LINUX KERNEL NETWORKING PDF

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Contribute to faquir/itBooks development by creating an account on GitHub. The Linux networking kernel code (including network device drivers) is a large There is a 10 pages Linux kernel networking walkthrouh document which was written nohalicanka.tk~snilsson/public/papers/trash/nohalicanka.tk 13) IPSec. Understanding the Linux. Kernel. Building Secure Servers with. Linux Inc. The Linux series designations, Understanding Linux Network Internals, images of.


Linux Kernel Networking Pdf

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Linux Kernel Networking info is scattered in too many places around the web "Writing Netfilter modules" (67 pages pdf) by Jan Engelhardt. Linux kernel networking is a complex topic, so the book won't burden you ISBN ; Digitally watermarked, DRM-free; Included format: PDF. While preparing this document, I asked for reviewers on #kernelnewbies on irc. nohalicanka.tk I got a lot of response. The following individuals helped me with .

When browsing kernel networking core source code, in various places you will probably encounter the term NAPI New API , which is a feature that most network device drivers implement nowadays. You should know what it is and why network device drivers use it. This proved to be inefficient in terms of performance under high load traffic.

NAPI was first introduced in the 2. With NAPI, under high load, the network device driver works in polling mode and not in interrupt-driven mode. This means that each received packet does not trigger an interrupt. Instead the packets are buffered in the driver, and the kernel polls the driver from time to time to fetch the packets. Using NAPI improves performance under high load.

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For sockets applications that need the lowest possible latency and are willing to pay a cost of higher CPU utilization, Linux has added a capability for Busy Polling on Sockets from kernel 3. With your new knowledge about network devices under your belt, it is time to learn about the traversal of a packet inside the Linux Kernel Networking stack.

The decision about whether a packet should be forwarded and on which interface it should be sent is done based on the result of the lookup in the routing subsystem, which I describe in depth in Chapters 5 and 6.

The lookup in the routing subsystem is not the only factor that determines the traversal of a packet in the network stack. For example, there are five points in the network stack where callbacks of the netfilter subsystem often referred to as netfilter hooks can be registered.

The kernel netfilter subsystem is the infrastructure for the well-known iptables userspace package.

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Chapter 9 describes the netfilter subsystem and the netfilter hooks, along with the connection tracking layer of netfilter. IPsec has two modes of operation: transport mode and tunnel mode. This ttl is decremented by 1 in each forwarding device. This is done to avoid an endless journey of a forwarded packet because of some error.

Moreover, each time a packet is forwarded successfully and the ttl is decremented by 1, the checksum of the IPv4 header should be recalculated, as its value depends on the IPv4 header, and the ttl is one of the IPv4 header members.

Chapter 4, which deals with the IPv4 subsystem, talks more about this. You will learn about this in Chapter 8, which deals with the IPv6 subsystem. A large part of the book discusses the traversal of a packet in the networking stack, whether it is in the receive path Rx path, also known as ingress traffic or the transmit path Tx path, also known as egress traffic.

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This traversal is complex and has many variations: large packets could be fragmented before they are sent; on the other hand, fragmented packets should be assembled discussed in Chapter 4. Packets of different types are handled differently. For example, multicast packets are packets that can be processed by a group of hosts as opposed to unicast packets, which are destined to a specified host.

Multicast can be used, for example, in applications of streaming media in order to consume less network resources. Handling IPv4 multicast traffic is discussed in Chapter 4. Duplication of this publication or parts thereof is permitted only under the provisions of the Copyright Law of the Publisher s location, in its current version, and permission for use must always be obtained from Springer. Violations are liable to prosecution under the respective Copyright Law.

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Linux Device Drivers, Third Edition

In the last 17 years he has been a software developer for three innovative startups and a semiconductor company. Rami lives in Israel and he has participated in highly advanced Linux kernel projects, in particular those related to networking. He has published several articles and given lectures about Linux kernel networking and virtualization. He has more than ten years of experience working with large UNIX systems and tuning the underlying hardware for optimal performance and stability.

Brendan s love for all forms of hardware has helped him throughout his IT career, from fixing laptops to tuning servers and their hardware in order to suit the needs of high-availability designs and ultra low-latency applications.

Brendan takes pride in the open source movement and is happy to say that every computer in his house is powered by open source technology. He resides in Hong Kong with his wife, Vikki, who continues daily to teach him more Cantonese.

I would like to thank the Linux kernel networking maintainer, David Miller, for the great work he has done over all these years and all the developers who continue to participate and contribute to the networking subsystem.

Rami Rosen xxix 30 Preface This book takes you on a guided, in-depth tour of the current Linux kernel networking implementation and the theory behind it.

For almost a decade, no new book about Linux networking has been written. A decade of dynamic and fast-paced Linux kernel development is quite a long time. This preview shows page 1 out of pages. Unformatted text preview: For your convenience Apress has placed some of the front matter material after the index.

Please use the Bookmarks and Contents at a Glance links to access them. You will find in the following pages an in-depth and detailed analysis of the networking subsystem and its architecture. I will not burden you with topics not directly related to networking, which you may encounter while reading kernel networking code for example, locking and synchronization, SMP, atomic operations, and so on. There are plenty of resources about such topics. On the other hand, there are very few up-to-date resources that focus on kernel networking proper.

This book is also not a cumbersome, line-by-line code walkthrough. I focus on the essence of the implementation of each network layer and the theory guidelines and principles that led to this implementation. The Linux operating system has proved itself in recent years as a successful, reliable, stable, and popular operating system.

And it seems that its popularity is growing steadily, in a wide variety of flavors, from mainframes, data centers, core routers, and web servers to embedded devices like wireless routers, set-top boxes, medical instruments, navigation equipment like GPS devices , and consumer electronics devices.

The Linux operating system, which started as a project of a Finnish student named Linus Torvalds back in , based on the UNIX operating system, proved to be a serious and reliable operating system and a rival for veteran proprietary operating systems. The Android operating system, based upon the Linux kernel, is common today in tablets and smartphones, and seems likely to gain popularity in the future in smart TVs.

Apart from Android, Google has also contributed some kernel networking features that were merged into the mainline kernel. Linux is an open source project, and as such it has an advantage over other proprietary operating systems: Other open source operating systems, like the different types of BSD, have much less popularity. This project, started by Sun Microsystems, has not achieved the popularity that Linux has. Among the large community of active Linux developers, some contribute code on behalf of the companies they work for, and some contribute code voluntarily.

All of the kernel development process is accessible via the kernel mailing lists. Contributing code is done via sending patches to the appropriate kernel mailing lists and to the maintainers, and these patches are discussed over the mailing lists. The Linux Kernel Networking stack is a very important subsystem of the Linux kernel. It is quite difficult to find a Linux-based system, whether it is a desktop, a server, a mobile device or any other embedded device, that does not use any kind of networking.

Linux Kernel Networking - Implementation and Theory.pdf -...

Even in the rare case when a machine doesn't have any hardware network devices, you will still be using networking maybe unconsciously when you use X-Windows, as X-Windows itself is based upon client-server networking.

A wide range of projects are related to the Linux Networking stack, from core routers to small embedded devices. Some of these projects deal with adding vendor-specific features. GSO is a networking feature of the kernel network stack that divides a large packet into smaller ones in the Tx path.

Many hardware vendors implement checksumming in hardware in their network devices. Many projects provide some security enhancements for Linux. In the embedded device arena there are, for example, many wireless routers that are Linux based; one example is the WRT54GL Linksys router, which runs Linux. There is also an open source, Linux-based operating system that can run on this device and on some other devices , named OpenWrt, with a large and active community of developers see.

Learning about how the various protocols are implemented by the Linux Kernel Networking stack and becoming familiar with the main data structures and the main paths of a packet in it are essential to understanding it better. The lowest layer is the physical layer, which is the hardware, and the highest layer is the application layer, where userspace software processes are running. The physical layer: Handles electrical signals and the low level details.NAPI was first introduced in the 2.

This traversal is complex and has many variations: large packets could be fragmented before they are sent; on the other hand, fragmented packets should be assembled discussed in Chapter 4. Provides network services to end-user applications. Rather than use a trademark symbol with every occurrence of a trademarked name, logo, or image we use the names, logos, and images only in an editorial fashion and to the benefit of the trademark owner, with no intention of infringement of the trademark.

He resides in Hong Kong with his wife, Vikki, who continues daily to teach him more Cantonese. A large part of the book discusses the traversal of a packet in the networking stack, whether it is in the receive path Rx path, also known as ingress traffic or the transmit path Tx path, also known as egress traffic.

IPsec Rosen, Rami Pages Moreover, each time a packet is forwarded successfully and the ttl is decremented by 1, the checksum of the IPv4 header should be recalculated, as its value depends on the IPv4 header, and the ttl is one of the IPv4 header members.

And it seems that its popularity is growing steadily, in a wide variety of flavors, from mainframes, data centers, core routers, and web servers to embedded devices like wireless routers, set-top boxes, medical instruments, navigation equipment like GPS devices , and consumer electronics devices.

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