enricobuehler
d4467a44e2
Networking-audit deferred plan §2. The host↔client offset was measured once at connect; an NTP step or slow drift silently corrupted the clock-based jump-to-live signal, the ABR one-way-delay signal, and every latency stat — 4a3b1ae2's disarm backstop stopped the IDR storm but lost the detector for the session. Now the client re-estimates mid-stream and recovers it. - quic: ClockResync — the connect-time 8-round probe/echo estimate as a select!-driven state machine (rounds matched by echoed t1, stale batches ignored), plus accept_resync (batch min-RTT ≤ max(2 ms, 1.5× connect RTT) so a congested window can never bias the offset). No wire change: the host has always answered ClockProbe at any time on the control stream. - client: the offset lives in an Arc<AtomicI64> seeded at connect; the control task re-probes every 60 s and immediately after the pump's FIRST no-op clock flush (the "clock stepped under me" signal, sent on the next report tick). On apply: store, reset stale_frames/noop_clock_flushes, re-arm the clock detector if a step had disarmed it. The disarm heuristic stays as the final backstop. Public NativeClient::clock_offset_ns keeps the connect-time value (ABI untouched); new clock_offset_now_ns() / clock_offset_shared() expose the live value. - consumers migrated to the live offset: pf-client-core session stats, the pf-presenter e2e stamp, Windows session/render, Android feeder/drain/ DisplayTracker (the tracker holds the shared handle, not the client, so the leaked render-callback refcount can't pin the session). - probe: --clock-resync runs a second full handshake mid-connection and asserts a sane, consistent estimate. Live against the local canary host: offsets 8646/2139 ns, disagreement 6 µs, 8/8 rounds — OK. Unit tests cover the round collection, stale-echo rejection, batch restart, min-RTT selection, and the acceptance guard. cargo ndk check green. Remaining manual validation: `sudo date -s "+2 sec"` on a live streaming client → expect one no-op flush, a re-sync, re-armed detector, no IDR pulse. 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