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authorRene Treffer <treffer@measite.de>2014-04-02 22:00:32 +0200
committerRene Treffer <treffer@measite.de>2014-04-02 22:00:32 +0200
commit32b27c53e03d3e1f25230efc48610efeab31f9a2 (patch)
tree89b60b17670b098cbb476b855c8fbe430a2edb80 /src/de/measite/minidns/Client.java
Initial commit
Diffstat (limited to 'src/de/measite/minidns/Client.java')
-rw-r--r--src/de/measite/minidns/Client.java161
1 files changed, 161 insertions, 0 deletions
diff --git a/src/de/measite/minidns/Client.java b/src/de/measite/minidns/Client.java
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+package de.measite.minidns;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.LineNumberReader;
+import java.net.DatagramPacket;
+import java.net.DatagramSocket;
+import java.net.InetAddress;
+import java.security.NoSuchAlgorithmException;
+import java.security.SecureRandom;
+import java.util.HashSet;
+import java.util.Random;
+
+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 {
+
+ /**
+ * The internal random class for sequence generation.
+ */
+ protected Random random;
+
+ /**
+ * 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.
+ * @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 {
+ 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), 53);
+ socket.setSoTimeout(5000);
+ socket.send(packet);
+ packet = new DatagramPacket(new byte[513], 513);
+ 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() {
+ 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")) {
+ server.add(value);
+ }
+ }
+ if (server.size() > 0) {
+ return server.toArray(new String[server.size()]);
+ }
+ } catch (IOException e) {
+ e.printStackTrace();
+ }
+ return null;
+ }
+}