Introducing Programmable Flow Protection: custom DDoS mitigation logic for Magic Transit customers (opens in new tab)
Programmable Flow Protection lets Magic Transit Enterprise customers define custom DDoS mitigation logic for proprietary UDP protocols. Customers write eBPF programs that identify valid and malicious packets, then deploy them across Cloudflare’s global network to pass, drop, or challenge traffic. Currently in beta for an additional cost, the system addresses the limitations of generic blocking and rate limiting. ## Custom Protection for Proprietary UDP - Existing Cloudflare protections understand established protocols such as TCP, DNS, NTP, RDP, and SIP. - Proprietary UDP protocols are harder to protect because Cloudflare cannot interpret their application-level payloads. - Customers can now define what constitutes “good” and “bad” traffic using their own protocol knowledge. - Programs can drop or challenge invalid packets before they reach the customer’s origin. ## Why Generic UDP Mitigation Falls Short - UDP is connectionless and optimized for speed, making it useful for gaming, VoIP, and streaming. - When traffic does not match a known protocol, mitigation typically falls back to: - Blocking a destination IP and port - Applying a generic rate limit - These approaches cannot distinguish legitimate packets from attack traffic, potentially causing lag or connection loss for real users. - Fixed rate limits may also be inappropriate: - A network expecting 1 Gbps may need stricter limits. - A network expecting 25 Gbps may require more permissive thresholds. ## How Programmable Flow Protection Works - Customers upload custom eBPF programs that run on every packet destined for their network. - Programs execute in userspace rather than kernel space, providing isolation and flexibility across different customers and use cases. - Execution occurs after Cloudflare’s existing DDoS protections, preserving baseline security coverage. - Like kernel-based XDP eBPF programs, these programs: - Compile to BPF bytecode - Pass safety and termination verification - Run inside a lightweight, isolated virtual machine - Cloudflare provides specialized helpers for: - Maintaining client state between packet executions - Performing cryptographic validation - Sending challenge packets to clients ## Example: Protecting a Proprietary Game Protocol - A gaming provider running on UDP port 207 could inspect its proprietary application header. - If the header contains a protocol-specific token, the customer’s eBPF program can: - Parse the packet - Extract part of the token, such as its final byte - Pass packets with the expected value - Drop packets that fail validation - This allows legitimate players’ traffic through even when attacks use randomized source addresses, ports, and payloads. Programmable Flow Protection is best suited to Magic Transit customers whose custom UDP protocols cannot be protected effectively by standard protocol-aware controls. By combining customer-specific packet logic with Cloudflare’s global network and stateful challenge mechanisms, it enables more precise mitigation than blanket blocking or generic rate limiting.