feat(rumble): host-authoritative self-terminating envelopes (0xCA v2)

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>
This commit is contained in:
2026-07-11 03:08:27 +02:00
parent 19e9828e8d
commit 73c911cae4
17 changed files with 734 additions and 91 deletions
+139 -15
View File
@@ -1388,7 +1388,9 @@ async fn serve_session(
&& std::env::var("PUNKTFUNK_TEST_FEEDBACK").as_deref() == Ok("1")
{
use punktfunk_core::quic::HidOutput;
let d = punktfunk_core::quic::encode_rumble_datagram(0, 0x4000, 0x8000);
// v2 envelope (seq 0, 400 ms TTL) so the loopback/probe assertion covers the self-
// terminating tail, not just the level.
let d = punktfunk_core::quic::encode_rumble_datagram_v2(0, 0x4000, 0x8000, 0, 400);
let _ = conn.send_datagram(d.to_vec().into());
for h in [
HidOutput::Led {
@@ -1826,6 +1828,49 @@ enum ClientInput {
Rich(punktfunk_core::quic::RichInput),
}
/// Default TTL stamped on a non-zero rumble envelope (0xCA v2): how long the client renders the
/// level before silencing unless the host renews it. Tolerates 23 lost renewals (same loss
/// margin the old flat 500 ms refresh gave) while capping a host-abandoned rumble at this on every
/// client — versus the per-platform client heuristics it replaces (SDL 1.5 s, Apple 1.6 s, Android
/// up to the QUIC idle-timeout). Overridable via `PUNKTFUNK_RUMBLE_TTL_MS` (floored at
/// [`RUMBLE_TTL_FLOOR_MS`] so expiry jitter stays below the clients' tick granularity).
const RUMBLE_TTL_MS: u16 = 400;
/// Floor for the `PUNKTFUNK_RUMBLE_TTL_MS` hatch — below this the ~50 ms client ticks make expiry
/// audible (see `rumble-envelope-plan.md` §5).
const RUMBLE_TTL_FLOOR_MS: u16 = 150;
/// Ceiling for the `PUNKTFUNK_RUMBLE_TTL_MS` hatch. A lease longer than a few seconds defeats the
/// design's "an abandoned rumble stops promptly" goal, and keeping it well under `u16::MAX` means
/// the wire never emits a TTL a narrower client-side slot could mistake for a sentinel.
const RUMBLE_TTL_CEIL_MS: u16 = 5_000;
/// Floor for the derived renewal interval (renew = ttl × 3/10) so an aggressive TTL hatch can't
/// spin the renewal loop faster than this.
const RUMBLE_RENEW_FLOOR_MS: u64 = 60;
/// How many times a transition-to-zero (a stop) is re-sent on the renewal ticks after the
/// immediate stop datagram, before the pad goes quiet. Covers stop-datagram loss for legacy
/// clients (a v2 client also self-silences at TTL); even a fully lost burst heals via the client's
/// own expiry. `3` total zero sends = the immediate one + this many renewal re-sends.
const RUMBLE_STOP_BURST: u8 = 2;
/// Send one rumble datagram on the universal 0xCA plane. `envelope_on` picks the self-terminating
/// v2 form (`[level][seq][ttl_ms]`, the default) or the legacy v1 level datagram (the
/// `PUNKTFUNK_RUMBLE_ENVELOPE=0` bisect hatch). Best-effort like every side-plane datagram.
fn send_rumble(
conn: &quinn::Connection,
envelope_on: bool,
pad: u16,
low: u16,
high: u16,
seq: u8,
ttl_ms: u16,
) {
let d: Vec<u8> = if envelope_on {
punktfunk_core::quic::encode_rumble_datagram_v2(pad, low, high, seq, ttl_ms).to_vec()
} else {
punktfunk_core::quic::encode_rumble_datagram(pad, low, high).to_vec()
};
let _ = conn.send_datagram(d.into());
}
/// The per-session input thread: route pointer/keyboard events to the host-lifetime injector
/// service (`inj_tx`) and gamepad events to this session's [`PadBackend`] (`gamepad` — the
/// resolved Hello preference: uinput X-Box pads or virtual DualSense pads), with rich
@@ -1834,6 +1879,12 @@ enum ClientInput {
/// LED/trigger feedback on the HID-output plane. The gamepads are created and torn down with
/// the session; the pointer/keyboard injector (and its portal grant) lives in the service,
/// across sessions.
///
/// Rumble is emitted as self-terminating 0xCA v2 envelopes (`[level][seq][ttl_ms]`): the host owns
/// the timeline, renewing an active level every ~`RUMBLE_TTL_MS × 3/10` ms and letting an
/// abandoned one expire client-side, so "stuck rumble" is inexpressible on the wire (see
/// `punktfunk-planning/design/rumble-envelope-plan.md`). `PUNKTFUNK_RUMBLE_ENVELOPE=0` reverts to
/// legacy v1 level datagrams + the flat 500 ms refresh (bisect hatch).
fn input_thread(
rx: std::sync::mpsc::Receiver<ClientInput>,
conn: quinn::Connection,
@@ -1852,12 +1903,31 @@ fn input_thread(
// Last applied snapshot seq per pad (`None` until the first one): the reorder gate for
// `InputKind::GamepadState` — a late datagram with an older seq must not roll held state back.
let mut pad_seq: [Option<u8>; MAX_WIRE_PADS] = [None; MAX_WIRE_PADS];
// Rumble is idempotent state on a lossy channel (client-side overflow drops datagrams),
// so re-send the current state of every rumbling-capable pad every 500 ms — a dropped
// transition (including a stop) heals on the next refresh.
// Rumble self-terminating envelopes (0xCA v2). Each non-zero level is authorized for
// `rumble_ttl_ms`; the host renews an active pad every `rumble_renew` and lets an abandoned
// one expire on the client, so a dropped transition heals on the next renewal and a stop that
// is lost heals via the stop burst (or the client's own TTL expiry). `rumble_seq` is the
// per-pad wrapping reorder counter (bumped on changes AND renewals) the client gates on;
// `rumble_stop_burst` counts the post-stop zero re-sends still owed. `PUNKTFUNK_RUMBLE_ENVELOPE=0`
// reverts to legacy v1 datagrams re-sent flat every 500 ms.
let mut rumble_state = [(0u16, 0u16); MAX_WIRE_PADS];
let mut rumble_seen = [false; MAX_WIRE_PADS];
let mut rumble_seq = [0u8; MAX_WIRE_PADS];
let mut rumble_stop_burst = [0u8; MAX_WIRE_PADS];
let mut last_refresh = std::time::Instant::now();
let rumble_envelope_on = std::env::var("PUNKTFUNK_RUMBLE_ENVELOPE").as_deref() != Ok("0");
let rumble_ttl_ms: u16 = std::env::var("PUNKTFUNK_RUMBLE_TTL_MS")
.ok()
.and_then(|s| s.parse::<u16>().ok())
.map(|v| v.clamp(RUMBLE_TTL_FLOOR_MS, RUMBLE_TTL_CEIL_MS))
.unwrap_or(RUMBLE_TTL_MS);
// Renew at 30 % of the TTL (≈120 ms for the 400 ms default) so 23 renewals cover the lease;
// in legacy mode the periodic block instead runs the old flat 500 ms full-state refresh.
let rumble_refresh_interval = if rumble_envelope_on {
std::time::Duration::from_millis((rumble_ttl_ms as u64 * 3 / 10).max(RUMBLE_RENEW_FLOOR_MS))
} else {
std::time::Duration::from_millis(500)
};
// Pointer buttons / keys the client currently holds down. The injector is host-lifetime, so a
// press left dangling by an abrupt client disconnect stays latched in the compositor across the
// reconnect (Mutter keeps the implicit pointer grab of the still-pressed button — a stuck
@@ -1976,17 +2046,43 @@ fn input_thread(
// plane; DualSense rich feedback (lightbar / player LEDs / adaptive triggers) → 0xCD.
pads.pump(
|pad, low, high| {
if let Some(s) = rumble_state.get_mut(pad as usize) {
let idx = pad as usize;
if idx < MAX_WIRE_PADS {
let prev = rumble_state[idx];
// Log the silent→active transition (once per buzz) so a live test can tell
// "host never gets rumble from the game" apart from "client doesn't render it".
if *s == (0, 0) && (low != 0 || high != 0) {
if prev == (0, 0) && (low != 0 || high != 0) {
tracing::info!(pad, low, high, "rumble: forwarding to client (0xCA)");
}
*s = (low, high);
rumble_seen[pad as usize] = true;
rumble_state[idx] = (low, high);
rumble_seen[idx] = true;
// Bump the reorder counter on every change, then arm the stop burst on a
// transition to zero (so a lost stop still reaches a legacy client) and clear
// it when the game re-asserts a non-zero level.
rumble_seq[idx] = rumble_seq[idx].wrapping_add(1);
if (low, high) == (0, 0) {
rumble_stop_burst[idx] = if prev != (0, 0) { RUMBLE_STOP_BURST } else { 0 };
} else {
rumble_stop_burst[idx] = 0;
}
let ttl = if (low, high) == (0, 0) {
0
} else {
rumble_ttl_ms
};
send_rumble(
&conn,
rumble_envelope_on,
pad,
low,
high,
rumble_seq[idx],
ttl,
);
} else {
// Out-of-range pad (a backend never produces these) — forward without gating.
send_rumble(&conn, rumble_envelope_on, pad, low, high, 0, rumble_ttl_ms);
}
let d = punktfunk_core::quic::encode_rumble_datagram(pad, low, high);
let _ = conn.send_datagram(d.to_vec().into());
},
|h| {
let _ = conn.send_datagram(h.encode().into());
@@ -1996,12 +2092,40 @@ fn input_thread(
// held-steady pad sends no wire events, so without a periodic re-emit the kernel/SDL drop
// it as unplugged. The 8 ms gap inside heartbeat() governs the rate, not this ≤4 ms tick.
pads.heartbeat();
if last_refresh.elapsed() >= std::time::Duration::from_millis(500) {
if last_refresh.elapsed() >= rumble_refresh_interval {
last_refresh = std::time::Instant::now();
for (i, &(low, high)) in rumble_state.iter().enumerate() {
if rumble_seen[i] {
let d = punktfunk_core::quic::encode_rumble_datagram(i as u16, low, high);
let _ = conn.send_datagram(d.to_vec().into());
if rumble_envelope_on {
// Renewal: refresh an active pad's lease (bump seq, fresh TTL), and drain each
// pad's post-stop zero burst, then let it go quiet — no perpetual zero refreshes.
for i in 0..MAX_WIRE_PADS {
if !rumble_seen[i] {
continue;
}
let (low, high) = rumble_state[i];
if (low, high) != (0, 0) {
rumble_seq[i] = rumble_seq[i].wrapping_add(1);
send_rumble(
&conn,
true,
i as u16,
low,
high,
rumble_seq[i],
rumble_ttl_ms,
);
} else if rumble_stop_burst[i] > 0 {
rumble_stop_burst[i] -= 1;
rumble_seq[i] = rumble_seq[i].wrapping_add(1);
send_rumble(&conn, true, i as u16, 0, 0, rumble_seq[i], 0);
}
}
} else {
// Legacy: re-send the current level of every seen pad every 500 ms (v1).
for (i, &(low, high)) in rumble_state.iter().enumerate() {
if rumble_seen[i] {
let d = punktfunk_core::quic::encode_rumble_datagram(i as u16, low, high);
let _ = conn.send_datagram(d.to_vec().into());
}
}
}
}