Tutorials :: The Linux Channel

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.

Here is a list of all The Linux Channel sponsors/donors (individual/companies).

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.

/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.

Here is my multi-episode video series on evaluation of Rockchip ROC-RK3566-PC from Firefly with stock OpenWRT firmware.

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.

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.

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.

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.

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.

Here are the quick links or architecture images of various Network Packet Processing Hardware Offload via NIC card. And also here is my detailed video and demo on GRO (Generic Receive Offload).