I have been working on the same problem in other areas. My ultimate goal is to rewrite nginx in Rust passing as much as the upstream tests as possible while leveraging the strongest aspects of Ruts ecosystem - i.e. rustls (modern memory safe OpenSSL), Tokio (async runtime), h2 (http 2 impl) rather than implementing from scratch like the upstream. I started with Lua, then porting over Valkey, and now working on nginx. The reason was because I wanted to learn the ins and outs before taking on the most complex portion.

[1]. https://github.com/ianm199/lua-rs/tree/main Lua

[2]. https://github.com/ianm199/valdr Valkey/ Redis

[3]. https://github.com/ianm199/nginx-rs-port nginx

Happy to answer any questions on the approach! When I started a few weeks ago the harnesses on their own were not good enough to get very far without a "meta harness" of sorts but that is changing largely with Claude Workloads and Mythos. A lot of the work is developing some custom tooling to move these along faster.