Make minidns Android agnostic

there is really no need for minidns to be Android exclusive. Replacing
the Android log API with JUL make minidns available for Android and Java
SE.

11 files changed, 1473 insertions, 0 deletions

diff --git a/src/main/java/de/measite/minidns/Client.java b/src/main/java/de/measite/minidns/Client.java
new file mode 100644
index 00000000..fb42cd25
--- /dev/null
+++ b/src/main/java/de/measite/minidns/Client.java
@@ -0,0 +1,290 @@
+package de.measite.minidns;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.LineNumberReader;
+import java.lang.reflect.Method;
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
+import java.net.InetAddress;
+import java.security.NoSuchAlgorithmException;
+import java.security.SecureRandom;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Random;
+import java.util.logging.Logger;
+
+import de.measite.minidns.Record.CLASS;
+import de.measite.minidns.Record.TYPE;
+
+/**
+ * A minimal DNS client for SRV/A/AAAA/NS and CNAME lookups, with IDN support.
+ * This circumvents the missing javax.naming package on android.
+ */
+public class Client {
+
+    private static final Logger LOGGER = Logger.getLogger(Client.class.getName());
+
+    /**
+     * The internal random class for sequence generation.
+     */
+    protected Random random;
+
+    /**
+     * The buffer size for dns replies.
+     */
+    protected int bufferSize = 1500;
+
+    /**
+     * DNS timeout.
+     */
+    protected int timeout = 5000;
+
+    /**
+     * Create a new DNS client.
+     */
+    public Client() {
+        try {
+            random = SecureRandom.getInstance("SHA1PRNG");
+        } catch (NoSuchAlgorithmException e1) {
+            random = new SecureRandom();
+        }
+    }
+
+    /**
+     * Query a nameserver for a single entry.
+     * @param name The DNS name to request.
+     * @param type The DNS type to request (SRV, A, AAAA, ...).
+     * @param clazz The class of the request (usually IN for Internet).
+     * @param host The DNS server host.
+     * @param port The DNS server port.
+     * @return 
+     * @throws IOException On IO Errors.
+     */
+    public DNSMessage query(String name, TYPE type, CLASS clazz, String host, int port)
+        throws IOException
+    {
+        Question q = new Question();
+        q.setClazz(clazz);
+        q.setType(type);
+        q.setName(name);
+        return query(q, host, port);
+    }
+
+    /**
+     * Query a nameserver for a single entry.
+     * @param name The DNS name to request.
+     * @param type The DNS type to request (SRV, A, AAAA, ...).
+     * @param clazz The class of the request (usually IN for Internet).
+     * @param host The DNS server host.
+     * @return 
+     * @throws IOException On IO Errors.
+     */
+    public DNSMessage query(String name, TYPE type, CLASS clazz, String host)
+        throws IOException
+    {
+        Question q = new Question();
+        q.setClazz(clazz);
+        q.setType(type);
+        q.setName(name);
+        return query(q, host);
+    }
+
+    /**
+     * Query the system nameserver for a single entry.
+     * @param name The DNS name to request.
+     * @param type The DNS type to request (SRV, A, AAAA, ...).
+     * @param clazz The class of the request (usually IN for Internet).
+     * @return The DNSMessage reply or null.
+     */
+    public DNSMessage query(String name, TYPE type, CLASS clazz)
+    {
+        Question q = new Question();
+        q.setClazz(clazz);
+        q.setType(type);
+        q.setName(name);
+        return query(q);
+    }
+
+    /**
+     * Query a specific server for one entry.
+     * @param q The question section of the DNS query.
+     * @param host The dns server host.
+     * @throws IOException On IOErrors.
+     */
+    public DNSMessage query(Question q, String host) throws IOException {
+        return query(q, host, 53);
+    }
+
+    /**
+     * Query a specific server for one entry.
+     * @param q The question section of the DNS query.
+     * @param host The dns server host.
+     * @param port the dns port.
+     * @throws IOException On IOErrors.
+     */
+    public DNSMessage query(Question q, String host, int port) throws IOException {
+        DNSMessage message = new DNSMessage();
+        message.setQuestions(new Question[]{q});
+        message.setRecursionDesired(true);
+        message.setId(random.nextInt());
+        byte[] buf = message.toArray();
+        DatagramSocket socket = new DatagramSocket();
+        DatagramPacket packet = new DatagramPacket(
+                buf, buf.length, InetAddress.getByName(host), port);
+        socket.setSoTimeout(timeout);
+        socket.send(packet);
+        packet = new DatagramPacket(new byte[bufferSize], bufferSize);
+        socket.receive(packet);
+        DNSMessage dnsMessage = DNSMessage.parse(packet.getData());
+        if (dnsMessage.getId() != message.getId()) {
+            return null;
+        }
+        return dnsMessage;
+    }
+
+    /**
+     * Query the system DNS server for one entry.
+     * @param q The question section of the DNS query.
+     */
+    public DNSMessage query(Question q) {
+        String dnsServer[] = findDNS();
+        for (String dns : dnsServer) {
+            try {
+                DNSMessage message = query(q, dns);
+                if (message == null) {
+                    continue;
+                }
+                if (message.getResponseCode() !=
+                    DNSMessage.RESPONSE_CODE.NO_ERROR) {
+                    continue;
+                }
+                for (Record record: message.getAnswers()) {
+                    if (record.isAnswer(q)) {
+                        return message;
+                    }
+                }
+            } catch (IOException ioe) {
+            }
+        }
+        return null;
+    }
+
+    /**
+     * Retrieve a list of currently configured DNS servers.
+     * @return The server array.
+     */
+    public String[] findDNS() {
+        String[] result = findDNSByReflection();
+        if (result != null) {
+            LOGGER.fine("Got DNS servers via reflection: " + Arrays.toString(result));
+            return result;
+        }
+
+        result = findDNSByExec();
+        if (result != null) {
+            LOGGER.fine("Got DNS servers via exec: " + Arrays.toString(result));
+            return result;
+        }
+
+        // fallback for ipv4 and ipv6 connectivity
+        // see https://developers.google.com/speed/public-dns/docs/using
+        LOGGER.fine("No DNS found? Using fallback [8.8.8.8, [2001:4860:4860::8888]]");
+
+        return new String[]{"8.8.8.8", "[2001:4860:4860::8888]"};
+    }
+
+    /**
+     * Try to retrieve the list of dns server by executing getprop.
+     * @return Array of servers, or null on failure.
+     */
+    protected String[] findDNSByExec() {
+        try {
+            Process process = Runtime.getRuntime().exec("getprop");
+            InputStream inputStream = process.getInputStream();
+            LineNumberReader lnr = new LineNumberReader(
+                new InputStreamReader(inputStream));
+            String line = null;
+            HashSet<String> server = new HashSet<String>(6);
+            while ((line = lnr.readLine()) != null) {
+                int split = line.indexOf("]: [");
+                if (split == -1) {
+                    continue;
+                }
+                String property = line.substring(1, split);
+                String value = line.substring(split + 4, line.length() - 1);
+                if (property.endsWith(".dns") || property.endsWith(".dns1") ||
+                    property.endsWith(".dns2") || property.endsWith(".dns3") ||
+                    property.endsWith(".dns4")) {
+
+                    // normalize the address
+
+                    InetAddress ip = InetAddress.getByName(value);
+
+                    if (ip == null) continue;
+
+                    value = ip.getHostAddress();
+
+                    if (value == null) continue;
+                    if (value.length() == 0) continue;
+
+                    server.add(value);
+                }
+            }
+            if (server.size() > 0) {
+                return server.toArray(new String[server.size()]);
+            }
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+        return null;
+    }
+
+    /**
+     * Try to retrieve the list of dns server by calling SystemProperties.
+     * @return Array of servers, or null on failure.
+     */
+    protected String[] findDNSByReflection() {
+        try {
+            Class<?> SystemProperties =
+                    Class.forName("android.os.SystemProperties");
+            Method method = SystemProperties.getMethod("get",
+                    new Class[] { String.class });
+
+            ArrayList<String> servers = new ArrayList<String>(5);
+
+            for (String propKey : new String[] {
+                    "net.dns1", "net.dns2", "net.dns3", "net.dns4"}) {
+
+                String value = (String)method.invoke(null, propKey);
+
+                if (value == null) continue;
+                if (value.length() == 0) continue;
+                if (servers.contains(value)) continue;
+
+                InetAddress ip = InetAddress.getByName(value);
+
+                if (ip == null) continue;
+
+                value = ip.getHostAddress();
+
+                if (value == null) continue;
+                if (value.length() == 0) continue;
+                if (servers.contains(value)) continue;
+
+                servers.add(value);
+            }
+
+            if (servers.size() > 0) {
+                return servers.toArray(new String[servers.size()]);
+            }
+        } catch (Exception e) {
+            // we might trigger some problems this way
+            e.printStackTrace();
+        }
+        return null;
+    }
+
+}
diff --git a/src/main/java/de/measite/minidns/DNSMessage.java b/src/main/java/de/measite/minidns/DNSMessage.java
new file mode 100644
index 00000000..14c8f04b
--- /dev/null
+++ b/src/main/java/de/measite/minidns/DNSMessage.java
@@ -0,0 +1,507 @@
+package de.measite.minidns;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.util.Arrays;
+
+/**
+ * A DNS message as defined by rfc1035. The message consists of a header and
+ * 4 sections: question, answer, nameserver and addition resource record
+ * section.
+ * A message can either be parsed ({@see #parse(byte[])}) or serialized
+ * ({@see #toArray()}).
+ */
+public class DNSMessage {
+
+    /**
+     * Possible DNS reply codes.
+     */
+    public static enum RESPONSE_CODE {
+        NO_ERROR(0), FORMAT_ERR(1), SERVER_FAIL(2), NX_DOMAIN(3),
+        NO_IMP(4), REFUSED(5), YXDOMAIN(6), YXRRSET(7),
+        NXRRSET(8), NOT_AUTH(9),NOT_ZONE(10);
+
+        /**
+         * Reverse lookup table for response codes.
+         */
+        private final static RESPONSE_CODE INVERSE_LUT[] = new RESPONSE_CODE[]{
+            NO_ERROR, FORMAT_ERR, SERVER_FAIL, NX_DOMAIN, NO_IMP,
+            REFUSED, YXDOMAIN, YXRRSET, NXRRSET, NOT_AUTH, NOT_ZONE,
+            null, null, null, null, null
+        };
+
+        /**
+         * The response code value.
+         */
+        private final byte value;
+
+        /**
+         * Create a new response code.
+         * @param value The response code value.
+         */
+        private RESPONSE_CODE(int value) {
+            this.value = (byte)value;
+        }
+
+        /**
+         * Retrieve the byte value of the response code.
+         * @return
+         */
+        public byte getValue() {
+            return (byte) value;
+        }
+
+        /**
+         * Retrieve the response code for a byte value.
+         * @param value The byte value.
+         * @return The symbolic response code or null.
+         * @throws IllegalArgumentException if the value is not in the range of
+         *         0..15.
+         */
+        public static RESPONSE_CODE getResponseCode(int value) {
+            if (value < 0 || value > 15) {
+                throw new IllegalArgumentException();
+            }
+            return INVERSE_LUT[value];
+        }
+
+    };
+
+    /**
+     * Symbolic DNS Opcode values.
+     */
+    public static enum OPCODE {
+        QUERY(0),
+        INVERSE_QUERY(1),
+        STATUS(2),
+        NOTIFY(4),
+        UPDATE(5);
+
+        /**
+         * Lookup table for for obcode reolution.
+         */
+        private final static OPCODE INVERSE_LUT[] = new OPCODE[]{
+            QUERY, INVERSE_QUERY, STATUS, null, NOTIFY, UPDATE, null,
+            null, null, null, null, null, null, null, null
+        };
+
+        /**
+         * The value of this opcode.
+         */
+        private final byte value;
+
+        /**
+         * Create a new opcode for a given byte value.
+         * @param value The byte value of the opcode.
+         */
+        private OPCODE(int value) {
+            this.value = (byte)value;
+        }
+
+        /**
+         * Retrieve the byte value of this opcode.
+         * @return The byte value of this opcode.
+         */
+        public byte getValue() {
+            return value;
+        }
+
+        /**
+         * Retrieve the symbolic name of an opcode byte.
+         * @param value The byte value of the opcode.
+         * @return The symbolic opcode or null.
+         * @throws IllegalArgumentException If the byte value is not in the
+         *         range 0..15.
+         */
+        public static OPCODE getOpcode(int value) {
+            if (value < 0 || value > 15) {
+                throw new IllegalArgumentException();
+            }
+            return INVERSE_LUT[value];
+        }
+
+    };
+
+    /**
+     * The DNS message id.
+     */
+    protected int id;
+
+    /**
+     * The DNS message opcode.
+     */
+    protected OPCODE opcode;
+
+    /**
+     * The response code of this dns message.
+     */
+    protected RESPONSE_CODE responseCode;
+
+    /**
+     * True if this is a query.
+     */
+    protected boolean query;
+
+    /**
+     * True if this is a authorative response.
+     */
+    protected boolean authoritativeAnswer;
+
+    /**
+     * True on truncate, tcp should be used.
+     */
+    protected boolean truncated;
+
+    /**
+     * True if the server should recurse.
+     */
+    protected boolean recursionDesired;
+
+    /**
+     * True if recursion is possible.
+     */
+    protected boolean recursionAvailable;
+
+    /**
+     * True if the server regarded the response as authentic.
+     */
+    protected boolean authenticData;
+
+    /**
+     * True if the server should not check the replies.
+     */
+    protected boolean checkDisabled;
+
+    /**
+     * The question section content.
+     */
+    protected Question questions[];
+
+    /**
+     * The answers section content.
+     */
+    protected Record answers[];
+
+    /**
+     * The nameserver records.
+     */
+    protected Record nameserverRecords[];
+
+    /**
+     * Additional resousrce records.
+     */
+    protected Record additionalResourceRecords[];
+
+    /**
+     * Retrieve the current DNS message id.
+     * @return The current DNS message id.
+     */
+    public int getId() {
+        return id;
+    }
+
+    /**
+     * Set the current DNS message id.
+     * @param id The new DNS message id.
+     */
+    public void setId(int id) {
+        this.id = id & 0xffff;
+    }
+
+    /**
+     * Retrieve the query type (true or false;
+     * @return True if this DNS message is a query.
+     */
+    public boolean isQuery() {
+        return query;
+    }
+
+    /**
+     * Set the query status of this message.
+     * @param query The new query status.
+     */
+    public void setQuery(boolean query) {
+        this.query = query;
+    }
+
+    /**
+     * True if the DNS message is an authoritative answer.
+     * @return True if this an authoritative DNS message.
+     */
+    public boolean isAuthoritativeAnswer() {
+        return authoritativeAnswer;
+    }
+
+    /**
+     * Set the authoritative answer flag.
+     * @param authoritativeAnswer Tge new authoritative answer value.
+     */
+    public void setAuthoritativeAnswer(boolean authoritativeAnswer) {
+        this.authoritativeAnswer = authoritativeAnswer;
+    }
+
+    /**
+     * Retrieve the truncation status of this message. True means that the
+     * client should try a tcp lookup.
+     * @return True if this message was truncated.
+     */
+    public boolean isTruncated() {
+        return truncated;
+    }
+
+    /**
+     * Set the truncation bit on this DNS message.
+     * @param truncated The new truncated bit status.
+     */
+    public void setTruncated(boolean truncated) {
+        this.truncated = truncated;
+    }
+
+    /**
+     * Check if this message preferes recursion.
+     * @return True if recursion is desired.
+     */
+    public boolean isRecursionDesired() {
+        return recursionDesired;
+    }
+
+    /**
+     * Set the recursion desired flag on this message.
+     * @param recursionDesired The new recusrion setting.
+     */
+    public void setRecursionDesired(boolean recursionDesired) {
+        this.recursionDesired = recursionDesired;
+    }
+
+    /**
+     * Retrieve the recursion available flag of this DNS message.
+     * @return The recursion available flag of this message.
+     */
+    public boolean isRecursionAvailable() {
+        return recursionAvailable;
+    }
+
+    /**
+     * Set the recursion available flog from this DNS message.
+     * @param recursionAvailable The new recursion available status.
+     */
+    public void setRecursionAvailable(boolean recursionAvailable) {
+        this.recursionAvailable = recursionAvailable;
+    }
+
+    /**
+     * Retrieve the authentic data flag of this message.
+     * @return The authentic data flag.
+     */
+    public boolean isAuthenticData() {
+        return authenticData;
+    }
+
+    /**
+     * Set the authentic data flag on this DNS message.
+     * @param authenticData The new authentic data flag value.
+     */
+    public void setAuthenticData(boolean authenticData) {
+        this.authenticData = authenticData;
+    }
+
+    /**
+     * Check if checks are disabled.
+     * @return The status of the CheckDisabled flag.
+     */
+    public boolean isCheckDisabled() {
+        return checkDisabled;
+    }
+
+    /**
+     * Change the check status of this packet.
+     * @param checkDisabled
+     */
+    public void setCheckDisabled(boolean checkDisabled) {
+        this.checkDisabled = checkDisabled;
+    }
+
+    /**
+     * Generate a binary dns packet out of this message.
+     * @return byte[] the binary representation.
+     * @throws IOException Should never happen.
+     */
+    public byte[] toArray() throws IOException {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream(512);
+        DataOutputStream dos = new DataOutputStream(baos);
+        int header = 0;
+        if (query) {
+            header += 1 << 15;
+        }
+        if (opcode != null) {
+            header += opcode.getValue() << 11;
+        }
+        if (authoritativeAnswer) {
+            header += 1 << 10;
+        }
+        if (truncated) {
+            header += 1 << 9;
+        }
+        if (recursionDesired) {
+            header += 1 << 8;
+        }
+        if (recursionAvailable) {
+            header += 1 << 7;
+        }
+        if (authenticData) {
+            header += 1 << 5;
+        }
+        if (checkDisabled) {
+            header += 1 << 4;
+        }
+        if (responseCode != null) {
+            header += responseCode.getValue();
+        }
+        dos.writeShort((short)id);
+        dos.writeShort((short)header);
+        if (questions == null) {
+            dos.writeShort(0);
+        } else {
+            dos.writeShort((short)questions.length);
+        }
+        if (answers == null) {
+            dos.writeShort(0);
+        } else {
+            dos.writeShort((short)answers.length);
+        }
+        if (nameserverRecords == null) {
+            dos.writeShort(0);
+        } else {
+            dos.writeShort((short)nameserverRecords.length);
+        }
+        if (additionalResourceRecords == null) {
+            dos.writeShort(0);
+        } else {
+            dos.writeShort((short)additionalResourceRecords.length);
+        }
+        for (Question question: questions) {
+            dos.write(question.toByteArray());
+        }
+        dos.flush();
+        return baos.toByteArray();
+    }
+
+    /**
+     * Build a DNS Message based on a binary DNS message.
+     * @param data The DNS message data.
+     * @return Parsed DNSMessage message.
+     * @throws IOException On read errors.
+     */
+    public static DNSMessage parse(byte data[]) throws IOException {
+        ByteArrayInputStream bis = new ByteArrayInputStream(data);
+        DataInputStream dis = new DataInputStream(bis);
+        DNSMessage message = new DNSMessage();
+        message.id = dis.readUnsignedShort();
+        int header = dis.readUnsignedShort();
+        message.query = ((header >> 15) & 1) == 0;
+        message.opcode = OPCODE.getOpcode((header >> 11) & 0xf);
+        message.authoritativeAnswer = ((header >> 10) & 1) == 1;
+        message.truncated = ((header >> 9) & 1) == 1;
+        message.recursionDesired = ((header >> 8) & 1) == 1;
+        message.recursionAvailable = ((header >> 7) & 1) == 1;
+        message.authenticData = ((header >> 5) & 1) == 1;
+        message.checkDisabled = ((header >> 4) & 1) == 1;
+        message.responseCode = RESPONSE_CODE.getResponseCode(header & 0xf);
+        int questionCount = dis.readUnsignedShort();
+        int answerCount = dis.readUnsignedShort();
+        int nameserverCount = dis.readUnsignedShort();
+        int additionalResourceRecordCount = dis.readUnsignedShort();
+        message.questions = new Question[questionCount];
+        while (questionCount-- > 0) {
+            Question q = new Question();
+            q.parse(dis, data);
+            message.questions[questionCount] = q;
+        }
+        message.answers = new Record[answerCount];
+        while (answerCount-- > 0) {
+            Record rr = new Record();
+            rr.parse(dis, data);
+            message.answers[answerCount] = rr;
+        }
+        message.nameserverRecords = new Record[nameserverCount];
+        while (nameserverCount-- > 0) {
+            Record rr = new Record();
+            rr.parse(dis, data);
+            message.nameserverRecords[nameserverCount] = rr;
+        }
+        message.additionalResourceRecords =
+                                    new Record[additionalResourceRecordCount];
+        while (additionalResourceRecordCount-- > 0) {
+            Record rr = new Record();
+            rr.parse(dis, data);
+            message.additionalResourceRecords[additionalResourceRecordCount] =
+                    rr;
+        }
+        return message;
+    }
+
+    /**
+     * Set the question part of this message.
+     * @param questions The questions.
+     */
+    public void setQuestions(Question ... questions) {
+        this.questions = questions;
+    }
+
+    /**
+     * Retrieve the opcode of this message.
+     * @return The opcode of this message.
+     */
+    public OPCODE getOpcode() {
+        return opcode;
+    }
+
+    /**
+     * Retrieve the response code of this message.
+     * @return The response code.
+     */
+    public RESPONSE_CODE getResponseCode() {
+        return responseCode;
+    }
+
+    /**
+     * Retrieve the question section of this message.
+     * @return The DNS question section.
+     */
+    public Question[] getQuestions() {
+        return questions;
+    }
+
+    /**
+     * Retrieve the answer records of this DNS message.
+     * @return The answer section of this DNS message.
+     */
+    public Record[] getAnswers() {
+        return answers;
+    }
+
+    /**
+     * Retrieve the nameserver records of this DNS message.
+     * @return The nameserver section of this DNS message.
+     */
+    public Record[] getNameserverRecords() {
+        return nameserverRecords;
+    }
+
+    /**
+     * Retrieve the additional resource records attached to this DNS message.
+     * @return The additional resource record section of this DNS message.
+     */
+    public Record[] getAdditionalResourceRecords() {
+        return additionalResourceRecords;
+    }
+
+    public String toString() {
+        return "-- DNSMessage " + id + " --\n" +
+               Arrays.toString(answers);
+    }
+
+}
diff --git a/src/main/java/de/measite/minidns/Question.java b/src/main/java/de/measite/minidns/Question.java
new file mode 100644
index 00000000..9d1e3f56
--- /dev/null
+++ b/src/main/java/de/measite/minidns/Question.java
@@ -0,0 +1,62 @@
+package de.measite.minidns;
+
+import java.io.ByteArrayOutputStream;
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+
+import de.measite.minidns.Record.CLASS;
+import de.measite.minidns.Record.TYPE;
+import de.measite.minidns.util.NameUtil;
+
+public class Question {
+
+    private String name;
+
+    private TYPE type;
+
+    private CLASS clazz = CLASS.IN;
+
+    public TYPE getType() {
+        return type;
+    }
+
+    public void setType(TYPE type) {
+        this.type = type;
+    }
+
+    public CLASS getClazz() {
+        return clazz;
+    }
+
+    public void setClazz(CLASS clazz) {
+        this.clazz = clazz;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public void parse(DataInputStream dis, byte[] data) throws IOException {
+        this.name = NameUtil.parse(dis, data);
+        this.type = TYPE.getType(dis.readUnsignedShort());
+        this.clazz = CLASS.getClass(dis.readUnsignedShort());
+    }
+
+    public byte[] toByteArray() throws IOException {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream(512);
+        DataOutputStream dos = new DataOutputStream(baos);
+
+        dos.write(NameUtil.toByteArray(this.name));
+        dos.writeShort(type.getValue());
+        dos.writeShort(clazz.getValue());
+
+        dos.flush();
+        return baos.toByteArray();
+    }
+
+}
diff --git a/src/main/java/de/measite/minidns/Record.java b/src/main/java/de/measite/minidns/Record.java
new file mode 100644
index 00000000..fb0b5d5f
--- /dev/null
+++ b/src/main/java/de/measite/minidns/Record.java
@@ -0,0 +1,297 @@
+package de.measite.minidns;
+
+import java.io.DataInputStream;
+import java.io.IOException;
+import java.util.HashMap;
+
+import de.measite.minidns.record.A;
+import de.measite.minidns.record.AAAA;
+import de.measite.minidns.record.CNAME;
+import de.measite.minidns.record.Data;
+import de.measite.minidns.record.NS;
+import de.measite.minidns.record.SRV;
+import de.measite.minidns.util.NameUtil;
+
+/**
+ * A generic DNS record.
+ */
+public class Record {
+
+    /**
+     * The record type.
+     * {@see http://www.iana.org/assignments/dns-parameters}
+     */
+    public static enum TYPE {
+        A(1),
+        NS(2),
+        MD(3),
+        MF(4),
+        CNAME(5),
+        SOA(6),
+        MB(7),
+        MG(8),
+        MR(9),
+        NULL(10),
+        WKS(11),
+        PTR(12),
+        HINFO(13),
+        MINFO(14),
+        MX(15),
+        TXT(16),
+        RP(17),
+        AFSDB(18),
+        X25(19),
+        ISDN(20),
+        RT(21),
+        NSAP(22),
+        NSAP_PTR(23),
+        SIG(24),
+        KEY(25),
+        PX(26),
+        GPOS(27),
+        AAAA(28),
+        LOC(29),
+        NXT(30),
+        EID(31),
+        NIMLOC(32),
+        SRV(33),
+        ATMA(34),
+        NAPTR(35),
+        KX(36),
+        CERT(37),
+        A6(38),
+        DNAME(39),
+        SINK(40),
+        OPT(41),
+        APL(42),
+        DS(43),
+        SSHFP(44),
+        IPSECKEY(45),
+        RRSIG(46),
+        NSEC(47),
+        DNSKEY(48),
+        DHCID(49),
+        NSEC3(50),
+        NSEC3PARAM(51),
+        HIP(55),
+        NINFO(56),
+        RKEY(57),
+        TALINK(58),
+        SPF(99),
+        UINFO(100),
+        UID(101),
+        GID(102),
+        TKEY(249),
+        TSIG(250),
+        IXFR(251),
+        AXFR(252),
+        MAILB(253),
+        MAILA(254),
+        ANY(255),
+        TA(32768),
+        DLV(32769);
+
+        /**
+         * The value of this DNS record type.
+         */
+        private final int value;
+
+        /**
+         * Internal lookup table to map values to types.
+         */
+        private final static HashMap<Integer, TYPE> INVERSE_LUT =
+                                        new HashMap<Integer, TYPE>();
+
+        /**
+         * Initialize the reverse lookup table.
+         */
+        static {
+            for(TYPE t: TYPE.values()) {
+                INVERSE_LUT.put(t.getValue(), t);
+            }
+        }
+
+        /**
+         * Create a new record type.
+         * @param value The binary value of this type.
+         */
+        private TYPE(int value) {
+            this.value = value;
+        }
+
+        /**
+         * Retrieve the binary value of this type.
+         * @return The binary value.
+         */
+        public int getValue() {
+            return value;
+        }
+
+        /**
+         * Retrieve the symbolic type of the binary value.
+         * @param value The binary type value.
+         * @return The symbolic tpye.
+         */
+        public static TYPE getType(int value) {
+            return INVERSE_LUT.get(value);
+        }
+    };
+
+    /**
+     * The symbolic class of a DNS record (usually IN for Internet).
+     */
+    public static enum CLASS {
+        IN(1),
+        CH(3),
+        HS(4),
+        NONE(254),
+        ANY(255);
+
+        /**
+         * Internal reverse lookup table to map binary class values to symbolic
+         * names.
+         */
+        private final static HashMap<Integer, CLASS> INVERSE_LUT =
+                                            new HashMap<Integer, CLASS>();
+
+        /**
+         * Initialize the interal reverse lookup table.
+         */
+        static {
+            for(CLASS c: CLASS.values()) {
+                INVERSE_LUT.put(c.getValue(), c);
+            }
+        }
+
+        /**
+         * The binary value of this dns class.
+         */
+        private final int value;
+
+        /**
+         * Create a new DNS class based on a binary value.
+         * @param value The binary value of this DNS class.
+         */
+        private CLASS(int value) {
+            this.value = value;
+        }
+
+        /**
+         * Retrieve the binary value of this DNS class.
+         * @return The binary value of this DNS class.
+         */
+        public int getValue() {
+            return value;
+        }
+
+        /**
+         * Retrieve the symbolic DNS class for a binary class value.
+         * @param value The binary DNS class value.
+         * @return The symbolic class instance.
+         */
+        public static CLASS getClass(int value) {
+            return INVERSE_LUT.get(value);
+        }
+
+    }
+
+    /**
+     * The generic name of this record.
+     */
+    protected String name;
+
+    /**
+     * The type (and payload type) of this record.
+     */
+    protected TYPE type;
+
+    /**
+     * The record class (usually CLASS.IN).
+     */
+    protected CLASS clazz;
+
+    /**
+     * The ttl of this record.
+     */
+    protected long ttl;
+
+    /**
+     * The payload object of this record.
+     */
+    protected Data payloadData;
+
+    /**
+     * Parse a given record based on the full message data and the current
+     * stream position.
+     * @param dis The DataInputStream positioned at the first record byte.
+     * @param data The full message data.
+     * @throws IOException In case of malformed replies.
+     */
+    public void parse(DataInputStream dis, byte[] data) throws IOException {
+        this.name = NameUtil.parse(dis, data);
+        this.type = TYPE.getType(dis.readUnsignedShort());
+        this.clazz = CLASS.getClass(dis.readUnsignedShort());
+        this.ttl = (((long)dis.readUnsignedShort()) << 32) +
+                   dis.readUnsignedShort();
+        int payloadLength = dis.readUnsignedShort();
+        switch (this.type) {
+        case SRV:
+            this.payloadData = new SRV();
+            break;
+        case AAAA:
+            this.payloadData = new AAAA();
+            break;
+        case A:
+            this.payloadData = new A();
+            break;
+        case NS:
+            this.payloadData = new NS();
+            break;
+        case CNAME:
+            this.payloadData = new CNAME();
+            break;
+        default:
+            System.out.println("Unparsed type " + type);
+            this.payloadData = null;
+            for (int i = 0; i < payloadLength; i++) {
+                dis.readByte();
+            }
+            break;
+        }
+        if (this.payloadData != null) {
+            this.payloadData.parse(dis, data, payloadLength);
+        }
+    }
+
+    /**
+     * Retrieve a textual representation of this resource record.
+     * @return String
+     */
+    @Override
+    public String toString() {
+        if (payloadData == null) {
+            return "RR " + type + "/" + clazz;
+        }
+        return "RR " + type + "/" + clazz + ": " + payloadData.toString();
+    };
+
+    /**
+     * Check if this record answers a given query.
+     * @param q The query.
+     * @return True if this record is a valid answer.
+     */
+    public boolean isAnswer(Question q) {
+        return ((q.getType() == type) || (q.getType() == TYPE.ANY)) &&
+               ((q.getClazz() == clazz) || (q.getClazz() == CLASS.ANY)) &&
+               (q.getName().equals(name));
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public Data getPayload() {
+        return payloadData;
+    }
+
+}
diff --git a/src/main/java/de/measite/minidns/record/A.java b/src/main/java/de/measite/minidns/record/A.java
new file mode 100644
index 00000000..a85a7af0
--- /dev/null
+++ b/src/main/java/de/measite/minidns/record/A.java
@@ -0,0 +1,37 @@
+package de.measite.minidns.record;
+
+import java.io.DataInputStream;
+import java.io.IOException;
+
+import de.measite.minidns.Record.TYPE;
+
+public class A implements Data {
+
+    private byte[] ip;
+
+    @Override
+    public TYPE getType() {
+        return TYPE.A;
+    }
+
+    @Override
+    public byte[] toByteArray() {
+        return ip;
+    }
+
+    @Override
+    public void parse(DataInputStream dis, byte[] data, int length)
+            throws IOException {
+        ip = new byte[4];
+        dis.readFully(ip);
+    }
+
+    @Override
+    public String toString() {
+        return Integer.toString(ip[0] & 0xff) + "." +
+               Integer.toString(ip[1] & 0xff) + "." +
+               Integer.toString(ip[2] & 0xff) + "." +
+               Integer.toString(ip[3] & 0xff);
+    }
+
+}
diff --git a/src/main/java/de/measite/minidns/record/AAAA.java b/src/main/java/de/measite/minidns/record/AAAA.java
new file mode 100644
index 00000000..d89147b2
--- /dev/null
+++ b/src/main/java/de/measite/minidns/record/AAAA.java
@@ -0,0 +1,43 @@
+package de.measite.minidns.record;
+
+import java.io.DataInputStream;
+import java.io.IOException;
+
+import de.measite.minidns.Record.TYPE;
+
+public class AAAA implements Data {
+
+    private byte[] ip;
+
+    @Override
+    public TYPE getType() {
+        return TYPE.AAAA;
+    }
+
+    @Override
+    public byte[] toByteArray() {
+        return ip;
+    }
+
+    @Override
+    public void parse(DataInputStream dis, byte[] data, int length)
+            throws IOException {
+        ip = new byte[16];
+        dis.readFully(ip);
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i < ip.length; i += 2) {
+            if (i != 0) {
+                sb.append(':');
+            }
+            sb.append(Integer.toHexString(
+                ((ip[i] & 0xff) << 8) + (ip[i + 1] & 0xff)
+            ));
+        }
+        return sb.toString();
+    }
+
+}
diff --git a/src/main/java/de/measite/minidns/record/CNAME.java b/src/main/java/de/measite/minidns/record/CNAME.java
new file mode 100644
index 00000000..4657b4a5
--- /dev/null
+++ b/src/main/java/de/measite/minidns/record/CNAME.java
@@ -0,0 +1,44 @@
+package de.measite.minidns.record;
+
+import java.io.DataInputStream;
+import java.io.IOException;
+
+import de.measite.minidns.Record.TYPE;
+import de.measite.minidns.util.NameUtil;
+
+public class CNAME implements Data {
+
+    protected String name;
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    @Override
+    public byte[] toByteArray() {
+        // TODO Auto-generated method stub
+        return null;
+    }
+
+    @Override
+    public void parse(DataInputStream dis, byte[] data, int length)
+        throws IOException
+    {
+        this.name = NameUtil.parse(dis, data);
+    }
+
+    @Override
+    public TYPE getType() {
+        return TYPE.CNAME;
+    }
+
+    @Override
+    public String toString() {
+        return "to \"" + name + "\"";
+    }
+
+}
diff --git a/src/main/java/de/measite/minidns/record/Data.java b/src/main/java/de/measite/minidns/record/Data.java
new file mode 100644
index 00000000..9cb80374
--- /dev/null
+++ b/src/main/java/de/measite/minidns/record/Data.java
@@ -0,0 +1,16 @@
+package de.measite.minidns.record;
+
+import java.io.DataInputStream;
+import java.io.IOException;
+
+import de.measite.minidns.Record.TYPE;
+
+public interface Data {
+
+    TYPE getType();
+
+    byte[] toByteArray();
+
+    void parse(DataInputStream dis, byte data[], int length) throws IOException;
+
+}
diff --git a/src/main/java/de/measite/minidns/record/NS.java b/src/main/java/de/measite/minidns/record/NS.java
new file mode 100644
index 00000000..bf07e8c4
--- /dev/null
+++ b/src/main/java/de/measite/minidns/record/NS.java
@@ -0,0 +1,12 @@
+package de.measite.minidns.record;
+
+import de.measite.minidns.Record.TYPE;
+
+public class NS extends CNAME {
+
+    @Override
+    public TYPE getType() {
+        return TYPE.NS;
+    }
+
+}
diff --git a/src/main/java/de/measite/minidns/record/SRV.java b/src/main/java/de/measite/minidns/record/SRV.java
new file mode 100644
index 00000000..32b70c4d
--- /dev/null
+++ b/src/main/java/de/measite/minidns/record/SRV.java
@@ -0,0 +1,74 @@
+package de.measite.minidns.record;
+
+import java.io.DataInputStream;
+import java.io.IOException;
+
+import de.measite.minidns.Record.TYPE;
+import de.measite.minidns.util.NameUtil;
+
+public class SRV implements Data {
+
+    protected int priority;
+    protected int weight;
+    protected int port;
+    protected String name;
+
+    public int getPriority() {
+        return priority;
+    }
+
+    public void setPriority(int priority) {
+        this.priority = priority;
+    }
+
+    public int getWeight() {
+        return weight;
+    }
+
+    public void setWeight(int weight) {
+        this.weight = weight;
+    }
+
+    public int getPort() {
+        return port;
+    }
+
+    public void setPort(int port) {
+        this.port = port;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    @Override
+    public byte[] toByteArray() {
+        // TODO Auto-generated method stub
+        return null;
+    }
+
+    @Override
+    public void parse(DataInputStream dis, byte[] data, int length)
+        throws IOException
+    {
+        this.priority = dis.readUnsignedShort();
+        this.weight = dis.readUnsignedShort();
+        this.port = dis.readUnsignedShort();
+        this.name = NameUtil.parse(dis, data);
+    }
+
+    @Override
+    public String toString() {
+        return "SRV " + name + ":" + port + " p:" + priority + " w:" + weight;
+    }
+
+    @Override
+    public TYPE getType() {
+        return TYPE.SRV;
+    }
+
+}
diff --git a/src/main/java/de/measite/minidns/util/NameUtil.java b/src/main/java/de/measite/minidns/util/NameUtil.java
new file mode 100644
index 00000000..91a6649d
--- /dev/null
+++ b/src/main/java/de/measite/minidns/util/NameUtil.java
@@ -0,0 +1,91 @@
+package de.measite.minidns.util;
+
+import java.io.ByteArrayOutputStream;
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.net.IDN;
+import java.util.HashSet;
+import java.util.Arrays;
+
+public class NameUtil {
+
+    public static int size(String name) {
+        return name.length() + 2;
+    }
+
+    public static boolean idnEquals(String name1, String name2) {
+        if (name1 == name2) return true; // catches null, null
+        if (name1 == null) return false;
+        if (name2 == null) return false;
+        if (name1.equals(name2)) return true;
+
+        try {
+            return Arrays.equals(toByteArray(name1),toByteArray(name2));
+        } catch (IOException e) {
+            return false; // impossible
+        }
+    }
+
+    public static byte[] toByteArray(String name) throws IOException {
+        ByteArrayOutputStream baos = new ByteArrayOutputStream(64);
+        DataOutputStream dos = new DataOutputStream(baos);
+        for (String s: name.split("[.\u3002\uFF0E\uFF61]")) {
+            byte[] buffer = IDN.toASCII(s).getBytes();
+            dos.writeByte(buffer.length);
+            dos.write(buffer);
+        }
+        dos.writeByte(0);
+        dos.flush();
+        return baos.toByteArray();
+    }   
+
+    public static String parse(DataInputStream dis, byte data[]) 
+        throws IOException
+    {
+        int c = dis.readUnsignedByte();
+        if ((c & 0xc0) == 0xc0) {
+            c = ((c & 0x3f) << 8) + dis.readUnsignedByte();
+            HashSet<Integer> jumps = new HashSet<Integer>();
+            jumps.add(c);
+            return parse(data, c, jumps);
+        }
+        if (c == 0) {
+            return "";
+        }
+        byte b[] = new byte[c];
+        dis.readFully(b);
+        String s = IDN.toUnicode(new String(b));
+        String t = parse(dis, data);
+        if (t.length() > 0) {
+            s = s + "." + t;
+        }
+        return s;
+    }
+
+    public static String parse(
+        byte data[],
+        int offset,
+        HashSet<Integer> jumps
+    ) {
+        int c = data[offset] & 0xff;
+        if ((c & 0xc0) == 0xc0) {
+            c = ((c & 0x3f) << 8) + (data[offset + 1] & 0xff);
+            if (jumps.contains(c)) {
+                throw new IllegalStateException("Cyclic offsets detected.");
+            }
+            jumps.add(c);
+            return parse(data, c, jumps);
+        }
+        if (c == 0) {
+            return "";
+        }
+        String s = new String(data,offset + 1, c);
+        String t = parse(data, offset + 1 + c, jumps);
+        if (t.length() > 0) {
+            s = s + "." + t;
+        }
+        return s;
+    }
+
+}