/// <summary>
/// Create a UDP header which will be added to the head of the udp payload
/// </summary>
/// <param name="realEndPoint">
/// The real IP endpoint that udp payload should be sent to
/// </param>
/// <returns>
/// bytes of the udp header
/// </returns>
public static byte[] CreateUdpHeader(IPEndPoint realEndPoint)
{
int headerStructLength = Marshal.SizeOf(typeof(LspUdpHeader));
LspUdpHeader udpHeader = new LspUdpHeader();
udpHeader.Port = realEndPoint.Port;
udpHeader.AddressFamily = (int)realEndPoint.AddressFamily;
string strAddress = realEndPoint.Address.ToString();
byte[] addressBytes = System.Text.Encoding.ASCII.GetBytes(strAddress);
udpHeader.HeaderLength = headerStructLength + addressBytes.Length;
//write header and address to a byte array
IntPtr p = Marshal.AllocHGlobal(headerStructLength);
Marshal.StructureToPtr(udpHeader, p, true);
byte[] ret = new byte[headerStructLength + addressBytes.Length];
Marshal.Copy(p, ret, 0, headerStructLength);
Marshal.FreeHGlobal(p);
Array.Copy(addressBytes, 0, ret, headerStructLength, addressBytes.Length);
return(ret);
}
public static void Visit(
IVisitorUdpReceiveLoop host, ITransport server,
UdpClient udpClient, ThreadManager thread, bool isLspHooked)
{
byte[] data = null;
// get the endpoint of tcp client.
IPEndPoint localEP = host.LspHookedLocalEP;
while (!thread.ShouldExit)
{
try
{
// received data from server.
IPEndPoint remoteEP = null;
data = udpClient.Receive(ref remoteEP);
if (data == null)
{
break;
}
if (isLspHooked)
{
int numBytesReceived = data.Length;
if (numBytesReceived < Marshal.SizeOf(typeof(LspUdpHeader)))
{
throw new FormatException("Invalid LSP udp packet received");
}
//Get udp header
byte[] udpHeaderBuffer = ArrayUtility.SubArray(data, 0, Marshal.SizeOf(typeof(LspUdpHeader)));
IntPtr p = Marshal.AllocHGlobal(udpHeaderBuffer.Length);
Marshal.Copy(udpHeaderBuffer, 0, p, udpHeaderBuffer.Length);
LspUdpHeader udpHeader = (LspUdpHeader)Marshal.PtrToStructure(p, typeof(LspUdpHeader));
Marshal.FreeHGlobal(p);
//get address
byte[] srcAddressArray = ArrayUtility.SubArray <byte>(data,
Marshal.SizeOf(typeof(LspUdpHeader)), udpHeader.HeaderLength -
Marshal.SizeOf(typeof(LspUdpHeader)));
string srcAddress = Encoding.ASCII.GetString(srcAddressArray);
//replacement
numBytesReceived = numBytesReceived - udpHeader.HeaderLength;
byte[] msgBody = new byte[numBytesReceived];
Array.Copy(data, udpHeader.HeaderLength, msgBody, 0, numBytesReceived);
//endPoint is real remote client endpoint, remoteEP is LspDll's endpoint
IPEndPoint endPoint = new IPEndPoint(IPAddress.Parse(srcAddress), udpHeader.Port);
//map from the real endpoint to the lsp dll endpoint
//when sending response to the real endpoint, response will be sent to the lsp dll endpoint
//and the lsp dll will relay it to the real endpoint
LspConsole.Instance.SetMappedIPEndPoint(
(IPEndPoint)udpClient.Client.LocalEndPoint, (IPEndPoint)endPoint,
(IPEndPoint)remoteEP, StackTransportType.Udp);
host.VisitorAddReceivedData(msgBody, localEP, (IPEndPoint)endPoint);
}
else
{
host.VisitorAddReceivedData(data, localEP, remoteEP);
}
}
catch (Exception ex)
{
// handle exception event, return.
server.AddEvent(new TransportEvent(EventType.Exception, localEP, ex));
break;
}
}
}