Implementing filter functionality in C#

I have ported filter sample to C#. Please refer the code below:

using System;

using System.Runtime.InteropServices;

using System.Threading;

using System.Net;

using NdisApiWrapper;



namespace Filter

{

class Program

{

static void Main(string[] args)

{

try

{

if (args.Length < 2)

{

Console.WriteLine(

"Command line syntax:ntfilter.exe index scenario ntindex - network interface index.ntscenario - sample set of filters to load.ntYou can use ListAdapters to determine correct index.");

Console.WriteLine("Available Scenarios:");

Console.WriteLine("1 - Redirect only IPv4 DNS packets for processing in user mode.");

Console.WriteLine("2 - Redirect only HTTP(TCP port 80) packets for processing in user mode. Both IPv4 and IPv6 protocols.");

Console.WriteLine("3 - Drop all IPv4 ICMP packets. Redirect all other packets to user mode (default behaviour).");

Console.WriteLine("4 - Block IPv4 access to http://www.ntkernel.com. Pass all other packets without processing in user mode.");

Console.WriteLine("5 - Redirect only ARP/RARP packets to user mode. Pass all others.");

return;

}



var adapterIndex = uint.Parse(args[0]);

var scena = uint.Parse(args[1]);



var driverPtr = Ndisapi.OpenFilterDriver();

if (!Ndisapi.IsDriverLoaded(driverPtr))

{

Console.WriteLine("Driver not installed on this system of failed to load.");

return;

}



// Retrieve adapter list

var adapters = new TCP_AdapterList();

Ndisapi.GetTcpipBoundAdaptersInfo(driverPtr, ref adapters);



// Set tunnel mode for the selected network interface

var mode = new ADAPTER_MODE

{

dwFlags = Ndisapi.MSTCP_FLAG_SENT_TUNNEL | Ndisapi.MSTCP_FLAG_RECV_TUNNEL,

hAdapterHandle = adapters.m_nAdapterHandle[adapterIndex]

};



Ndisapi.SetAdapterMode(driverPtr, ref mode);



// Create and set event for the adapter

var manualResetEvent = new ManualResetEvent(false);

Ndisapi.SetPacketEvent(driverPtr, adapters.m_nAdapterHandle[adapterIndex], manualResetEvent.SafeWaitHandle);



var filtersTable = new STATIC_FILTER_TABLE();

filtersTable.m_StaticFilters = new STATIC_FILTER[256];



switch(scena)

{

case 1:

filtersTable.m_TableSize = 3;



//**************************************************************************************

// 1. Outgoing DNS requests filter: REDIRECT OUT UDP packets with destination PORT 53

// Common values

filtersTable.m_StaticFilters[0].m_Adapter = 0; // applied to all adapters

filtersTable.m_StaticFilters[0].m_ValidFields = Ndisapi.NETWORK_LAYER_VALID | Ndisapi.TRANSPORT_LAYER_VALID;

filtersTable.m_StaticFilters[0].m_FilterAction = Ndisapi.FILTER_PACKET_REDIRECT;

filtersTable.m_StaticFilters[0].m_dwDirectionFlags = Ndisapi.PACKET_FLAG_ON_SEND;



// Network layer filter

filtersTable.m_StaticFilters[0].m_NetworkFilter.m_dwUnionSelector = Ndisapi.IPV4;

filtersTable.m_StaticFilters[0].m_NetworkFilter.m_IPv4.m_ValidFields = Ndisapi.IP_V4_FILTER_PROTOCOL;

filtersTable.m_StaticFilters[0].m_NetworkFilter.m_IPv4.m_Protocol = 17; //IPPROTO_UDP



// Transport layer filter

filtersTable.m_StaticFilters[0].m_TransportFilter.m_dwUnionSelector = Ndisapi.TCPUDP;

filtersTable.m_StaticFilters[0].m_TransportFilter.m_TcpUdp.m_ValidFields = Ndisapi.TCPUDP_DEST_PORT;

filtersTable.m_StaticFilters[0].m_TransportFilter.m_TcpUdp.m_DestPort.m_StartRange = 53; // DNS

filtersTable.m_StaticFilters[0].m_TransportFilter.m_TcpUdp.m_DestPort.m_EndRange = 53;



//****************************************************************************************

// 2. Incoming DNS responses filter: REDIRECT IN UDP packets with source PORT 53

// Common values

filtersTable.m_StaticFilters[1].m_Adapter = 0; // applied to all adapters

filtersTable.m_StaticFilters[1].m_ValidFields = Ndisapi.NETWORK_LAYER_VALID | Ndisapi.TRANSPORT_LAYER_VALID;

filtersTable.m_StaticFilters[1].m_FilterAction = Ndisapi.FILTER_PACKET_REDIRECT;

filtersTable.m_StaticFilters[1].m_dwDirectionFlags = Ndisapi.PACKET_FLAG_ON_RECEIVE;



// Network layer filter

filtersTable.m_StaticFilters[1].m_NetworkFilter.m_dwUnionSelector = Ndisapi.IPV4;

filtersTable.m_StaticFilters[1].m_NetworkFilter.m_IPv4.m_ValidFields = Ndisapi.IP_V4_FILTER_PROTOCOL;

filtersTable.m_StaticFilters[1].m_NetworkFilter.m_IPv4.m_Protocol = 17;//IPPROTO_UDP



// Transport layer filter

filtersTable.m_StaticFilters[1].m_TransportFilter.m_dwUnionSelector = Ndisapi.TCPUDP;

filtersTable.m_StaticFilters[1].m_TransportFilter.m_TcpUdp.m_ValidFields = Ndisapi.TCPUDP_SRC_PORT;

filtersTable.m_StaticFilters[1].m_TransportFilter.m_TcpUdp.m_SourcePort.m_StartRange = 53; // DNS

filtersTable.m_StaticFilters[1].m_TransportFilter.m_TcpUdp.m_SourcePort.m_EndRange = 53;



//***************************************************************************************

// 3. Pass all packets (skipped by previous filters) without processing in user mode

// Common values

filtersTable.m_StaticFilters[2].m_Adapter = 0; // applied to all adapters

filtersTable.m_StaticFilters[2].m_ValidFields = 0;

filtersTable.m_StaticFilters[2].m_FilterAction = Ndisapi.FILTER_PACKET_PASS;

filtersTable.m_StaticFilters[2].m_dwDirectionFlags = Ndisapi.PACKET_FLAG_ON_RECEIVE | Ndisapi.PACKET_FLAG_ON_SEND;



break;



case 2:

filtersTable.m_TableSize = 5;



//**************************************************************************************

// 1. Outgoing HTTP requests filter: REDIRECT OUT TCP packets with destination PORT 80 IPv4

// Common values

filtersTable.m_StaticFilters[0].m_Adapter = 0; // applied to all adapters

filtersTable.m_StaticFilters[0].m_ValidFields = Ndisapi.NETWORK_LAYER_VALID | Ndisapi.TRANSPORT_LAYER_VALID;

filtersTable.m_StaticFilters[0].m_FilterAction = Ndisapi.FILTER_PACKET_REDIRECT;

filtersTable.m_StaticFilters[0].m_dwDirectionFlags = Ndisapi.PACKET_FLAG_ON_SEND;



// Network layer filter

filtersTable.m_StaticFilters[0].m_NetworkFilter.m_dwUnionSelector = Ndisapi.IPV4;

filtersTable.m_StaticFilters[0].m_NetworkFilter.m_IPv4.m_ValidFields = Ndisapi.IP_V4_FILTER_PROTOCOL;

filtersTable.m_StaticFilters[0].m_NetworkFilter.m_IPv4.m_Protocol = 6;//IPPROTO_TCP



// Transport layer filter

filtersTable.m_StaticFilters[0].m_TransportFilter.m_dwUnionSelector = Ndisapi.TCPUDP;

filtersTable.m_StaticFilters[0].m_TransportFilter.m_TcpUdp.m_ValidFields = Ndisapi.TCPUDP_DEST_PORT;

filtersTable.m_StaticFilters[0].m_TransportFilter.m_TcpUdp.m_DestPort.m_StartRange = 80; // HTTP

filtersTable.m_StaticFilters[0].m_TransportFilter.m_TcpUdp.m_DestPort.m_EndRange = 80;



//****************************************************************************************

// 2. Incoming HTTP responses filter: REDIRECT IN TCP packets with source PORT 80 IPv4

// Common values

filtersTable.m_StaticFilters[1].m_Adapter = 0; // applied to all adapters

filtersTable.m_StaticFilters[1].m_ValidFields = Ndisapi.NETWORK_LAYER_VALID | Ndisapi.TRANSPORT_LAYER_VALID;

filtersTable.m_StaticFilters[1].m_FilterAction = Ndisapi.FILTER_PACKET_REDIRECT;

filtersTable.m_StaticFilters[1].m_dwDirectionFlags = Ndisapi.PACKET_FLAG_ON_RECEIVE;



// Network layer filter

filtersTable.m_StaticFilters[1].m_NetworkFilter.m_dwUnionSelector = Ndisapi.IPV4;

filtersTable.m_StaticFilters[1].m_NetworkFilter.m_IPv4.m_ValidFields = Ndisapi.IP_V4_FILTER_PROTOCOL;

filtersTable.m_StaticFilters[1].m_NetworkFilter.m_IPv4.m_Protocol = 6; //IPPROTO_TCP



// Transport layer filter

filtersTable.m_StaticFilters[1].m_TransportFilter.m_dwUnionSelector = Ndisapi.TCPUDP;

filtersTable.m_StaticFilters[1].m_TransportFilter.m_TcpUdp.m_ValidFields = Ndisapi.TCPUDP_SRC_PORT;

filtersTable.m_StaticFilters[1].m_TransportFilter.m_TcpUdp.m_SourcePort.m_StartRange = 80; // HTTP

filtersTable.m_StaticFilters[1].m_TransportFilter.m_TcpUdp.m_SourcePort.m_EndRange = 80;



//****************************************************************************************

// 3. Outgoing HTTP requests filter: REDIRECT OUT TCP packets with destination PORT 80 IPv6

// Common values

filtersTable.m_StaticFilters[2].m_Adapter = 0; // applied to all adapters

filtersTable.m_StaticFilters[2].m_ValidFields = Ndisapi.NETWORK_LAYER_VALID | Ndisapi.TRANSPORT_LAYER_VALID;

filtersTable.m_StaticFilters[2].m_FilterAction = Ndisapi.FILTER_PACKET_REDIRECT;

filtersTable.m_StaticFilters[2].m_dwDirectionFlags = Ndisapi.PACKET_FLAG_ON_SEND;



// Network layer filter

filtersTable.m_StaticFilters[2].m_NetworkFilter.m_dwUnionSelector = Ndisapi.IPV6;

filtersTable.m_StaticFilters[2].m_NetworkFilter.m_IPv4.m_ValidFields = Ndisapi.IP_V6_FILTER_PROTOCOL;

filtersTable.m_StaticFilters[2].m_NetworkFilter.m_IPv4.m_Protocol = 6; //IPPROTO_TCP



// Transport layer filter

filtersTable.m_StaticFilters[2].m_TransportFilter.m_dwUnionSelector = Ndisapi.TCPUDP;

filtersTable.m_StaticFilters[2].m_TransportFilter.m_TcpUdp.m_ValidFields = Ndisapi.TCPUDP_DEST_PORT;

filtersTable.m_StaticFilters[2].m_TransportFilter.m_TcpUdp.m_DestPort.m_StartRange = 80; // HTTP

filtersTable.m_StaticFilters[2].m_TransportFilter.m_TcpUdp.m_DestPort.m_EndRange = 80;



//****************************************************************************************

// 4. Incoming HTTP responses filter: REDIRECT IN TCP packets with source PORT 80 IPv6

// Common values

filtersTable.m_StaticFilters[3].m_Adapter = 0; // applied to all adapters

filtersTable.m_StaticFilters[3].m_ValidFields = Ndisapi.NETWORK_LAYER_VALID | Ndisapi.TRANSPORT_LAYER_VALID;

filtersTable.m_StaticFilters[3].m_FilterAction = Ndisapi.FILTER_PACKET_REDIRECT;

filtersTable.m_StaticFilters[3].m_dwDirectionFlags = Ndisapi.PACKET_FLAG_ON_RECEIVE;



// Network layer filter

filtersTable.m_StaticFilters[3].m_NetworkFilter.m_dwUnionSelector = Ndisapi.IPV6;

filtersTable.m_StaticFilters[3].m_NetworkFilter.m_IPv4.m_ValidFields = Ndisapi.IP_V6_FILTER_PROTOCOL;

filtersTable.m_StaticFilters[3].m_NetworkFilter.m_IPv4.m_Protocol = 6;// IPPROTO_TCP



// Transport layer filter

filtersTable.m_StaticFilters[3].m_TransportFilter.m_dwUnionSelector = Ndisapi.TCPUDP;

filtersTable.m_StaticFilters[3].m_TransportFilter.m_TcpUdp.m_ValidFields = Ndisapi.TCPUDP_SRC_PORT;

filtersTable.m_StaticFilters[3].m_TransportFilter.m_TcpUdp.m_SourcePort.m_StartRange = 80; // HTTP

filtersTable.m_StaticFilters[3].m_TransportFilter.m_TcpUdp.m_SourcePort.m_EndRange = 80;



//***************************************************************************************

// 5. Pass all packets (skipped by previous filters) without processing in user mode

// Common values

filtersTable.m_StaticFilters[4].m_Adapter = 0; // applied to all adapters

filtersTable.m_StaticFilters[4].m_ValidFields = 0;

filtersTable.m_StaticFilters[4].m_FilterAction = Ndisapi.FILTER_PACKET_PASS;

filtersTable.m_StaticFilters[4].m_dwDirectionFlags = Ndisapi.PACKET_FLAG_ON_RECEIVE | Ndisapi.PACKET_FLAG_ON_SEND;



break;



case 3:

filtersTable.m_TableSize = 5;



//**************************************************************************************

// 1. Block all ICMP packets

// Common values

filtersTable.m_StaticFilters[0].m_Adapter = 0; // applied to all adapters

filtersTable.m_StaticFilters[0].m_ValidFields = Ndisapi.NETWORK_LAYER_VALID;

filtersTable.m_StaticFilters[0].m_FilterAction = Ndisapi.FILTER_PACKET_DROP;

filtersTable.m_StaticFilters[0].m_dwDirectionFlags = Ndisapi.PACKET_FLAG_ON_SEND | Ndisapi.PACKET_FLAG_ON_RECEIVE;



// Network layer filter

filtersTable.m_StaticFilters[0].m_NetworkFilter.m_dwUnionSelector = Ndisapi.IPV4;

filtersTable.m_StaticFilters[0].m_NetworkFilter.m_IPv4.m_ValidFields = Ndisapi.IP_V4_FILTER_PROTOCOL;

filtersTable.m_StaticFilters[0].m_NetworkFilter.m_IPv4.m_Protocol = 1;//IPPROTO_ICMP



break;



case 4:



filtersTable.m_TableSize = 2;



//**************************************************************************************

// 1. Outgoing HTTP requests filter: DROP OUT TCP packets with destination IP 190.120.229.77 PORT 80 (http://www.ntkernel.com)

// Common values

filtersTable.m_StaticFilters[0].m_Adapter = 0; // applied to all adapters

filtersTable.m_StaticFilters[0].m_ValidFields = Ndisapi.NETWORK_LAYER_VALID | Ndisapi.TRANSPORT_LAYER_VALID;

filtersTable.m_StaticFilters[0].m_FilterAction = Ndisapi.FILTER_PACKET_DROP;

filtersTable.m_StaticFilters[0].m_dwDirectionFlags = Ndisapi.PACKET_FLAG_ON_SEND;



// Network layer filter

var address = new in_addr();

var mask = new in_addr();



// IP address 190.120.229.77

address.s_b1 = 23;

address.s_b2 = 97;

address.s_b3 = 138;

address.s_b4 = 240;



// Network mask 255.255.255.255

mask.s_b1 = 255;

mask.s_b2 = 255;

mask.s_b3 = 255;

mask.s_b4 = 255;



filtersTable.m_StaticFilters[0].m_NetworkFilter.m_dwUnionSelector = Ndisapi.IPV4;

filtersTable.m_StaticFilters[0].m_NetworkFilter.m_IPv4.m_ValidFields = Ndisapi.IP_V4_FILTER_PROTOCOL | Ndisapi.IP_V4_FILTER_DEST_ADDRESS;

filtersTable.m_StaticFilters[0].m_NetworkFilter.m_IPv4.m_DestAddress.m_AddressType = Ndisapi.IP_SUBNET_V4_TYPE;

filtersTable.m_StaticFilters[0].m_NetworkFilter.m_IPv4.m_DestAddress.m_IpSubnet.m_Ip = address.s_addr; // IP address

filtersTable.m_StaticFilters[0].m_NetworkFilter.m_IPv4.m_DestAddress.m_IpSubnet.m_IpMask = mask.s_addr; // network mask

filtersTable.m_StaticFilters[0].m_NetworkFilter.m_IPv4.m_Protocol = 6; //IPPROTO_TCP



// Transport layer filter

filtersTable.m_StaticFilters[0].m_TransportFilter.m_dwUnionSelector = Ndisapi.TCPUDP;

filtersTable.m_StaticFilters[0].m_TransportFilter.m_TcpUdp.m_ValidFields = Ndisapi.TCPUDP_DEST_PORT;

filtersTable.m_StaticFilters[0].m_TransportFilter.m_TcpUdp.m_DestPort.m_StartRange = 80; // HTTP

filtersTable.m_StaticFilters[0].m_TransportFilter.m_TcpUdp.m_DestPort.m_EndRange = 80;



//***************************************************************************************

// 2. Pass all packets (skipped by previous filters) without processing in user mode

// Common values

filtersTable.m_StaticFilters[1].m_Adapter = 0; // applied to all adapters

filtersTable.m_StaticFilters[1].m_ValidFields = 0;

filtersTable.m_StaticFilters[1].m_FilterAction = Ndisapi.FILTER_PACKET_PASS;

filtersTable.m_StaticFilters[1].m_dwDirectionFlags = Ndisapi.PACKET_FLAG_ON_RECEIVE | Ndisapi.PACKET_FLAG_ON_SEND;



break;



case 5:



filtersTable.m_TableSize = 3;



//**************************************************************************************

// 1. Redirects all ARP packets to be processes by user mode application

// Common values

filtersTable.m_StaticFilters[0].m_Adapter = 0; // applied to all adapters

filtersTable.m_StaticFilters[0].m_ValidFields = Ndisapi.DATA_LINK_LAYER_VALID;

filtersTable.m_StaticFilters[0].m_FilterAction = Ndisapi.FILTER_PACKET_REDIRECT;

filtersTable.m_StaticFilters[0].m_dwDirectionFlags = Ndisapi.PACKET_FLAG_ON_SEND | Ndisapi.PACKET_FLAG_ON_RECEIVE;

filtersTable.m_StaticFilters[0].m_DataLinkFilter.m_dwUnionSelector = Ndisapi.ETH_802_3;

filtersTable.m_StaticFilters[0].m_DataLinkFilter.m_Eth8023Filter.m_ValidFields = Ndisapi.ETH_802_3_PROTOCOL;

filtersTable.m_StaticFilters[0].m_DataLinkFilter.m_Eth8023Filter.m_Protocol = 0x0806; // ETH_P_ARP;





//**************************************************************************************

// 1. Redirects all RARP packets to be processes by user mode application

// Common values

filtersTable.m_StaticFilters[1].m_Adapter = 0; // applied to all adapters

filtersTable.m_StaticFilters[1].m_ValidFields = Ndisapi.DATA_LINK_LAYER_VALID;

filtersTable.m_StaticFilters[1].m_FilterAction = Ndisapi.FILTER_PACKET_REDIRECT;

filtersTable.m_StaticFilters[1].m_dwDirectionFlags = Ndisapi.PACKET_FLAG_ON_SEND | Ndisapi.PACKET_FLAG_ON_RECEIVE;

filtersTable.m_StaticFilters[1].m_DataLinkFilter.m_dwUnionSelector = Ndisapi.ETH_802_3;

filtersTable.m_StaticFilters[1].m_DataLinkFilter.m_Eth8023Filter.m_ValidFields = Ndisapi.ETH_802_3_PROTOCOL;

filtersTable.m_StaticFilters[1].m_DataLinkFilter.m_Eth8023Filter.m_Protocol = 0x0806; // ETH_P_ARP;





//***************************************************************************************

// 2. Pass all packets (skipped by previous filters) without processing in user mode

// Common values

filtersTable.m_StaticFilters[2].m_Adapter = 0; // applied to all adapters

filtersTable.m_StaticFilters[2].m_ValidFields = 0;

filtersTable.m_StaticFilters[2].m_FilterAction = Ndisapi.FILTER_PACKET_PASS;

filtersTable.m_StaticFilters[2].m_dwDirectionFlags = Ndisapi.PACKET_FLAG_ON_RECEIVE | Ndisapi.PACKET_FLAG_ON_SEND;



break;

default:

Console.WriteLine ("Unknown test scenario specified. Exiting.");

return;

}



// Load filters into driver

Ndisapi.SetPacketFilterTable(driverPtr, ref filtersTable);



// Allocate and initialize packet structures

var request = new ETH_REQUEST();

var buffer = new INTERMEDIATE_BUFFER();

var bufferPtr = Marshal.AllocHGlobal(Marshal.SizeOf(buffer));



Win32Api.ZeroMemory(bufferPtr, Marshal.SizeOf(buffer));



request.hAdapterHandle = adapters.m_nAdapterHandle[adapterIndex];

request.EthPacket.Buffer = bufferPtr;



while(true)

{

manualResetEvent.WaitOne();



while (Ndisapi.ReadPacket(driverPtr, ref request))

{

buffer = (INTERMEDIATE_BUFFER)Marshal.PtrToStructure(bufferPtr, typeof(INTERMEDIATE_BUFFER));



WriteToConsole(buffer, bufferPtr);



if (buffer.m_dwDeviceFlags == Ndisapi.PACKET_FLAG_ON_SEND)

Ndisapi.SendPacketToAdapter(driverPtr, ref request);

else

Ndisapi.SendPacketToMstcp(driverPtr, ref request);

}



manualResetEvent.Reset();

}

}

catch (Exception ex)

{

Console.WriteLine(ex);

}

}



private unsafe static void WriteToConsole(INTERMEDIATE_BUFFER packetBuffer, IntPtr packetBufferPtr)

{

Console.WriteLine(packetBuffer.m_dwDeviceFlags == Ndisapi.PACKET_FLAG_ON_SEND ? "nMSTCP --> Interface" : "nInterface --> MSTCP");

Console.WriteLine("Packet size = {0}", packetBuffer.m_Length);



var ethernetHeader = (ETHER_HEADER*)((byte*)packetBufferPtr + (Marshal.OffsetOf(typeof(INTERMEDIATE_BUFFER), "m_IBuffer")).ToInt32());

Console.WriteLine(

"tETHERNET {0:X2}{1:X2}{2:X2}{3:X2}{4:X2}{5:X2} --> {6:X2}{7:X2}{8:X2}{9:X2}{10:X2}{11:X2}",

ethernetHeader->source.b1,

ethernetHeader->source.b2,

ethernetHeader->source.b3,

ethernetHeader->source.b4,

ethernetHeader->source.b5,

ethernetHeader->source.b6,

ethernetHeader->dest.b1,

ethernetHeader->dest.b2,

ethernetHeader->dest.b3,

ethernetHeader->dest.b4,

ethernetHeader->dest.b5,

ethernetHeader->dest.b6

);



switch (ntohs(ethernetHeader->proto))

{

case ETHER_HEADER.ETH_P_IP:

{

var ipHeader = (IPHeader*)((byte*)ethernetHeader + Marshal.SizeOf(typeof(ETHER_HEADER)));



var sourceAddress = new IPAddress(ipHeader->Src);

var destinationAddress = new IPAddress(ipHeader->Dest);



Console.WriteLine("tIP {0} --> {1} PROTOCOL: {2}", sourceAddress, destinationAddress, ipHeader->P);



var tcpHeader = ipHeader->P == IPHeader.IPPROTO_TCP ? (TcpHeader*)((byte*)ipHeader + ((ipHeader->IPLenVer) & 0xF) * 4) : null;

var udpHeader = ipHeader->P == IPHeader.IPPROTO_UDP ? (UdpHeader*)((byte*)ipHeader + ((ipHeader->IPLenVer) & 0xF) * 4) : null;



if (udpHeader != null)

Console.WriteLine("tUDP SRC PORT: {0} DST PORT: {1}", ntohs(udpHeader->th_sport), ntohs(udpHeader->th_dport));



if (tcpHeader != null)

Console.WriteLine("tTCP SRC PORT: {0} DST PORT: {1}", ntohs(tcpHeader->th_sport), ntohs(tcpHeader->th_dport));

}

break;

case ETHER_HEADER.ETH_P_RARP:

Console.WriteLine("tReverse Addr Res packet");

break;

case ETHER_HEADER.ETH_P_ARP:

Console.WriteLine("tAddress Resolution packet");

break;

}

}



static ushort ntohs(ushort netshort)

{

var hostshort = (ushort)(((netshort >> 8) & 0x00FF) | ((netshort << 8) & 0xFF00));

return hostshort;

}



[StructLayout(LayoutKind.Explicit, Size = 4)]

internal struct in_addr

{

[FieldOffset(0)]

internal byte s_b1;

[FieldOffset(1)]

internal byte s_b2;

[FieldOffset(2)]

internal byte s_b3;

[FieldOffset(3)]

internal byte s_b4;



[FieldOffset(0)]

internal ushort s_w1;

[FieldOffset(2)]

internal ushort s_w2;



[FieldOffset(0)]

internal uint S_addr;



/// 


/// can be used for most tcp & ip code

/// 


internal uint s_addr

{

get { return S_addr; }

}



/// 


/// host on imp

/// 


internal byte s_host

{

get { return s_b2; }

}



/// 


/// network

/// 


internal byte s_net

{

get { return s_b1; }

}



/// 


/// imp

/// 


internal ushort s_imp

{

get { return s_w2; }

}



/// 


/// imp #

/// 


internal byte s_impno

{

get { return s_b4; }

}



/// 


/// logical host

/// 


internal byte s_lh

{

get { return s_b3; }

}

}

}

}