VIDEOS 》 Linux Kernel Network Programming - struct net - struct netns_ipv4 - /proc/sys/net/ipv4

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.

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.

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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.

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.

/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.

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Here is a quick reference of important Linux Kernel Data Structures of various assorted Kernel Subsystems such as: Process, Memory Management, Networking, File System, Device Drives, IPC and so on. So when you write custom Kernel code, it is often you may need to populate a new instance of one of these data-structures or just access the existing ones. Hence it is very important to know some of these and get familiarized with. You can bookmark this page, so that you can use this as a quick reference when you write your own custom Linux Kernel Modules.

A circular buffer, circular queue, cyclic buffer or ring buffer is a data structure is a fixed-size buffer as if it were connected end-to-end or can be a dynamic one if implemented via Linked Lists. This is a data-structure quite popularly used in many parts of Linux Kernel such as Device Drivers, especially Network Hardware drivers, Network Packet Buffer such as sk_buff and so on. We can use a Ring Buffer in user-space application programming too. These kind of buffers are more suited for holding steady stream of incoming data. For example Network Packets. If the buffer gets full, we can discard the oldest buffer elements (such as packets). And to avoid we can increase the buffer size. So circular ring buffers plays a major role especially in Network Appliances such as Routers, Firewalls, etc.