feat: relay ping with RTT, server TOFU, lock icons (Phase 2 backport)

Rust JNI:
- nativePingRelay: QUIC connect with 3s timeout, returns RTT + server
  certificate fingerprint as JSON. Static method, no engine needed.

Kotlin:
- WzpEngine.pingRelay() static wrapper
- SettingsRepository: TOFU fingerprint persistence (tofu_{address} keys)
- CallViewModel: pingAllServers() coroutine, lockStatus() helper,
  PingResult/LockStatus data types
- InCallScreen: server chips show lock icon + RTT color (green/yellow),
  "Ping All" button

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

android/app/src/main/java/com/wzp/data/SettingsRepository.kt

@@ -29,6 +29,7 @@ class SettingsRepository(context: Context) {
         private const val KEY_IDENTITY_SEED = "identity_seed_hex"
         private const val KEY_AEC_ENABLED = "aec_enabled"
         private const val KEY_RECENT_ROOMS = "recent_rooms"
+        private const val TOFU_PREFIX = "tofu_"
     }
 
     // --- Servers ---
@@ -168,4 +169,14 @@ class SettingsRepository(context: Context) {
     fun clearRecentRooms() {
         prefs.edit().remove(KEY_RECENT_ROOMS).apply()
     }
+
+    // --- Server fingerprint TOFU ---
+
+    fun saveServerFingerprint(address: String, fingerprint: String) {
+        prefs.edit().putString("$TOFU_PREFIX$address", fingerprint).apply()
+    }
+
+    fun loadServerFingerprint(address: String): String? {
+        return prefs.getString("$TOFU_PREFIX$address", null)
+    }
 }

android/app/src/main/java/com/wzp/engine/WzpEngine.kt

@@ -158,6 +158,15 @@ class WzpEngine(private val callback: WzpCallback) {
         init {
             System.loadLibrary("wzp_android")
         }
+
+        /**
+         * Ping a relay server. Returns JSON `{"rtt_ms":N,"server_fingerprint":"hex"}`
+         * or null if unreachable. Does not require an engine instance.
+         */
+        fun pingRelay(address: String): String? = nativePingRelay(address)
+
+        @JvmStatic
+        private external fun nativePingRelay(relay: String): String?
     }
 }
 

android/app/src/main/java/com/wzp/ui/call/CallViewModel.kt

@@ -12,6 +12,7 @@ import com.wzp.engine.CallStats
 import com.wzp.service.CallService
 import com.wzp.engine.WzpCallback
 import com.wzp.engine.WzpEngine
+import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.MutableStateFlow
@@ -19,6 +20,8 @@ import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import org.json.JSONObject
 import java.io.File
 import java.net.Inet4Address
 import java.net.Inet6Address
@@ -26,6 +29,13 @@ import java.net.InetAddress
 
 data class ServerEntry(val address: String, val label: String)
 
+data class PingResult(
+    val rttMs: Int,
+    val serverFingerprint: String,
+)
+
+enum class LockStatus { UNKNOWN, OFFLINE, NEW, VERIFIED, CHANGED }
+
 class CallViewModel : ViewModel(), WzpCallback {
 
     private var engine: WzpEngine? = null
@@ -73,6 +83,13 @@ class CallViewModel : ViewModel(), WzpCallback {
     private val _recentRooms = MutableStateFlow<List<com.wzp.data.SettingsRepository.RecentRoom>>(emptyList())
     val recentRooms: StateFlow<List<com.wzp.data.SettingsRepository.RecentRoom>> = _recentRooms.asStateFlow()
 
+    /** Ping results keyed by server address. */
+    private val _pingResults = MutableStateFlow<Map<String, PingResult>>(emptyMap())
+    val pingResults: StateFlow<Map<String, PingResult>> = _pingResults.asStateFlow()
+
+    /** Known server fingerprints (TOFU). */
+    private val _knownFingerprints = MutableStateFlow<Map<String, String>>(emptyMap())
+
     private val _playoutGainDb = MutableStateFlow(0f)
     val playoutGainDb: StateFlow<Float> = _playoutGainDb.asStateFlow()
 
@@ -186,6 +203,51 @@ class CallViewModel : ViewModel(), WzpCallback {
         settings?.saveSelectedServer(_selectedServer.value)
     }
 
+    /** Ping all servers in background, update results. */
+    fun pingAllServers() {
+        viewModelScope.launch {
+            val results = mutableMapOf<String, PingResult>()
+            val known = mutableMapOf<String, String>()
+            _servers.value.forEach { server ->
+                val pr = withContext(Dispatchers.IO) {
+                    try {
+                        val json = WzpEngine.pingRelay(server.address) ?: return@withContext null
+                        val obj = JSONObject(json)
+                        PingResult(
+                            rttMs = obj.getInt("rtt_ms"),
+                            serverFingerprint = obj.optString("server_fingerprint", ""),
+                        )
+                    } catch (e: Exception) {
+                        Log.w(TAG, "ping ${server.address} failed: ${e.message}")
+                        null
+                    }
+                }
+                if (pr != null) {
+                    results[server.address] = pr
+                    // TOFU: save fingerprint on first contact
+                    if (pr.serverFingerprint.isNotEmpty()) {
+                        val saved = settings?.loadServerFingerprint(server.address)
+                        if (saved == null) {
+                            settings?.saveServerFingerprint(server.address, pr.serverFingerprint)
+                        }
+                        known[server.address] = saved ?: pr.serverFingerprint
+                    }
+                }
+            }
+            _pingResults.value = results
+            _knownFingerprints.value = known
+        }
+    }
+
+    /** Get lock status for a server. */
+    fun lockStatus(address: String): LockStatus {
+        val pr = _pingResults.value[address] ?: return LockStatus.UNKNOWN
+        val known = _knownFingerprints.value[address]
+        if (pr.serverFingerprint.isEmpty()) return LockStatus.NEW
+        if (known == null) return LockStatus.NEW
+        return if (pr.serverFingerprint == known) LockStatus.VERIFIED else LockStatus.CHANGED
+    }
+
     fun setRoomName(name: String) {
         _roomName.value = name
         settings?.saveRoom(name)

android/app/src/main/java/com/wzp/ui/call/InCallScreen.kt

@@ -48,6 +48,7 @@ import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
 import com.wzp.engine.CallStats
+import com.wzp.ui.call.LockStatus
 import kotlin.math.roundToInt
 
 @OptIn(ExperimentalLayoutApi::class)
@@ -118,18 +119,31 @@ fun InCallScreen(
                     color = MaterialTheme.colorScheme.onSurfaceVariant
                 )
                 Spacer(modifier = Modifier.height(4.dp))
+                val pingResults by viewModel.pingResults.collectAsState()
+
                 FlowRow(
                     modifier = Modifier.fillMaxWidth(),
                     horizontalArrangement = Arrangement.Center
                 ) {
                     servers.forEachIndexed { idx, entry ->
                         val isSelected = selectedServer == idx
+                        val ping = pingResults[entry.address]
+                        val lockStatus = viewModel.lockStatus(entry.address)
+                        val lockIcon = when (lockStatus) {
+                            LockStatus.VERIFIED -> "\uD83D\uDD12" // 🔒
+                            LockStatus.NEW -> "\uD83D\uDD13"      // 🔓
+                            LockStatus.CHANGED -> "⚠\uFE0F"       // ⚠️
+                            LockStatus.OFFLINE -> "\uD83D\uDD34"   // 🔴
+                            LockStatus.UNKNOWN -> ""
+                        }
+                        val rttText = ping?.let { "${it.rttMs}ms" } ?: ""
+
                         FilledTonalIconButton(
                             onClick = { viewModel.selectServer(idx) },
                             modifier = Modifier
                                 .padding(2.dp)
-                                .height(36.dp)
-                                .width(140.dp),
+                                .height(40.dp)
+                                .width(160.dp),
                             shape = RoundedCornerShape(8.dp),
                             colors = if (isSelected) {
                                 IconButtonDefaults.filledTonalIconButtonColors(
@@ -140,11 +154,28 @@ fun InCallScreen(
                                 IconButtonDefaults.filledTonalIconButtonColors()
                             }
                         ) {
+                            Row(verticalAlignment = Alignment.CenterVertically) {
+                                if (lockIcon.isNotEmpty()) {
+                                    Text(text = lockIcon, fontSize = 12.sp)
+                                    Spacer(modifier = Modifier.width(4.dp))
+                                }
                                 Text(
                                     text = entry.label,
                                     style = MaterialTheme.typography.labelSmall,
                                     maxLines = 1
                                 )
+                                if (rttText.isNotEmpty()) {
+                                    Spacer(modifier = Modifier.width(4.dp))
+                                    Text(
+                                        text = rttText,
+                                        style = MaterialTheme.typography.labelSmall.copy(fontSize = 9.sp),
+                                        color = when {
+                                            (ping?.rttMs ?: 0) > 200 -> Color(0xFFFACC15) // yellow
+                                            else -> Color(0xFF4ADE80) // green
+                                        }
+                                    )
+                                }
+                            }
                         }
                     }
                     // + Add button
@@ -152,13 +183,18 @@ fun InCallScreen(
                         onClick = { showAddServerDialog = true },
                         modifier = Modifier
                             .padding(2.dp)
-                            .height(36.dp),
+                            .height(40.dp),
                         shape = RoundedCornerShape(8.dp)
                     ) {
                         Text("+", style = MaterialTheme.typography.labelMedium)
                     }
                 }
 
+                // Ping button
+                TextButton(onClick = { viewModel.pingAllServers() }) {
+                    Text("Ping All", style = MaterialTheme.typography.labelSmall)
+                }
+
                 // IPv4/IPv6 preference
                 Spacer(modifier = Modifier.height(8.dp))
                 Row(

crates/wzp-android/src/jni_bridge.rs

@@ -317,3 +317,79 @@ pub unsafe extern "system" fn Java_com_wzp_engine_WzpEngine_nativeDestroy(
         drop(h);
     }));
 }
+
+/// Ping a relay server — returns JSON `{"rtt_ms":N,"server_fingerprint":"hex"}` or null on failure.
+/// Does NOT require an engine handle — creates a temporary QUIC connection.
+#[unsafe(no_mangle)]
+pub unsafe extern "system" fn Java_com_wzp_engine_WzpEngine_nativePingRelay<'a>(
+    mut env: JNIEnv<'a>,
+    _class: JClass,
+    relay_j: JString,
+) -> jstring {
+    let result = panic::catch_unwind(panic::AssertUnwindSafe(|| {
+        let relay: String = env.get_string(&relay_j).map(|s| s.into()).unwrap_or_default();
+        let addr: std::net::SocketAddr = match relay.parse() {
+            Ok(a) => a,
+            Err(_) => return None,
+        };
+
+        let _ = rustls::crypto::ring::default_provider().install_default();
+
+        let rt = match tokio::runtime::Builder::new_current_thread()
+            .enable_all()
+            .build()
+        {
+            Ok(rt) => rt,
+            Err(_) => return None,
+        };
+
+        rt.block_on(async {
+            let bind: std::net::SocketAddr = "0.0.0.0:0".parse().unwrap();
+            let endpoint = match wzp_transport::create_endpoint(bind, None) {
+                Ok(e) => e,
+                Err(_) => return None,
+            };
+            let client_cfg = wzp_transport::client_config();
+            let start = std::time::Instant::now();
+
+            match tokio::time::timeout(
+                std::time::Duration::from_secs(3),
+                wzp_transport::connect(&endpoint, addr, "ping", client_cfg),
+            )
+            .await
+            {
+                Ok(Ok(conn)) => {
+                    let rtt_ms = start.elapsed().as_millis() as u64;
+                    let server_fp = conn
+                        .peer_identity()
+                        .and_then(|id| {
+                            id.downcast::<Vec<rustls::pki_types::CertificateDer>>().ok()
+                        })
+                        .and_then(|certs| {
+                            certs.first().map(|c| {
+                                use std::hash::{Hash, Hasher};
+                                let mut h = std::collections::hash_map::DefaultHasher::new();
+                                c.as_ref().hash(&mut h);
+                                format!("{:016x}", h.finish())
+                            })
+                        })
+                        .unwrap_or_default();
+                    conn.close(0u32.into(), b"ping");
+                    Some(format!(
+                        r#"{{"rtt_ms":{},"server_fingerprint":"{}"}}"#,
+                        rtt_ms, server_fp
+                    ))
+                }
+                _ => None,
+            }
+        })
+    }));
+
+    let json = match result {
+        Ok(Some(s)) => s,
+        _ => return JObject::null().into_raw(),
+    };
+    env.new_string(&json)
+        .map(|s| s.into_raw())
+        .unwrap_or(JObject::null().into_raw())
+}