/// <summary>
/// Write IP and UDP headers and payload data into a
/// byte array.
/// </summary>
/// <param name="pkt">Array of bytes representing
/// packet to be sent.</param>
/// <param name="offset">Offset of IP Header within
/// packet.</param>
/// <param name="ipHeader">IP header to be written
/// to packet.</param>
/// <param name="udpHeader">UDP header to be written
/// to packet.</param>
/// <param name="payload">Payload of UDP Packet.</param>
/// <param name="payloadOffset">The offset of start
/// of the payload data within the payload
/// array.</param>
/// <param name="payloadLength">The size of the payload data.</param>
public static void WriteUdpPacket(byte[] !pkt,
int offset,
IPFormat.IPHeader !ipHeader,
ref UdpHeader udpHeader,
byte[] payload,
int payloadOffset,
int payloadLength)
{
int udpStart = IPFormat.WriteIPHeader(pkt, offset, ipHeader);
int udpEnd = WriteUdpHeader(pkt, udpStart, ref udpHeader);
if (pkt != payload || udpEnd != payloadOffset)
{
Array.Copy(payload, payloadOffset,
pkt, udpEnd, payloadLength);
}
SetUdpChecksum(pkt, offset, ref udpHeader);
}
// a helper method to write the TCP segment (without data)
public static void WriteTcpSegment(byte[] !pktData,
ushort localPort,
ushort destPort,
uint ackSeq,
uint seq,
ushort wnd,
IPv4 sIP,
IPv4 dIP,
ushort dataLen,
bool isAck,
bool isSyn,
bool isRst,
bool isFin,
bool withOptions)
{
// now create the IP,TCP headers!
int start = EthernetFormat.Size;
// prepare it...
TcpFormat.TcpHeader tcpHeader = new TcpFormat.TcpHeader();
tcpHeader.sourcePort = localPort;
tcpHeader.destPort = destPort;
if (withOptions)
{
tcpHeader.off_res1 = 0x60;
}
else
{
tcpHeader.off_res1 = 0x50;
}
tcpHeader.ackSeq = ackSeq;
tcpHeader.seq = seq;
tcpHeader.window = wnd;
if (isFin)
{
TcpFormat.SetFIN(ref tcpHeader);
}
if (isSyn)
{
TcpFormat.SetSYN(ref tcpHeader);
}
if (isAck)
{
TcpFormat.SetACK(ref tcpHeader);
}
if (isRst)
{
TcpFormat.SetReset(ref tcpHeader);
}
IPFormat.IPHeader ipHeader = new IPFormat.IPHeader();
ipHeader.SetDefaults(IPFormat.Protocol.TCP);
ipHeader.totalLength = (ushort)(IPFormat.Size + TcpFormat.Size + dataLen);
ipHeader.srcAddr = sIP;
ipHeader.destAddr = dIP;
IPFormat.SetDontFragBit(ipHeader);
// write the ip header + ip checksum
start = IPFormat.WriteIPHeader(pktData, start, ipHeader);
// write TCP header, no checksum
start = TcpFormat.WriteTcpHeader(pktData, start, ref tcpHeader);
// calc the checksum...
TcpFormat.SetTcpChecksum(pktData, EthernetFormat.Size, ref tcpHeader);
}