/// <summary>
/// Tries to read the option from a buffer starting from the option value (after the type and length).
/// </summary>
/// <param name="buffer">The buffer to read the option from.</param>
/// <param name="offset">The offset to the first byte to read the buffer. Will be incremented by the number of bytes read.</param>
/// <param name="valueLength">The number of bytes the option value should take according to the length field that was already read.</param>
/// <returns>On success - the complex option read. On failure - null.</returns>
Option IOptionComplexFactory.CreateInstance(byte[] buffer, ref int offset, byte valueLength)
{
if (valueLength != OptionValueLength)
{
return(null);
}
ushort identification = buffer.ReadUShort(ref offset, Endianity.Big);
ushort outboundHopCount = buffer.ReadUShort(ref offset, Endianity.Big);
ushort returnHopCount = buffer.ReadUShort(ref offset, Endianity.Big);
IpV4Address originatorIpAddress = buffer.ReadIpV4Address(ref offset, Endianity.Big);
return(new IpV4OptionTraceRoute(identification, outboundHopCount, returnHopCount, originatorIpAddress));
}
internal static IpV4Address CalculateDestination(IpV4Address currentDestination, IpV4Options options)
{
if (options == null)
{
return(currentDestination);
}
IpV4OptionRoute destinationControllerRouteOption =
(IpV4OptionRoute)options.OptionsCollection.FirstOrDefault(option => option.OptionType == IpV4OptionType.LooseSourceRouting ||
option.OptionType == IpV4OptionType.StrictSourceRouting);
if (destinationControllerRouteOption != null)
{
ReadOnlyCollection <IpV4Address> route = destinationControllerRouteOption.Route;
if (destinationControllerRouteOption.PointedAddressIndex < route.Count)
{
return(route[route.Count - 1]);
}
}
return(currentDestination);
}
private static ushort CalculateTransportChecksum(byte[] buffer, int offset, int headerLength, ushort transportLength, int transportChecksumOffset, bool isChecksumOptional, IpV4Address destination)
{
int offsetAfterChecksum = offset + headerLength + transportChecksumOffset + sizeof(ushort);
uint sum = Sum16Bits(buffer, offset + Offset.Source, IpV4Address.SizeOf) +
Sum16Bits(destination) +
buffer[offset + Offset.Protocol] + transportLength +
Sum16Bits(buffer, offset + headerLength, transportChecksumOffset) +
Sum16Bits(buffer, offsetAfterChecksum, transportLength - transportChecksumOffset - sizeof(ushort));
ushort checksumResult = Sum16BitsToChecksum(sum);
if (checksumResult == 0 && isChecksumOptional)
{
return(0xFFFF);
}
return(checksumResult);
}
internal static void WriteTransportChecksum(byte[] buffer, int offset, int headerLength, ushort transportLength, int transportChecksumOffset, bool isChecksumOptional, ushort?checksum, IpV4Address destination)
{
ushort checksumValue =
checksum == null
? CalculateTransportChecksum(buffer, offset, headerLength, transportLength, transportChecksumOffset, isChecksumOptional, destination)
: checksum.Value;
buffer.Write(offset + headerLength + transportChecksumOffset, checksumValue, Endianity.Big);
}
/// <summary>
/// Create the trace route option from the trace route option values.
/// </summary>
/// <param name="identification">
/// An arbitrary number used by the originator of the Outbound Packet to identify the ICMP Traceroute messages.
/// It is NOT related to the ID number in the IP header.
/// </param>
/// <param name="outboundHopCount">
/// Outbound Hop Count (OHC)
/// The number of routers through which the Outbound Packet has passed.
/// This field is not incremented by the Outbound Packet's destination.
/// </param>
/// <param name="returnHopCount"></param>
/// Return Hop Count (RHC)
/// The number of routers through which the Return Packet has passed.
/// This field is not incremented by the Return Packet's destination.
/// <param name="originatorIpAddress">
/// The IP address of the originator of the Outbound Packet.
/// This isneeded so the routers know where to send the ICMP Traceroute message for Return Packets.
/// It is also needed for Outbound Packets which have a Source Route option.
/// </param>
public IpV4OptionTraceRoute(ushort identification, ushort outboundHopCount, ushort returnHopCount, IpV4Address originatorIpAddress)
: base(IpV4OptionType.TraceRoute)
{
_identification = identification;
_outboundHopCount = outboundHopCount;
_returnHopCount = returnHopCount;
_originatorIpAddress = originatorIpAddress;
}
/// <summary>
/// Two addresses are equal if the have the exact same value.
/// </summary>
public bool Equals(IpV4Address other)
{
return(ToValue() == other.ToValue());
}
/// <summary>
/// Create a timed address accroding to the given values.
/// </summary>
/// <param name="address">The address in the pair.</param>
/// <param name="timeOfDay">The time passed since midnight UT.</param>
public IpV4OptionTimedAddress(IpV4Address address, IpV4TimeOfDay timeOfDay)
{
_address = address;
_timeOfDay = timeOfDay;
}