⚡ Bolt: fast path for data-plane packet classification

[igorls]

💡 What

Extracted the msg_type == 4 (WireGuard transport data) case in PacketType.classify into an explicit if check before the switch statement, and marked the function inline.

🎯 Why

PacketType.classify is called on the absolute hottest path: every single incoming UDP packet. Standard switch statements compile to jump tables. Since the vast majority of traffic is data-plane packets (type 4), an explicit if check allows the CPU to better predict the dominant branch and avoids the overhead of setting up and executing a jump table for every data packet. Inlining further eliminates function call overhead across module boundaries.

📊 Impact

Expected improvement: Eliminates a jump table lookup and a function call for every single data-plane packet received, reducing CPU overhead on the main control thread's receive loop.

🔬 How to verify

1. zig build test
2. zig build -Doptimize=ReleaseFast

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PR created automatically by Jules for task 14152184934151083494 started by @igorls

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[Copilot]

Pull request overview

Optimizes WireGuard packet classification on the UDP receive hot path by adding a fast-path for transport data packets and encouraging inlining to reduce per-packet overhead.

Changes:

• Added an early if (msg_type == 4) return for .wg_transport before the switch in PacketType.classify.
• Marked PacketType.classify as inline.
• Documented the optimization rationale in .jules/bolt.md.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/wireguard/device.zig	Adds a fast-path branch for transport packets and marks classifier inline to reduce overhead in the hottest path.
.jules/bolt.md	Captures the optimization “learning” and recommended action for future hot-path work.

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[igorls]

Closing: superseded by docs audit fixes and direct commits to main. See PR #67 (merged) for codec bounds check, and direct commit for timing-safe fix in noise.zig.

[google-labs-jules]

Closing: superseded by docs audit fixes and direct commits to main. See PR #67 (merged) for codec bounds check, and direct commit for timing-safe fix in noise.zig.

Understood. Acknowledging that this work is now obsolete and stopping work on this task.