Cloudfare: Why we use the Linux kernel's TCP stack - networking

Why we use the Linux kernel's TCP stack: "There are two general themes: first, there is no stable open-source partial kernel bypass technology yet. We hope Netmap will occupy this niche, and we are actively supporting it with our patches. Second, the Linux TCP stack has many critical features and very good debugging capabilities. It will take years to compete with this rich ecosystem.



For these reasons it's unlikely userspace networking will become mainstream. In practice I can think only of a few reasonable applications of kernel bypass techniques:

• Software switches or routers. Here you want to hand over network cards to the application, deal with raw packets and skip the kernel altogether. 
• Dedicated loadbalancers. Similarly, if the machine is only doing packet shuffling skipping the kernel makes sense. 

• Partial bypass for selected high throughput / low latency applications. This is the setup we use for our DDoS mitigations. Unfortunately I'm not aware of a stable open source TCP stack that fits this category.

 For the general user the Linux network stack is the right choice. Although it's less exciting than rewriting TCP stacks, we should focus on understanding the Linux stack performance and fixing its problems. There are some serious initiatives underway to improve the performance of the good old Linux TCP stack."



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