BPF, XDP, Packet Filters and UDP

The text discusses the use of eBPF (extended Berkeley Packet Filter) for deploying UDP applications on Fly.io, a content distribution network for Docker containers. It delves into the history and evolution of packet filters, from CSPF to BPF+ and eventually eBPF, highlighting their role in observability and access control. The author explains how eBPF is used in TC (traffic classifier) system and XDP (eXpress Data Path), allowing for real-time decision making, modification of packets, and routing them to the appropriate interfaces or sockets. The text also provides advice on writing BPF C code, debugging tools like dropwatch and perf, and emphasizes the potential benefits of using eBPF in various networking scenarios.