enricobuehler
4f9071b980
Until now there was one Xbox identity, `device_type = 4` / `045E:0B13`, and Windows folded a client's `XboxOne` request onto it because the only Windows Xbox backend was the XUSB companion, which presents one fixed 360 identity and cannot vary it. The HID backend can, so the fold goes and two identities join it: devtype 4 045E:0B13 pf_xboxwireless Xbox Wireless Controller devtype 5 045E:02FD pf_xboxones Xbox Wireless Controller (One S) devtype 6 045E:0B22 pf_xboxelite Xbox Elite Wireless Controller Series 2 `GamepadPref::XboxElite` takes wire byte 11 — the first unassigned one, and the round-trip test previously asserted `from_u8(11) == Auto` with a comment saying assigning it must update that; the sentinel moved to 12. The C ABI mirror and the generated header moved with it. ⭐ ALL THREE SHARE ONE REPORT DESCRIPTOR, deliberately. In HID terms they are the same pad; the descriptor is the report shape, not the identity. §3 of the handoff records that our single hand-written descriptor already cost three separate bugs, and inventing two more would multiply that debt for no measured gain. They differ in VID/PID, product string, hardware id and Device Manager description only. ⚠️ All three install `pfGamepadXbox`, the section that attaches the `xinputhid` bus filter. That was the open risk: Microsoft's `xinputhid.inf` promotes by an explicit hardware-id allow-list containing `02D1, 02DD, 02E3, 02EA, 0B00, 0B0A, 0B13, 02FF` — and NEITHER `02FD` NOR `0B22` is on it. Measured on .173: promotion does not care, because it comes from our own AddReg rather than from matching Microsoft's ids. All three gain `IG_00`, register an XUSB interface, and are read live by classic XInput. Had this gone the other way the two new identities would have been strictly worse than the one they joined. The XUSB escape hatch needed a runtime degrade to stay honest. `pick_gamepad` is compile-time only, so with `PUNKTFUNK_XBOX_BACKEND=xusb` the host would have resolved and echoed `xboxelite` in its `Welcome` while actually building a 360 pad. `degrade_xbox_identity` folds the identity back at runtime, mirroring `degrade_if_no_uhid`. VERIFIED ON WINDOWS (.173 — none of this compiles on macOS; the driver needs the WDK and the rest is `cfg(windows)`): * `cargo test -p pf-inject --lib` 104/104 — including `hwid_matches_inf`, `hwid_devtype_table_matches_the_driver` and `only_the_xbox_identity_installs_the_xinputhid_section`, all now sweeping the whole identity set and asserting the section split in both directions. * `cargo test -p punktfunk-core --lib gamepad` 7/7; `cargo check -p punktfunk-host` clean. * Driver builds and signs; the descriptor/`wReportLength` const asserts still hold with the descriptor shared three ways. * ON GLASS, per identity, via the new `--xboxones` / `--xboxelite` devtest legs: each gets its own devnode (`PF_XBOX_0` / `PF_XBOX_ONES_0` / `PF_XBOX_ELITE_0`), each HID child gains `IG_00`, each registers an XUSB interface, and XInput reads each live (packets advancing, `buttons=0x1000`). * macOS: `cargo fmt --all --check` clean in both workspaces. NOT VERIFIED / NOT DONE * **Elite paddles are NOT implemented.** `BTN_PADDLE1..4` would need descriptor buttons, and once `xinputhid` promotes the pad it claims the HID collection exclusively — XInput has no paddle fields and the HID consumers that do may be locked out, so the buttons would likely reach nobody. The decisive measurement is cheap and named in the code: hold a paddle bit set and see whether a user-mode HID reader still gets reports. Until then the Edge remains the only virtual pad with native back-button slots and nothing should be advertised otherwise. * **No client picker offers the Elite**, and none can auto-detect it — SDL3's `GamepadType` has no Elite variant. It is reachable today only via `PUNKTFUNK_GAMEPAD=xboxelite` or a hand-edited client setting. All five clients ship the same curated six options by deliberate parity, so adding one is a cross-client UX change, not part of this. * Nothing here has run in a real streaming session; every measurement came from the devtest.
punktfunk-core
The shared protocol core — the one place where punktfunk's transport, forward error correction, and crypto live. It's linked into the host and every native client, so there's exactly one implementation of the wire format everywhere.
Written in Rust with no async on the per-frame path (native threads only). It exposes both a normal Rust API and a stable, versioned C ABI, so the Swift and Kotlin clients — and any C embedder — link the same code as the Rust ones.
What's in here
- Transport & session (
session.rs,transport/,packet.rs) — thepunktfunk/1data plane over raw UDP: packetization, reassembly (with attacker-bounded limits), pacing, and socket tuning. - FEC (
fec/) — the wall-breaker. Two codes:- GF(2⁸) classic Reed–Solomon with the Cauchy generator matrix — byte-identical to the
nanorslibrary Moonlight uses, so our parity is decodable by a stock Moonlight client. - GF(2¹⁶) Leopard-RS (SIMD, O(n log n)) — up to 65535 shards/block, which removes the ~1 Gbps
FEC ceiling.
punktfunk/1negotiates this one.
- GF(2⁸) classic Reed–Solomon with the Cauchy generator matrix — byte-identical to the
- Crypto (
crypto.rs) — AES-128-GCM session encryption with per-direction nonce salts and sequence-as-AAD; SPAKE2 PIN pairing lives behind thequicfeature. - QUIC control plane (
quic.rs,client.rs, featurequic) — the Hello/Welcome/Start handshake, cert pinning/TOFU, reverse audio, and the embeddableNativeClientconnector. This is the only placetokio/quinnare allowed; the feature is off by default so the core stays runtime-free. - C ABI (
abi.rs) — the versioned surface (punktfunk_abi_version(),PunktfunkConfigcarrying its ownstruct_size) that generatesinclude/punktfunk_core.hvia cbindgen at build time.
Build outputs
The crate builds three ways at once (crate-type = ["lib", "cdylib", "staticlib"]):
| Output | Used by |
|---|---|
lib (rlib) |
the host, probe, and tools link it as a normal Rust crate |
cdylib (.so/.dylib) |
the Swift / Kotlin clients via the C ABI |
staticlib (.a) |
the C test harness and static embedding |
Test
cargo test -p punktfunk-core # unit + proptest + loopback
cargo run -p loss-harness # FEC loss-resilience sweep (no network needed)
bash crates/punktfunk-core/tests/c/run.sh # standalone C-ABI link + round-trip proof
Design invariants (do not regress)
- One core, linked everywhere — protocol/FEC/crypto live only here, behind the stable C ABI.
- No async on the hot path — the per-frame pipeline is native threads only;
quic(tokio/quinn) is control-plane only, feature-gated, off by default. - Security hardening stays intact — the reassembler bounds attacker-controlled fields before
allocating; AES-GCM keeps per-direction nonce salts + seq-as-AAD; the ABI checks
struct_size. Regression tests exist — keep them green.
Related
punktfunk-host— the streaming host built on this core- Clients — the apps that link this core over the C ABI (or directly, in Rust)
- punktfunk-planning:
implementation-plan.md(internal planning repo) — why GF(2¹⁶) FEC, the latency budget, and the architecture thesis