Video datagrams are sealed at a shard payload sized for a clean 1500-byte
MTU (1472-byte UDP payloads). A host whose route to the client crosses a
smaller-MTU hop (a VPN/overlay adapter claiming the LAN route, a lowered
NIC MTU) delivers every small flow — QUIC control, hole punch, input,
audio — while 100% of video datagrams die: the client sits on a black
screen reporting zero loss and the host streams into the void with every
gauge green. Field-reported as 'connects fine, black screen forever'.

Three legs, none of which changes a session on a healthy path:

- PUNKTFUNK_WIRE_MTU operator override: shard payload derived from a
  given on-wire IP MTU. Wire-compatible — Welcome::shard_payload is
  already negotiated per session (the v4/v6 split ships two values
  today) and every client follows the negotiated value.
- Detection: the QUIC MTU-discovery probe ceiling moves from quinn's
  stock 1452 to exactly the sealed video-datagram size (1472), so a
  control connection's settled MTU becomes a verdict on the path:
  settled at the ceiling proves it carries video, settled below proves
  it cannot. A per-session watcher samples after the search has settled
  (live-connection guard against mid-search false learns) and logs an
  actionable WARN naming the failure shape and the diagnosis commands.
- Healing: the measured budget is recorded per peer IP; the next
  handshake clamps shard_payload to fit, so a reconnect self-heals. A
  later session that reaches the ceiling erases the record.

Verified: core 286/286 --features quic + clippy -D warnings (macOS);
host clippy -D warnings + native:: tests 44/44 (pf-lxcheck container).
The regenerated C header picks up the new MIN_SHARD_PAYLOAD constant.

2026-08-04 18:30:33 +02:00

benches

feat(core+host): negotiate ChaCha20-Poly1305 as the session cipher for soft-AES clients

2026-07-21 22:50:00 +02:00

src

feat(host/wire): MTU resilience for the video data plane

2026-08-04 18:30:33 +02:00

tests

feat(core+host): negotiate ChaCha20-Poly1305 as the session cipher for soft-AES clients

2026-07-21 22:50:00 +02:00

vendor/fec-rs

fix(core): remaining 15 sweep lows — client, clipboard, C ABI (v10), FEC, GSO, GTK

2026-07-20 18:26:43 +02:00

build.rs

chore(core): fix build.rs + crate-doc drift left by the W7/W8 splits

2026-07-20 18:08:39 +02:00

Cargo.toml

chore(unsafe): the workspace adopts the drivers' unsafe discipline

2026-07-28 21:31:41 +02:00

cbindgen.toml

fix(core,host): make the native data plane survive real Wi-Fi links

2026-07-07 07:35:08 +02:00

README.md

docs: repo-wide housekeeping — sync README & docs with the code as shipped

2026-07-10 09:13:42 +02:00

README.md

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 Reed–Solomon 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

README.md Unescape Escape

punktfunk-core

What's in here

Build outputs

Test

Design invariants (do not regress)

Related

README.md