Android Open Source - azilink Udp Driver

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Back to project page azilink.

License

The source code is released under:

GNU General Public License

Java Source Code

/* AziLink: USB tethering for Android
 * Copyright (C) 2009 by James Perry// w ww.  jav  a 2 s  .  co  m
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) version 3 of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package org.lfx.azilink.net;

import java.io.IOException;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.DatagramChannel;
import java.nio.channels.SelectionKey;

import android.util.Log;

/**
 * Driver for a single UDP connection.
 * 
 * @author Jim Perry
 *
 */
public class UdpDriver extends SocketHandler implements TimerCallback {
  /** NIO socket for this link */
  DatagramChannel mChannel;
  /** src/dest ip/port */
  UdpKey mAddr = new UdpKey();
  /** VPN engine */
  VpnNatEngine mEngine;
  /** Timer key for the connection expiration */
  long mTimerKey;
  /** Last received packet. Used to generate ICMP unreachable and for ICMP ping translation. */
  UdpPacket mLastPacket;
  /** Is this an ICMP <-> UDP translated packet? */
  boolean mIcmp;
  /** Statistics reporter */
  TransferStatistics mStats;
  
  /** Time to keep an idle UDP connection in the table (ms) */
  static final int mTimeIdle = 120000;
  /** Time to keep an idle DNS UDP connection in the table (ms) */
  static final int mTimeIdleDNS = 12000;
  /** Time to keep an ICMP<->UDP connection in the table (ms) */
  static final int mTimeIdleIcmp = 12000;
  
  /**
   * Construct a new UDP link
   * 
   * @param engine pointer to the vpn engine
   * @param nk addresses of both endpoints
   * @param pkt the first udp packet
   * @param icmp is this an icmp-in-udp packet?
   * @throws IOException
   */
  public UdpDriver(VpnNatEngine engine, UdpKey nk, UdpPacket pkt, boolean icmp) throws IOException {
    super( DatagramChannel.open() );
    mChannel = (DatagramChannel) super.mChannel;
    mEngine = engine;
    mStats = mEngine;
    mChannel.configureBlocking(false);
    mIcmp = icmp;
    mAddr = nk;
  
    int destIp = mAddr.mDestIp;
    if( mAddr.mDestPort == 53 && mAddr.mDestIp == 0xC0A83801 ) {  // 192.168.56.1
      // Redirect 192.168.56.1:53 to the actual dns server
      if(VpnNatEngine.sLog) Log.v("AziLink", "Redirecting DNS packet");
      destIp = VpnNatEngine.getDnsIp();      
    }
    
    byte[] addr = new byte[4];
    addr[0] = (byte)(destIp >> 24);
    addr[1] = (byte)(destIp >> 16);
    addr[2] = (byte)(destIp >> 8);
    addr[3] = (byte)(destIp >> 0);
        
    if(VpnNatEngine.sLog) Log.v("AziLink", "Connect to foreign host (udp) " + InetAddress.getByAddress(addr).getHostAddress() + ":" + nk.mDestPort );    
    mChannel.connect( new InetSocketAddress( InetAddress.getByAddress( addr ), nk.mDestPort ) );
    mChannel.register( mEngine.mSelectThread.mSelector, SelectionKey.OP_READ, this );
    setTimer();
    mLastPacket = pkt;
  }
  
  /**
   * Restart the teardown timer
   */
  void setTimer() {
    if( mAddr.mDestPort == 53 ) {
      mTimerKey = mEngine.mTimers.changeTimer( mTimerKey, mTimeIdleDNS, this );
    } else if( mIcmp ) {
      mTimerKey = mEngine.mTimers.changeTimer( mTimerKey, mTimeIdleIcmp, this );
    } else {
      mTimerKey = mEngine.mTimers.changeTimer( mTimerKey, mTimeIdle, this );
    }
  }
  
  /**
   * New UDP packet received from the VPN
   * @param pkt udp packet
   */
  public void readRawPacket(UdpPacket pkt) {
    if(VpnNatEngine.sLog) Log.v("AziLink", "UDP Host->Foreign" );
    mLastPacket = pkt;
    mEngine.mBytesSent += pkt.getDataLength();
    setTimer();
    ByteBuffer dat = ByteBuffer.allocate( pkt.getDataLength() );
    dat.put( pkt.getData(), 0, pkt.getDataLength() );
    dat.flip();
    try {
      int len = mChannel.write( dat );
      if( len > 0 ) {
        mStats.addBytes(0,len);
      }
    } catch (IOException e) {  
    }    
  }    
    
  /**
   * New data available from the NIO link
   * @param k selection key
   */
  @Override public void onRead( SelectionKey k ) {
    if(VpnNatEngine.sLog) Log.v("AziLink", "UDP Foreign->Host " + mAddr.mSrcPort + " and " + mAddr.mDestPort );
    ByteBuffer dat = ByteBuffer.allocate( 1500 );
    
    if(mIcmp) {
      if(VpnNatEngine.sLog) Log.v("AziLink", "UDP convert back to ICMP");
      try {
        int len = mChannel.read(dat);
        if( len > 0 ) mStats.addBytes(len,0);
      } catch (IOException e) {}
      IcmpPacket ip = new IcmpPacket(mLastPacket.getData());
      ip.swapHosts();
      ip.setType(IcmpPacket.TYPE_ICMP_ECHO_REPLY);
      ip.setCode(IcmpPacket.PROTO_ICMP_ECHO_REPLY);
      ip.complete();
      mEngine.vpnWrite( ip.mRaw.array(), (short) ip.mPacketLength );
      return;
    }
    setTimer();
    
    try {
      for( ;; ) {
        dat.clear();
        int rlen = mChannel.read( dat );
        if( rlen < 0 ) {
          if(VpnNatEngine.sLog) Log.v("AziLink", "UDP read len was " + rlen );
          return;
        } else if( rlen == 0 ) {
          if(VpnNatEngine.sLog) Log.v("AziLink", "UDP read len was " + rlen );
          break;
        }
        mStats.addBytes(rlen, 0);
        dat.flip();
        mEngine.mBytesRecv += dat.limit();
        
        if( !mEngine.isVpnWriteOk() ) return;    // just toss the packet
        
        UdpKey addr = mAddr;
        UdpPacket tp = new UdpPacket( addr );
        tp.setData( dat.array(), rlen );
        tp.complete();
        mEngine.vpnWrite( tp.mRaw.array(), (short) tp.mPacketLength );        
      }            
    } catch (IOException e) {
      if(VpnNatEngine.sLog) Log.v("AziLink","UDP exception, rewrite to ICMP");
      IcmpKey addr = new IcmpKey();
      addr.mSrcIp = mAddr.mSrcIp;
      addr.mDestIp = mAddr.mDestIp;
      IcmpPacket ip = new IcmpPacket( addr );
      ip.setType(IcmpPacket.TYPE_ICMP_UNREACHABLE);
      ip.setCode(IcmpPacket.PROTO_ICMP_UNREACHABLE_PORT);
      ip.setData(mLastPacket.mRaw.array(), mLastPacket.mPacketLength);
      ip.complete();
      mEngine.vpnWrite( ip.mRaw.array(), (short) ip.mPacketLength );
    }
  }

  /**
   * Timer to teardown idle UDP links 
   */
  public void onTimer() {
    if(VpnNatEngine.sLog) Log.v("AziLink", "UDP timeout" );
    mEngine.mUDP.close( this );    
  }
}

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