//Get SynAck Packet and increase the ACK number by one
public IncompletePacket SynAck()
{
var synAck = new IncompletePacket(SYNACK_SIZE);
connection.AckNumber++;
SetIpLayer(synAck);
SetTcpLayer(synAck, new byte[] { 2, 4, 5, 0x8c, 1, 1, 4, 2, 1, 3, 3, 7 });
return(synAck);
}
private void SetIpLayer(IncompletePacket packet)
{
var bytes = packet.Bytes;
bytes[0] = 69;
bytes[1] = 184;
bytes[2] = (byte)((bytes.Length >> 8) & 0xff);
bytes[3] = (byte)(bytes.Length & 0xff);
var id = connection.Identity();
bytes[4] = (byte)((id >> 8) & 0xff);
bytes[5] = (byte)(id & 0xff);
bytes[6] = 0;
bytes[7] = 0;
bytes[8] = 128;
bytes[9] = 6;
bytes[10] = 0;
bytes[11] = 0;
var srcIp = connection.SrcIp;
bytes[12] = (byte)(srcIp >> 24);
bytes[13] = (byte)((srcIp >> 16) & 0xff);
bytes[14] = (byte)((srcIp >> 8) & 0xff);
bytes[15] = (byte)(srcIp & 0xff);
var destIp = connection.DestIp;
bytes[16] = (byte)(destIp >> 24);
bytes[17] = (byte)((destIp >> 16) & 0xff);
bytes[18] = (byte)((destIp >> 8) & 0xff);
bytes[19] = (byte)(destIp & 0xff);
}
private void SetTcpLayer(IncompletePacket packet, byte[] options)
{
var bytes = packet.Bytes;
var tcpStartIndex = (bytes[0] & 15) * 4;
var index = tcpStartIndex;
var srcPort = connection.SrcPort;
bytes[index++] = (byte)((srcPort >> 8) & 0xff);
bytes[index++] = (byte)(srcPort & 0xff);
var destPort = connection.DestPort;
bytes[index++] = (byte)((destPort >> 8) & 0xff);
bytes[index++] = (byte)(destPort & 0xff);
uint seqNumber;
if (connection.CurrnetTcpState == OnewayConnection.TcpState.Closed)
{
seqNumber = (uint)(new Random().Next() % uint.MaxValue);
}
else
{
seqNumber = connection.SeqNumber;
}
bytes[index++] = (byte)(seqNumber >> 24);
bytes[index++] = (byte)((seqNumber >> 16) & 0xff);
bytes[index++] = (byte)((seqNumber >> 8) & 0xff);
bytes[index++] = (byte)(seqNumber & 0xff);
uint ackNumber;
if (connection.CurrnetTcpState == OnewayConnection.TcpState.Closed)
{
ackNumber = (uint)(new Random().Next() % uint.MaxValue);
}
else
{
ackNumber = connection.AckNumber;
}
bytes[index++] = (byte)(ackNumber >> 24);
bytes[index++] = (byte)((ackNumber >> 16) & 0xff);
bytes[index++] = (byte)((ackNumber >> 8) & 0xff);
bytes[index++] = (byte)(ackNumber & 0xff);
bytes[index++] = 80;
bytes[index++] = 18;
bytes[index++] = (32383 >> 8) & 0xff;
bytes[index++] = 32383 & 0xff;
bytes[index++] = 0;
bytes[index++] = 0;
bytes[index++] = 0;
bytes[index++] = 0;
for (int i = 0; i < options.Length; i++)
{
bytes[index + i] = options[i];
}
}
