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我正在使用PcapDorNetDLL，并尝试分割我的流量：

private IEnumerable<Packet> SplitPacket(Packet packet, int numberOfFragments)
        {
            IpV4Datagram ipV4Datagram = packet.Ethernet.IpV4;
            Datagram datagram = packet.Ethernet.IpV4.Payload;
            TransportLayer transportlayer = GetTransportLayer(packet);
            if (transportlayer != null)
            {
                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
                    transportlayer.Checksum = null;
                    yield return PacketBuilder.Build(packetTimestamp, ethernet, ipV4Layer, transportlayer, newPayload);
                    offset += (ushort)fragmentLength; //next offset
                }
            }
        }

我的输入数据包是TCP packet，输出是 4 个数据包：3 个IPv4 packets，最后一个数据包是，TCP但我收到的这个数据包在 TCP 层字段下显示此消息：

Checksum: 0x5d17 [不正确，应该是0xabb7（可能是“TCP checksum offload”引起的？）]

使用 UDP 似乎每个 UDP 数据包也分成几个 IPv4 数据包，最后一个是 UDP，但在 UDP 情况下它看起来很好。我做错了什么？

请查看原始数据包和分片：http ://www.filedropper.com/desktop_122

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1 回答 1

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Pcap.Net 站点中似乎有一个非常相似的问题，并对代码进行了更正。

我相信遵循那里的建议将有助于解决您的问题。

于 2015-02-13T09:54:14.627 回答