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Tutorials :: The Linux Channel

Watch on Youtube - [406//0] x265 VPN Stack Architecture | Virtual Network Interfaces | OpenVPN | Wireguard | VTun | IPsec ↗

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☆ Tutorials :: Arduino UNO Projects ↗


Tutorials :: Network Software Development

Design & Architecture of custom Dynamic Routing Protocols ↗
Saturday' 13-Mar-2021

Linux Kernel Module to Drop Packets captured via netfilter hooks ↗
Saturday' 13-Mar-2021
Here is my sample Kernel Module to drop packets (i.e sk_buff instance) captured via netfilter hooks. When you want to drop packets in your custom netfilter hooks make sure you never do a manual kfree_skb(skb) API call. Since it is anyway performed once the flow of the code moves out of your kernel module netfilter hook. All you need to do is to return NF_DROP to drop gracefully the desired packet. Here is my detailed video and a sample Linux Kernel module.

Tail Drop - by Network Schedulers to Drop Packets in Network Appliances ↗
Saturday' 13-Mar-2021

Linux Networking Stack :: RFS: Receive Flow Steering ↗
Saturday' 13-Mar-2021
Linux Networking Stack Receive Flow Steering (RFS) aim is to increase data-cache hitrate by steering kernel processing of packets to the CPU where the application thread consuming the packet is running. RFS relies on the same RPS mechanisms to enqueue packets onto the backlog of another CPU and to wake up that CPU.

Código de soquete de amostra UDP para desenvolvedores de software de sistemas e redes ↗
Saturday' 13-Mar-2021
Aqui está meu código de soquete UDP de amostra escrito em C. Ao contrário de outras versões, você costuma obter on-line, esta versão é voltada para desenvolvedores de software de rede e sistemas e como uma referência rápida até mesmo para programadores de software experientes. Neste exemplo / modelo, estou enviando bytes de dados binários brutos de teste do cliente de amostra UDP para o servidor de amostra UDP registrado. O código já possui documentação na forma de comentários (como você pode ver abaixo). Você pode baixar meu código-fonte abaixo e você pode usá-lo diretamente em seus projetos ou você pode usar o mesmo para fins de aprendizagem para entender sobre a programação de soquete de espaço do usuário via protocolo de camada de transporte UDP IPv4.

TCP Link Bonding vs Multipath TCP (MPTCP) ↗
Thursday' 03-Nov-2022
Here is a video series on TCP Link bonding (a.k.a Multihoming) and Multipath TCP (MPTCP). MPTCP is an ongoing effort of the Internet Engineering Task Force's (IETF) Multipath TCP working group, that aims at allowing a Transmission Control Protocol (TCP) connection to use multiple paths (via TCP sub-flows) to maximize throughput and increase redundancy.

UDP sample socket code for Systems and Network software developers ↗
Saturday' 13-Mar-2021
Here is my sample UDP socket code written in C. Unlike other versions you get commonly on-line this version is focused towards systems and network software developers and as a quick reference even for experienced software programmers. In this example/template, I am sending test raw binary data bytes from UDP sample client to registered UDP sample server. The code has documentation already in the form of comments (as you can see below). You can download my source below and you can use it directly in your projects or you can use the same for learning purposes to understand about user-space socket programming via IPv4 UDP transport layer protocol.

Introduction to Network Processors (NPU) ↗
Saturday' 13-Mar-2021

iPerf tool - for network channel analysis, bandwidth tests and system & network benchmarking ↗
Saturday' 13-Mar-2021

Smart NIC Cards ↗
Saturday' 13-Mar-2021
NIC Cards (Network Interface Cards) traditionally contain controller chip which takes care of the core aspects, such as packet reception, buffering (till they are read by OS device drivers), etc. But these days increasingly modern NIC cards can perform several CPU Network Offload functions such as packet/frame checksum, etc. Such hardware offload features of modern NIC cards is crucial to process packets and support packet data transfer rates of around 1Gbps, 10Gbps, even 40Gbps and so on. But beyond that such as 100Gbps and so on, at times even a high-end Xeon/ Intel/ AMD processors will struggle if need to support transfer rates of around 100Gbps or beyond (situations like Link Bonding). These are the situations we need what we call as Smart NIC Cards. A Smart NIC card implements most of the network traffic processing on the NIC itself that would necessarily be performed by the CPU (i.e Operating System) in the case of a traditional NIC card.

IP-in-IP Tunneling Demystified - VPN Tunnels ↗
Saturday' 13-Mar-2021
There can be many ways one can architect VPN Networks. The end objective is to tunnel private IP (typically LAN subnets) within public IP Networks (such as Internet). You can establish such a tunnel in various creative ways, such as Transport Mode, Tunnel Mode, IP-in-IP tunneling, etc. Also you can choose any transport layer protocol of your choice such as send VPN traffic via TCP, or via UDP and so on.

TCP vs UDP an Expert Opinion ↗
Saturday' 01-Jan-2022

Socket Options - Socket Programming - setsockopt(), getsockopt() ↗
Saturday' 13-Mar-2021

Multi-Client TCP Server with pthreads Mutex Synchronized - Code-walk of viewer code - Sekhar Pariga ↗
Saturday' 01-Jan-2022
Here is a code-walk of a git-hub source submitted by a viewer Sekhar Pariga, which is a Multi-client TCP Server with pthreads Mutex synchronized. Basically it is a Directory Listing Server, that serves ls, cd, pwd of directory functions to connecting TCP clients which are remotely (locally) executed by the server. Server is implemented using multi-thread pthread library, to serve multiple clients simultaneously. Server keeps the each accepted client session details in the queue data structure. Client session queue contains each clients socket-fd and present working directory as a queue node.

C code to check valid IP Address (IPv4) - Live Demo and Example ↗
Saturday' 13-Mar-2021

Data-Plane and Control-Plane of a Networking Device ↗
Saturday' 28-Oct-2023

Bufferbloat in a Networking Device or an Appliance ↗
Saturday' 13-Mar-2021

Layer-2 (L2) Multicast Frame Deep Analysis ↗
Saturday' 13-Mar-2021

Network MTU and Path MTU Discovery PMTUD - WAN and Internet Performance Optimization ↗
Saturday' 13-Mar-2021


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☆ Tutorials :: Linux Kernel Software Development ↗


☆ Tutorials :: Linux Kernel Internals (PDFs) - by Ramin Farajpour ↗


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Watch on Youtube - [512//0] x267 Linux Kernel Programming | Memory Allocation and Buffer Management | Performance Tuneup ↗

libpcap Library | Linux User-space Network Stack Development ↗
Sunday' 06-Aug-2023
libpcap is a very popular user-space networking library, with which you can capture and or generate packets. libpcap is the underlying framework for many popular packet capture tools such as tcpdump, Wireshark and so on. In fact libpcap is a part of tcpdump project. But besides just using it as a packet capture tool, you can use libpcap in various applications, such as user-space based networking stack development, etc. In some cases libpcap is yet another alternative to raw-sockets and tun/tap interfaces.

The Linux Channel :: Sponsors ↗
Monday' 30-May-2022
Here is a list of all The Linux Channel sponsors/donors (individual/companies).

Inline Programming | Assembly | Scripts | php, python, shell, etc | Rust in Linux Kernel ↗
Friday' 12-May-2023
Inline programming is a technique where code statements are included directly in the text of a program, instead of being contained in separate files or modules. Inline programming can be useful for small or simple tasks, as it can eliminate the need for a separate script or function. One common example of inline programming is using JavaScripts, Php, etc in HTML documents to create dynamic content. Similarly in Linux Kernel we can find lot of instances where we can find inline programming such as inline assembly and now Rust within the Kernel source.

Linux Kernel /sysfs Interface ↗
Saturday' 14-May-2022
/sysfs is one of the most popular kernel to user-space interface which you can leverage to add an interface to your Kernel code such as Kernel modules, Kernel Device Drivers, etc. Although personally I prefer /proc interface than other alternatives such as /sysfs, ioctl() and so on for my personal Kernel modules/stack. So here is my detailed multi-episode Youtube video series on /sysfs Interface.

Rockchip ROC-RK3566-PC from Firefly | OpenWRT ↗
Thursday' 19-Oct-2023
Here is my multi-episode video series on evaluation of Rockchip ROC-RK3566-PC from Firefly with stock OpenWRT firmware.

What is purpose of Kernel Development - Example SMOAD Networks SDWAN Orchestrator Firewall Kernel Engine ↗
Monday' 18-Jul-2022
Often aspiring students may have this question, that what is the purpose of Linux Kernel Development. Since Linux Kernel is very mature and it has almost everything one would need. Usually, we need custom kernel development in the case of any new driver development for new upcoming hardware. And this happens on and on. But at times we may also come across few features/modules/components which are already provided by the Linux Kernel which are not adequate or atleast not the way we exactly intended to use. So, this is the real-world example, sometimes no matter what Linux Kernel provides as a part of stock Kernel/OS features, sometimes we have to write our own custom kernel stack or module(s) which can specifically cater our exact needs.

Linux Kernel Driver Device Trees ↗
Tuesday' 17-Jan-2023
The Linux kernel is the backbone of the Linux operating system. A device tree is a hierarchical tree structure that describes the various devices that are present in a system, including their properties and relationships to one another. The device tree is used by the Linux kernel to identify and initialize the different devices on a system, and to provide a consistent interface for interacting with them.

Linux Kernel vs User-space - Library APIs - Linux Kernel Programming ↗
Friday' 27-Oct-2023
One of the important aspects a beginner who is into Linux Kernel space systems software development has to understand is that unlike user-space C/C++ programming, where you can freely include any library APIs via respective #include files (which are dynamically linked during run-time via those /lib .so files), in the case of Kernel space programming, these library APIs are written within the Kernel source itself. These are the fundamental APIs which we commonly use, such as memcpy(), memcmp(), strlen(), strcpy(), strcpy() and so on. So here is my detailed Youtube video episode on the same with live demo, walk-through and examples.

Porting Sample libpcap C code to Raw Sockets | User-space Network Stack Framework ↗
Monday' 04-Sep-2023
Here is my multi-episode video series where I demonstrate how you can port the my libpcap sample code, discussed in the earlier episode to raw-socket. This code should further help you to design and architect your own user-space Network stack on top of this fundamental framework.

Roadmap - How to become Systems Software Developer ↗
Friday' 13-May-2022
When you are at the beginning of your career or a student, and aspire to become a software developer, one of the avenues to choose is to become a hard-core Systems Software Developer. However it is easier said than done, since there are many aspects to it as you explore further. As a part of systems developer, you can get into core kernel space developer, kernel device drivers developer, embedded developer and get into things like board bring-up, porting, etc, or can become a user-space systems programmer, and so on. So here is my detailed multi-episode Youtube video series on Roadmap - How to become Systems Software Developer.


Trending Video:
Watch on Youtube - [967//0] Linux Kernel skbuff data-structure - part9 - skb_trim() ↗

How to upgrade or install a latest current release Linux Kernel version manually in Ubuntu? ↗
Saturday' 13-Mar-2021



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