C# 拆分数据包（碎片化）后-只有TCP数据包带有错误的TCP校验和

我正在使用

PcapDotNet

dll拆分数据包，似乎

TCP数据包

带有

错误的TCP校验和

，但

UDP数据包

接收正常

这是我收到

数据包并返回
IEnumerable
的代码：

private IEnumerable SplitPacket（数据包包，int numberOfFragments）
{
IpV4数据报IpV4数据报=packet.Ethernet.IpV4；
if（ipV4Datagram.Protocol==IpV4Protocol.Tcp | | ipV4Datagram.Protocol==IpV4Protocol.Udp）
{
EthernetLayer ethernet=（EthernetLayer）packet.ethernet.ExtractLayer（）；
ILayer layer=packet.Ethernet.IpV4.ExtractLayer（）；
IpV4Layer IpV4Layer=（IpV4Layer）packet.Ethernet.IpV4.ExtractLayer（）；
ipV4Layer.HeaderChecksum=null；
DateTime packetTimestamp=packet.Timestamp；
PayloadLayer有效负载=（PayloadLayer）packet.Ethernet.IpV4.payload.ExtractLayer（）；//提取数据
int totalLength=有效载荷长度；
int partialLength=totalLength/numberOfFragments；//将数据分割成更小的段
partialLength=（partialLength/8）*8；//确保它可以被8整除
if（partialLength==0）
部分长度=8；
//(http://en.wikipedia.org/wiki/IPv4#Fragmentation_and_reassembly)
ushort offset=0；//逐个发送
而（偏移量<总长度）
{
int fragmentLength=partialLength；//获取此片段的长度
IpV4FragmentationOptions=IpV4FragmentationOptions.MoreFragments；
if（offset+fragmentLength>=totalLength）//这是最后一个片段吗？如果需要，修剪长度
{
选项=IPV4碎片选项。无；
碎片长度=总长度-偏移量；
}
byte[]newBuffer=ipV4Datagram.Payload.ToArray（）；//将实际数据复制到新的缓冲区中
PayloadLayer newPayload=new PayloadLayer{Data=new Datagram（newBuffer，offset，fragmentLength）}；
ipV4Layer.Fragmentation=新IpV4Fragmentation（选项，偏移量）；//更改IP层碎片选项
数据包newPacket=null；
if（packet.Ethernet.IpV4.Protocol==IpV4Protocol.Tcp）
{
TcpLayer TcpLayer=（TcpLayer）packet.Ethernet.IpV4.Tcp.ExtractLayer（）；
tcpLayer.Checksum=null；
newPacket=PacketBuilder.Build（packetTimestamp、以太网、ipV4Layer、tcpLayer、newPayload）；
}
else if（packet.Ethernet.IpV4.Protocol==IpV4Protocol.Udp）
{
UdpLayer UdpLayer=（UdpLayer）packet.Ethernet.IpV4.Udp.ExtractLayer（）；
udpLayer.Checksum=null；
newPacket=PacketBuilder.Build（packetTimestamp、以太网、ipV4Layer、udpLayer、newPayload）；
}
产生返回新包；
//yield return PacketBuilder.Build（packetTimestamp，ethernet，ipV4Layer，tcpLayer，newPayload）；//return
偏移量+=（ushort）碎片长度；//下一个偏移量
}
}
}

知道为什么吗？
原始TCP数据包是由您的代码生成的还是由其他程序发送的？你是说输入数据包有一个错误的校验和，还是所有的输出都有一个错误的校验和？原始数据包来自没有错误校验和的Pcap文件，代码tcpLayer.checksum=null；应该计算校验和
    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();
            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
            if (partialLength == 0)
                partialLength = 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
                Packet newPacket = null;

                if (packet.Ethernet.IpV4.Protocol == IpV4Protocol.Tcp)
                {
                    TcpLayer tcpLayer = (TcpLayer)packet.Ethernet.IpV4.Tcp.ExtractLayer();
                    tcpLayer.Checksum = null;
                    newPacket = PacketBuilder.Build(packetTimestamp, ethernet, ipV4Layer, tcpLayer, newPayload);
                }
                else if (packet.Ethernet.IpV4.Protocol == IpV4Protocol.Udp)
                {
                    UdpLayer udpLayer = (UdpLayer)packet.Ethernet.IpV4.Udp.ExtractLayer();
                    udpLayer.Checksum = null;
                    newPacket = PacketBuilder.Build(packetTimestamp, ethernet, ipV4Layer, udpLayer, newPayload);
                }

                yield return newPacket;
                //yield return PacketBuilder.Build(packetTimestamp, ethernet, ipV4Layer, tcpLayer, newPayload); //return
                offset += (ushort)fragmentLength; //next offset
            }
        }
    }