feat(android): native mDNS discovery, host naming, touch mouse, stock selects

Discovery: replace the flaky per-OEM NsdManager with the same mdns-sd browse
the Linux/Windows clients use, in the Rust core over JNI and polled by Kotlin
(discovery.rs + nativeDiscovery{Start,Poll,Stop}); Kotlin keeps only the Wi-Fi
MulticastLock + permission UX. IPv4-only (the core can't dial a bare/scoped v6
literal); daemon + fold-thread cleanup on every failure path; field
sanitization so a rogue advert can't corrupt the picker snapshot. Discovery
now starts regardless of NEARBY_WIFI_DEVICES (raw multicast only needs the
MulticastLock) — a denial no longer kills it forever. ParseTxtTest replaced by
ParseRecordTest.

Hosts: hide already-saved hosts from the "Discovered" section (match by
fingerprint, else address:port — mirrors the Apple client); add an optional
Name field to the Add-host sheet and a Rename action on saved cards.

Input: touch -> absolute mouse "direct pointing" like the Apple client — the
host cursor follows the finger (new nativeSendPointerAbs -> MouseMoveAbs). Tap
= left click, two-finger tap = right click, two-finger drag = scroll,
tap-then-drag = left-drag, three-finger tap = HUD toggle.

Settings: revert the dropdowns to the stock ExposedDropdownMenuBox look (a
controller-focus UI will come separately); even out the Add-host field gaps.

Docs updated (CLAUDE.md, client READMEs, docs-site status).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

clients/android/native/Cargo.toml

@@ -19,6 +19,12 @@ crate-type = ["cdylib"]
 punktfunk-core = { path = "../../../crates/punktfunk-core", features = ["quic"] }
 jni = "0.21"
 log = "0.4"
+# LAN host discovery: browse the host's `_punktfunk._udp` mDNS advert — the SAME crate + service the
+# Linux/Windows clients use (`clients/linux/src/discovery.rs`), replacing Android's per-OEM
+# `NsdManager` system daemon with one tested browse path. Pure Rust (socket2/if-addrs/mio), so it
+# cross-compiles to the Android targets AND builds on the host (the JNI seam links into
+# `cargo build --workspace`). Kotlin keeps only the Wi-Fi `MulticastLock` + permission UX.
+mdns-sd = "0.20"
 
 # Android-only deps. Gated so `cargo build --workspace` on the Linux/macOS dev boxes + CI still
 # compiles this crate (as a host cdylib) — the Android-framework glue (logging now; AMediaCodec via

clients/android/native/src/discovery.rs

@@ -0,0 +1,303 @@
+//! LAN host discovery over mDNS, in Rust via `mdns-sd` — the same crate + service type the
+//! Linux/Windows clients use (`clients/linux/src/discovery.rs`), exposed to Kotlin over JNI.
+//!
+//! Why not `NsdManager`: that API delegates to a per-OEM system mDNS daemon whose reliability
+//! varies wildly (the Android client's discovery was "mostly broken"). Browsing in our own Rust
+//! core — the crate is already linked for the whole protocol — gives one tested code path across
+//! every desktop + mobile client and removes the system-daemon dependency. Kotlin still holds the
+//! Wi-Fi `MulticastLock` for the browse lifetime (raw multicast *reception* needs it) and owns the
+//! permission UX; this module owns the socket + resolve.
+//!
+//! Shape: [`Java_io_unom_punktfunk_kit_NativeBridge_nativeDiscoveryStart`] spins up a
+//! [`ServiceDaemon`] browsing `_punktfunk._udp.local.` on a background thread that folds
+//! resolve/remove events into a shared map; Kotlin polls `nativeDiscoveryPoll` ~1 Hz for a
+//! newline-joined snapshot and calls `nativeDiscoveryStop` to tear it down. Polling (not a JVM
+//! callback) mirrors `nativeVideoStats`: no `AttachCurrentThread`/global-ref lifecycle to get
+//! wrong, and 1 Hz is plenty for a host picker.
+
+use crate::session::jni_guard;
+use jni::objects::JObject;
+use jni::sys::jlong;
+use jni::JNIEnv;
+use mdns_sd::{ResolvedService, ServiceDaemon, ServiceEvent};
+use std::collections::HashMap;
+use std::sync::{Arc, Mutex};
+use std::thread::JoinHandle;
+
+/// DNS-SD service type punktfunk hosts advertise (host side: `punktfunk_host::discovery`).
+const SERVICE_TYPE: &str = "_punktfunk._udp.local.";
+/// Wire protocol id in the `proto` TXT record; a host advertising anything else is skipped.
+const PROTO: &str = "punktfunk/1";
+/// Field separator inside one serialized record (ASCII Unit Separator — never in a field value).
+const FIELD_SEP: char = '\u{1f}';
+
+/// One resolved host, serialized to Kotlin as `key␟name␟addr␟port␟fp␟pair` (`␟` = [`FIELD_SEP`]).
+/// Records are newline-joined in a poll snapshot; [`Host::encode`] strips the framing bytes from
+/// every field so no value can break it.
+#[derive(Clone, PartialEq)]
+struct Host {
+    key: String,
+    name: String,
+    addr: String,
+    port: u16,
+    fp: String,
+    pair: String,
+}
+
+impl Host {
+    fn encode(&self) -> String {
+        // mDNS instance labels + TXT values are arbitrary UTF-8 from an UNauthenticated source, so
+        // strip the field/record separators: a rogue advert that smuggled '\n'/U+001F could otherwise
+        // inject or suppress picker rows. (Trust is still gated on connect — this only protects the
+        // list's integrity.)
+        fn clean(s: &str) -> String {
+            s.replace(['\n', '\r', FIELD_SEP], "")
+        }
+        format!(
+            "{}{FIELD_SEP}{}{FIELD_SEP}{}{FIELD_SEP}{}{FIELD_SEP}{}{FIELD_SEP}{}",
+            clean(&self.key),
+            clean(&self.name),
+            clean(&self.addr),
+            self.port,
+            clean(&self.fp),
+            clean(&self.pair),
+        )
+    }
+}
+
+/// A running browse behind the `jlong` handle: the daemon, the shared resolved-host map keyed by
+/// mDNS fullname (stable across re-announce and present on both resolve *and* remove — which fixes
+/// the old `NsdManager` key mismatch that leaked stale hosts), and the event-fold thread.
+struct Discovery {
+    daemon: ServiceDaemon,
+    hosts: Arc<Mutex<HashMap<String, Host>>>,
+    thread: Option<JoinHandle<()>>,
+}
+
+impl Discovery {
+    fn start() -> Option<Discovery> {
+        let daemon = match ServiceDaemon::new() {
+            Ok(d) => d,
+            Err(e) => {
+                log::error!("mDNS daemon failed — discovery disabled: {e}");
+                return None;
+            }
+        };
+        let rx = match daemon.browse(SERVICE_TYPE) {
+            Ok(r) => r,
+            Err(e) => {
+                log::error!("mDNS browse failed — discovery disabled: {e}");
+                let _ = daemon.shutdown();
+                return None;
+            }
+        };
+        let hosts: Arc<Mutex<HashMap<String, Host>>> = Arc::new(Mutex::new(HashMap::new()));
+        let map = hosts.clone();
+        let spawned = std::thread::Builder::new()
+            .name("pf-mdns".into())
+            .spawn(move || {
+                // Exits when the daemon is shut down (the browse channel closes → recv errors).
+                while let Ok(event) = rx.recv() {
+                    match event {
+                        ServiceEvent::ServiceResolved(info) => {
+                            if let Some(host) = resolve(&info) {
+                                map.lock()
+                                    .unwrap()
+                                    .insert(info.get_fullname().to_string(), host);
+                            }
+                        }
+                        ServiceEvent::ServiceRemoved(_ty, fullname) => {
+                            map.lock().unwrap().remove(&fullname);
+                        }
+                        _ => {}
+                    }
+                }
+            });
+        let thread = match spawned {
+            Ok(t) => t,
+            Err(e) => {
+                // The daemon thread + bound :5353 socket outlive a dropped handle (no Drop impl), so
+                // shut it down explicitly — same cleanup as the browse-failure path above.
+                log::error!("mDNS fold thread spawn failed: {e}");
+                let _ = daemon.shutdown();
+                return None;
+            }
+        };
+        log::info!("native mDNS discovery started ({SERVICE_TYPE})");
+        Some(Discovery {
+            daemon,
+            hosts,
+            thread: Some(thread),
+        })
+    }
+
+    /// Current resolved-host set, newline-joined (empty string = none). Sorted for a stable order
+    /// across polls; Kotlin re-sorts by display name.
+    fn snapshot(&self) -> String {
+        let mut records: Vec<String> = self
+            .hosts
+            .lock()
+            .unwrap()
+            .values()
+            .map(Host::encode)
+            .collect();
+        records.sort();
+        records.join("\n")
+    }
+
+    fn stop(mut self) {
+        let _ = self.daemon.shutdown(); // closes the browse channel → the fold thread exits
+        if let Some(t) = self.thread.take() {
+            let _ = t.join();
+        }
+    }
+}
+
+/// Build a [`Host`] from a resolved mDNS record, or `None` if it isn't a usable punktfunk host
+/// (incompatible advertised proto, or no IPv4 address). IPv4 only on purpose: the core dials with
+/// `format!("{host}:{port}").parse::<SocketAddr>()`, which can't parse a bare/scoped IPv6 literal
+/// (it needs the `[addr%scope]:port` form), so surfacing a v6-only host would present a card that
+/// fails on every tap. Dropping it shows the honest "not found" instead.
+fn resolve(info: &ResolvedService) -> Option<Host> {
+    let val = |k: &str| info.get_property_val_str(k).unwrap_or("").to_string();
+    let proto = val("proto");
+    if !proto.is_empty() && proto != PROTO {
+        return None; // some other DNS-SD service sharing the type — ignore
+    }
+    let addr = info
+        .get_addresses_v4()
+        .iter()
+        .next()
+        .map(|a| a.to_string())?;
+    let id = val("id");
+    let fullname = info.get_fullname();
+    Some(Host {
+        key: if id.is_empty() {
+            fullname.to_string()
+        } else {
+            id
+        },
+        name: fullname.split('.').next().unwrap_or("?").to_string(),
+        addr,
+        port: info.get_port(),
+        fp: val("fp"),
+        pair: val("pair"),
+    })
+}
+
+/// `NativeBridge.nativeDiscoveryStart(): Long` — start browsing `_punktfunk._udp`; returns an opaque
+/// handle, or `0` on failure (logged). Pair with exactly one [`nativeDiscoveryStop`]. Kotlin must
+/// hold the Wi-Fi `MulticastLock` for the browse lifetime.
+///
+/// [`nativeDiscoveryStop`]: Java_io_unom_punktfunk_kit_NativeBridge_nativeDiscoveryStop
+#[no_mangle]
+pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeDiscoveryStart(
+    _env: JNIEnv,
+    _this: JObject,
+) -> jlong {
+    jni_guard(0, || match Discovery::start() {
+        Some(d) => Box::into_raw(Box::new(d)) as jlong,
+        None => 0,
+    })
+}
+
+/// `NativeBridge.nativeDiscoveryPoll(handle): String` — the current resolved-host snapshot,
+/// newline-joined records of `key␟name␟addr␟port␟fp␟pair` (`␟` = U+001F). Empty string = no hosts /
+/// `0` handle. Poll ~1 Hz from the UI thread (cheap: a mutex lock + string build).
+#[no_mangle]
+pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeDiscoveryPoll<'local>(
+    env: JNIEnv<'local>,
+    _this: JObject<'local>,
+    handle: jlong,
+) -> jni::sys::jstring {
+    jni_guard(std::ptr::null_mut(), || {
+        let out = if handle == 0 {
+            String::new()
+        } else {
+            // SAFETY: live handle per the start/stop contract — Kotlin owns the lifecycle and never
+            // polls after stop (it nulls the handle first).
+            let d = unsafe { &*(handle as *const Discovery) };
+            d.snapshot()
+        };
+        match env.new_string(out) {
+            Ok(s) => s.into_raw(),
+            Err(_) => std::ptr::null_mut(),
+        }
+    })
+}
+
+/// `NativeBridge.nativeDiscoveryStop(handle)` — stop the browse, shut the daemon down and join its
+/// thread. No-op on `0`.
+///
+/// # Safety contract
+/// `handle` must be `0` or a live handle from [`nativeDiscoveryStart`], stopped exactly once and not
+/// concurrently with [`nativeDiscoveryPoll`] (Kotlin owns this; all calls are on the main thread).
+///
+/// [`nativeDiscoveryStart`]: Java_io_unom_punktfunk_kit_NativeBridge_nativeDiscoveryStart
+/// [`nativeDiscoveryPoll`]: Java_io_unom_punktfunk_kit_NativeBridge_nativeDiscoveryPoll
+#[no_mangle]
+pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeDiscoveryStop(
+    _env: JNIEnv,
+    _this: JObject,
+    handle: jlong,
+) {
+    jni_guard((), || {
+        if handle != 0 {
+            // SAFETY: live handle from nativeDiscoveryStart, stopped exactly once per the contract.
+            let d = unsafe { Box::from_raw(handle as *mut Discovery) };
+            d.stop();
+        }
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn encode_round_trips_all_fields_with_unit_separator() {
+        let h = Host {
+            key: "host-123".into(),
+            name: "home-worker-2".into(),
+            addr: "192.168.1.70".into(),
+            port: 9777,
+            fp: "ab".repeat(32),
+            pair: "required".into(),
+        };
+        let encoded = h.encode();
+        let fields: Vec<&str> = encoded.split(FIELD_SEP).collect();
+        assert_eq!(fields.len(), 6);
+        assert_eq!(fields[0], "host-123");
+        assert_eq!(fields[1], "home-worker-2");
+        assert_eq!(fields[2], "192.168.1.70");
+        assert_eq!(fields[3], "9777");
+        assert_eq!(fields[4], "ab".repeat(32));
+        assert_eq!(fields[5], "required");
+        assert!(
+            !encoded.contains('\n'),
+            "a record must never contain the record separator"
+        );
+    }
+
+    #[test]
+    fn encode_strips_injected_separators_from_a_hostile_advert() {
+        // A rogue advert could carry framing bytes in its instance label / TXT; encode must strip
+        // them so the snapshot stays exactly one record of exactly six fields.
+        let h = Host {
+            key: "k\u{1f}injected".into(),
+            name: "evil\nhost\r".into(),
+            addr: "10.0.0.5".into(),
+            port: 9777,
+            fp: "ab\u{1f}cd".into(),
+            pair: "required\n".into(),
+        };
+        let encoded = h.encode();
+        assert_eq!(encoded.matches(FIELD_SEP).count(), 5, "exactly six fields");
+        assert!(!encoded.contains('\n') && !encoded.contains('\r'));
+        let fields: Vec<&str> = encoded.split(FIELD_SEP).collect();
+        assert_eq!(fields[0], "kinjected");
+        assert_eq!(fields[1], "evilhost");
+        assert_eq!(fields[4], "abcd");
+        assert_eq!(fields[5], "required");
+    }
+}

clients/android/native/src/lib.rs

@@ -3,13 +3,17 @@
 //! Architecture: the **Rust-heavy** client model (like `punktfunk-client-linux`, *not* the
 //! thin-native-over-C-ABI Apple model). This `cdylib` links `punktfunk-core` directly and drives
 //! the whole `punktfunk/1` protocol through [`punktfunk_core::client::NativeClient`]; Kotlin owns
-//! only the Android-framework surface (Compose UI, `SurfaceView` lifecycle, input capture,
-//! `NsdManager` discovery, Keystore). The JNI seam below is the one place the two languages meet.
+//! only the Android-framework surface (Compose UI, `SurfaceView` lifecycle, input capture, the
+//! Wi-Fi `MulticastLock` + permission UX, Keystore). The JNI seam below is the one place the two
+//! languages meet.
 //!
 //! Why Rust-heavy: Kotlin cannot `import` the cbindgen C header the way Swift can, so a native
 //! bridge is unavoidable. Writing it in Rust lets the Android client reuse the Linux client's
 //! orchestration verbatim — audio jitter ring, the VK keymap inverse, latency/skew math, the
-//! input capture state machine, trust/pairing logic — instead of re-porting it into Kotlin.
+//! input capture state machine, trust/pairing logic, **mDNS discovery** ([`discovery`], the same
+//! `mdns-sd` browse the Linux/Windows clients use) — instead of re-porting it into Kotlin. Kotlin
+//! keeps only the Android-framework surface it must (Compose UI, `SurfaceView`, input capture, the
+//! Wi-Fi `MulticastLock` + permission UX, Keystore identity).
 //!
 //! JNI symbols map to `io.unom.punktfunk.kit.NativeBridge` in the `:kit` Gradle module
 //! (`clients/android`). The current surface is the scaffold's native-link proof
@@ -25,6 +29,9 @@ use jni::JNIEnv;
 mod audio;
 #[cfg(target_os = "android")]
 mod decode;
+// Ungated: pure `mdns-sd` + `jni`, so the browse + its JNI seam link into the host workspace build
+// (and its unit test runs there) exactly like `session`/`stats`. Kotlin only ever calls it on device.
+mod discovery;
 mod feedback;
 #[cfg(target_os = "android")]
 mod mic;

clients/android/native/src/session.rs

@@ -557,6 +557,38 @@ pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeSendPointer
     });
 }
 
+/// `NativeBridge.nativeSendPointerAbs(handle, x, y, surfaceWidth, surfaceHeight)` — absolute cursor
+/// position: the host moves the pointer to `x`/`y` in a `surfaceWidth`×`surfaceHeight` pixel space,
+/// normalizing against the size packed into `flags` as `(w << 16) | h` and mapping into the output
+/// region (it drops the event if that size is zero). This is the touch "direct pointing" path — the
+/// cursor jumps to the finger — and matches the Apple client's absolute touch forwarding.
+#[no_mangle]
+pub extern "system" fn Java_io_unom_punktfunk_kit_NativeBridge_nativeSendPointerAbs(
+    _env: JNIEnv,
+    _this: JObject,
+    handle: jlong,
+    x: jint,
+    y: jint,
+    surface_width: jint,
+    surface_height: jint,
+) {
+    if handle == 0 {
+        return;
+    }
+    // SAFETY: live handle per the contract.
+    let h = unsafe { &*(handle as *const SessionHandle) };
+    let w = (surface_width.max(0) as u32) & 0xffff;
+    let ht = (surface_height.max(0) as u32) & 0xffff;
+    let _ = h.client.send_input(&InputEvent {
+        kind: InputKind::MouseMoveAbs,
+        _pad: [0; 3],
+        code: 0,
+        x,
+        y,
+        flags: (w << 16) | ht,
+    });
+}
+
 /// `NativeBridge.nativeSendPointerButton(handle, button, down)` — one button transition.
 /// `button`: GameStream id (1=left, 2=middle, 3=right, 4=X1, 5=X2). `down`: 1=press, 0=release.
 #[no_mangle]