enricobuehler
bcfb833ff7
`abi.rs`'s header states "panics never cross the boundary: every entry point is wrapped in `catch_unwind`". Of its 78 `extern "C"` entry points, 16 were not. Ten of those are fine and were always fine — `punktfunk_abi_version` returns a constant, and the nine `punktfunk_connect*` shims forward every argument unchanged into a guarded implementation — but five ran real code bare: `session_free`, `connection_close`, `connection_disconnect_quit`, `reanchor_gate_free`, `reanchor_gate_arm`. The three `*_free`/`close` ones are the point. They run `Drop` for an entire `Session` or `Connection` — transports, threads, mutexes — and a `Drop` impl that unwraps a poisoned lock panics. Since Rust 1.81 that unwind is a hard abort rather than undefined behaviour, so this is not a soundness hole; it is worse-behaved than it looks. Aborting the CALLER'S process because one of our teardown paths hit a poisoned mutex is not an acceptable failure mode for a library, and it would present as "the app died in punktfunk_session_free" with no Rust backtrace to explain it. Adds `guard_void`, the sibling of `guard` for entry points with no status to report through: it catches, logs, and returns — right for teardown, where the object is going away regardless. The five are wrapped in it. The header now says what is actually true, including WHICH entry points are deliberately bare and why, so the next reader can check the claim instead of trusting it. That is the same failure this sweep found in `MappedView`'s `Sync` proof: a stated invariant that a reviewer would rely on and that had quietly stopped holding. Verified: Linux .21 fmt + both CI clippy steps rc=0, and the C ABI harness — which exercises the `*_free`/`close` paths it touches — still passes, 4 frames byte-exact through lossy loopback.
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