ARPFields.cs

/*
This file is part of PacketDotNet

PacketDotNet is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

PacketDotNet 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 Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License
along with PacketDotNet.  If not, see <http://www.gnu.org/licenses/>.
*/
/*
 *  Copyright 2009 Chris Morgan <chmorgan@gmail.com>
 */
namespace PacketDotNet
{
    /// <summary> IP protocol field encoding information.
    /// 
    /// </summary>
    /// FIXME: These fields are partially broken because they assume the offset for
    /// several fields and the offset is actually based on the accumulated offset
    /// into the structure determined by the fields that indicate sizes
    public class ARPFields
    {
        /// <summary> Type code for ethernet addresses.</summary>
        public readonly static int EthernetProtocolType = 0x0001;
        /// <summary> Type code for MAC addresses.</summary>
        public readonly static int IPv4ProtocolType = 0x0800;

        /// <summary> Operation type length in bytes.</summary>
        public readonly static int OperationLength = 2;
        /// <summary>
        /// The length of the address type fields in bytes,
        /// eg. the length of hardware type or protocol type
        /// </summary>
        public readonly static int AddressTypeLength = 2;
        /// <summary>
        /// The length of the address length fields in bytes.
        /// </summary>
        public readonly static int AddressLengthLength = 1;
        /// <summary> Position of the hardware address type.</summary>
        public readonly static int HardwareAddressTypePosition = 0;
        /// <summary> Position of the protocol address type.</summary>
        public readonly static int ProtocolAddressTypePosition;
        /// <summary> Position of the hardware address length.</summary>
        public readonly static int HardwareAddressLengthPosition;
        /// <summary> Position of the protocol address length.</summary>
        public readonly static int ProtocolAddressLengthPosition;
        /// <summary> Position of the operation type.</summary>
        public readonly static int OperationPosition;
        /// <summary> Position of the sender hardware address.</summary>
        public readonly static int SenderHardwareAddressPosition;
        /// <summary> Position of the sender protocol address.</summary>
        public readonly static int SenderProtocolAddressPosition;
        /// <summary> Position of the target hardware address.</summary>
        public readonly static int TargetHardwareAddressPosition;
        /// <summary> Position of the target protocol address.</summary>
        public readonly static int TargetProtocolAddressPosition;
        /// <summary> Total length in bytes of an ARP header.</summary>
        public readonly static int HeaderLength; // == 28

        static ARPFields()
        {
            // NOTE: We use IPv4Fields_Fields.IP_ADDRESS_WIDTH because arp packets are
            //       only used in IPv4 networks. Neighbor discovery is used with IPv6
            //FIXME: we really should use the sizes given by the length fields to determine
            // the position offsets here instead of assuming the hw address is an ethernet mac address
            ProtocolAddressTypePosition = HardwareAddressTypePosition + AddressTypeLength;
            HardwareAddressLengthPosition = ProtocolAddressTypePosition + AddressTypeLength;
            ProtocolAddressLengthPosition = HardwareAddressLengthPosition + AddressLengthLength;
            OperationPosition = ProtocolAddressLengthPosition + AddressLengthLength;
            SenderHardwareAddressPosition = OperationPosition + OperationLength;
            SenderProtocolAddressPosition = SenderHardwareAddressPosition + EthernetFields.MacAddressLength;
            TargetHardwareAddressPosition = SenderProtocolAddressPosition + IPv4Fields.AddressLength;
            TargetProtocolAddressPosition = TargetHardwareAddressPosition + EthernetFields.MacAddressLength;

            HeaderLength = TargetProtocolAddressPosition + IPv4Fields.AddressLength;
        }
    }
}