Split packet (fragmentation) using PcapDotNet

Question

I try to Split packet (fragmentation) using PcapDotNet and found this

So this is my function:

private IEnumerable<Packet> SplitPacket(Packet packet, int numberOfFragments)
{
    IpV4Datagram ipV4Datagram = packet.Ethernet.IpV4;

    if (ipV4Datagram.Protocol == IpV4Protocol.Tcp || ipV4Datagram.Protocol == IpV4Protocol.Udp)
    {
        EthernetLayer ethernet = (EthernetLayer)packet.Ethernet.ExtractLayer();
        ILayer layer = packet.Ethernet.IpV4.ExtractLayer();
        TcpLayer tcpLayer = (TcpLayer)packet.Ethernet.IpV4.Tcp.ExtractLayer();
        tcpLayer.Checksum = null;
        IpV4Layer ipV4Layer = (IpV4Layer)packet.Ethernet.IpV4.ExtractLayer();
        ipV4Layer.HeaderChecksum = null;
        DateTime packetTimestamp = packet.Timestamp;
        PayloadLayer payload = (PayloadLayer)packet.Ethernet.IpV4.Payload.ExtractLayer(); //extract the data
        int totalLength = payload.Length;
        int partialLength = totalLength / numberOfFragments; //split data into smaller segments
        partialLength = (partialLength / 8) * 8; //make sure it's divisible with 8
        //(http://en.wikipedia.org/wiki/IPv4#Fragmentation_and_reassembly)
        ushort offset = 0; //send one by one

        while (offset < totalLength)
        {
            int fragmentLength = partialLength; //get length for this fragment
            IpV4FragmentationOptions options = IpV4FragmentationOptions.MoreFragments;

            if (offset + fragmentLength >= totalLength) //is this the last fragment ? trim length if needed
            {
                options = IpV4FragmentationOptions.None;
                fragmentLength = totalLength - offset;
            }

            byte[] newBuffer = ipV4Datagram.Payload.ToArray(); //copy the actual data into a new buffer
            PayloadLayer newPayload = new PayloadLayer { Data = new Datagram(newBuffer, offset, fragmentLength) };
            ipV4Layer.Fragmentation = new IpV4Fragmentation(options, offset); //change IP layer fragmentation options
            yield return PacketBuilder.Build(packetTimestamp, ethernet, ipV4Layer, tcpLayer, newPayload); //return
            offset += (ushort)fragmentLength; //next offset
        }
    }
}

The problem is that after play this file i can see the same number of packets like in the original Wireshark file so it mean that something not working and the protocol field in Wiresahrk recognized this packet as IPV4 and this is how this packet looks (i think i have build this packet in invalid way):

enter image description here

Split packet (fragmentation) using PcapDotNet

0 Answers0