Comment by masklinn

> I can see why they rewrote QUIC in Rust and for use in userspace

As far as I know, while they might have either way, they did not ("rewrite QUICK [...] for use in userspace"): the linux kernel implementation only landed late 2025. Quiche was started ca 2018 (that's when Cloudflare started beta-deploying QUIC, the first public alpha of quiche was january 2019).

I don't know that there even was an in-kernel implementation of quic before msquic.sys which I believe first shipped in Server 2022 circa mid 2021 (and is used as the implementation backend by MsQuic on Server 2022 and W11).