core/java/android/net/DnsPinger.java - platform/frameworks/base - Gitiles

 /*
  * Copyright (C) 2011 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 package android.net;

 import android.content.Context;
 import android.os.Handler;
 import android.os.Looper;
 import android.os.Message;
 import android.os.SystemClock;
 import android.provider.Settings;
 import android.util.Slog;

 import com.android.internal.util.Protocol;

 import java.io.IOException;
 import java.net.DatagramPacket;
 import java.net.DatagramSocket;
 import java.net.InetAddress;
 import java.net.NetworkInterface;
 import java.net.SocketTimeoutException;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Random;
 import java.util.concurrent.atomic.AtomicInteger;

 /**
  * Performs a simple DNS "ping" by sending a "server status" query packet to the
  * DNS server. As long as the server replies, we consider it a success.
  * <p>
  * We do not use a simple hostname lookup because that could be cached and the
  * API may not differentiate between a time out and a failure lookup (which we
  * really care about).
  * <p>
  *
  * @hide
  */
 public final class DnsPinger extends Handler {
     private static final boolean V = true;

     private static final int RECEIVE_POLL_INTERVAL_MS = 30;
     private static final int DNS_PORT = 53;

     /** Short socket timeout so we don't block one any 'receive' call */
     private static final int SOCKET_TIMEOUT_MS = 1;

     /** Used to generate IDs */
     private static final Random sRandom = new Random();
     private static final AtomicInteger sCounter = new AtomicInteger();

     private ConnectivityManager mConnectivityManager = null;
     private final Context mContext;
     private final int mConnectionType;
     private final Handler mTarget;
     private final InetAddress mDefaultDns;
     private String TAG;

     private static final int BASE = Protocol.BASE_DNS_PINGER;

     /**
      * Async response packet for dns pings.
      * arg1 is the ID of the ping, also returned by {@link #pingDnsAsync(InetAddress, int, int)}
      * arg2 is the delay, or is negative on error.
      */
     public static final int DNS_PING_RESULT = BASE;
     /** An error code for a {@link #DNS_PING_RESULT} packet */
     public static final int TIMEOUT = -1;
     /** An error code for a {@link #DNS_PING_RESULT} packet */
     public static final int SOCKET_EXCEPTION = -2;

     /**
      * Send a new ping via a socket.  arg1 is ID, arg2 is timeout, obj is InetAddress to ping
      */
     private static final int ACTION_PING_DNS = BASE + 1;
     private static final int ACTION_LISTEN_FOR_RESPONSE = BASE + 2;
     private static final int ACTION_CANCEL_ALL_PINGS = BASE + 3;

     private List<ActivePing> mActivePings = new ArrayList<ActivePing>();
     private int mEventCounter;

     private class ActivePing {
         DatagramSocket socket;
         int internalId;
         short packetId;
         int timeout;
         Integer result;
         long start = SystemClock.elapsedRealtime();
     }

     public DnsPinger(Context context, String TAG, Looper looper,
             Handler target, int connectionType) {
         super(looper);
         this.TAG = TAG;
         mContext = context;
         mTarget = target;
         mConnectionType = connectionType;
         if (!ConnectivityManager.isNetworkTypeValid(connectionType)) {
             throw new IllegalArgumentException("Invalid connectionType in constructor: "
                     + connectionType);
         }
         mDefaultDns = getDefaultDns();
         mEventCounter = 0;
     }

     @Override
     public void handleMessage(Message msg) {
         switch (msg.what) {
             case ACTION_PING_DNS:
                 try {
                     ActivePing newActivePing = new ActivePing();
                     InetAddress dnsAddress = (InetAddress) msg.obj;
                     newActivePing.internalId = msg.arg1;
                     newActivePing.timeout = msg.arg2;
                     newActivePing.socket = new DatagramSocket();
                     // Set some socket properties
                     newActivePing.socket.setSoTimeout(SOCKET_TIMEOUT_MS);

                     // Try to bind but continue ping if bind fails
                     try {
                         newActivePing.socket.setNetworkInterface(NetworkInterface.getByName(
                                 getCurrentLinkProperties().getInterfaceName()));
                     } catch (Exception e) {
                         Slog.w(TAG,"sendDnsPing::Error binding to socket", e);
                     }

                     newActivePing.packetId = (short) sRandom.nextInt();
                     byte[] buf = mDnsQuery.clone();
                     buf[0] = (byte) (newActivePing.packetId >> 8);
                     buf[1] = (byte) newActivePing.packetId;

                     // Send the DNS query
                     DatagramPacket packet = new DatagramPacket(buf,
                             buf.length, dnsAddress, DNS_PORT);
                     if (V) {
                         Slog.v(TAG, "Sending a ping to " + dnsAddress.getHostAddress()
                                 + " with ID " + newActivePing.packetId + ".");
                     }

                     newActivePing.socket.send(packet);
                     mActivePings.add(newActivePing);
                     mEventCounter++;
                     sendMessageDelayed(obtainMessage(ACTION_LISTEN_FOR_RESPONSE, mEventCounter, 0),
                             RECEIVE_POLL_INTERVAL_MS);
                 } catch (IOException e) {
                     sendResponse((short) msg.arg1, SOCKET_EXCEPTION);
                 }
                 break;
             case ACTION_LISTEN_FOR_RESPONSE:
                 if (msg.arg1 != mEventCounter) {
                     break;
                 }
                 for (ActivePing curPing : mActivePings) {
                     try {
                         /** Each socket will block for {@link #SOCKET_TIMEOUT_MS} in receive() */
                         byte[] responseBuf = new byte[2];
                         DatagramPacket replyPacket = new DatagramPacket(responseBuf, 2);
                         curPing.socket.receive(replyPacket);
                         // Check that ID field matches (we're throwing out the rest of the packet)
                         if (responseBuf[0] == (byte) (curPing.packetId >> 8) &&
                                 responseBuf[1] == (byte) curPing.packetId) {
                             curPing.result =
                                     (int) (SystemClock.elapsedRealtime() - curPing.start);
                         } else {
                             if (V) {
                                 Slog.v(TAG, "response ID didn't match, ignoring packet");
                             }
                         }
                     } catch (SocketTimeoutException e) {
                         // A timeout here doesn't mean anything - squelsh this exception
                     } catch (Exception e) {
                         if (V) {
                             Slog.v(TAG, "DnsPinger.pingDns got socket exception: ", e);
                         }
                         curPing.result = SOCKET_EXCEPTION;
                     }
                 }
                 Iterator<ActivePing> iter = mActivePings.iterator();
                 while (iter.hasNext()) {
                    ActivePing curPing = iter.next();
                    if (curPing.result != null) {
                        sendResponse(curPing.internalId, curPing.result);
                        curPing.socket.close();
                        iter.remove();
                    } else if (SystemClock.elapsedRealtime() >
                                   curPing.start + curPing.timeout) {
                        sendResponse(curPing.internalId, TIMEOUT);
                        curPing.socket.close();
                        iter.remove();
                    }
                 }
                 if (!mActivePings.isEmpty()) {
                     sendMessageDelayed(obtainMessage(ACTION_LISTEN_FOR_RESPONSE, mEventCounter, 0),
                             RECEIVE_POLL_INTERVAL_MS);
                 }
                 break;
             case ACTION_CANCEL_ALL_PINGS:
                 for (ActivePing activePing : mActivePings)
                     activePing.socket.close();
                 mActivePings.clear();
                 removeMessages(ACTION_PING_DNS);
                 break;
         }
     }

     /**
      * @return The first DNS in the link properties of the specified connection
      *         type or the default system DNS if the link properties has null
      *         dns set. Should not be null.
      */
     public InetAddress getDns() {
         LinkProperties curLinkProps = getCurrentLinkProperties();
         if (curLinkProps == null) {
             Slog.e(TAG, "getCurLinkProperties:: LP for type" + mConnectionType + " is null!");
             return mDefaultDns;
         }

         Collection<InetAddress> dnses = curLinkProps.getDnses();
         if (dnses == null || dnses.size() == 0) {
             Slog.v(TAG, "getDns::LinkProps has null dns - returning default");
             return mDefaultDns;
         }

         return dnses.iterator().next();
     }

     /**
      * Send a ping.  The response will come via a {@link #DNS_PING_RESULT} to the handler
      * specified at creation.
      * @param dns address of dns server to ping
      * @param timeout timeout for ping
      * @return an ID field, which will also be included in the {@link #DNS_PING_RESULT} message.
      */
     public int pingDnsAsync(InetAddress dns, int timeout, int delay) {
         int id = sCounter.incrementAndGet();
         sendMessageDelayed(obtainMessage(ACTION_PING_DNS, id, timeout, dns), delay);
         return id;
     }

     public void cancelPings() {
         obtainMessage(ACTION_CANCEL_ALL_PINGS).sendToTarget();
     }

     private void sendResponse(int internalId, int responseVal) {
         if(V) {
             Slog.v(TAG, "Responding with id " + internalId + " and val " + responseVal);
         }
         mTarget.sendMessage(obtainMessage(DNS_PING_RESULT, internalId, responseVal));
     }

     private LinkProperties getCurrentLinkProperties() {
         if (mConnectivityManager == null) {
             mConnectivityManager = (ConnectivityManager) mContext.getSystemService(
                     Context.CONNECTIVITY_SERVICE);
         }

         return mConnectivityManager.getLinkProperties(mConnectionType);
     }

     private InetAddress getDefaultDns() {
         String dns = Settings.Secure.getString(mContext.getContentResolver(),
                 Settings.Secure.DEFAULT_DNS_SERVER);
         if (dns == null || dns.length() == 0) {
             dns = mContext.getResources().getString(
                     com.android.internal.R.string.config_default_dns_server);
         }
         try {
             return NetworkUtils.numericToInetAddress(dns);
         } catch (IllegalArgumentException e) {
             Slog.w(TAG, "getDefaultDns::malformed default dns address");
             return null;
         }
     }

     private static final byte[] mDnsQuery = new byte[] {
         0, 0, // [0-1] is for ID (will set each time)
         0, 0, // [2-3] are flags.  Set byte[2] = 1 for recursion desired (RD) on.  Currently off.
         0, 1, // [4-5] bytes are for number of queries (QCOUNT)
         0, 0, // [6-7] unused count field for dns response packets
         0, 0, // [8-9] unused count field for dns response packets
         0, 0, // [10-11] unused count field for dns response packets
         3, 'w', 'w', 'w',
         6, 'g', 'o', 'o', 'g', 'l', 'e',
         3, 'c', 'o', 'm',
         0,    // null terminator of address (also called empty TLD)
         0, 1, // QTYPE, set to 1 = A (host address)
         0, 1  // QCLASS, set to 1 = IN (internet)
     };
 }
	/*
	* Copyright (C) 2011 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	package android.net;

	import android.content.Context;
	import android.os.Handler;
	import android.os.Looper;
	import android.os.Message;
	import android.os.SystemClock;
	import android.provider.Settings;
	import android.util.Slog;

	import com.android.internal.util.Protocol;

	import java.io.IOException;
	import java.net.DatagramPacket;
	import java.net.DatagramSocket;
	import java.net.InetAddress;
	import java.net.NetworkInterface;
	import java.net.SocketTimeoutException;
	import java.util.ArrayList;
	import java.util.Collection;
	import java.util.Iterator;
	import java.util.List;
	import java.util.Random;
	import java.util.concurrent.atomic.AtomicInteger;

	/**
	* Performs a simple DNS "ping" by sending a "server status" query packet to the
	* DNS server. As long as the server replies, we consider it a success.
	* <p>
	* We do not use a simple hostname lookup because that could be cached and the
	* API may not differentiate between a time out and a failure lookup (which we
	* really care about).
	* <p>
	*
	* @hide
	*/
	public final class DnsPinger extends Handler {
	private static final boolean V = true;

	private static final int RECEIVE_POLL_INTERVAL_MS = 30;
	private static final int DNS_PORT = 53;

	/** Short socket timeout so we don't block one any 'receive' call */
	private static final int SOCKET_TIMEOUT_MS = 1;

	/** Used to generate IDs */
	private static final Random sRandom = new Random();
	private static final AtomicInteger sCounter = new AtomicInteger();

	private ConnectivityManager mConnectivityManager = null;
	private final Context mContext;
	private final int mConnectionType;
	private final Handler mTarget;
	private final InetAddress mDefaultDns;
	private String TAG;

	private static final int BASE = Protocol.BASE_DNS_PINGER;

	/**
	* Async response packet for dns pings.
	* arg1 is the ID of the ping, also returned by {@link #pingDnsAsync(InetAddress, int, int)}
	* arg2 is the delay, or is negative on error.
	*/
	public static final int DNS_PING_RESULT = BASE;
	/** An error code for a {@link #DNS_PING_RESULT} packet */
	public static final int TIMEOUT = -1;
	/** An error code for a {@link #DNS_PING_RESULT} packet */
	public static final int SOCKET_EXCEPTION = -2;

	/**
	* Send a new ping via a socket. arg1 is ID, arg2 is timeout, obj is InetAddress to ping
	*/
	private static final int ACTION_PING_DNS = BASE + 1;
	private static final int ACTION_LISTEN_FOR_RESPONSE = BASE + 2;
	private static final int ACTION_CANCEL_ALL_PINGS = BASE + 3;

	private List<ActivePing> mActivePings = new ArrayList<ActivePing>();
	private int mEventCounter;

	private class ActivePing {
	DatagramSocket socket;
	int internalId;
	short packetId;
	int timeout;
	Integer result;
	long start = SystemClock.elapsedRealtime();
	}

	public DnsPinger(Context context, String TAG, Looper looper,
	Handler target, int connectionType) {
	super(looper);
	this.TAG = TAG;
	mContext = context;
	mTarget = target;
	mConnectionType = connectionType;
	if (!ConnectivityManager.isNetworkTypeValid(connectionType)) {
	throw new IllegalArgumentException("Invalid connectionType in constructor: "
	+ connectionType);
	}
	mDefaultDns = getDefaultDns();
	mEventCounter = 0;
	}

	@Override
	public void handleMessage(Message msg) {
	switch (msg.what) {
	case ACTION_PING_DNS:
	try {
	ActivePing newActivePing = new ActivePing();
	InetAddress dnsAddress = (InetAddress) msg.obj;
	newActivePing.internalId = msg.arg1;
	newActivePing.timeout = msg.arg2;
	newActivePing.socket = new DatagramSocket();
	// Set some socket properties
	newActivePing.socket.setSoTimeout(SOCKET_TIMEOUT_MS);

	// Try to bind but continue ping if bind fails
	try {
	newActivePing.socket.setNetworkInterface(NetworkInterface.getByName(
	getCurrentLinkProperties().getInterfaceName()));
	} catch (Exception e) {
	Slog.w(TAG,"sendDnsPing::Error binding to socket", e);
	}

	newActivePing.packetId = (short) sRandom.nextInt();
	byte[] buf = mDnsQuery.clone();
	buf[0] = (byte) (newActivePing.packetId >> 8);
	buf[1] = (byte) newActivePing.packetId;

	// Send the DNS query
	DatagramPacket packet = new DatagramPacket(buf,
	buf.length, dnsAddress, DNS_PORT);
	if (V) {
	Slog.v(TAG, "Sending a ping to " + dnsAddress.getHostAddress()
	+ " with ID " + newActivePing.packetId + ".");
	}

	newActivePing.socket.send(packet);
	mActivePings.add(newActivePing);
	mEventCounter++;
	sendMessageDelayed(obtainMessage(ACTION_LISTEN_FOR_RESPONSE, mEventCounter, 0),
	RECEIVE_POLL_INTERVAL_MS);
	} catch (IOException e) {
	sendResponse((short) msg.arg1, SOCKET_EXCEPTION);
	}
	break;
	case ACTION_LISTEN_FOR_RESPONSE:
	if (msg.arg1 != mEventCounter) {
	break;
	}
	for (ActivePing curPing : mActivePings) {
	try {
	/** Each socket will block for {@link #SOCKET_TIMEOUT_MS} in receive() */
	byte[] responseBuf = new byte[2];
	DatagramPacket replyPacket = new DatagramPacket(responseBuf, 2);
	curPing.socket.receive(replyPacket);
	// Check that ID field matches (we're throwing out the rest of the packet)
	if (responseBuf[0] == (byte) (curPing.packetId >> 8) &&
	responseBuf[1] == (byte) curPing.packetId) {
	curPing.result =
	(int) (SystemClock.elapsedRealtime() - curPing.start);
	} else {
	if (V) {
	Slog.v(TAG, "response ID didn't match, ignoring packet");
	}
	}
	} catch (SocketTimeoutException e) {
	// A timeout here doesn't mean anything - squelsh this exception
	} catch (Exception e) {
	if (V) {
	Slog.v(TAG, "DnsPinger.pingDns got socket exception: ", e);
	}
	curPing.result = SOCKET_EXCEPTION;
	}
	}
	Iterator<ActivePing> iter = mActivePings.iterator();
	while (iter.hasNext()) {
	ActivePing curPing = iter.next();
	if (curPing.result != null) {
	sendResponse(curPing.internalId, curPing.result);
	curPing.socket.close();
	iter.remove();
	} else if (SystemClock.elapsedRealtime() >
	curPing.start + curPing.timeout) {
	sendResponse(curPing.internalId, TIMEOUT);
	curPing.socket.close();
	iter.remove();
	}
	}
	if (!mActivePings.isEmpty()) {
	sendMessageDelayed(obtainMessage(ACTION_LISTEN_FOR_RESPONSE, mEventCounter, 0),
	RECEIVE_POLL_INTERVAL_MS);
	}
	break;
	case ACTION_CANCEL_ALL_PINGS:
	for (ActivePing activePing : mActivePings)
	activePing.socket.close();
	mActivePings.clear();
	removeMessages(ACTION_PING_DNS);
	break;
	}
	}

	/**
	* @return The first DNS in the link properties of the specified connection
	* type or the default system DNS if the link properties has null
	* dns set. Should not be null.
	*/
	public InetAddress getDns() {
	LinkProperties curLinkProps = getCurrentLinkProperties();
	if (curLinkProps == null) {
	Slog.e(TAG, "getCurLinkProperties:: LP for type" + mConnectionType + " is null!");
	return mDefaultDns;
	}

	Collection<InetAddress> dnses = curLinkProps.getDnses();
	if (dnses == null \|\| dnses.size() == 0) {
	Slog.v(TAG, "getDns::LinkProps has null dns - returning default");
	return mDefaultDns;
	}

	return dnses.iterator().next();
	}

	/**
	* Send a ping. The response will come via a {@link #DNS_PING_RESULT} to the handler
	* specified at creation.
	* @param dns address of dns server to ping
	* @param timeout timeout for ping
	* @return an ID field, which will also be included in the {@link #DNS_PING_RESULT} message.
	*/
	public int pingDnsAsync(InetAddress dns, int timeout, int delay) {
	int id = sCounter.incrementAndGet();
	sendMessageDelayed(obtainMessage(ACTION_PING_DNS, id, timeout, dns), delay);
	return id;
	}

	public void cancelPings() {
	obtainMessage(ACTION_CANCEL_ALL_PINGS).sendToTarget();
	}

	private void sendResponse(int internalId, int responseVal) {
	if(V) {
	Slog.v(TAG, "Responding with id " + internalId + " and val " + responseVal);
	}
	mTarget.sendMessage(obtainMessage(DNS_PING_RESULT, internalId, responseVal));
	}

	private LinkProperties getCurrentLinkProperties() {
	if (mConnectivityManager == null) {
	mConnectivityManager = (ConnectivityManager) mContext.getSystemService(
	Context.CONNECTIVITY_SERVICE);
	}

	return mConnectivityManager.getLinkProperties(mConnectionType);
	}

	private InetAddress getDefaultDns() {
	String dns = Settings.Secure.getString(mContext.getContentResolver(),
	Settings.Secure.DEFAULT_DNS_SERVER);
	if (dns == null \|\| dns.length() == 0) {
	dns = mContext.getResources().getString(
	com.android.internal.R.string.config_default_dns_server);
	}
	try {
	return NetworkUtils.numericToInetAddress(dns);
	} catch (IllegalArgumentException e) {
	Slog.w(TAG, "getDefaultDns::malformed default dns address");
	return null;
	}
	}

	private static final byte[] mDnsQuery = new byte[] {
	0, 0, // [0-1] is for ID (will set each time)
	0, 0, // [2-3] are flags. Set byte[2] = 1 for recursion desired (RD) on. Currently off.
	0, 1, // [4-5] bytes are for number of queries (QCOUNT)
	0, 0, // [6-7] unused count field for dns response packets
	0, 0, // [8-9] unused count field for dns response packets
	0, 0, // [10-11] unused count field for dns response packets
	3, 'w', 'w', 'w',
	6, 'g', 'o', 'o', 'g', 'l', 'e',
	3, 'c', 'o', 'm',
	0, // null terminator of address (also called empty TLD)
	0, 1, // QTYPE, set to 1 = A (host address)
	0, 1 // QCLASS, set to 1 = IN (internet)
	};
	}