High-Performance Edge Tunnelling: Zero-Copy I/O, NAT Traversal, and QUIC 0-RTT Architecture
Building a fast, resilient tunnel client means working around limits at three distinct layers: Kernel-to-userspace overhead : every byte a proxy forwards is copied across the kernel/user boundary twice, and each chunk costs two system calls. Network topology : hard (endpoint-dependent) NATs and Carrier-Grade NAT (CGNAT) get in the way of direct peer-to-peer paths. Transport latency : a fresh TCP + TLS connection spends round trips on handshakes before the first request byte can be sent, which hurts short-lived requests. This guide covers the kernel primitives, protocols and design trade-offs for each layer. It also says where each technique stops helping, because the three layers interact in ways that are easy to get wrong. Every code sample below was compiled and run, either against a loopback echo test or against a mock server. Part 1: Cutting the user-space copy with splice() A conventional user-space forwarder reads from one socket into an application buffer, then writes ...
