reimplement dns resolver cache + add timeout for cache

src/main/java/eu/siacs/conversations/persistance/DatabaseBackend.java

@@ -55,6 +55,7 @@ import eu.siacs.conversations.utils.CryptoHelper;
 import eu.siacs.conversations.utils.CursorUtils;
 import eu.siacs.conversations.utils.FtsUtils;
 import eu.siacs.conversations.utils.MimeUtils;
+import eu.siacs.conversations.utils.Resolver;
 import eu.siacs.conversations.xmpp.InvalidJid;
 import eu.siacs.conversations.xmpp.mam.MamReference;
 import rocks.xmpp.addr.Jid;
@@ -62,7 +63,7 @@ import rocks.xmpp.addr.Jid;
 public class DatabaseBackend extends SQLiteOpenHelper {
 
     private static final String DATABASE_NAME = "history";
-    private static final int DATABASE_VERSION = 46;
+    private static final int DATABASE_VERSION = 47;
     private static DatabaseBackend instance = null;
     private static String CREATE_CONTATCS_STATEMENT = "create table "
             + Contact.TABLENAME + "(" + Contact.ACCOUNT + " TEXT, "
@@ -149,6 +150,20 @@ public class DatabaseBackend extends SQLiteOpenHelper {
             + ") ON CONFLICT IGNORE"
             + ");";
 
+    private static String RESOLVER_RESULTS_TABLENAME = "resolver_results";
+
+    private static String CREATE_RESOLVER_RESULTS_TABLE = "create table " + RESOLVER_RESULTS_TABLENAME + "("
+            + Resolver.Result.DOMAIN + " TEXT,"
+            + Resolver.Result.HOSTNAME + " TEXT,"
+            + Resolver.Result.IP + " BLOB,"
+            + Resolver.Result.PRIORITY + " NUMBER,"
+            + Resolver.Result.DIRECT_TLS + " NUMBER,"
+            + Resolver.Result.AUTHENTICATED + " NUMBER,"
+            + Resolver.Result.PORT + " NUMBER,"
+            + Resolver.Result.TIME_REQUESTED + " NUMBER,"
+            + "UNIQUE(" + Resolver.Result.DOMAIN + ") ON CONFLICT REPLACE"
+            + ");";
+
     private static String CREATE_MESSAGE_TIME_INDEX = "create INDEX message_time_index ON " + Message.TABLENAME + "(" + Message.TIME_SENT + ")";
     private static String CREATE_MESSAGE_CONVERSATION_INDEX = "create INDEX message_conversation_index ON " + Message.TABLENAME + "(" + Message.CONVERSATION + ")";
     private static String CREATE_MESSAGE_DELETED_INDEX = "create index message_deleted_index ON " + Message.TABLENAME + "(" + Message.DELETED + ")";
@@ -243,6 +258,7 @@ public class DatabaseBackend extends SQLiteOpenHelper {
         db.execSQL(CREATE_SIGNED_PREKEYS_STATEMENT);
         db.execSQL(CREATE_IDENTITIES_STATEMENT);
         db.execSQL(CREATE_PRESENCE_TEMPLATES_STATEMENT);
+        db.execSQL(CREATE_RESOLVER_RESULTS_TABLE);
         db.execSQL(CREATE_MESSAGE_INDEX_TABLE);
         db.execSQL(CREATE_MESSAGE_INSERT_TRIGGER);
         db.execSQL(CREATE_MESSAGE_UPDATE_TRIGGER);
@@ -537,7 +553,12 @@ public class DatabaseBackend extends SQLiteOpenHelper {
             Log.d(Config.LOGTAG,"deleted old edit information in "+diff+"ms");
         }
 
-	db.execSQL("DROP TABLE IF EXISTS resolver_results");
+	if (oldVersion < 47 && newVersion >= 47) {
+          // values in resolver_result are cache and not worth to store 
+          db.execSQL("DROP TABLE IF EXISTS " + RESOLVER_RESULTS_TABLENAME);
+          db.execSQL(CREATE_RESOLVER_RESULTS_TABLE);
+        }
+
     }
 
     private void canonicalizeJids(SQLiteDatabase db) {
@@ -660,6 +681,34 @@ public class DatabaseBackend extends SQLiteOpenHelper {
         return result;
     }
 
+    public void saveResolverResult(String domain, Resolver.Result result) {
+        SQLiteDatabase db = this.getWritableDatabase();
+        ContentValues contentValues = result.toContentValues();
+        contentValues.put(Resolver.Result.DOMAIN, domain);
+        db.insert(RESOLVER_RESULTS_TABLENAME, null, contentValues);
+    }
+
+    public synchronized Resolver.Result findResolverResult(String domain) {
+        SQLiteDatabase db = this.getReadableDatabase();
+        String where = Resolver.Result.DOMAIN + "=?";
+        String[] whereArgs = {domain};
+        final Cursor cursor = db.query(RESOLVER_RESULTS_TABLENAME, null, where, whereArgs, null, null, null);
+        Resolver.Result result = null;
+        if (cursor != null) {
+            try {
+                if (cursor.moveToFirst()) {
+                    result = Resolver.Result.fromCursor(cursor);
+                }
+            } catch (Exception e) {
+                Log.d(Config.LOGTAG, "unable to find cached resolver result in database " + e.getMessage());
+                return null;
+            } finally {
+                cursor.close();
+            }
+        }
+        return result;
+    }
+
     public void insertPresenceTemplate(PresenceTemplate template) {
         SQLiteDatabase db = this.getWritableDatabase();
         String whereToDelete = PresenceTemplate.MESSAGE + "=?";

src/main/java/eu/siacs/conversations/utils/Resolver.java

@@ -353,12 +353,14 @@ public class Resolver {
     }
 
     public static class Result implements Comparable<Result>, Callable<Result> {
+        public static final String DOMAIN = "domain";
         public static final String IP = "ip";
         public static final String HOSTNAME = "hostname";
         public static final String PORT = "port";
         public static final String PRIORITY = "priority";
         public static final String DIRECT_TLS = "directTls";
         public static final String AUTHENTICATED = "authenticated";
+        public static final String TIME_REQUESTED = "time_requested";
 
         private InetAddress ip;
         private DNSName hostname;
@@ -366,12 +368,14 @@ public class Resolver {
         private boolean directTls = false;
         private boolean authenticated = false;
         private int priority;
+        private long timeRequested;
         private Socket socket;
 
         private String logID = "";
 
         static Result fromRecord(SRV srv, boolean directTls) {
             Result result = new Result();
+            result.timeRequested = System.currentTimeMillis();
             result.port = srv.port;
             result.hostname = srv.name;
             result.directTls = directTls;
@@ -381,6 +385,7 @@ public class Resolver {
  
         static Result createDefault(DNSName hostname, InetAddress ip, int port) {
             Result result = new Result();
+            result.timeRequested = System.currentTimeMillis();
             result.port = port;
             result.hostname = hostname;
             result.ip = ip;
@@ -425,6 +430,10 @@ public class Resolver {
             return authenticated;
         }
 
+        public boolean isOutdated() {
+            return (System.currentTimeMillis() - timeRequested) > 300_000;
+        }
+
         public Socket getSocket() {
             return socket;
         }
@@ -498,6 +507,24 @@ public class Resolver {
             throw new Exception("Resolver.Result was not possible to connect - should be catched by executor");
         }
 
+        public static Result fromCursor(Cursor cursor) {
+            final Result result = new Result();
+            try {
+                result.ip = InetAddress.getByAddress(cursor.getBlob(cursor.getColumnIndex(IP)));
+            } catch (UnknownHostException e) {
+                result.ip = null;
+            }
+            final String hostname = cursor.getString(cursor.getColumnIndex(HOSTNAME));
+            result.hostname = hostname == null ? null : DNSName.from(hostname);
+            result.port = cursor.getInt(cursor.getColumnIndex(PORT));
+            result.directTls = cursor.getInt(cursor.getColumnIndex(DIRECT_TLS)) > 0;
+            result.authenticated = cursor.getInt(cursor.getColumnIndex(AUTHENTICATED)) > 0;
+            result.priority = cursor.getInt(cursor.getColumnIndex(PRIORITY));
+            result.timeRequested = cursor.getLong(cursor.getColumnIndex(TIME_REQUESTED));
+            return result;
+        }
+
+
         public ContentValues toContentValues() {
             final ContentValues contentValues = new ContentValues();
             contentValues.put(IP, ip == null ? null : ip.getAddress());
@@ -506,6 +533,7 @@ public class Resolver {
             contentValues.put(PRIORITY, priority);
             contentValues.put(DIRECT_TLS, directTls ? 1 : 0);
             contentValues.put(AUTHENTICATED, authenticated ? 1 : 0);
+            contentValues.put(TIME_REQUESTED, timeRequested);
             return contentValues;
         }
     }

src/main/java/eu/siacs/conversations/xmpp/XmppConnection.java

@@ -291,11 +291,17 @@ public class XmppConnection implements Runnable {
                 }
             } else {
                 final String domain = account.getJid().getDomain();
-                final Resolver.Result result;
+                final Resolver.Result storedBackupResult = mXmppConnectionService.databaseBackend.findResolverResult(domain);
+                Resolver.Result result = null;
                 final boolean hardcoded = extended && !account.getHostname().isEmpty();
                 if (hardcoded) {
                     result = Resolver.fromHardCoded(account.getHostname(), account.getPort());
-                } else {
+                } else if (storedBackupResult != null && !storedBackupResult.isOutdated()) {
+                    storedBackupResult.connect();
+                    result = storedBackupResult;
+                    Log.d(Config.LOGTAG, account.getJid().asBareJid() + ": loaded backup resolver result from db: " + storedBackupResult);
+                }
+                if (result == null || result.getSocket() == null) {
                     result = Resolver.resolve(domain);
                 }
                 if (result == null) {
@@ -322,6 +328,9 @@ public class XmppConnection implements Runnable {
                     localSocket.setSoTimeout(Config.SOCKET_TIMEOUT * 1000);
                     if (startXmpp(localSocket)) {
                         localSocket.setSoTimeout(0); //reset to 0; once the connection is established we don’t want this
+                        if (!hardcoded && !result.equals(storedBackupResult)) {
+                            mXmppConnectionService.databaseBackend.saveResolverResult(domain, result);
+                        }
                         // successfully connected to server that speaks xmpp
                     } else {
                         FileBackend.close(localSocket);