Made rcode configurable

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

@@ -223,12 +223,14 @@ public class ActivitySettings extends AppCompatActivity implements SharedPrefere
         EditTextPreference pref_dns1 = (EditTextPreference) screen.findPreference("dns");
         EditTextPreference pref_dns2 = (EditTextPreference) screen.findPreference("dns2");
         EditTextPreference pref_ttl = (EditTextPreference) screen.findPreference("ttl");
+        EditTextPreference pref_rcode = (EditTextPreference) screen.findPreference("rcode");
         List<String> def_dns = Util.getDefaultDNS(this);
         pref_dns1.getEditText().setHint(def_dns.get(0));
         pref_dns2.getEditText().setHint(def_dns.get(1));
         pref_dns1.setTitle(getString(R.string.setting_dns, prefs.getString("dns", def_dns.get(0))));
         pref_dns2.setTitle(getString(R.string.setting_dns, prefs.getString("dns2", def_dns.get(1))));
         pref_ttl.setTitle(getString(R.string.setting_ttl, prefs.getString("ttl", "259200")));
+        pref_rcode.setTitle(getString(R.string.setting_rcode, prefs.getString("rcode", "3")));
 
         // SOCKS5 parameters
         screen.findPreference("socks5_addr").setTitle(getString(R.string.setting_socks5_addr, prefs.getString("socks5_addr", "-")));
@@ -245,9 +247,10 @@ public class ActivitySettings extends AppCompatActivity implements SharedPrefere
 
         // Show resolved
         Preference pref_show_resolved = screen.findPreference("show_resolved");
-        if (Util.isPlayStoreInstall(this))
+        if (Util.isPlayStoreInstall(this)) {
             cat_advanced.removePreference(pref_show_resolved);
-        else
+            cat_advanced.removePreference(pref_rcode);
+        } else
             pref_show_resolved.setOnPreferenceClickListener(new Preference.OnPreferenceClickListener() {
                 @Override
                 public boolean onPreferenceClick(Preference preference) {
@@ -671,7 +674,12 @@ public class ActivitySettings extends AppCompatActivity implements SharedPrefere
             getPreferenceScreen().findPreference(name).setTitle(
                     getString(R.string.setting_ttl, prefs.getString(name, "259200")));
 
-        else if ("socks5_enabled".equals(name))
+        else if ("rcode".equals(name)) {
+            getPreferenceScreen().findPreference(name).setTitle(
+                    getString(R.string.setting_rcode, prefs.getString(name, "3")));
+            ServiceSinkhole.reload("changed " + name, this);
+
+        } else if ("socks5_enabled".equals(name))
             ServiceSinkhole.reload("changed " + name, this);
 
         else if ("socks5_addr".equals(name)) {

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

@@ -176,7 +176,7 @@ public class ServiceSinkhole extends VpnService implements SharedPreferences.OnS
 
     private native void jni_init();
 
-    private native void jni_start(int tun, boolean fwd53, int loglevel);
+    private native void jni_start(int tun, boolean fwd53, int rcode, int loglevel);
 
     private native void jni_stop(int tun, boolean clr);
 
@@ -1187,6 +1187,7 @@ public class ServiceSinkhole extends VpnService implements SharedPreferences.OnS
 
         if (log || log_app || filter) {
             int prio = Integer.parseInt(prefs.getString("loglevel", Integer.toString(Log.WARN)));
+            int rcode = Integer.parseInt(prefs.getString("rcode", "3"));
             if (prefs.getBoolean("socks5_enabled", false))
                 jni_socks5(
                         prefs.getString("socks5_addr", ""),
@@ -1195,7 +1196,7 @@ public class ServiceSinkhole extends VpnService implements SharedPreferences.OnS
                         prefs.getString("socks5_password", ""));
             else
                 jni_socks5("", 0, "", "");
-            jni_start(vpn.getFd(), mapForward.containsKey(53), prio);
+            jni_start(vpn.getFd(), mapForward.containsKey(53), rcode, prio);
         }
     }
 

app/src/main/jni/netguard/dns.c

@@ -232,9 +232,9 @@ int check_domain(const struct arguments *args, const struct udp_session *u,
         else
             inet_pton(AF_INET6, "::1", addr);
 
-        // Experiment
+        // Send selected negative response
         rlen = datalen;
-        rh->rcode = 3; // NXDOMAIN
+        rh->rcode = (uint16_t) args->rcode;
         rh->ans_count = 0;
 
         // Send response

app/src/main/jni/netguard/netguard.c

@@ -130,7 +130,7 @@ Java_eu_faircode_netguard_ServiceSinkhole_jni_1init(JNIEnv *env, jobject instanc
 
 JNIEXPORT void JNICALL
 Java_eu_faircode_netguard_ServiceSinkhole_jni_1start(
-        JNIEnv *env, jobject instance, jint tun, jboolean fwd53, jint loglevel_) {
+        JNIEnv *env, jobject instance, jint tun, jboolean fwd53, jint rcode, jint loglevel_) {
 
     loglevel = loglevel_;
     max_tun_msg = 0;
@@ -157,6 +157,7 @@ Java_eu_faircode_netguard_ServiceSinkhole_jni_1start(
         args->instance = (*env)->NewGlobalRef(env, instance);
         args->tun = tun;
         args->fwd53 = fwd53;
+        args->rcode = rcode;
 
         // Start native thread
         int err = pthread_create(&thread_id, NULL, handle_events, (void *) args);

app/src/main/jni/netguard/netguard.h

@@ -70,6 +70,7 @@ struct arguments {
     jobject instance;
     int tun;
     jboolean fwd53;
+    jint rcode;
 };
 
 struct allowed {

app/src/main/res/values/strings.xml

@@ -96,6 +96,7 @@ however it is impossible to guarantee NetGuard will work correctly on every devi
     <string name="setting_vpn6">VPN IPv6: %s</string>
     <string name="setting_dns">VPN DNS: %s</string>
     <string name="setting_ttl">Minimum DNS TTL: %s s</string>
+    <string name="setting_rcode">DNS response code: %s</string>
     <string name="setting_socks5_enabled">Use SOCKS5 proxy</string>
     <string name="setting_socks5_addr">SOCKS5 address: %s</string>
     <string name="setting_socks5_port">SOCKS5 port: %s</string>

app/src/main/res/xml-v14/preferences.xml

@@ -200,6 +200,10 @@
                 android:dependency="filter"
                 android:inputType="number"
                 android:key="ttl" />
+            <EditTextPreference
+                android:dependency="filter"
+                android:inputType="number"
+                android:key="rcode" />
             <CheckBoxPreference
                 android:defaultValue="false"
                 android:dependency="filter"

app/src/main/res/xml-v21/preferences.xml

@@ -200,6 +200,10 @@
                 android:dependency="filter"
                 android:inputType="number"
                 android:key="ttl" />
+            <EditTextPreference
+                android:dependency="filter"
+                android:inputType="number"
+                android:key="rcode" />
             <eu.faircode.netguard.SwitchPreference
                 android:defaultValue="false"
                 android:dependency="filter"