enricobuehler
73c911cae4
Rumble was level-triggered, unbounded state on a lossy channel: a non-zero level meant "buzz until further notice", healed only by the host re-sending state every 500 ms, and every client guessed when the host had died with its own magic timeout (SDL 1.5 s, Apple 1.6 s, Android up to 60 s). A lost stop, a reordered start, or a dead host could drone the motor for seconds. Make "stuck rumble" inexpressible on the wire. The 0xCA datagram grows a length-tolerant tail — [u8 seq][u16 ttl_ms] — so it self-terminates: the host authorizes a level for at most ttl_ms and renews it (~120 ms) while it holds, letting an abandoned one lapse client-side. seq is a per-pad wrapping reorder gate (reusing GamepadSnapshot::seq_newer) so a reordered stale start can't re-light a stopped motor. Decoders read the first 7 bytes as a plain level and ignore the tail, so no wire-version bump: an old client renders a new host's levels, and a new client falls back to its prior staleness heuristic against an old host (ttl = None). All four generation pairings render correctly. - core: encode_rumble_datagram_v2 / decode_rumble_envelope (datagram.rs); the client demux applies the seq gate then forwards (pad, low, high, Option<ttl>); next_rumble is unchanged (drops ttl), next_rumble_ttl keeps it; ABI adds punktfunk_connection_next_rumble2 + PUNKTFUNK_RUMBLE_NO_TTL, ABI_VERSION 4->5 (WIRE_VERSION unchanged — the tail is backward-compatible). - host (punktfunk1.rs): the flat 500 ms refresh becomes a renewal loop that bumps seq + stamps a fresh TTL on active pads and drains a short post-stop zero burst, then goes quiet. Hatches: PUNKTFUNK_RUMBLE_ENVELOPE=0 (legacy v1 + flat refresh, a bisect switch), PUNKTFUNK_RUMBLE_TTL_MS (clamped [150, 5000]). - renderers honor the TTL as their playback duration/deadline and keep their old heuristic only for a legacy (ttl=None) update: pf-client-core (the Deck haptic keep-alive is now deadline-bounded so it can't sustain a host-stopped rumble), clients/windows (SDL duration), android (JNI packs the lease out-of-band in bit 48 so any u16 ttl is unambiguous; Kotlin createOneShot(ttl)), apple (RumbleRenderer.envelopeDeadline + nextRumble2; sessionStaleSeconds demoted to the legacy fallback). - tests: codec round-trip + tail tolerance + seq-gate reorder (Rust); the probe asserts the v2 tail arrived under PUNKTFUNK_TEST_FEEDBACK; the Apple loopback asserts ttlMs round-trips end to end; RumbleTuning lease-decision cases. The host-side idle-timeout from the previous commit is defense in depth on the game side; this is the guarantee on the client side. Design: punktfunk-planning/design/rumble-envelope-plan.md. 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