2026-05-07
When a critical Linux kernel privilege escalation was publicly disclosed, Cloudflare's security and engineering teams detected, investigated, and mitigated the threat across our global fleet, confirming zero customer impact and no malicious exploitation....
2025-10-29
Many products at Cloudflare aren’t possible without pushing the limits of network hardware and software to deliver improved performance, increased efficiency, or novel capabilities such as soft-unicast, our method for sharing IP subnets across data centers. Happily, most people do not need to know the intricacies of how your operating system handles network and Internet access in general. Yes, even most people within Cloudflare. But sometimes we try to push well beyond the design intentions of Linux’s networking stack. This is a story about one of those attempts....
2025-10-29
WARP’s initial implementation resembled a VPN that allows Internet access through it. Here’s how we built it – and how you can, too. ...
2025-10-21
This post explores the performance of BPF LPM tries, a critical data structure used for IP matching. ...
2025-09-25
We are further hardening Cloudflare Workers with the latest software and hardware features. We use defense-in-depth, including V8 sandboxes and the CPU's memory protection keys to keep your data safe....
2025-05-07
udpgrm is a lightweight daemon for graceful restarts of UDP servers. It leverages SO_REUSEPORT and eBPF to route new and existing flows to the correct server instance....
2025-04-02
Yarn tests fail consistently at the 27-second mark. The usual suspects are swiftly eliminated. A deep dive is taken to comb through traces, only to be derailed into an unexpected crash investigation....
2025-02-14
The Linux kernel can produce a hung task warning. Searching the Internet and the kernel docs, you can find a brief explanation that the process is stuck in the uninterruptible state....
2025-01-03
Multi-Path TCP (MPTCP) leverages multiple network interfaces, like Wi-Fi and cellular, to provide seamless mobility for more reliable connectivity. While promising, MPTCP is still in its early stages,...
2024-03-06
This post illustrates some of the Linux Kernel features, which are helping us to keep our production systems more secure. We will deep dive into how they work and why you may consider enabling them as well...
2024-02-08
This is our story of what we learned about the connect() implementation for TCP in Linux. Both its strong and weak points. How connect() latency changes under pressure, and how to open connection so that the syscall latency is deterministic and time-bound...
2023-11-17
The initial posts are dedicated to the x86 architecture. Since then, the fleet of our working machines has expanded to include a large and growing number of ARM CPUs. This time we’ll repeat this exercise for the aarch64 architecture....
2023-05-11
If you run your software on Linux, the Linux Kernel itself can satisfy all your cryptographic needs! In this post we will explore Linux Crypto API for user applications and try to understand its pros and cons...
2023-03-20
If I navigate to https://blog.cloudflare.com/, my browser will connect to a remote TCP address from the local IP address assigned to my machine, and a randomly chosen local TCP port. What happens if I then decide to head to another site?...
2023-01-31
In the Linux kernel before 6.1.6, a NULL pointer dereference bug in the traffic control subsystem allows an unprivileged user to trigger a denial of service (system crash) via a crafted traffic control configuration that is set up with "tc qdisc" and "tc class" commands....
2023-01-16
A race condition in the virtual ethernet driver of the Linux kernel led to occasional packet content corruptions, which resulted in unwanted packet drops by one of our DDoS mitigation systems. This blogpost describes the thought process and technique we used to debug this complex issue....
2022-11-28
Many leaks happen because of software bugs and security vulnerabilities. In this post we will learn how the Linux kernel can help protect cryptographic keys from a whole class of potential security vulnerabilities: memory access violations....
2022-07-26
In this blog post I'll share my journey deep into the Linux networking stack, trying to understand the memory and window management of the receiving side of a TCP connection...
2022-07-18
A crash in a development version of flowtrackd (the daemon that powers our Advanced TCP Protection) highlighted that libxdp (and specifically the AF_XDP part) was not Linux network namespace aware. ...
2022-07-04
Here’s a short list of recent technical blog posts to give you something to read today...
