/// <summary>
/// Process request
/// </summary>
/// <param name="ip">IP</param>
/// <param name="id">ID</param>
/// <param name="seq">Sequence number</param>
/// <param name="data">Packet data</param>
/// <param name="length">Packet length</param>
private static unsafe void EchoReply(byte[] ip, ushort id, ushort seq, byte *data, int length)
{
NetPacketDesc *packet = NetPacket.Alloc();
ICMPHeader *hdr = (ICMPHeader *)(packet->buffer + packet->start);
hdr->Type = TYPE_ECHO_REPLY;
hdr->ID = id;
hdr->SeqNum = seq;
hdr->Code = 0;
hdr->CheckSum = 0;
packet->end += (short)sizeof(ICMPHeader);
Memory.Memcpy(packet->buffer + packet->end, data, length);
packet->end += (short)length;
hdr->CheckSum = NetworkTools.Checksum((byte *)(packet->buffer + packet->start), sizeof(ICMPHeader) + length);
IPV4.Send(packet, ip, 0x01);
NetPacket.Free(packet);
}
/// <summary>
/// Finish header and create checksum
/// </summary>
/// <param name="packet"></param>
/// <param name="header"></param>
/// <param name="sourceIp"></param>
/// <param name="packetLength"></param>
/// <param name="dataLength"></param>
/// <returns></returns>
private static unsafe bool FinishHeader(NetPacketDesc *packet, TCPHeader *header, byte[] sourceIp, int packetLength, int dataLength)
{
// Welp!
if (packetLength % 4 != 0)
{
return(false);
}
header->Length = (byte)((packetLength / 4) << 4);
ushort size = (ushort)packetLength;
size += (ushort)sizeof(TCPChecksum);
// Let's introduce some junk (i love that :))
TCPChecksum *checksumHeader = (TCPChecksum *)(packet->buffer + packet->start - sizeof(TCPChecksum));
Memory.Memcpy(checksumHeader->SrcIP, Network.Settings->IP, 4);
Memory.Memcpy(checksumHeader->DstIP, Util.ObjectToVoidPtr(sourceIp), 4);
checksumHeader->Protocol = PROTOCOL_TCP;
checksumHeader->Reserved = 0;
checksumHeader->Length = Byte.ReverseBytes((ushort)((ushort)packetLength + dataLength));
byte *ptr = packet->buffer + packet->start - sizeof(TCPChecksum);
header->Checksum = NetworkTools.Checksum(ptr, size + dataLength);
return(true);
}
/// <summary>
/// Add IPV4 header to packet
/// </summary>
/// <param name="packet">Packet structure</param>
/// <param name="sourceIP">Source IP</param>
/// <param name="destIP">Destination IP</param>
/// <param name="protocol">Protocol</param>
/// <returns></returns>
private static unsafe IPV4Header *addHeader(NetPacketDesc *packet, byte[] sourceIP, byte[] destIP, byte protocol)
{
packet->start -= (short)sizeof(IPV4Header);
IPV4Header *header = (IPV4Header *)(packet->buffer + packet->start);
header->Version = (4 << 4) | 5;
header->ServicesField = 0;
header->totalLength = Byte.ReverseBytes((ushort)(packet->end - packet->start));
header->ID = Byte.ReverseBytes(0xa836); // TODO: FIX THIS!
header->FragmentOffset = 0;
header->TTL = 250;
header->Protocol = protocol;
// The checksum calculation needs to be done with header checksum filled in as zero
// then it is filled in later
header->HeaderChecksum = 0;
Memory.Memcpy(header->Source, Util.ObjectToVoidPtr(sourceIP), 4);
Memory.Memcpy(header->Destination, Util.ObjectToVoidPtr(destIP), 4);
header->HeaderChecksum = (NetworkTools.Checksum(packet->buffer + packet->start, sizeof(IPV4Header)));
return(header);
}
