org.savarese.vserv.tcpip.ICMPPacket Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of vserv-tcpip Show documentation
Virtual Services TCP/IP, or VServ TCP/IP for short, is a Java library that enables you to easily manipulate IP and TCP packets.
The newest version!
/*
 * $Id: ICMPPacket.java 5347 2005-05-25 22:45:54Z dfs $
 *
 * Copyright 2004-2005 Daniel F. Savarese
 * Contact Information: http://www.savarese.org/contact.html
 *
 * 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.savarese.org/software/ApacheLicense-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 org.savarese.vserv.tcpip;

/**
 * ICMPPacket extends {@link IPPacket} to handle ICMP packets. The ICMP packet
 * structure is described in RFC 792.
 *
 * @author Daniel F. Savarese
 */
public abstract class ICMPPacket extends IPPacket {
  /**
   * Offset into the ICMP packet of the type header value.
   */
  public static final int OFFSET_TYPE = 0;

  /**
   * Offset into the ICMP packet of the code header value.
   */
  public static final int OFFSET_CODE = 1;

  /**
   * Offset into the ICMP packet of the ICMP checksum.
   */
  public static final int OFFSET_ICMP_CHECKSUM = 2;

  /**
   * Offset into the ICMP packet of the identifier header value.
   */
  public static final int OFFSET_IDENTIFIER = 4;

  /**
   * Offset into the ICMP packet of the sequence number header value.
   */
  public static final int OFFSET_SEQUENCE = 6;

  /**
   * The ICMP type number for an echo request.
   */
  public static final int TYPE_ECHO_REQUEST = 8;

  /**
   * The ICMP type number for an echo reply.
   */
  public static final int TYPE_ECHO_REPLY = 0;

  /**
   * The byte offset into the IP packet where the ICMP packet begins.
   */
  int _offset;

  /**
   * Creates a new ICMP packet of a given size.
   *
   * @param size The number of bytes in the packet.
   */
  public ICMPPacket(int size) {
    super(size);
    _offset = 0;
  }

  /**
   * Creates a new ICMP packet that is a copy of a given packet.
   *
   * @param packet The packet to replicate.
   */
  public ICMPPacket(ICMPPacket packet) {
    super(packet.size());
    copy(packet);
    _offset = packet._offset;
  }

  /**
   * @return The number of bytes in the ICMP packet header.
   */
  public abstract int getICMPHeaderByteLength();

  @Override
  public void setIPHeaderLength(int length) {
    super.setIPHeaderLength(length);
    _offset = getIPHeaderByteLength();
  }

  /**
   * @return The total number of bytes in the IP and ICMP headers.
   */
  public final int getCombinedHeaderByteLength() {
    return _offset + getICMPHeaderByteLength();
  }

  /**
   * @return The number of bytes in the ICMP data payload.
   */
  public final int getICMPDataByteLength() {
    return getIPPacketLength() - getCombinedHeaderByteLength();
  }

  /**
   * Sets the length of the ICMP data payload.
   *
   * @param length The length of the ICMP data payload in bytes.
   */
  public final void setICMPDataByteLength(int length) {
    if (length < 0) {
      length = 0;
    }

    setIPPacketLength(getCombinedHeaderByteLength() + length);
  }

  /**
   * @return The ICMP packet length. This is the size of the IP packet minus the
   * size of the IP header.
   */
  public final int getICMPPacketByteLength() {
    return getIPPacketLength() - _offset;
  }

  /**
   * Copies the contents of an ICMPPacket. If the current data array is of
   * insufficient length to store the contents, a new array is allocated.
   *
   * @param packet The TCPPacket to copy.
   */
  public final void copyData(ICMPPacket packet) {
    if (_data_.length < packet._data_.length) {
      byte[] data = new byte[packet._data_.length];
      System.arraycopy(_data_, 0, data, 0, getCombinedHeaderByteLength());
      _data_ = data;
    }
    int length = packet.getICMPDataByteLength();
    System.arraycopy(packet._data_, packet.getCombinedHeaderByteLength(), _data_, getCombinedHeaderByteLength(), length);
    setICMPDataByteLength(length);
  }

  @Override
  public void setData(byte[] data) {
    super.setData(data);
    _offset = getIPHeaderByteLength();
  }

  /**
   * @return The ICMP type header field.
   */
  public final int getType() {
    return (_data_[_offset + OFFSET_TYPE] & 0xff);
  }

  /**
   * Sets the ICMP type header field.
   *
   * @param type The new type.
   */
  public final void setType(int type) {
    _data_[_offset + OFFSET_TYPE] = (byte) (type & 0xff);
  }

  /**
   * @return The ICMP code header field.
   */
  public final int getCode() {
    return (_data_[_offset + OFFSET_CODE] & 0xff);
  }

  /**
   * Sets the ICMP code header field.
   *
   * @param code The new type.
   */
  public final void setCode(int code) {
    _data_[_offset + OFFSET_CODE] = (byte) (code & 0xff);
  }

  /**
   * @return The ICMP checksum.
   */
  public final int getICMPChecksum() {
    return (((_data_[_offset + OFFSET_ICMP_CHECKSUM] & 0xff) << 8) | (_data_[_offset + OFFSET_ICMP_CHECKSUM + 1] & 0xff));
  }

  /**
   * Computes the ICMP checksum, optionally updating the ICMP checksum header.
   *
   * @param update Specifies whether or not to update the ICMP checksum header after
   *               computing the checksum. A value of true indicates the header
   *               should be updated, a value of false indicates it should not be
   *               updated.
   * @return The computed ICMP checksum.
   */
  public final int computeICMPChecksum(boolean update) {
    return _computeChecksum_(_offset, _offset + OFFSET_ICMP_CHECKSUM, getIPPacketLength(), 0, update);
  }

  /**
   * Same as computeICMPChecksum(true);
   *
   * @return The computed ICMP checksum value.
   */
  public final int computeICMPChecksum() {
    return computeICMPChecksum(true);
  }
}