fix(proto): Send CONNECTION_CLOSE also during the handshake

[matheus23]

Description

There are places handling CONNECTION_CLOSE frames in noq-proto. One is in process_early_packet, which processes frames during the handshake, and process_packet, handling frames any other time.
When we received a CONNECTION_CLOSE frame over the wire, the latter would move the state to draining and set connection_close_pending = true. The former would do almost the same, except it wouldn't set the close frame to pending.
This meant that connections that were closed by the server during the handshake would close on the client side without it sending a CONNECTION_CLOSE frame itself. The server side was thus left hanging and wouldn't close "gracefully".

This PR just aligns the behavior between these two places.

Breaking Changes

None

Notes & open questions

Disclosure: Heavily assisted by GLM 5.2.

Change checklist

• Self-review.
• Tests if relevant.
• All breaking changes documented.

[github-actions]

Documentation for this PR has been generated and is available at: https://n0-computer.github.io/noq/pr/718/docs/noq/

Last updated: 2026-06-19T13:20:38Z

[github-actions]

Performance Comparison Report

709f2cfef98fb4b581632c2c486220f946700d03 - artifacts

Raw Benchmarks (localhost)

Scenario	noq	upstream	Delta	CPU (avg/max)
large-single	5362.2 Mbps	7881.5 Mbps	-32.0%	95.4% / 147.0%
medium-concurrent	5422.9 Mbps	7908.0 Mbps	-31.4%	96.6% / 148.0%
medium-single	3822.1 Mbps	4592.2 Mbps	-16.8%	97.6% / 149.0%
small-concurrent	3734.0 Mbps	5314.2 Mbps	-29.7%	95.3% / 103.0%
small-single	3452.0 Mbps	4760.8 Mbps	-27.5%	93.4% / 102.0%

Netsim Benchmarks (network simulation)

Condition	noq	upstream	Delta
ideal	3082.0 Mbps	4106.9 Mbps	-25.0%
lan	782.4 Mbps	797.8 Mbps	-1.9%
lossy	69.8 Mbps	69.8 Mbps	~0%
wan	83.8 Mbps	83.8 Mbps	~0%

Summary

noq is 27.3% slower on average

[matheus23]

This makes the validate_then_reject_manually test flaky. I'm still looking into it. I suspect this test used to depend on the buggy behavior.

[flub]

Why not test this in proto-only? The fix is only in proto. It is a bit strange to start testing protocol behaviour in noq itself, we don't really do that genereally.

[matheus23]

No particular reason. Will change, if I actually want to do this.

[matheus23]

I investigated the validate_then_reject_manually flakyness, and this PR is not quite the right way to handle this.

E.g. it might mean we only reciprocate the CONNECTION_CLOSE only in the Initial space, even though the server might've sent it to us in the Initial, Handshake and Data space.

The current code architecture isn't quite set up to start processing more frames properly after it received a CONNECTION_CLOSE in the Initial space.

This means there's this weird "limbo" state, where if both ends are noq, then connections that are closed fully in the Initial space (i.e. if the server side uses noq_proto::Endpoint::refuse) work, and if connections are full established and the server uses noq_proto::Connection::close work, but when you use noq::Connecting::drop(), you'll not close gracefully.

That said, this isn't terribly important so I might have to re-visit this later.

[flub]

just making sure you're aware this section exists: https://www.rfc-editor.org/rfc/rfc9000.html#name-immediate-close-during-the-