enricobuehler
4d26ac5c85
Renegotiation (no reconnect on resize): the handshake bi-stream stays open; the client
sends Reconfigure{mode} (typed post-handshake message), the host validates + acks
Reconfigured and rebuilds capture/encoder/virtual output at the new mode while the data
plane (keys, ports, FEC) runs untouched — the first new-mode AU is an IDR with in-band
parameter sets. NativeClient::request_mode / punktfunk_connection_request_mode; mode()
reflects the active mode. Validated live on KWin: one continuous stream, 225 frames
@1280x720 then 395 @1920x1080, ~90 ms pipeline rebuild (ffprobe shows both resolutions).
PIN pairing (mutual trust, kills TOFU MITM): clients get persistent self-signed
identities presented via QUIC client auth (generate_identity / client auth offered but
optional server-side — legacy clients still connect). Ceremony on the control stream:
PairRequest{name} → host shows a 4-digit PIN (log) + PairChallenge{salt} → client proves
with HMAC-SHA256(PIN‖salt, client_fp‖host_fp) — binding both certs means a MITM can't
forward a proof, single attempt per PIN, constant-time compare → PairResult; host
persists the fingerprint (~/.config/punktfunk/punktfunk1-paired.json), client pins the
host's. m3-host --require-pairing gates sessions on the paired set.
NativeClient::pair + punktfunk_pair/punktfunk_generate_identity in the ABI; reference
client: --pair PIN --name LABEL + auto-generated persistent identity, --remode for live
renegotiation testing. Swift wrapper: ClientIdentity/generateIdentity()/pair(),
requestMode()/currentMode(); README handoff updated.
Tested: reconfigure/pairing wire roundtrips, C-ABI mode switch ack, full in-process
ceremony (wrong PIN → Crypto, anonymous-vs-gate rejection, success → pinned session);
live wrong-PIN ceremony against the serving host (PIN logged, proof rejected).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
154 lines
10 KiB
Markdown
154 lines
10 KiB
Markdown
# punktfunk Apple client (SwiftUI)
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The native macOS/iOS client for **`punktfunk/1`** (the post-GameStream protocol). All
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networking/protocol work — QUIC control plane, UDP data plane, GF(2¹⁶) FEC, AES-GCM,
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input datagrams, Opus audio, cert pinning — lives in the shared Rust core (statically
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linked as `PunktfunkCore.xcframework`); this package is the Swift shell: decode
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(VideoToolbox), present (SwiftUI), input capture.
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## Status — first light achieved (2026-06-10)
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Validated live, Mac ↔ Linux box over the LAN: gamescope virtual output → NVENC HEVC →
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`punktfunk/1` (GF(2¹⁶) FEC + AES-GCM over UDP, QUIC control) → VideoToolbox →
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`AVSampleBufferDisplayLayer` on glass at 1280×720@60, with mouse/keyboard flowing back as
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QUIC datagrams into the host's gamescope EIS injector (thousands of events injected during
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the session). Headless variant of the same proof: `RemoteFirstLightTests` decoded 60/60
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received AUs spanning 983 ms of host capture clock.
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The connector underneath (`punktfunk_core::client::NativeClient` over the C ABI) carries the
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full session: video AUs, **Opus audio** (`nextAudio()`), **rumble** (`nextRumble()`),
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input incl. gamepads, and **cert pinning + TOFU** (`pinSHA256:`/`hostFingerprint`) — see
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`m3.rs::tests::c_abi_connection_roundtrip` (three sequential sessions: TOFU, pinned
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reconnect, wrong-pin rejection). The host (`punktfunk-host m3-host`) is a persistent listener:
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reconnect at will during development.
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What's here, all compiled and tested on macOS (Xcode 26.5 / Swift 6.3):
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- **`PunktfunkKit`** (library)
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- `PunktfunkConnection.swift` — wrapper over the C ABI. AUs/audio are copied into `Data`
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(the C pointer is only valid until the next call of the same kind). `close()` is safe
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from any thread: per-plane locks enforce the C contract ("never close with a
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`next_au`/`next_audio` in flight") instead of leaving it to callers. Pinning + TOFU
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via `pinSHA256:`/`hostFingerprint`.
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- `AnnexB.swift` — in-band VPS/SPS/PPS → `CMVideoFormatDescription`; Annex-B → AVCC
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`CMSampleBuffer` with `DisplayImmediately` set.
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- `StreamView.swift` — SwiftUI `NSViewRepresentable` over `AVSampleBufferDisplayLayer`
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(stage-1 presenter: the layer hardware-decodes compressed HEVC itself). One pump
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thread per view, token-cancelled so reconnects can't double-pump.
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- `InputCapture.swift` — `GCMouse` raw deltas + `GCKeyboard` HID→VK mapping (the host's
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`vk_to_evdev` consumes Windows VKs), with fractional-delta accumulation so sub-pixel
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motion isn't truncated away. Buttons use GameStream ids (1=left … 5=X2); scroll is
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WHEEL_DELTA(120)-scaled.
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- **`PunktfunkClient`** (the app): hosts grid (saved in UserDefaults), "+" toolbar
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sheet to add hosts, stream mode in Settings (⌘,), trust-on-first-use fingerprint prompt
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over the live-but-blurred stream → pinned reconnects, fps/Mb-s HUD. (Audio playback and
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gamepad capture are not wired into the app yet — the connector surface is there; see
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notes 5–6.)
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- **Tests** (`swift test`): byte-level Annex-B units; a real-codec round trip
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(VTCompressionSession-encoded HEVC rebuilt as the host's wire shape → `AnnexB` →
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VTDecompressionSession → pixels); loopback integration against a real local host
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(`test-loopback.sh`); the remote first-light test above.
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## Build / run / test (on a Mac)
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```sh
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rustup target add aarch64-apple-darwin x86_64-apple-darwin
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bash scripts/build-xcframework.sh # → clients/apple/PunktfunkCore.xcframework
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cd clients/apple
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swift build && swift test # loopback/remote tests self-skip without a host
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swift run PunktfunkClient # the unbundled dev shell (CLI)
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open Punktfunk.xcodeproj # the real app: ⌘R builds + runs Punktfunk.app
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bash test-loopback.sh # full loopback proof: builds punktfunk-host
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# (synthetic source — runs on macOS), streams
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# byte-verified frames into the Swift client
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# against the real host (Linux box, see CLAUDE.md "Running on this box") — m3-host is a
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# persistent listener, reconnect at will:
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# PUNKTFUNK_COMPOSITOR=gamescope PUNKTFUNK_GAMESCOPE_APP=vkcube PUNKTFUNK_ZEROCOPY=1 \
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# cargo run -rp punktfunk-host -- m3-host --source virtual --seconds 60
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PUNKTFUNK_REMOTE_HOST=<box-ip> swift test --filter RemoteFirstLightTests # headless
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PUNKTFUNK_AUTOCONNECT=<box-ip> PUNKTFUNK_MODE=1280x720x60 swift run PunktfunkClient # on glass
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```
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## Xcode project (`Punktfunk.xcodeproj`)
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The app target **Punktfunk** wraps the same sources as the `swift run` shell
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(`Sources/PunktfunkClient`, a synchronized folder — no duplication) plus `App/` (asset
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catalog) and links `PunktfunkKit` from the local package. Generated Info.plist, ad-hoc
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signing, bundle id `io.unom.punktfunk`. Notes:
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- **App icon**: `App/Assets.xcassets` ships an empty `AppIcon` slot. For an Icon Composer
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`.icon`: add the file to the project (target Punktfunk), set it as the App Icon in the
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target's General tab, and delete the placeholder `AppIcon.appiconset`. Heads-up: CLI
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`actool` (Xcode 26.5) crashed compiling `punktfunk_Logo.icon` — if Xcode does the same,
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suspect the icon bundle (it has a duplicate-named layer, "…Layer-3 2.svg"), not the
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project.
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- **Tests from Xcode**: the package tests run with `swift test`; to get them on ⌘U, add
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`PunktfunkKitTests` once via Edit Scheme → Test → + (Xcode persists it into the shared
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scheme — a hand-written package-test reference doesn't resolve headlessly).
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- `xcodebuild -project Punktfunk.xcodeproj -scheme Punktfunk build` works headlessly.
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## Notes for whoever picks this up next
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1. **cbindgen import quirk** (the predicted "small compile fixes", now fixed): the
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C17-compatible header spells `PunktfunkStatus`/`PunktfunkInputKind` as integer typedefs while
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the enum *constants* import into Swift as a distinct same-named type — bridge with
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`.rawValue` (see the top of `PunktfunkConnection.swift`). Don't fight the generated header.
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2. **ABI contract**: one video pump thread per connection, plus optionally one *separate*
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audio drain thread for `nextAudio()`/`nextRumble()` (the core keeps per-plane borrow
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slots, so the planes never alias); `send()` is enqueue-only and safe alongside all of
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them. The wrapper's per-plane locks make `close()` safe from anywhere (it waits out
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in-flight polls, ≤ their timeouts).
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3. **Decode flow**: the host opens every stream with an IDR carrying VPS/SPS/PPS in-band
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and recovery keyframes re-send them — "refresh the format description on every IDR"
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(what `StreamView` does) is sufficient; there is no out-of-band extradata, ever.
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4. **Stage 2 (next)**: explicit `VTDecompressionSession` + `CAMetalLayer` for frame-pacing
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control (ProMotion/120 Hz), glass-to-glass measurement via `tools/latency-probe` (the
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host stamps `pts_ns` with its capture wall clock; across machines you need a clock
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offset estimate from the QUIC RTT).
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5. **Audio**: `nextAudio()` yields raw Opus packets (48 kHz stereo, one 5 ms frame each,
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sequence-numbered). Decode with libopus or `AVAudioConverter`/`kAudioFormatOpus` into an
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`AVAudioEngine` source node; conceal gaps (drop/dup) rather than blocking — the Rust
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side buffers 320 ms and drops the newest packet when the puller lags. Wall-clock
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`ptsNs` shares the host clock with video AUs for A/V sync. Wiring this into
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`PunktfunkClient` is the next app-side task.
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6. **Gamepads**: `GCController` → `.gamepadButton(...)`/`.gamepadAxis(...)` events (wire
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contract documented on the constructors; the host accumulates them into a virtual
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Xbox 360 pad). Poll `nextRumble()` and feed `GCDeviceHaptics` for force feedback.
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Client-side capture isn't in `InputCapture` yet.
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7. **Trust — the full ceremony exists now.** `generateIdentity()` once (persist both
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PEMs in the Keychain), then `pair(host:identity:pin:name:)` with the 4-digit PIN the
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host displays (its log; UI later) — returns the host's VERIFIED fingerprint; persist
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it and pass `pinSHA256:` + `identity:` to every connect. A wrong-size pin throws
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`.invalidPin`, a wrong PIN `.wrongPIN`. The TOFU flow `PunktfunkClient` already
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implements (fingerprint confirmation sheet, per-host `HostStore`, "Forget Identity")
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keeps working against hosts not running `--require-pairing`; upgrading the sheet to a
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PIN-entry field closes the remaining gap — with `--require-pairing` the host now
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authorizes clients too (the "other direction" is no longer open, opt-in per host).
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7b. **Resize without reconnect**: `requestMode(width:height:refreshHz:)` mid-stream —
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the host rebuilds at the new mode in ~90 ms; the first new-mode AU is an IDR with
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fresh parameter sets (the refresh-on-IDR decode flow handles it untouched) and
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`currentMode()` reflects the switch. Wire it to window-resize events.
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8. **Input capture caveats** (stage 1): GC handlers only fire while the app has focus —
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on focus loss `InputCapture` auto-releases everything still held (keys + buttons) so
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nothing sticks down host-side. While the stream has focus the LOCAL cursor is hidden
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and frozen mid-view (`CursorCapture` in StreamView.swift — the host renders its own
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cursor; the local one diverges from it and a stray click would focus another app);
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Cmd+Tab frees it, ⌘D disconnects. Local shortcuts (⌘-anything) still also reach the
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host; a capture toggle is a small follow-up. One live capture per process (the GC
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mouse/keyboard singletons have a single handler slot — ownership is tracked so a stale
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capture's stop() can't clobber a newer one).
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9. **iOS**: same package (`BUILD_IOS=1` for the xcframework slice); `StreamView` needs the
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`UIViewRepresentable` twin and touch→input mapping.
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## Known limitations of the current host (relevant to client UX)
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- One session **at a time** (the listener is persistent, but a second concurrent client
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waits in the accept queue until the current session ends — the virtual output and
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encoder are single-tenant).
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- Mid-stream renegotiation (resolution change without reconnect) is designed-for but not
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implemented (the Welcome is one-shot today).
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- Host-side gamepad injection needs `/dev/uinput` access on the box (udev rule from
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`docs/linux-setup.md`).
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