package com.qiniu.android.dns.local;
import com.qiniu.android.dns.DnsException;
import com.qiniu.android.dns.Record;
import com.qiniu.android.dns.util.BitSet;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.IDN;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.HashSet;
//import java.util.logging.Level;
//import java.util.logging.Logger;
/**
* reference github/rtreffer/minidns.
*/
public final class DnsMessage {
public static byte[] buildQuery(String domain, int id) {
ByteArrayOutputStream baos = new ByteArrayOutputStream(512);
DataOutputStream dos = new DataOutputStream(baos);
BitSet bits = new BitSet();
// recursionDesired
bits.set(8);
try {
dos.writeShort((short) id);
dos.writeShort((short) bits.value());
// questions count
dos.writeShort(1);
// no answer
dos.writeShort(0);
// no nameserverRecords
dos.writeShort(0);
// no additionalResourceRecords
dos.writeShort(0);
dos.flush();
writeQuestion(baos, domain);
} catch (IOException e) {
throw new AssertionError(e);
}
return baos.toByteArray();
}
private static void writeDomain(OutputStream out, String domain) throws IOException {
for (String s : domain.split("[.\u3002\uFF0E\uFF61]")) {
byte[] buffer = IDN.toASCII(s).getBytes();
out.write(buffer.length);
out.write(buffer, 0, buffer.length); // ?
}
out.write(0);
}
private static void writeQuestion(OutputStream out, String domain) throws IOException {
DataOutputStream dos = new DataOutputStream(out);
writeDomain(out, domain);
// type A
dos.writeShort(1);
// class internet
dos.writeShort(1);
}
public static Record[] parseResponse(byte[] response, int id, String domain) throws IOException {
ByteArrayInputStream bis = new ByteArrayInputStream(response);
DataInputStream dis = new DataInputStream(bis);
int answerId = dis.readUnsignedShort();
if (answerId != id) {
throw new DnsException(domain, "the answer id " + answerId + " is not match " + id);
}
int header = dis.readUnsignedShort();
boolean recursionDesired = ((header >> 8) & 1) == 1;
boolean recursionAvailable = ((header >> 7) & 1) == 1;
if (!(recursionAvailable && recursionDesired)) {
throw new DnsException(domain, "the dns server cant support recursion ");
}
int questionCount = dis.readUnsignedShort();
int answerCount = dis.readUnsignedShort();
// nameserver Count
dis.readUnsignedShort();
// additionalResourceRecordCount
dis.readUnsignedShort();
// ignore questions
readQuestions(dis, response, questionCount);
return readAnswers(dis, response, answerCount);
// ignore auth
// ignore additional
}
/**
* Parse a domain name starting at the current offset and moving the input
* stream pointer past this domain name (even if cross references occure).
*
* @param dis The input stream.
* @param data The raw data (for cross references).
* @return The domain name string.
* @throws IOException Should never happen.
*/
private static String readName(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 readName(data, c, jumps);
}
if (c == 0) {
return "";
}
byte b[] = new byte[c];
dis.readFully(b);
String s = IDN.toUnicode(new String(b));
String t = readName(dis, data);
if (t.length() > 0) {
s = s + "." + t;
}
return s;
}
/**
* Parse a domain name starting at the given offset.
*
* @param data The raw data.
* @param offset The offset.
* @param jumps The list of jumps (by now).
* @return The parsed domain name.
* @throws IOException on cycles.
*/
private static String readName(
byte data[],
int offset,
HashSet<Integer> jumps
) throws IOException {
int c = data[offset] & 0xff;
if ((c & 0xc0) == 0xc0) {
c = ((c & 0x3f) << 8) + (data[offset + 1] & 0xff);
if (jumps.contains(c)) {
throw new DnsException("", "Cyclic offsets detected.");
}
jumps.add(c);
return readName(data, c, jumps);
}
if (c == 0) {
return "";
}
String s = new String(data, offset + 1, c);
String t = readName(data, offset + 1 + c, jumps);
if (t.length() > 0) {
s = s + "." + t;
}
return s;
}
private static void readQuestions(DataInputStream dis, byte[] data, int count) throws IOException {
while (count-- > 0) {
readName(dis, data);
// type
dis.readUnsignedShort();
// class
dis.readUnsignedShort();
}
}
private static Record[] readAnswers(DataInputStream dis, byte[] data, int count) throws IOException {
int offset = 0;
Record[] ret = new Record[count];
while (count-- > 0) {
ret[offset++] = readRecord(dis, data);
}
return ret;
}
private static Record readRecord(DataInputStream dis, byte[] data) throws IOException {
readName(dis, data);
int type = dis.readUnsignedShort();
// class
dis.readUnsignedShort();
long ttl = (((long) dis.readUnsignedShort()) << 16) +
dis.readUnsignedShort();
int payloadLength = dis.readUnsignedShort();
String payload = null;
switch (type) {
case Record.TYPE_A:
byte[] ip = new byte[4];
dis.readFully(ip);
payload = InetAddress.getByAddress(ip).getHostAddress();
break;
case Record.TYPE_CNAME:
payload = readName(dis, data);
break;
default:
payload = null;
for (int i = 0; i < payloadLength; i++) {
dis.readByte();
}
break;
}
if (payload == null) {
throw new UnknownHostException("no record");
}
return new Record(payload, type, (int) ttl, System.currentTimeMillis() / 1000);
}
}
