/// <summary>
/// Deserializes an IcmpPacket instance from the specified sequence of
/// bytes.
/// </summary>
/// <param name="data">The sequence of bytes to deserialize an IcmpPacket
/// object from.</param>
/// <returns>A deserialized IpPacket object.</returns>
/// <exception cref="ArgumentNullException">Thrown if the data argument is
/// null.</exception>
/// <exception cref="SerializationException">Thrown if the ICMP packet could
/// not be deserialized from the specified byte array.</exception>
public static IcmpPacket Deserialize(byte[] data)
{
data.ThrowIfNull("data");
using (var ms = new MemoryStream(data)) {
using (var reader = new BinaryReader(ms)) {
var type = (IcmpType)reader.ReadByte();
var code = (IcmpCode)reader.ReadByte();
var checksum = reader.ReadUInt16();
var icmpData = reader.ReadAllBytes();
var packet = new IcmpPacket(type, code, checksum, icmpData);
if (ComputeChecksum(packet, true) != 0)
{
throw new SerializationException("The ICMP header is corrupted.");
}
return(packet);
}
}
}
/// <summary>
/// Computes the 16-bit checksum of the specified ICMP packet.
/// </summary>
/// <param name="packet">The packet to compute the checksum for.</param>
/// <param name="withChecksumField">true to include the packet's
/// checksum field in the calculation; otherwise false.</param>
/// <returns>The checksum of the specified ICMP packet.</returns>
/// <exception cref="ArgumentNullException">Thrown if the packet
/// argument is null.</exception>
public static ushort ComputeChecksum(IcmpPacket packet,
bool withChecksumField = false)
{
packet.ThrowIfNull("packet");
var bytes = new ByteBuilder()
.Append((byte)packet.Type)
.Append((byte)packet.Code)
.Append(withChecksumField ? packet.Checksum : (ushort)0)
.Append(packet.Data)
.ToArray();
var sum = 0;
// Treat the header bytes as a sequence of unsigned 16-bit values and
// sum them up.
for (var n = 0; n < bytes.Length; n += 2)
{
sum += BitConverter.ToUInt16(bytes, n);
}
// Use carries to compute the 1's complement sum.
sum = (sum >> 16) + (sum & 0xFFFF);
// Return the inverted 16-bit result.
return((ushort)(~sum));
}
/// <summary>
/// Computes the 16-bit checksum of the specified ICMP packet.
/// </summary>
/// <param name="packet">The packet to compute the checksum for.</param>
/// <param name="withChecksumField">true to include the packet's
/// checksum field in the calculation; otherwise false.</param>
/// <returns>The checksum of the specified ICMP packet.</returns>
/// <exception cref="ArgumentNullException">Thrown if the packet
/// argument is null.</exception>
public static ushort ComputeChecksum(IcmpPacket packet,
bool withChecksumField = false) {
packet.ThrowIfNull("packet");
var bytes = new ByteBuilder()
.Append((byte) packet.Type)
.Append((byte) packet.Code)
.Append(withChecksumField ? packet.Checksum : (ushort) 0)
.Append(packet.Data)
.ToArray();
var sum = 0;
// Treat the header bytes as a sequence of unsigned 16-bit values and
// sum them up.
for (var n = 0; n < bytes.Length; n += 2)
sum += BitConverter.ToUInt16(bytes, n);
// Use carries to compute the 1's complement sum.
sum = (sum >> 16) + (sum & 0xFFFF);
// Return the inverted 16-bit result.
return (ushort) (~sum);
}
/// <summary>
/// Deserializes an IcmpPacket instance from the specified sequence of
/// bytes.
/// </summary>
/// <param name="data">The sequence of bytes to deserialize an IcmpPacket
/// object from.</param>
/// <returns>A deserialized IpPacket object.</returns>
/// <exception cref="ArgumentNullException">Thrown if the data argument is
/// null.</exception>
/// <exception cref="SerializationException">Thrown if the ICMP packet could
/// not be deserialized from the specified byte array.</exception>
public static IcmpPacket Deserialize(byte[] data) {
data.ThrowIfNull("data");
using (var ms = new MemoryStream(data)) {
using (var reader = new BinaryReader(ms)) {
var type = (IcmpType) reader.ReadByte();
var code = (IcmpCode) reader.ReadByte();
var checksum = reader.ReadUInt16();
var icmpData = reader.ReadAllBytes();
var packet = new IcmpPacket(type, code, checksum, icmpData);
if(ComputeChecksum(packet, true) != 0)
throw new SerializationException("The ICMP header is corrupted.");
return packet;
}
}
}
