network-dns-slice (part 2/2): Setup DNS UI in Usage

controller/app/src/main/java/org/iiab/controller/Preferences.java

@@ -24,8 +24,6 @@ public class Preferences {
     public static final String SOCKS_PORT = "SocksPort";
     public static final String SOCKS_USER = "SocksUser";
     public static final String SOCKS_PASS = "SocksPass";
-    public static final String DNS_IPV4 = "DnsIpv4";
-    public static final String DNS_IPV6 = "DnsIpv6";
     public static final String IPV4 = "Ipv4";
     public static final String IPV6 = "Ipv6";
     public static final String GLOBAL = "Global";
@@ -92,26 +90,6 @@ public void setSocksPassword(String pass) {
         editor.commit();
     }
 
-    public String getDnsIpv4() {
-        return prefs.getString(DNS_IPV4, "8.8.8.8");
-    }
-
-    public void setDnsIpv4(String addr) {
-        SharedPreferences.Editor editor = prefs.edit();
-        editor.putString(DNS_IPV4, addr);
-        editor.commit();
-    }
-
-    public String getDnsIpv6() {
-        return prefs.getString(DNS_IPV6, "2001:4860:4860::8888");
-    }
-
-    public void setDnsIpv6(String addr) {
-        SharedPreferences.Editor editor = prefs.edit();
-        editor.putString(DNS_IPV6, addr);
-        editor.commit();
-    }
-
     public String getMappedDns() {
         return "198.18.0.2";
     }

controller/app/src/main/java/org/iiab/controller/UsageFragment.java

@@ -32,6 +32,11 @@
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
+import androidx.lifecycle.ViewModelProvider;
+
+import org.iiab.controller.network.presentation.DnsSettingsUiState;
+import org.iiab.controller.network.presentation.DnsSettingsViewModel;
+import org.iiab.controller.network.presentation.DnsSettingsViewModelFactory;
 
 import com.google.android.material.snackbar.Snackbar;
 
@@ -43,7 +48,7 @@ public class UsageFragment extends Fragment implements View.OnClickListener {
 
     private MainActivity mainActivity;
     // INTERFACE VARS
-    private EditText edittext_socks_addr, edittext_socks_udp_addr, edittext_socks_port, edittext_socks_user, edittext_socks_pass, edittext_dns_ipv4, edittext_dns_ipv6;
+    private EditText edittext_socks_addr, edittext_socks_udp_addr, edittext_socks_port, edittext_socks_user, edittext_socks_pass;
     private CheckBox checkbox_udp_in_tcp, checkbox_remote_dns, checkbox_global, checkbox_maintenance, checkbox_ipv4, checkbox_ipv6;
     private TextView textview_maintenance_warning, configLabel, advConfigLabel, logLabel, logWarning, logSizeText, connectionLog;
     private Button button_apps, button_save, button_control, button_browse_content, btnClearLog, btnCopyLog;
@@ -53,6 +58,17 @@ public class UsageFragment extends Fragment implements View.OnClickListener {
 
     private DashboardManager dashboardManager;
 
+    // Setup DNS (network slice, PR B)
+    private CheckBox setup_dns_check;
+    private LinearLayout dns_setup_fields;
+    private EditText dns_primary, dns_secondary;
+    private Button dns_accept;
+    private TextView dns_result;
+    private TextView dns_settings_label;
+    private LinearLayout dns_settings_section;
+    private DnsSettingsViewModel dnsViewModel;
+    private boolean suppressDnsToggle = false;
+
     @Override
     public void onAttach(@NonNull Context context) {
         super.onAttach(context);
@@ -78,8 +94,25 @@ public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceStat
         edittext_socks_port = view.findViewById(R.id.socks_port);
         edittext_socks_user = view.findViewById(R.id.socks_user);
         edittext_socks_pass = view.findViewById(R.id.socks_pass);
-        edittext_dns_ipv4 = view.findViewById(R.id.dns_ipv4);
-        edittext_dns_ipv6 = view.findViewById(R.id.dns_ipv6);
+        setup_dns_check = view.findViewById(R.id.setup_dns_check);
+        dns_setup_fields = view.findViewById(R.id.dns_setup_fields);
+        dns_primary = view.findViewById(R.id.dns_primary);
+        dns_secondary = view.findViewById(R.id.dns_secondary);
+        dns_accept = view.findViewById(R.id.dns_accept);
+        dns_result = view.findViewById(R.id.dns_result);
+        dns_settings_label = view.findViewById(R.id.dns_settings_label);
+        dns_settings_section = view.findViewById(R.id.dns_settings_section);
+        dns_settings_label.setText(String.format(getString(R.string.label_separator_up), getString(R.string.network_advanced_label)));
+        dns_settings_label.setOnClickListener(v -> toggleVisibility(dns_settings_section, dns_settings_label, getString(R.string.network_advanced_label)));
+        dnsViewModel = new ViewModelProvider(this, new DnsSettingsViewModelFactory(requireContext()))
+                .get(DnsSettingsViewModel.class);
+        dnsViewModel.state().observe(getViewLifecycleOwner(), this::renderDnsState);
+        setup_dns_check.setOnCheckedChangeListener((btn, checked) -> {
+            if (suppressDnsToggle) return;
+            dnsViewModel.onSetupToggled(checked);
+        });
+        dns_accept.setOnClickListener(v -> dnsViewModel.onAccept(
+                dns_primary.getText().toString(), dns_secondary.getText().toString()));
         checkbox_ipv4 = view.findViewById(R.id.ipv4);
         checkbox_ipv6 = view.findViewById(R.id.ipv6);
         checkbox_global = view.findViewById(R.id.global);
@@ -210,8 +243,6 @@ public void updateUI() {
         edittext_socks_port.setText(String.valueOf(mainActivity.prefs.getSocksPort()));
         edittext_socks_user.setText(mainActivity.prefs.getSocksUsername());
         edittext_socks_pass.setText(mainActivity.prefs.getSocksPassword());
-        edittext_dns_ipv4.setText(mainActivity.prefs.getDnsIpv4());
-        edittext_dns_ipv6.setText(mainActivity.prefs.getDnsIpv6());
         checkbox_ipv4.setChecked(mainActivity.prefs.getIpv4());
         checkbox_ipv6.setChecked(mainActivity.prefs.getIpv6());
         checkbox_global.setChecked(mainActivity.prefs.getGlobal());
@@ -450,10 +481,42 @@ public void savePrefsFromUI() {
         mainActivity.prefs.setRemoteDns(true);
         mainActivity.prefs.setGlobal(true);
 
-        mainActivity.prefs.setDnsIpv4(edittext_dns_ipv4.getText().toString());
-        mainActivity.prefs.setDnsIpv6(edittext_dns_ipv6.getText().toString());
         mainActivity.prefs.setMaintenanceMode(checkbox_maintenance.isChecked());
     }
+
+    private void renderDnsState(DnsSettingsUiState st) {
+        if (setup_dns_check == null) return;
+        suppressDnsToggle = true;
+        setup_dns_check.setChecked(st.customEnabled);
+        suppressDnsToggle = false;
+        dns_setup_fields.setVisibility(st.customEnabled ? View.VISIBLE : View.GONE);
+        if (st.status == DnsSettingsUiState.Status.IDLE || st.status == DnsSettingsUiState.Status.UNREACHABLE) {
+            dns_primary.setText(st.primary);
+            dns_secondary.setText(st.secondary);
+        }
+        switch (st.status) {
+            case TESTING:
+                dns_result.setVisibility(View.VISIBLE);
+                dns_result.setText(getString(R.string.dns_status_testing));
+                dns_result.setTextColor(ContextCompat.getColor(requireContext(), R.color.text_secondary));
+                break;
+            case APPLIED:
+                dns_result.setVisibility(View.VISIBLE);
+                dns_result.setText(getString(R.string.dns_status_ok));
+                dns_result.setTextColor(ContextCompat.getColor(requireContext(), R.color.status_success));
+                break;
+            case INVALID:
+            case UNREACHABLE:
+                dns_result.setVisibility(View.VISIBLE);
+                dns_result.setText(st.message != null ? st.message : "");
+                dns_result.setTextColor(ContextCompat.getColor(requireContext(), R.color.status_warning));
+                break;
+            default:
+                dns_result.setVisibility(View.GONE);
+                break;
+        }
+    }
+
     public void highlightServerButton() {
         if (deckContainer == null || !isAdded()) return;
 

controller/app/src/main/java/org/iiab/controller/network/data/UdpDnsConnectivityProbe.java

@@ -0,0 +1,88 @@
+/*
+ * ============================================================================
+ * Name        : UdpDnsConnectivityProbe.java
+ * Author      : AppDevForAll
+ * Copyright   : Copyright (c) 2026 AppDevForAll
+ * Description : UDP DNS-query probe: sends a query to the server and waits for a reply.
+ * ============================================================================
+ */
+package org.iiab.controller.network.data;
+
+import android.util.Log;
+
+import org.iiab.controller.network.domain.DnsConnectivityProbe;
+
+import java.io.ByteArrayOutputStream;
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
+import java.net.InetAddress;
+import java.nio.charset.StandardCharsets;
+
+/**
+ * {@link DnsConnectivityProbe} that sends a tiny DNS A-query (for a fixed, stable
+ * name) over UDP to the given server on port 53 and waits for a valid reply.
+ * Pure {@code java.net}; works for IPv4 and IPv6 servers. Never throws — any
+ * error (timeout, unreachable, malformed) means "not reachable".
+ */
+public final class UdpDnsConnectivityProbe implements DnsConnectivityProbe {
+
+    private static final String TAG = "IIAB-DNS";
+    private static final String PROBE_NAME = "example.com";
+    private static final int DNS_PORT = 53;
+
+    @Override
+    public boolean isReachable(String dnsServer, long timeoutMs) {
+        if (dnsServer == null || dnsServer.trim().isEmpty()) return false;
+        DatagramSocket socket = null;
+        try {
+            byte[] query = buildQuery(PROBE_NAME);
+            InetAddress addr = InetAddress.getByName(dnsServer.trim());
+            socket = new DatagramSocket();
+            socket.setSoTimeout((int) Math.max(1, Math.min(timeoutMs, Integer.MAX_VALUE)));
+            socket.send(new DatagramPacket(query, query.length, addr, DNS_PORT));
+
+            byte[] buf = new byte[512];
+            DatagramPacket response = new DatagramPacket(buf, buf.length);
+            socket.receive(response);
+
+            if (response.getLength() < 12) return false;
+            boolean idMatches = buf[0] == query[0] && buf[1] == query[1];
+            boolean isResponse = (buf[2] & 0x80) != 0;
+            int rcode = buf[3] & 0x0F;
+            return idMatches && isResponse && rcode == 0;
+        } catch (Exception e) {
+            Log.i(TAG, "DNS probe to " + dnsServer + " failed: " + e.getMessage());
+            return false;
+        } finally {
+            if (socket != null) socket.close();
+        }
+    }
+
+    private static byte[] buildQuery(String name) {
+        ByteArrayOutputStream out = new ByteArrayOutputStream();
+        int id = (int) (System.nanoTime() & 0xFFFF);
+        out.write((id >> 8) & 0xFF);
+        out.write(id & 0xFF);
+        out.write(0x01);
+        out.write(0x00);
+        out.write(0x00);
+        out.write(0x01);
+        out.write(0x00);
+        out.write(0x00);
+        out.write(0x00);
+        out.write(0x00);
+        out.write(0x00);
+        out.write(0x00);
+        for (String label : name.split("\\.")) {
+            byte[] b = label.getBytes(StandardCharsets.US_ASCII);
+            out.write(b.length);
+            out.write(b, 0, b.length);
+        }
+        out.write(0x00);
+        out.write(0x00);
+        out.write(0x01);
+        out.write(0x00);
+        out.write(0x01);
+        return out.toByteArray();
+    }
+}

controller/app/src/main/java/org/iiab/controller/network/domain/ConfigureDnsUseCase.java

@@ -0,0 +1,66 @@
+/*
+ * ============================================================================
+ * Name        : ConfigureDnsUseCase.java
+ * Author      : AppDevForAll
+ * Copyright   : Copyright (c) 2026 AppDevForAll
+ * Description : Validate, netplan-try probe, then save (or revert to defaults).
+ * ============================================================================
+ */
+package org.iiab.controller.network.domain;
+
+/**
+ * Orchestrates applying a user-entered DNS config, netplan-try style:
+ * <ol>
+ *   <li>validate (fail-closed) — invalid input is never saved;</li>
+ *   <li>probe the server(s) for an actual DNS reply;</li>
+ *   <li>if reachable, persist as custom; otherwise revert to defaults and report.</li>
+ * </ol>
+ * Pure domain logic over the {@link DnsConfigRepository} and {@link DnsConnectivityProbe}
+ * ports — unit-testable with fakes.
+ */
+public final class ConfigureDnsUseCase {
+
+    public enum Outcome { APPLIED, INVALID, UNREACHABLE }
+
+    public static final class Result {
+        public final Outcome outcome;
+        public final String message;
+        private Result(Outcome outcome, String message) { this.outcome = outcome; this.message = message; }
+        static Result applied() { return new Result(Outcome.APPLIED, null); }
+        static Result invalid(String reason) { return new Result(Outcome.INVALID, reason); }
+        static Result unreachable() { return new Result(Outcome.UNREACHABLE, "DNS did not respond"); }
+    }
+
+    private static final long DEFAULT_TIMEOUT_MS = 4000L;
+
+    private final DnsConfigRepository repository;
+    private final DnsConnectivityProbe probe;
+    private final long timeoutMs;
+
+    public ConfigureDnsUseCase(DnsConfigRepository repository, DnsConnectivityProbe probe) {
+        this(repository, probe, DEFAULT_TIMEOUT_MS);
+    }
+
+    public ConfigureDnsUseCase(DnsConfigRepository repository, DnsConnectivityProbe probe, long timeoutMs) {
+        this.repository = repository;
+        this.probe = probe;
+        this.timeoutMs = timeoutMs;
+    }
+
+    public Result execute(DnsConfig candidate) {
+        DnsValidator.Result validation = DnsValidator.validate(candidate);
+        if (!validation.valid) {
+            return Result.invalid(validation.reason);
+        }
+        boolean reachable = probe.isReachable(candidate.primary(), timeoutMs);
+        if (!reachable && candidate.hasSecondary()) {
+            reachable = probe.isReachable(candidate.secondary(), timeoutMs);
+        }
+        if (reachable) {
+            repository.saveCustom(candidate);
+            return Result.applied();
+        }
+        repository.disableCustom();
+        return Result.unreachable();
+    }
+}

controller/app/src/main/java/org/iiab/controller/network/domain/DnsConnectivityProbe.java

@@ -0,0 +1,24 @@
+/*
+ * ============================================================================
+ * Name        : DnsConnectivityProbe.java
+ * Author      : AppDevForAll
+ * Copyright   : Copyright (c) 2026 AppDevForAll
+ * Description : Domain port: can a DNS server actually answer (netplan-try style).
+ * ============================================================================
+ */
+package org.iiab.controller.network.domain;
+
+/**
+ * Domain port that probes whether a DNS server is a working resolver reachable
+ * from the device. The Data layer implements it (a small UDP DNS query). Used for
+ * the netplan-try style verification before committing a user-chosen DNS.
+ */
+public interface DnsConnectivityProbe {
+
+    /**
+     * @param dnsServer IPv4/IPv6 literal of the server to test
+     * @param timeoutMs how long to wait for a reply
+     * @return {@code true} if the server answered a DNS query within the timeout
+     */
+    boolean isReachable(String dnsServer, long timeoutMs);
+}

controller/app/src/main/java/org/iiab/controller/network/presentation/DnsSettingsUiState.java

@@ -0,0 +1,55 @@
+/*
+ * ============================================================================
+ * Name        : DnsSettingsUiState.java
+ * Author      : AppDevForAll
+ * Copyright   : Copyright (c) 2026 AppDevForAll
+ * Description : Immutable UI state for the Setup DNS panel.
+ * ============================================================================
+ */
+package org.iiab.controller.network.presentation;
+
+/**
+ * Immutable UI state for the Setup DNS panel, exposed by {@link DnsSettingsViewModel}.
+ * {@code customEnabled} drives the checkbox; {@code primary}/{@code secondary} prefill
+ * the fields; {@code status} + {@code message} drive the result indicator.
+ */
+public final class DnsSettingsUiState {
+
+    public enum Status { IDLE, TESTING, APPLIED, INVALID, UNREACHABLE }
+
+    public final boolean customEnabled;
+    public final String primary;
+    public final String secondary;
+    public final Status status;
+    public final String message;
+
+    private DnsSettingsUiState(boolean customEnabled, String primary, String secondary, Status status, String message) {
+        this.customEnabled = customEnabled;
+        this.primary = primary == null ? "" : primary;
+        this.secondary = secondary == null ? "" : secondary;
+        this.status = status;
+        this.message = message;
+    }
+
+    public static DnsSettingsUiState idle(boolean customEnabled, String primary, String secondary) {
+        return new DnsSettingsUiState(customEnabled, primary, secondary, Status.IDLE, null);
+    }
+
+    public static DnsSettingsUiState testing(String primary, String secondary) {
+        return new DnsSettingsUiState(true, primary, secondary, Status.TESTING, null);
+    }
+
+    public static DnsSettingsUiState applied(String primary, String secondary) {
+        return new DnsSettingsUiState(true, primary, secondary, Status.APPLIED, null);
+    }
+
+    public static DnsSettingsUiState invalid(String primary, String secondary, String message) {
+        return new DnsSettingsUiState(true, primary, secondary, Status.INVALID, message);
+    }
+
+    /** Probe failed: the use case reverted to defaults, so the panel shows defaults again. */
+    public static DnsSettingsUiState unreachable(String defaultPrimary, String defaultSecondary) {
+        return new DnsSettingsUiState(false, defaultPrimary, defaultSecondary, Status.UNREACHABLE,
+                "DNS did not respond — reverted to defaults");
+    }
+}