Android Open Source - azilink Tcp Engine

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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//ww w. j a  va 2  s. c o  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.nio.ByteBuffer;
import java.util.HashMap;

import android.util.Log;

/**
 * Engine driving all active TCP links.
 * 
 * @author Jim Perry
 *
 */
public class TcpEngine implements TcpDriverPacketSink {
  /** HashMap containing all active connections, indexed by ip/port */
  HashMap< TcpKey, TcpDriver > mNat = new HashMap<TcpKey, TcpDriver>();
  /** Pointer to the VPN engine */
  VpnNatEngine mEngine;
  /** Stores addresses of connections that were accepted, so we can automatically accept them again
   * without waiting for the TMobile timeout.  Entries last 30 seconds.
   */
  TmAccept mTM = new TmAccept();
  
  TcpEngine( VpnNatEngine e ) {
    mEngine = e;
  }
  
  /**
   * Close all active TCP connections (via RST, not FIN)
   */
  public void closeAll() {
    if(VpnNatEngine.sLog) Log.v("AziLink","closeAll");
    synchronized(mEngine.mSelectThread) {
      while( !mNat.isEmpty() ) {
        mNat.values().iterator().next().destroy();          
      }
    }
  }
  
  /**
   * Parse a new packet received over the VPN.  Figure out which tcp link it belongs to, and dispatch.
   * @param d tcp packet
   */
  void readRawPacket( byte[] d ) {
    ByteBuffer bb = ByteBuffer.wrap( d );
    int headerLength = (((int) bb.get(0)) & 0x0F) * 4;
    
    if( d.length < headerLength + 20 ) {
      if(VpnNatEngine.sLog) Log.v("AziLink", "Packet under minimum TCP length" );
      return;
    }
    
    TcpPacket pkt = new TcpPacket( d );
    TcpKey nk = pkt.getAddresses();
    
    TcpDriver te = mNat.get( nk );
    if( te == null && pkt.isConnectRequest() ) {      
      try {
        if(VpnNatEngine.sLog) Log.v("AziLink","Engine::read forming new TCP link");
        TcpToNio cb = new TcpToNio(this, mEngine.mSelectThread.mSelector);
        te = new TcpDriverImpl(cb, mEngine.mTimers, this);
        cb.setDriver(te);
        mNat.put( nk, te );
        te.newPacket(pkt);
      } catch( IOException e ) {}      
    } else if( te != null ) {
      if(VpnNatEngine.sLog) Log.v("AziLink","Engine::pass packet");
      te.newPacket(pkt);
    } else {
      if(VpnNatEngine.sLog) Log.v("AziLink", "Issuing a reset for an unknown TCP connection" );
      TcpPacket tp = new TcpPacket( nk, pkt.getAck(), pkt.getSeq() + pkt.getDataLength(), 1 );
      tp.setResetFlag();
      tp.complete();
      mEngine.vpnWrite( tp.mRaw.array(), (short) tp.mPacketLength );              
    }
  }

  /**
   * Callback from TcpDriver indicating that it wants to send a packet to the VPN
   */
  public void write(TcpPacket pkt) {
    mEngine.vpnWrite( pkt.mRaw.array(), (short) pkt.mPacketLength );
  }
}

Java Source Code List

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