/// <summary>
/// Parses a raw packet (e.g. from
/// <seealso cref="WinDivertRecv(IntPtr, WinDivertBuffer, ref WinDivertAddress, ref uint)" />)
/// into the various packet headers and/or payloads that may or may not be present.
/// </summary>
/// <param name="packet">
/// The packet to be parsed.
/// </param>
/// <param name="packetDataLength">
/// The total length of the packet pPacket.
/// </param>
/// <returns>
/// TRUE if all expected (non-NULL) outputs were present, FALSE otherwise. Note that FALSE
/// may sometimes be a legitimate return value, e.g., when both ppIpHdr and ppIpv6Hdr are non-NULL.
/// </returns>
/// <remarks>
/// Each output parameter may be NULL or non-NULL. For non-NULL parameters, this function
/// will write the pointer to the corresponding header/payload if it exists, or will write
/// NULL otherwise. Any non-NULL pointer that is returned Is pointer into the original
/// pPacket packet, and, there is enough space in pPacket to fit the header. This function
/// does not do any verification of the header/payload contents beyond checking the header
/// length and any other minimal information required for parsing.
/// </remarks>
public static WinDivertParseResult WinDivertHelperParsePacket(WinDivertBuffer packet, uint packetDataLength)
{
IPv4Header* _pip4Header = null;
IPv6Header* _pip6Header = null;
IcmpV4Header* _picmp4Header = null;
IcmpV6Header* _picmp6Header = null;
TcpHeader* _ptcpHdr = null;
UdpHeader* _pudpHdr = null;
byte* _pdataPtr;
uint _dataLen = 0;
var retVal = new WinDivertParseResult();
WinDivertNative.WinDivertHelperParsePacket(packet.BufferPointer, packetDataLength, &_pip4Header, &_pip6Header, &_picmp4Header, &_picmp6Header, &_ptcpHdr, &_pudpHdr, &_pdataPtr, ref _dataLen);
retVal._pip4Header = _pip4Header;
retVal._pip6Header = _pip6Header;
retVal._picmp4Header = _picmp4Header;
retVal._picmp6Header = _picmp6Header;
retVal._ptcpHdr = _ptcpHdr;
retVal._pudpHdr = _pudpHdr;
retVal._pdataPtr = _pdataPtr;
retVal._dataLen = _dataLen;
return retVal;
}
private static unsafe void RunDiversion(IntPtr handle)
{
var packet = new WinDivertBuffer();
var addr = new WinDivertAddress();
uint readLen = 0;
IPv4Header * ipv4Header = null;
IPv6Header * ipv6Header = null;
IcmpV4Header *icmpV4Header = null;
IcmpV6Header *icmpV6Header = null;
TcpHeader * tcpHeader = null;
UdpHeader * udpHeader = null;
Span <byte> packetData = null;
NativeOverlapped recvOverlapped;
IntPtr recvEvent = IntPtr.Zero;
uint recvAsyncIoLen = 0;
do
{
if (s_running)
{
packetData = null;
readLen = 0;
recvAsyncIoLen = 0;
recvOverlapped = new NativeOverlapped();
recvEvent = Kernel32.CreateEvent(IntPtr.Zero, false, false, IntPtr.Zero);
if (recvEvent == IntPtr.Zero)
{
Console.WriteLine("Failed to initialize receive IO event.");
continue;
}
addr.Reset();
recvOverlapped.EventHandle = recvEvent;
Console.WriteLine("Read");
if (!WinDivert.WinDivertRecvEx(handle, packet, 0, ref addr, ref readLen, ref recvOverlapped))
{
var error = Marshal.GetLastWin32Error();
// 997 == ERROR_IO_PENDING
if (error != 997)
{
Console.WriteLine(string.Format("Unknown IO error ID {0} while awaiting overlapped result.", error));
Kernel32.CloseHandle(recvEvent);
continue;
}
while (Kernel32.WaitForSingleObject(recvEvent, 1000) == (uint)WaitForSingleObjectResult.WaitTimeout)
{
;
}
if (!Kernel32.GetOverlappedResult(handle, ref recvOverlapped, ref recvAsyncIoLen, false))
{
Console.WriteLine("Failed to get overlapped result.");
Kernel32.CloseHandle(recvEvent);
continue;
}
readLen = recvAsyncIoLen;
}
Kernel32.CloseHandle(recvEvent);
Console.WriteLine("Read packet {0}", readLen);
var parseResult = WinDivert.WinDivertHelperParsePacket(packet, readLen);
ipv4Header = parseResult.IPv4Header;
ipv6Header = parseResult.IPv6Header;
icmpV4Header = parseResult.IcmpV4Header;
icmpV6Header = parseResult.IcmpV6Header;
tcpHeader = parseResult.TcpHeader;
udpHeader = parseResult.UdpHeader;
if (addr.Direction == WinDivertDirection.Inbound)
{
Console.WriteLine("inbound!");
}
if (ipv4Header != null && tcpHeader != null)
{
Console.WriteLine($"V4 TCP packet {addr.Direction} from {ipv4Header->SrcAddr}:{tcpHeader->SrcPort.ReverseBytes()} to {ipv4Header->DstAddr}:{tcpHeader->DstPort.ReverseBytes()}");
}
else if (ipv6Header != null && tcpHeader != null)
{
Console.WriteLine($"V4 TCP packet {addr.Direction} from {ipv6Header->SrcAddr}:{tcpHeader->SrcPort.ReverseBytes()} to {ipv6Header->DstAddr}:{tcpHeader->DstPort.ReverseBytes()}");
}
if (packetData != null)
{
Console.WriteLine("Packet has {0} byte payload.", packetData.Length);
}
Console.WriteLine($"{nameof(addr.Direction)} - {addr.Direction}");
Console.WriteLine($"{nameof(addr.Impostor)} - {addr.Impostor}");
Console.WriteLine($"{nameof(addr.Loopback)} - {addr.Loopback}");
Console.WriteLine($"{nameof(addr.IfIdx)} - {addr.IfIdx}");
Console.WriteLine($"{nameof(addr.SubIfIdx)} - {addr.SubIfIdx}");
Console.WriteLine($"{nameof(addr.Timestamp)} - {addr.Timestamp}");
Console.WriteLine($"{nameof(addr.PseudoIPChecksum)} - {addr.PseudoIPChecksum}");
Console.WriteLine($"{nameof(addr.PseudoTCPChecksum)} - {addr.PseudoTCPChecksum}");
Console.WriteLine($"{nameof(addr.PseudoUDPChecksum)} - {addr.PseudoUDPChecksum}");
// Console.WriteLine(WinDivert.WinDivertHelperCalcChecksums(packet, ref addr, WinDivertChecksumHelperParam.All));
if (!WinDivert.WinDivertSendEx(handle, packet, readLen, 0, ref addr))
{
Console.WriteLine("Write Err: {0}", Marshal.GetLastWin32Error());
}
}
}while (s_running);
}
