Tracing System CPU on Debian Stretch
May 13, 2018 4:00 PM
How an innocent OS upgrade triggered a cascade of issues and forced us into tracing Linux networking internals....
mmproxy - Creative Linux routing to preserve client IP addresses in L7 proxies
April 17, 2018 10:11 PM
In previous blog post we discussed how we use the TPROXY iptables module to power Cloudflare Spectrum. With TPROXY we solved a major technical issue on the server side, and we thought we might find another use for it on the client side of our product....
Abusing Linux's firewall: the hack that allowed us to build Spectrum
April 12, 2018 1:00 PM
Introducing Spectrum: a new Cloudflare feature that brings DDoS protection, load balancing, and content acceleration to any TCP-based protocol.Today we are releasing Spectrum. ...
Using Go as a scripting language in Linux
February 20, 2018 7:49 PM
At Cloudflare we like Go. We use it in many in-house software projects as well as parts of bigger pipeline systems. But can we take Go to the next level and use it as a scripting language for our favourite operating system, Linux?...
How to Monkey-Patch the Linux Kernel
October 23, 2017 11:28 PM
I have a weird setup. I type in Dvorak. But, when I hold ctrl or alt, my keyboard reverts to Qwerty. You see, the classic text-editing hotkeys, ctrl+Z, ctrl+X, ctrl+C, and ctrl+V are all located optimally for a Qwerty layout....
MORE POSTS
April 05, 2016 12:05 PM
The revenge of the listening sockets
Back in November we wrote a blog post about one latency spike. Today I'd like to share a continuation of that story. As it turns out, the misconfigured rmem setting wasn't the only source of added latency. It looked like Mr Wolf hadn't finished his job....
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December 17, 2015 2:15 PM
Partial kernel bypass merged into netmap main
In a previous post we described our work on a new netmap mode called single-rx-queue. After submitting the pull request, the netmap maintainers told us that the patch was interesting, but they would prefer something more configurable instead of a tailored custom mode....
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September 07, 2015 9:52 AM
Kernel bypass
In two previous posts we've discussed how to receive 1M UDP packets per second and how to reduce the round trip time. We did the experiments on Linux and the performance was very good considering it's a general purpose operating system....
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June 16, 2015 1:47 PM
How to receive a million packets per second
Last week during a casual conversation I overheard a colleague saying: "The Linux network stack is slow! You can't expect it to do more than 50 thousand packets per second per core!"...
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May 11, 2015 10:08 AM
CloudFlare "Interview Questions"
For quite some time we've been grilling our candidates about dirty corners of TCP/IP stack. Every engineer here must prove his/her comprehensive understanding of the full network stack. For example: what are the differences in checksumming algorithms between IPv4 and IPv6 stacks?...
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March 05, 2014 12:00 AM
It's Go Time on Linux
Some interesting changes related to timekeeping in the upcoming Go 1.3 release inspired us to take a closer look at how Go programs keep time with the help of the Linux kernel. Timekeeping is a complex topic and determining the current time isn’t as simple as it might seem at fir...
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October 03, 2013 5:00 AM
Ensuring Randomness with Linux's Random Number Generator
When building secure systems, having a source of random numbers is essential. Without them, most cryptographic systems break down and the privacy and authenticity of communications between two parties can be subverted....
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