Warn about local destinations named by host, not just by address

app/src/main/java/eu/faircode/netguard/ActivitySettings.java

@@ -978,6 +978,11 @@ else if ("domain_based_blocking".equals(name)) {
         // Asked at most once per visit: writing back a trimmed value re-enters
         // this listener, and a second request while the dialog is up is dropped
         // by the framework.
+        if (LocalNetworkAccess.isRelevantSetting(name))
+            // The new value may point somewhere else entirely; what we saw the
+            // old one reach says nothing about it.
+            LocalNetworkAccess.forgetObservations();
+
         if (!requestedLocalNetwork && LocalNetworkAccess.isRelevantSetting(name)
                 && LocalNetworkAccess.isMissing(this)) {
             requestedLocalNetwork = true;

app/src/main/java/net/kollnig/missioncontrol/LocalNetworkAccess.java

@@ -121,7 +121,56 @@ public static boolean isGranted(Context context) {
     public static boolean isMissing(Context context) {
         // Cheapest checks first: nothing to do below Android 17, and parsing the
         // WireGuard config is pointless once the permission is granted.
-        return isEnforced() && !isGranted(context) && isConfigured(context);
+        return isEnforced() && !isGranted(context)
+                && (observedLocalDestination || isConfigured(context));
+    }
+
+    /**
+     * A destination we resolved to a local network address, seen while running.
+     * Covers what {@link #isConfigured(SharedPreferences)} structurally cannot:
+     * a configuration that names a <em>host</em> rather than an address —
+     * {@code https://pi.hole/dns-query}, a WireGuard endpoint on a dynamic DNS
+     * name — where classifying it up front would mean resolving a name on
+     * whichever thread asked, including the main one.
+     *
+     * <p>Not persisted. A stale observation survives no longer than the
+     * process, and anything still pointing at the LAN re-reports itself as soon
+     * as it is used again.
+     */
+    private static volatile boolean observedLocalDestination;
+
+    /**
+     * Report an address TrackerControl is about to talk to. Callers pass what
+     * they already resolved, so this never performs a lookup itself and is safe
+     * to call from any thread.
+     *
+     * <p>Only the destination matters, not whether the connection succeeded: if
+     * it is local and the permission is missing, that traffic is blocked.
+     */
+    public static void reportDestination(String address) {
+        // Deliberately not gated on isEnforced(): isMissing() applies that gate
+        // anyway, and keeping this branch out makes the latch testable under
+        // Robolectric, which runs below the enforcement level.
+        if (observedLocalDestination)
+            return;
+        if (isLocalAddress(address)) {
+            Log.i(TAG, "Local network destination observed at runtime");
+            observedLocalDestination = true;
+        }
+    }
+
+    /** Whether a local destination has been seen since the last reset. */
+    static boolean hasObservedLocalDestination() {
+        return observedLocalDestination;
+    }
+
+    /**
+     * Drop what we observed, so a configuration that no longer points at the
+     * LAN stops warning. Called when a relevant setting changes; anything still
+     * local reports itself again on next use.
+     */
+    public static void forgetObservations() {
+        observedLocalDestination = false;
     }
 
     /** Whether the current configuration makes TrackerControl talk to the LAN. */

app/src/main/java/net/kollnig/missioncontrol/dns/DnsOverHttpsClient.java

@@ -19,6 +19,7 @@
 import androidx.preference.PreferenceManager;
 
 import net.kollnig.missioncontrol.BuildConfig;
+import net.kollnig.missioncontrol.LocalNetworkAccess;
 
 import org.xbill.DNS.Message;
 import org.xbill.DNS.Record;
@@ -27,6 +28,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.net.InetAddress;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Objects;
@@ -36,6 +38,7 @@
 
 import okhttp3.Cache;
 import okhttp3.ConnectionPool;
+import okhttp3.Dns;
 import okhttp3.HttpUrl;
 import okhttp3.MediaType;
 import okhttp3.OkHttpClient;
@@ -80,6 +83,17 @@ private DnsOverHttpsClient(Context context, String endpoint) {
                 .connectionPool(new ConnectionPool(2, 30, TimeUnit.SECONDS))
                 .cache(getResponseCache(context))
                 .retryOnConnectionFailure(true)
+                // An endpoint given as a host name can still be a resolver on
+                // the user's own network, which Android 17 blocks us from
+                // reaching without ACCESS_LOCAL_NETWORK. OkHttp resolves it
+                // anyway, so note the address it got rather than looking it up
+                // a second time (#701).
+                .dns(hostname -> {
+                    List<InetAddress> addresses = Dns.SYSTEM.lookup(hostname);
+                    for (InetAddress address : addresses)
+                        LocalNetworkAccess.reportDestination(address.getHostAddress());
+                    return addresses;
+                })
                 .build();
 
         Log.i(TAG, "DoH client initialized with endpoint: " + endpoint);

app/src/main/java/net/kollnig/missioncontrol/wg/WgEgress.kt

@@ -5,6 +5,7 @@ import android.os.Handler
 import android.os.Looper
 import android.os.ParcelFileDescriptor
 import android.util.Log
+import net.kollnig.missioncontrol.LocalNetworkAccess
 import net.kollnig.missioncontrol.wgbridge.Logger as WgLogger
 import net.kollnig.missioncontrol.wgbridge.Protector as WgProtector
 import net.kollnig.missioncontrol.wgbridge.Tunnel as WgTunnel
@@ -815,6 +816,10 @@ object WgEgress {
         val resolved = try {
             val addr = resolveHostBounded(host)
             val ip = addr.hostAddress ?: throw IllegalStateException("getHostAddress null for $host")
+            // A peer named by host name can still sit on the user's own network,
+            // which Android 17 blocks without ACCESS_LOCAL_NETWORK (#701). The
+            // address is in hand here, so no extra lookup is needed to notice.
+            LocalNetworkAccess.reportDestination(ip)
             if (addr is java.net.Inet6Address) "[$ip]:$port" else "$ip:$port"
         } catch (e: Exception) {
             // DNS often fails exactly when we resolve: the resolver runs over

app/src/test/java/net/kollnig/missioncontrol/LocalNetworkAccessTest.java

@@ -55,6 +55,46 @@ public class LocalNetworkAccessTest {
     public void setUp() {
         prefs = PreferenceManager.getDefaultSharedPreferences(RuntimeEnvironment.getApplication());
         prefs.edit().clear().commit();
+        LocalNetworkAccess.forgetObservations();
+    }
+
+    @Test
+    public void runtimeDestinationOnTheLanIsRemembered() {
+        assertFalse(LocalNetworkAccess.hasObservedLocalDestination());
+
+        // What a host name in a DoH URL or WireGuard endpoint resolved to.
+        LocalNetworkAccess.reportDestination("192.168.1.10");
+        assertTrue(LocalNetworkAccess.hasObservedLocalDestination());
+    }
+
+    @Test
+    public void runtimeDestinationOffTheLanIsIgnored() {
+        LocalNetworkAccess.reportDestination("9.9.9.9");
+        assertFalse(LocalNetworkAccess.hasObservedLocalDestination());
+
+        // Never resolved here — callers pass an address they already have.
+        LocalNetworkAccess.reportDestination("pi.hole");
+        assertFalse(LocalNetworkAccess.hasObservedLocalDestination());
+
+        LocalNetworkAccess.reportDestination(null);
+        assertFalse(LocalNetworkAccess.hasObservedLocalDestination());
+    }
+
+    @Test
+    public void observationsAreForgottenOnReset() {
+        LocalNetworkAccess.reportDestination("fd00::1");
+        assertTrue(LocalNetworkAccess.hasObservedLocalDestination());
+
+        LocalNetworkAccess.forgetObservations();
+        assertFalse(LocalNetworkAccess.hasObservedLocalDestination());
+    }
+
+    @Test
+    public void observationDoesNotAffectConfigurationDetection() {
+        // isConfigured() answers "does the stored configuration name the LAN",
+        // which a runtime observation must not fake up.
+        LocalNetworkAccess.reportDestination("192.168.1.10");
+        assertFalse(LocalNetworkAccess.isConfigured(prefs));
     }
 
     @Test