network-dns-slice (part 1/2): DNS Clean-Arch slice + single injection point

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

@@ -1096,9 +1096,8 @@ public void onComplete(String destDir) {
                                     }
                                 }
 
-                                // Freshly fast-installed rootfs ships without resolv.conf; give it
-                                // DNS before the companion-data (maps/kiwix) steps that need network.
-                                ensureRuntimeNetworkConfig(debianRootfs);
+                                // DNS is written at the single chokepoint (PRootEngine.executeInContainer),
+                                // so the companion-data proot steps below get a working resolv.conf for free.
 
                                 if (chkCompanionData.isChecked()) {
                                     editLocalVarsForMaps(debianRootfs, safeTier);
@@ -1307,16 +1306,8 @@ public void onComplete(String downloadPath) {
                                                 // 4. BOOTSTRAP IIAB
                                                 mainAct.runOnUiThread(() -> btnAdvancedReset.setText(getString(R.string.install_status_bootstrapping)));
 
-                                                File resolvConf = new File(debianRootfs, "etc/resolv.conf");
-                                                if (resolvConf.exists()) resolvConf.delete();
-                                                java.io.FileOutputStream fos = new java.io.FileOutputStream(resolvConf);
-                                                fos.write("nameserver 1.1.1.1\nnameserver 8.8.8.8\n".getBytes());
-                                                fos.close();
-
-                                                File hostsFile = new File(debianRootfs, "etc/hosts");
-                                                java.io.FileOutputStream fosH = new java.io.FileOutputStream(hostsFile);
-                                                fosH.write("127.0.0.1 localhost\n".getBytes());
-                                                fosH.close();
+                                                // DNS is written at the chokepoint (PRootEngine) before the
+                                                // bootstrap proot run below; no inline write needed here.
 
                                                 if (prootEngine == null)
                                                     prootEngine = new PRootEngine();
@@ -2147,8 +2138,6 @@ private void refreshRestoreButtonLogic() {
                 tarExtractor.startExtraction(requireContext(), backupFile.getAbsolutePath(), iiabRootDir.getAbsolutePath(), new TarExtractor.ExtractionListener() {
                     @Override
                     public void onComplete(String destDir) {
-                        // Restored artifact ships without resolv.conf; the app owns runtime DNS.
-                        ensureRuntimeNetworkConfig(new File(iiabRootDir, "installed-rootfs/iiab"));
                         mainAct.runOnUiThread(() -> {
                             isRestoring = false;
                             disableSystemProtection();
@@ -2175,33 +2164,6 @@ public void onError(String error) {
         }
     }
 
-    // Runtime network config for the proot guest: proot has no resolver daemon, and our build
-    // artifact ships WITHOUT /etc/resolv.conf on purpose (the app is the single owner of runtime
-    // network state). Mirrors the reset path. Called from fast-install and restore.
-    // TODO [tech-debt]: imperative side-effect inside DeployFragment (god-object); not Clean
-    // Architecture. Fold into the rootfs domain/data slice during the strangler refactor.
-    private void ensureRuntimeNetworkConfig(File debianRootfs) {
-        try {
-            File etc = new File(debianRootfs, "etc");
-            if (!etc.isDirectory()) {
-                Log.w(TAG, "ensureRuntimeNetworkConfig: missing " + etc.getAbsolutePath() + " - skipping DNS write");
-                return;
-            }
-            File resolvConf = new File(etc, "resolv.conf");
-            if (resolvConf.exists()) resolvConf.delete();
-            try (java.io.FileOutputStream fos = new java.io.FileOutputStream(resolvConf)) {
-                fos.write("nameserver 1.1.1.1\nnameserver 8.8.8.8\n".getBytes());
-            }
-            File hostsFile = new File(etc, "hosts");
-            try (java.io.FileOutputStream fosH = new java.io.FileOutputStream(hostsFile)) {
-                fosH.write("127.0.0.1 localhost\n".getBytes());
-            }
-            Log.i(TAG, "ensureRuntimeNetworkConfig: wrote resolv.conf + hosts under " + etc.getAbsolutePath());
-        } catch (Exception e) {
-            Log.w(TAG, "ensureRuntimeNetworkConfig failed", e);
-        }
-    }
-
     private void importBackupSafely(Uri sourceUri) {
         isImporting = true;
         updateDynamicButtons();

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

@@ -20,6 +20,10 @@
 import java.util.ArrayList;
 import java.util.List;
 
+import org.iiab.controller.network.data.FileResolvConfWriter;
+import org.iiab.controller.network.data.PrefsDnsConfigRepository;
+import org.iiab.controller.network.domain.ApplyDnsUseCase;
+
 public class PRootEngine {
     private static final String TAG = "IIAB-PRootEngine";
     private Process currentProcess;
@@ -44,6 +48,19 @@ public void executeInContainer(Context context, String rootfsDir, String command
                     throw new Exception("libproot.so not found in native library directory!");
                 }
 
+                // Single DNS injection point: every proot launch passes through here, so we write
+                // the effective DNS (user's custom config when enabled, else defaults) into the
+                // guest's resolv.conf BEFORE launching. Replaces the scattered writes that used to
+                // live in DeployFragment / MainActivity.
+                try {
+                    new ApplyDnsUseCase(
+                            new PrefsDnsConfigRepository(context),
+                            new FileResolvConfWriter()
+                    ).execute(new File(rootfsDir));
+                } catch (Exception dnsEx) {
+                    Log.w(TAG, "DNS apply skipped: " + dnsEx.getMessage());
+                }
+
                 // =========================================================
                 // THE W^X TROJAN HORSE: FAKE TERMUX PREFIX
                 // =========================================================

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

@@ -0,0 +1,58 @@
+/*
+ * ============================================================================
+ * Name        : FileResolvConfWriter.java
+ * Author      : AppDevForAll
+ * Copyright   : Copyright (c) 2026 AppDevForAll
+ * Description : Writes resolv.conf (+ minimal hosts) into a rootfs; migrates the #25 helper logic.
+ * ============================================================================
+ */
+package org.iiab.controller.network.data;
+
+import android.util.Log;
+
+import org.iiab.controller.network.domain.DnsConfig;
+import org.iiab.controller.network.domain.ResolvConfWriter;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.nio.charset.StandardCharsets;
+
+/**
+ * {@link ResolvConfWriter} that writes {@code etc/resolv.conf} (and a minimal
+ * {@code etc/hosts} if absent) into a guest rootfs. This is the single home for the
+ * DNS-write logic previously duplicated in {@code DeployFragment}/{@code MainActivity}.
+ * Guards on {@code etc/} existence and never throws.
+ */
+public final class FileResolvConfWriter implements ResolvConfWriter {
+
+    private static final String TAG = "IIAB-DNS";
+
+    @Override
+    public boolean write(DnsConfig config, File rootfsDir) {
+        try {
+            File etc = new File(rootfsDir, "etc");
+            if (!etc.isDirectory()) {
+                Log.w(TAG, "resolv.conf skipped: missing " + etc.getAbsolutePath());
+                return false;
+            }
+            File resolv = new File(etc, "resolv.conf");
+            if (resolv.exists() && !resolv.delete()) {
+                Log.w(TAG, "could not remove old resolv.conf at " + resolv.getAbsolutePath());
+            }
+            try (FileOutputStream fos = new FileOutputStream(resolv)) {
+                fos.write(config.toResolvConf().getBytes(StandardCharsets.UTF_8));
+            }
+            File hosts = new File(etc, "hosts");
+            if (!hosts.exists()) {
+                try (FileOutputStream fos = new FileOutputStream(hosts)) {
+                    fos.write("127.0.0.1 localhost\n".getBytes(StandardCharsets.UTF_8));
+                }
+            }
+            Log.i(TAG, "wrote resolv.conf (" + config + ") under " + etc.getAbsolutePath());
+            return true;
+        } catch (Exception e) {
+            Log.w(TAG, "FileResolvConfWriter.write failed", e);
+            return false;
+        }
+    }
+}

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

@@ -0,0 +1,67 @@
+/*
+ * ============================================================================
+ * Name        : PrefsDnsConfigRepository.java
+ * Author      : AppDevForAll
+ * Copyright   : Copyright (c) 2026 AppDevForAll
+ * Description : SharedPreferences-backed DnsConfigRepository (new keys; not the vestigial VPN ones).
+ * ============================================================================
+ */
+package org.iiab.controller.network.data;
+
+import android.content.Context;
+import android.content.SharedPreferences;
+
+import org.iiab.controller.network.domain.DnsConfig;
+import org.iiab.controller.network.domain.DnsConfigRepository;
+
+/**
+ * {@link DnsConfigRepository} backed by a dedicated SharedPreferences file. Uses
+ * fresh keys (NOT the vestigial VPN-era {@code DnsIpv4}/{@code DnsIpv6} in
+ * {@code Preferences}, which this feature will retire). {@code MODE_MULTI_PROCESS}
+ * matches the rest of the app.
+ */
+public final class PrefsDnsConfigRepository implements DnsConfigRepository {
+
+    private static final String PREFS = "NetworkDnsPrefs";
+    private static final String K_CUSTOM = "dns.custom.enabled";
+    private static final String K_PRIMARY = "dns.primary";
+    private static final String K_SECONDARY = "dns.secondary";
+
+    private final SharedPreferences prefs;
+
+    public PrefsDnsConfigRepository(Context context) {
+        this.prefs = context.getSharedPreferences(PREFS, Context.MODE_MULTI_PROCESS);
+    }
+
+    @Override
+    public DnsConfig loadEffective() {
+        return isCustomEnabled() ? loadCustom() : DnsConfig.defaults();
+    }
+
+    @Override
+    public DnsConfig loadCustom() {
+        DnsConfig d = DnsConfig.defaults();
+        String primary = prefs.getString(K_PRIMARY, d.primary());
+        String secondary = prefs.getString(K_SECONDARY, d.secondary());
+        return new DnsConfig(primary, secondary);
+    }
+
+    @Override
+    public boolean isCustomEnabled() {
+        return prefs.getBoolean(K_CUSTOM, false);
+    }
+
+    @Override
+    public void saveCustom(DnsConfig config) {
+        prefs.edit()
+                .putBoolean(K_CUSTOM, true)
+                .putString(K_PRIMARY, config.primary())
+                .putString(K_SECONDARY, config.secondary())
+                .commit();
+    }
+
+    @Override
+    public void disableCustom() {
+        prefs.edit().putBoolean(K_CUSTOM, false).commit();
+    }
+}

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

@@ -0,0 +1,32 @@
+/*
+ * ============================================================================
+ * Name        : ApplyDnsUseCase.java
+ * Author      : AppDevForAll
+ * Copyright   : Copyright (c) 2026 AppDevForAll
+ * Description : Use case: write the effective DNS config into a rootfs (boot-time apply).
+ * ============================================================================
+ */
+package org.iiab.controller.network.domain;
+
+import java.io.File;
+
+/**
+ * Writes the effective DNS config (custom or defaults) into a guest rootfs. Called
+ * at server boot (and wherever a rootfs is about to run network operations) so the
+ * proot guest always has a working {@code resolv.conf} without a resolver daemon.
+ */
+public final class ApplyDnsUseCase {
+
+    private final DnsConfigRepository repository;
+    private final ResolvConfWriter writer;
+
+    public ApplyDnsUseCase(DnsConfigRepository repository, ResolvConfWriter writer) {
+        this.repository = repository;
+        this.writer = writer;
+    }
+
+    /** @return {@code true} if resolv.conf was written into {@code rootfsDir}. */
+    public boolean execute(File rootfsDir) {
+        return writer.write(repository.loadEffective(), rootfsDir);
+    }
+}

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

@@ -0,0 +1,65 @@
+/*
+ * ============================================================================
+ * Name        : DnsConfig.java
+ * Author      : AppDevForAll
+ * Copyright   : Copyright (c) 2026 AppDevForAll
+ * Description : DNS configuration: two mixed slots (primary/secondary), each one IPv4 or IPv6.
+ * ============================================================================
+ */
+package org.iiab.controller.network.domain;
+
+/**
+ * Immutable DNS configuration: a {@code primary} and an optional {@code secondary}
+ * nameserver. Each slot holds a SINGLE address that may be IPv4 <em>or</em> IPv6
+ * (mixed allowed in any order); no comma-separated lists. This keeps the model and
+ * validation simple while covering every combination the user might want.
+ *
+ * <p>Pure domain value object (no Android, no I/O). {@link #defaults()} is the
+ * preconfigured set the app ships with, so the user never has to configure anything.
+ */
+public final class DnsConfig {
+
+    private final String primary;
+    private final String secondary;
+
+    public DnsConfig(String primary, String secondary) {
+        this.primary = norm(primary);
+        this.secondary = norm(secondary);
+    }
+
+    /** Preconfigured defaults: Cloudflare (primary) + Google (secondary), both IPv4. */
+    public static DnsConfig defaults() {
+        return new DnsConfig("1.1.1.1", "8.8.8.8");
+    }
+
+    /** The primary nameserver (IPv4 or IPv6); "" if unset. */
+    public String primary() { return primary; }
+
+    /** The secondary nameserver (IPv4 or IPv6); "" if unset. */
+    public String secondary() { return secondary; }
+
+    public boolean hasSecondary() { return !secondary.isEmpty(); }
+
+    public boolean isEmpty() { return primary.isEmpty() && secondary.isEmpty(); }
+
+    /** Body for {@code /etc/resolv.conf}: one {@code nameserver X} line per non-empty slot. */
+    public String toResolvConf() {
+        StringBuilder sb = new StringBuilder();
+        if (!primary.isEmpty()) sb.append("nameserver ").append(primary).append("\n");
+        if (!secondary.isEmpty()) sb.append("nameserver ").append(secondary).append("\n");
+        return sb.toString();
+    }
+
+    private static String norm(String s) { return s == null ? "" : s.trim(); }
+
+    @Override public boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof DnsConfig)) return false;
+        DnsConfig d = (DnsConfig) o;
+        return primary.equals(d.primary) && secondary.equals(d.secondary);
+    }
+
+    @Override public int hashCode() { return 31 * primary.hashCode() + secondary.hashCode(); }
+
+    @Override public String toString() { return "DnsConfig{primary=" + primary + ", secondary=" + secondary + "}"; }
+}

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

@@ -0,0 +1,35 @@
+/*
+ * ============================================================================
+ * Name        : DnsConfigRepository.java
+ * Author      : AppDevForAll
+ * Copyright   : Copyright (c) 2026 AppDevForAll
+ * Description : Domain port: persistence of the user's DNS choice.
+ * ============================================================================
+ */
+package org.iiab.controller.network.domain;
+
+/**
+ * Domain port for persisting the user's DNS choice. The Data layer backs this with
+ * SharedPreferences. Semantics support the "Setup DNS" checkbox:
+ * <ul>
+ *   <li>custom disabled (default) &rarr; effective config is {@link DnsConfig#defaults()};</li>
+ *   <li>custom enabled &rarr; effective config is the saved custom config.</li>
+ * </ul>
+ */
+public interface DnsConfigRepository {
+
+    /** Config to actually apply: saved custom when enabled, otherwise {@link DnsConfig#defaults()}. */
+    DnsConfig loadEffective();
+
+    /** The saved custom config (or {@link DnsConfig#defaults()} if none saved yet). */
+    DnsConfig loadCustom();
+
+    /** Whether the user enabled custom DNS (the "Setup DNS" check). */
+    boolean isCustomEnabled();
+
+    /** Persist {@code config} as the custom config and mark custom DNS enabled. */
+    void saveCustom(DnsConfig config);
+
+    /** Turn custom DNS off (revert to defaults). Used on test failure / unchecking. */
+    void disableCustom();
+}