by the DST
How different kinds of garbage collection keep the size of the cache under control
How the DST provides a rate-limiting mechanism for egress ICMP REDIRECT messages
Routing Cache Initialization
The routing cache is implemented as
a hash table. It is initialized in ip_rt_init, which is
the initialization
function of the routing subsystem and is described in the section "Routing Subsystem Initialization" in Chapter 32.
The size ...
Become 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,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
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.