Refactoring

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

@@ -117,6 +117,14 @@ public class ApplicationEx extends Application {
 
         registerReceiver(onScreenOff, new IntentFilter(Intent.ACTION_SCREEN_OFF));
 
+        if (BuildConfig.DEBUG)
+            new Thread(new Runnable() {
+                @Override
+                public void run() {
+                    DnsHelper.test(ApplicationEx.this);
+                }
+            }).start();
+
         long end = new Date().getTime();
         Log.i("App created " + (end - start) + " ms");
     }

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

@@ -38,6 +38,7 @@ import org.xbill.DNS.Type;
 
 import java.net.InetAddress;
 import java.net.UnknownHostException;
+import java.util.ArrayList;
 import java.util.List;
 
 import javax.mail.Address;
@@ -107,28 +108,54 @@ public class DnsHelper {
     }
 
     @NonNull
-    static Record[] lookup(Context context, String name, int type) throws TextParseException, UnknownHostException {
+    static DnsRecord[] lookup(Context context, String name, String type) throws UnknownHostException {
-        Lookup lookup = new Lookup(name, type);
+        int rtype;
+        switch (type) {
+            case "mx":
+                rtype = Type.MX;
+                break;
+            case "srv":
+                rtype = Type.SRV;
+                break;
+            default:
+                throw new IllegalArgumentException(type);
+        }
 
-        SimpleResolver resolver = new SimpleResolver(getDnsServer(context));
+        try {
-        lookup.setResolver(resolver);
+            Lookup lookup = new Lookup(name, rtype);
-        Log.i("Lookup name=" + name + " @" + resolver.getAddress() + " type=" + type);
-        Record[] records = lookup.run();
 
-        if (lookup.getResult() != Lookup.SUCCESSFUL)
+            SimpleResolver resolver = new SimpleResolver(getDnsServer(context));
-            if (lookup.getResult() == Lookup.HOST_NOT_FOUND ||
+            lookup.setResolver(resolver);
-                    lookup.getResult() == Lookup.TYPE_NOT_FOUND)
+            Log.i("Lookup name=" + name + " @" + resolver.getAddress() + " type=" + rtype);
-                throw new UnknownHostException(name);
+            Record[] records = lookup.run();
-            else
+
-                throw new UnknownHostException(lookup.getErrorString());
+            if (lookup.getResult() != Lookup.SUCCESSFUL)
+                if (lookup.getResult() == Lookup.HOST_NOT_FOUND ||
+                        lookup.getResult() == Lookup.TYPE_NOT_FOUND)
+                    throw new UnknownHostException(name);
+                else
+                    throw new UnknownHostException(lookup.getErrorString());
 
-        if (records.length == 0)
+            if (records.length == 0)
-            throw new UnknownHostException(name);
+                throw new UnknownHostException(name);
 
-        for (Record record : records)
+            List<DnsRecord> result = new ArrayList<>();
-            Log.i("Found record=" + record);
+            for (Record record : records) {
+                Log.i("Found record=" + record);
+                if (record instanceof MXRecord) {
+                    MXRecord mx = (MXRecord) record;
+                    result.add(new DnsRecord(mx.getTarget().toString(true)));
+                } else if (record instanceof SRVRecord) {
+                    SRVRecord srv = (SRVRecord) record;
+                    result.add(new DnsRecord(srv.getTarget().toString(true), srv.getPort()));
+                } else
+                    throw new IllegalArgumentException(record.getClass().getName());
+            }
 
-        return records;
+            return result.toArray(new DnsRecord[0]);
+        } catch (TextParseException ex) {
+            throw new UnknownHostException(ex.getMessage());
+        }
     }
 
     static String getParentDomain(String host) {
@@ -174,14 +201,27 @@ public class DnsHelper {
             return dns.get(0).getHostAddress();
     }
 
+    static class DnsRecord {
+        String name;
+        Integer port;
+
+        DnsRecord(String name) {
+            this.name = name;
+        }
+
+        DnsRecord(String name, int port) {
+            this.name = name;
+            this.port = port;
+        }
+    }
+
     static void test(Context context) {
         try {
             String domain = "gmail.com";
             boolean ok = lookupMx(context, new Address[]{Log.myAddress()});
             InetAddress iaddr = lookupMx(context, domain);
-            Record[] records = DnsHelper.lookup(context, "_imaps._tcp." + domain, Type.SRV);
+            DnsRecord[] records = DnsHelper.lookup(context, "_imaps._tcp." + domain, "srv");
-            SRVRecord srv = (SRVRecord) records[0];
+            Log.i("DNS ok=" + ok + " iaddr=" + iaddr + " srv=" + records[0].name + ":" + records[0].port);
-            Log.i("DNS ok=" + ok + " iaddr=" + iaddr + " srv=" + srv.getTarget().toString());
         } catch (Throwable ex) {
             Log.e("DNS", ex);
         }

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

@@ -25,11 +25,6 @@ import android.text.TextUtils;
 
 import androidx.annotation.NonNull;
 
-import org.xbill.DNS.MXRecord;
-import org.xbill.DNS.Record;
-import org.xbill.DNS.SRVRecord;
-import org.xbill.DNS.TextParseException;
-import org.xbill.DNS.Type;
 import org.xmlpull.v1.XmlPullParser;
 import org.xmlpull.v1.XmlPullParserException;
 import org.xmlpull.v1.XmlPullParserFactory;
@@ -226,9 +221,9 @@ public class EmailProvider {
 
             try {
                 // Retry at MX server addresses
-                Record[] records = DnsHelper.lookup(context, domain, Type.MX);
+                DnsHelper.DnsRecord[] records = DnsHelper.lookup(context, domain, "mx");
-                for (Record record : records) {
+                for (DnsHelper.DnsRecord record : records) {
-                    String target = ((MXRecord) record).getTarget().toString(true);
+                    String target = record.name;
                     while (autoconfig == null && target != null && target.indexOf('.') > 0) {
                         try {
                             autoconfig = _fromDomain(context, target.toLowerCase(Locale.ROOT), email, discover);
@@ -498,35 +493,32 @@ public class EmailProvider {
     }
 
     @NonNull
-    private static EmailProvider fromDNS(Context context, String domain, Discover discover) throws TextParseException, UnknownHostException {
+    private static EmailProvider fromDNS(Context context, String domain, Discover discover) throws UnknownHostException {
         // https://tools.ietf.org/html/rfc6186
         EmailProvider provider = new EmailProvider(domain);
 
         if (discover == Discover.ALL || discover == Discover.IMAP) {
             try {
                 // Identifies an IMAP server where TLS is initiated directly upon connection to the IMAP server.
-                Record[] records = DnsHelper.lookup(context, "_imaps._tcp." + domain, Type.SRV);
+                DnsHelper.DnsRecord[] records = DnsHelper.lookup(context, "_imaps._tcp." + domain, "srv");
                 // ... service is not supported at all at a particular domain by setting the target of an SRV RR to "."
-                SRVRecord srv = (SRVRecord) records[0];
+                provider.imap.host = records[0].name;
-                provider.imap.host = srv.getTarget().toString(true);
+                provider.imap.port = records[0].port;
-                provider.imap.port = srv.getPort();
                 provider.imap.starttls = false;
             } catch (UnknownHostException ex) {
                 // Identifies an IMAP server that MAY ... require the MUA to use the "STARTTLS" command
-                Record[] records = DnsHelper.lookup(context, "_imap._tcp." + domain, Type.SRV);
+                DnsHelper.DnsRecord[] records = DnsHelper.lookup(context, "_imap._tcp." + domain, "srv");
-                SRVRecord srv = (SRVRecord) records[0];
+                provider.imap.host = records[0].name;
-                provider.imap.host = srv.getTarget().toString(true);
+                provider.imap.port = records[0].port;
-                provider.imap.port = srv.getPort();
                 provider.imap.starttls = (provider.imap.port == 143);
             }
         }
 
         if (discover == Discover.ALL || discover == Discover.SMTP) {
             // Note that this covers connections both with and without Transport Layer Security (TLS)
-            Record[] records = DnsHelper.lookup(context, "_submission._tcp." + domain, Type.SRV);
+            DnsHelper.DnsRecord[] records = DnsHelper.lookup(context, "_submission._tcp." + domain, "srv");
-            SRVRecord srv = (SRVRecord) records[0];
+            provider.smtp.host = records[0].name;
-            provider.smtp.host = srv.getTarget().toString(true);
+            provider.smtp.port = records[0].port;
-            provider.smtp.port = srv.getPort();
             provider.smtp.starttls = (provider.smtp.port == 587);
         }