---
title: "UDP"
description: "1 posts about UDP, summarised, each linking to the original."
---

# UDP
> 1 posts about UDP, summarised, each linking to the original.

## Articles

### [BPF, XDP, Packet Filters and UDP](https://yomu.fyi/post/bpf-xdp-packet-filters-and-udp.md)
- Company: [Fly.io](https://yomu.fyi/company/fly-io.md)
- Published: Oct 20, 2020
- Type: Explainer

Deploying unmodified UDP applications across an anycast edge and worker network is harder than proxying HTTP, because UDP carries no convenient metadata for forwarding the original socket addresses. The initial implementation used userland services, AF\_PACKET sockets, and custom proxying, but the post argues that kernel-level packet handling is a better fit than adding and monitoring another service. It explains BPF’s evolution into eBPF, then describes using XDP for fast ingress processing, XDP\_REDIRECT around WireGuard limitations, and TC BPF on the worker side; Firecracker tap devices make reply traffic appear as host ingress. The verifier requires bounds checks and debugging benefits from dropwatch and perf-based packet tracing. The result is a beta deployment path for UDP applications on Fly.io.