Switch to a small DNS library for DNS resolving.

This commit is contained in:
Rene Treffer 2014-04-03 09:42:58 +02:00
parent d53dc28f4c
commit ff88dc0eaa
4 changed files with 107 additions and 92 deletions

4
.gitmodules vendored
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@ -1,3 +1,7 @@
[submodule "libs/openpgp-keychain"]
path = libs/openpgp-keychain
url = https://github.com/openpgp-keychain/openpgp-keychain.git
[submodule "libs/minidns"]
path = libs/minidns
url = https://github.com/rtreffer/minidns.git

1
libs/minidns Submodule

@ -0,0 +1 @@
Subproject commit d5cca3b3a48cfaed3008050fcab9574d97d771cc

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@ -13,3 +13,4 @@
# Project target.
target=android-19
android.library.reference.1=libs/openpgp-keychain/OpenPGP-Keychain-API/libraries/openpgp-api-library
android.library.reference.2=libs/minidns

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@ -1,125 +1,134 @@
package eu.siacs.conversations.utils;
import java.io.ByteArrayOutputStream;
import de.measite.minidns.Client;
import de.measite.minidns.DNSMessage;
import de.measite.minidns.Record;
import de.measite.minidns.Record.TYPE;
import de.measite.minidns.Record.CLASS;
import de.measite.minidns.record.SRV;
import de.measite.minidns.record.Data;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Random;
import java.util.TreeMap;
import android.os.Bundle;
import android.util.Log;
public class DNSHelper {
public static Bundle getSRVRecord(String host) throws IOException {
InetAddress ip = InetAddress.getByName("8.8.8.8");
try {
Class<?> SystemProperties = Class
.forName("android.os.SystemProperties");
Method method = SystemProperties.getMethod("get",
new Class[] { String.class });
ArrayList<String> servers = new ArrayList<String>();
for (String name : new String[] { "net.dns1", "net.dns2",
"net.dns3", "net.dns4", }) {
String value = (String) method.invoke(null, name);
protected static Client client = new Client();
if (value != null && !"".equals(value)
&& !servers.contains(value)) {
ip = InetAddress.getByName(value);
servers.add(value);
Bundle result = queryDNS(host, ip);
if (!result.containsKey("error")||("nosrv".equals(result.getString("error")))) {
return result;
}
public static Bundle getSRVRecord(String host) throws IOException {
String dns[] = client.findDNS();
if (dns != null) {
// we have a list of DNS servers, let's go
for (String dnsserver : dns) {
InetAddress ip = InetAddress.getByName(dnsserver);
Bundle b = queryDNS(host, ip);
if (b.containsKey("name")) {
return b;
}
}
} catch (Exception e) {
Log.d("xmppService","error during system calls");
}
ip = InetAddress.getByName("8.8.8.8");
return queryDNS(host, ip);
// fallback
return queryDNS(host, InetAddress.getByName("8.8.8.8"));
}
public static Bundle queryDNS(String host, InetAddress dnsServer) {
Bundle namePort = new Bundle();
try {
Log.d("xmppService", "using dns server: " + dnsServer.toString()
Log.d("xmppService", "using dns server: " + dnsServer.getHostAddress()
+ " to look up " + host);
String[] hostParts = host.split("\\.");
byte[] transId = new byte[2];
Random random = new Random();
random.nextBytes(transId);
byte[] header = { 0x01, 0x20, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00,
0x00, 0x01, 0x0c, 0x5f, 0x78, 0x6d, 0x70, 0x70, 0x2d, 0x63,
0x6c, 0x69, 0x65, 0x6e, 0x74, 0x04, 0x5f, 0x74, 0x63, 0x70 };
byte[] rest = { 0x00, 0x00, 0x21, 0x00, 0x01, 0x00, 0x00, 0x29,
0x10, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
ByteArrayOutputStream output = new ByteArrayOutputStream();
output.write(transId);
output.write(header);
for (int i = 0; i < hostParts.length; ++i) {
char[] tmpChars = hostParts[i].toCharArray();
byte[] tmp = new byte[tmpChars.length];
for (int j = 0; j < tmpChars.length; ++j) {
tmp[j] = (byte) tmpChars[j];
}
output.write(tmp.length);
output.write(tmp);
}
output.write(rest);
byte[] sendPaket = output.toByteArray();
int realLenght = sendPaket.length - 11;
DatagramPacket packet = new DatagramPacket(sendPaket,
sendPaket.length, dnsServer, 53);
DatagramSocket datagramSocket = new DatagramSocket();
datagramSocket.send(packet);
byte[] receiveData = new byte[1024];
DNSMessage message =
client.query(
"_xmpp-client._tcp." + host,
TYPE.SRV,
CLASS.IN,
dnsServer.getHostAddress());
DatagramPacket receivePacket = new DatagramPacket(receiveData,
receiveData.length);
datagramSocket.setSoTimeout(7000); //die sieben ist meine zahl
datagramSocket.receive(receivePacket);
if (receiveData[3] != -128) {
namePort.putString("error", "nosrv");
return namePort;
}
namePort.putInt(
"port",
calcPort(receiveData[realLenght + 16],
receiveData[realLenght + 17]));
int i = realLenght + 18;
int wordLenght = 0;
StringBuilder builder = new StringBuilder();
while (receiveData[i] != 0) {
if (wordLenght > 0) {
builder.append((char) receiveData[i]);
--wordLenght;
} else {
wordLenght = receiveData[i];
builder.append(".");
// How should we handle priorities and weight?
// Wikipedia has a nice article about priorities vs. weights:
// https://en.wikipedia.org/wiki/SRV_record#Provisioning_for_high_service_availability
// we bucket the SRV records based on priority, pick per priority
// a random order respecting the weight, and dump that priority by
// priority
TreeMap<Integer, ArrayList<SRV>> priorities =
new TreeMap<Integer, ArrayList<SRV>>();
for (Record rr : message.getAnswers()) {
Data d = rr.getPayload();
if (d instanceof SRV) {
SRV srv = (SRV) d;
if (!priorities.containsKey(srv.getPriority())) {
priorities.put(srv.getPriority(), new ArrayList<SRV>(2));
}
priorities.get(srv.getPriority()).add(srv);
}
++i;
}
builder.replace(0, 1, "");
byte type = receiveData[i + 1];
byte type2 = receiveData[i + 2];
if ((type == -64) || (type == type2)) {
namePort.putString("name", builder.toString());
return namePort;
} else {
Log.d("xmppService", "type=" + type + " type2=" + type2 + " "
+ builder.toString());
Random rnd = new Random();
ArrayList<SRV> result = new ArrayList<SRV>(priorities.size() * 2 + 1);
for (ArrayList<SRV> s: priorities.values()) {
// trivial case
if (s.size() <= 1) {
result.addAll(s);
continue;
}
long totalweight = 0l;
for (SRV srv: s) {
totalweight += srv.getWeight();
}
while (totalweight > 0l && s.size() > 0) {
long p = (rnd.nextLong() & 0x7fffffffffffffffl) % totalweight;
int i = 0;
while (p > 0) {
p -= s.get(i++).getPriority();
}
i--;
// remove is expensive, but we have only a few entries anyway
SRV srv = s.remove(i);
totalweight -= srv.getWeight();
result.add(srv);
}
Collections.shuffle(s, rnd);
result.addAll(s);
}
if (result.size() == 0) {
namePort.putString("error", "nosrv");
return namePort;
}
// we now have a list of servers to try :-)
// classic name/port pair
namePort.putString("name", result.get(0).getName());
namePort.putInt("port", result.get(0).getPort());
// add all other records
int i = 0;
for (SRV srv : result) {
namePort.putString("name" + i, srv.getName());
namePort.putInt("port" + i, srv.getPort());
i++;
}
} catch (IOException e) {
Log.d("xmppService", "io execpiton during dns");
Log.e("xmppService", "io execpiton during dns", e);
namePort.putString("error", "timeout");
return namePort;
}
return namePort;
}
static int calcPort(byte hb, byte lb) {