network – Oleg Kutkov personal blog

Printing sk_buff data

Oleg Kutkov — Wed, 16 Oct 2019 22:41:31 +0000

Sometimes when working with network packets inside the Linux kernel, it might be very useful to print packet contents to see what is actually going on. Here I’m describing how to print packet from sk_buff structure and analyze this data with Wireshark. In this short note, I will not describe capturing the packets inside the kernel but only show how…

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Modifying Linux network routes using netlink

Oleg Kutkov — Wed, 28 Aug 2019 23:14:11 +0000

Last time we talked about getting a Linux routing table with a simple Netlink code. Now it’s time to do more interesting stuff. Let’s add and delete some routes using the power of the Netlink! At the end of this article, we will create a command-line utility with syntax similar to ip route command, which can add and delete custom…

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Monitoring Linux networking state using netlink

Oleg Kutkov — Tue, 13 Feb 2018 23:38:20 +0000

Once in my work, I needed to monitor all changes in the Linux networking subsystem: adding or deleting IP addresses, routes, etc. Maybe the best way to do this is to use socket-based Netlink technology. Using Netlink, we can “subscribe” to some network-related notifications from the kernel. It’s also possible to send commands to the network stack and change the…

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