Disable DNSSEC for Android 7-

app/src/main/java/eu/faircode/email/DnsHelper.java

@@ -322,6 +322,9 @@ public class DnsHelper {
         SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
         boolean dns_custom = prefs.getBoolean("dns_custom", false);
 
+        if (!hasDnsSec())
+            dnssec = false;
+
         if (!dns_custom && !dnssec)
             return InetAddress.getByName(host);
 
@@ -335,6 +338,9 @@ public class DnsHelper {
         SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
         boolean dns_custom = prefs.getBoolean("dns_custom", false);
 
+        if (!hasDnsSec())
+            dnssec = false;
+
         if (!dns_custom && !dnssec)
             return InetAddress.getAllByName(host);
 
@@ -360,6 +366,9 @@ public class DnsHelper {
     }
 
     static void verifyDane(X509Certificate[] chain, String server, int port) throws CertificateException {
+        if (!hasDnsSec())
+            return;
+
         Handler handler = new Handler() {
             @Override
             public void publish(LogRecord record) {
@@ -452,6 +461,11 @@ public class DnsHelper {
         editor.apply();
     }
 
+    static boolean hasDnsSec() {
+        // DNSSEC causes crashes in libc
+        return (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O);
+    }
+
     static void test(Context context) throws UnknownHostException {
         test(context, "gmail.com", "ns");
         test(context, "web.de", "mx");

app/src/main/java/eu/faircode/email/FragmentAccount.java

@@ -633,10 +633,18 @@ public class FragmentAccount extends FragmentBase {
         btnAutoConfig.setEnabled(false);
         pbAutoConfig.setVisibility(View.GONE);
 
+        if (!DnsHelper.hasDnsSec()) {
+            Helper.hide(cbDnsSec);
+            Helper.hide(view.findViewById(R.id.tvDnsRemark));
+            Helper.hide(cbDane);
+            Helper.hide(view.findViewById(R.id.tvDaneRemark));
+        }
+
         if (!SSLHelper.customTrustManager()) {
             Helper.hide(cbInsecure);
             Helper.hide(tvInsecureRemark);
             Helper.hide(cbDane);
+            Helper.hide(view.findViewById(R.id.tvDaneRemark));
         }
 
         if (id < 0)

app/src/main/java/eu/faircode/email/FragmentIdentity.java

@@ -33,6 +33,7 @@ import android.database.Cursor;
 import android.graphics.Color;
 import android.graphics.Paint;
 import android.net.Uri;
+import android.os.Build;
 import android.os.Bundle;
 import android.provider.ContactsContract;
 import android.text.Editable;
@@ -580,10 +581,18 @@ public class FragmentIdentity extends FragmentBase {
         btnAutoConfig.setEnabled(false);
         pbAutoConfig.setVisibility(View.GONE);
 
+        if (!DnsHelper.hasDnsSec()) {
+            Helper.hide(cbDnsSec);
+            Helper.hide(view.findViewById(R.id.tvDnsRemark));
+            Helper.hide(cbDane);
+            Helper.hide(view.findViewById(R.id.tvDaneRemark));
+        }
+
         if (!SSLHelper.customTrustManager()) {
             Helper.hide(cbInsecure);
             Helper.hide(tvInsecureRemark);
             Helper.hide(cbDane);
+            Helper.hide(view.findViewById(R.id.tvDaneRemark));
         }
 
         btnAdvanced.setVisibility(View.GONE);

app/src/main/java/eu/faircode/email/FragmentPop.java

@@ -365,10 +365,18 @@ public class FragmentPop extends FragmentBase {
         Helper.setViewsEnabled(view, false);
         FragmentDialogTheme.setBackground(getContext(), view, false);
 
+        if (!DnsHelper.hasDnsSec()) {
+            Helper.hide(cbDnsSec);
+            Helper.hide(view.findViewById(R.id.tvDnsRemark));
+            Helper.hide(cbDane);
+            Helper.hide(view.findViewById(R.id.tvDaneRemark));
+        }
+
         if (!SSLHelper.customTrustManager()) {
             Helper.hide(cbInsecure);
             Helper.hide(tvInsecureRemark);
             Helper.hide(cbDane);
+            Helper.hide(view.findViewById(R.id.tvDaneRemark));
         }
 
         if (id < 0)