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punktfunk/crates/punktfunk-core
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fix(core): remaining 15 sweep lows — client, clipboard, C ABI (v10), FEC, GSO, GTK
Second and final batch from the 2026-07-20 core-sweep lows:

client:
- connect() timeout now sets `quit` before shutdown, so a handshake that
  completes after the deadline closes with QUIT_CLOSE_CODE instead of
  leaving the host lingering (virtual display up) for a reconnect that
  never comes.
- probe_result: saturating_add on the wire-supplied wire_packets +
  send_dropped counters (debug-build overflow panic / release wrap).
- the standing-latency bleed no longer sets flush_in_window: that flag
  is the ABR's SEVERE (×0.7) verdict, and the bleed fires only on
  provably loss-free windows the controller itself scores as fine.

clipboard:
- fetch_cancels pruned on every new fetch (was: one dead oneshot per
  paste for the session).
- serve chunks gated on a parked waiter + capped at CLIP_FETCH_CAP with
  an Error event (was: unbounded silent accumulation under any req_id).
- serve_inbound park bounded by FETCH_STALL_SECS + send.stopped() (was:
  an unanswered FetchRequest parked the task, waiter, and bi-stream
  forever; ~100 of them exhaust the connection's bidi budget).

C ABI (ABI_VERSION 9 → 10, header regenerated, additive only):
- new punktfunk_connection_clock_offset_now_ns — the LIVE re-synced
  offset (Swift/Kotlin latency math read the frozen connect-time value
  ~40ms wrong after a wall-clock step).
- to_config: checked u64→usize narrowing of max_frame_bytes (32-bit
  armeabi truncated >4GiB to a plausible residue).
- host_poll_input: no &mut held across the embedder callback (re-entry
  aliased it — UB under noalias); mid-drain callback clears now stick.
- next_audio_pcm: DTX (empty) payloads skipped — decode synthesized
  120ms of concealment per 5ms slot and grew the playout ring forever.
- next_clipboard releases the parked payload on an empty poll (a one-off
  50MiB paste stayed resident all session).
- frames_dropped / wants_decode_latency write their documented 0/false
  defaults before the NULL-handle check.
- gamepad constant docs match pick_gamepad() reality (DualSenseEdge/
  SwitchPro landed; DualSense/DS4 honored on Windows UMDF too).

FEC:
- gf8 reconstruct/reconstruct_into reuse the (k,m) codec cache like
  encode_into (was: fresh 230×200 generator + decode inversion per
  lossy block on the pump thread).
- vendored fec-rs: the 8 safe wrap_mul_slice shims assert equal lengths
  (x86 SIMD callees bound stores on input.len() — safe-code OOB write);
  ReconstructShard's safety contract gains the len()==get().len()
  clause and reconstruct_internal sizes raw slices from the slice.

transport/GTK:
- Linux GSO super-buffer capped at the real UDP payload ceiling (65487)
  not 65535 — seg sizes ≥1024 could EMSGSIZE and latch GSO off
  process-wide, blamed on the network.
- GTK settings dialog no longer rewrites an unlisted-but-valid stored
  gamepad preference to "auto" on close.

Already fixed on main (verified stale, skipped): the reassembler FEC
ceiling, wants_decode_latency's third term, request_probe rollback +
the generalized probe watchdog.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
2026-07-20 18:26:43 +02:00
..

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) — the punktfunk/1 data plane over raw UDP: packetization, reassembly (with attacker-bounded limits), pacing, and socket tuning.
  • FEC (fec/) — the wall-breaker. Two codes:
    • GF(2⁸) classic ReedSolomon with the Cauchy generator matrix — byte-identical to the nanors library 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/1 negotiates this one.
  • Crypto (crypto.rs) — AES-128-GCM session encryption with per-direction nonce salts and sequence-as-AAD; SPAKE2 PIN pairing lives behind the quic feature.
  • QUIC control plane (quic.rs, client.rs, feature quic) — the Hello/Welcome/Start handshake, cert pinning/TOFU, reverse audio, and the embeddable NativeClient connector. This is the only place tokio/quinn are allowed; the feature is off by default so the core stays runtime-free.
  • C ABI (abi.rs) — the versioned surface (punktfunk_abi_version(), PunktfunkConfig carrying its own struct_size) that generates include/punktfunk_core.h via 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.
  • 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