Katerina Barone-Adesi

Driven by the needs of scientific computing, rapid rises in memory bandwidth have made it possible to implement high-performance network functions in a radically simpler way. Snabb Switch rides this wave, bypassing the kernel to process network packets in terse Lua, leaving the programmer free to focus on the essence of their problem. This talk presents our experiences delivering a carrier-grade implementation of "lightweight 4 over 6", an IPv4-as-a-service architecture that tunnels access to the IPv4 internet through specialized Snabb appliances.

We report on our recent experience implementing a carrier-grade virtualized network function, with observations on what it is like to build real-world, high-performance Snabb applications. (and kernel bypass). Each instance runs at essentially line speed on two ten-gigabit Ethernet cards.

Lightweight 4-over-6 (lw4o6) defines an IPv4-as-a-service architecture that allows ISPs to internally operate an IPv6-only network, tunneling IPv4 connections between lw4o6-aware endpoints installed at the customer's site (e.g. in OpenWRT) and an internet-facing "lwAFTR". Lw4o6 was specified in 2015 as RFC 7596 and has the architectural advantage that the carrier-side lwAFTR only needs per-customer state, not per-flow state. An lw4o6 system can also be configured to share IPv4 addresses between multiple customers as part of an IPv4 exhaustion strategy. It allows IPv4 networks to interoperate smoothly, while a carrier between them runs a pure-IPv6 network.

Igalia has built an open source "lwAFTR" implementation that is ready to deploy in production. We describe the joys of hacking with Snabb, giving a quick intro to Snabb, modern x86, and lw4o6 along the way.

Discover property-based testing, and see how it works on a real project, the pflua compiler.

How do you find a lot of non-obvious bugs in an afternoon? Write a property that should always be true (like "this code should have the same result before and after it's optimized"), generate random valid expressions, and study the counter-examples!

Property-based testing is a powerful technique for finding bugs quickly. It can partly replace unit tests, leading to a more flexible test suite that generates more cases and finds more bugs in less time.

It's really quick and easy to get started with property-based testing. You can use existing tools like QuickCheck, or write your own: Andy Windo and I wrote pflua-quickcheck and found a half-dozen bugs with it in one afternoon, using pure Lua and no external libraries.

In this talk, I will introduce property-based testing, demonstrate a tool for using it in Lua - and how to write your own property-based testing tool from scratch, and explain how simple properties found bugs in pflua.