enricobuehler
01266ff18d
Community-contributed round 5 of the Steam Controller 2 passthrough, reviewed + verified. A Puck-captured pad now presents the dongle's real seven-interface identity (CDC pair, four controller HID slots, management HID) instead of relabelling its reports as a wired 1302 — Steam's Puck feature dances (wireless_transport / esb/bond / 0xB4 slot status) get capture-shaped answers, and the wired identity's canned replies are corrected to the real captures (attribute count, string-attr framing, 0xF2 firmware info, bcdDevice nibble encoding). - new wire pref 10 = SteamController2Puck (Hello/Welcome byte; older peers degrade to Auto), selected by the Android capture link when the transport is a dongle, or by VID/PID in the degraded InputDevice path - TRITON_RDESC is now the captured numbered descriptor (mouse/keyboard lizard collections + per-id vendor reports); unnumbered framing made hidraw mangle feature report 2 and Steam eventually closed the device - interrupt-IN now queues sparse reports (battery/RSSI/wireless edges) instead of keeping latest-only, so a 250 Hz state packet can no longer erase them before the USB/IP poll observes them; EP0 SET_REPORT is split by wValue report type (OUTPUT parsed for rumble vs FEATURE) - vendored usbip-sim: config attributes/max-power, IAD prefix + BOS descriptor support, correct BCD minor.patch encoding (Deck's 0x0300/ 0x0200 values are nibble-zero, so its bytes are unchanged), and full-speed interrupt pacing in ms (was 8 kHz from the HS formula) - Triton feedback is serviced at 1 kHz while an SC2 backend exists so Steam's trackpad haptic writes reach the client unbatched Verified: clippy -D warnings + 319 host tests green on Linux, core wire tests green, Android kit/app compile + unit tests green. On-glass Puck retest owed. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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