TCP Packet Sender


2004-10-15 11:19:12 PM
delphi106
hi,
i want to build my own tcp packet incl. the header,
after a couple of hourse i got this source, but
i think there is a small bug in the checksum
calculation, so i can not send the generated packet.
can someone help me please?
unit unit1;
interface
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
StdCtrls, OleCtrls, Registry;
const
SrcIP = '192.168.0.1';
SrcPort = 4086;
DestIP = '192.168.0.2';
DestPort = 6969;
Max_Message = 4068;
Max_Packet = 4096;
type
TPacketBuffer = array[0..Max_Packet-1] of byte;
TForm1 = class(TForm)
Button1: TButton;
Memo1: TMemo;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
procedure SendIt;
end;
// Заголово?IP пакета
type
T_IP_Header = record
ip_verlen : Byte;
ip_tos : Byte;
ip_totallength : Word;
ip_id : Word;
ip_offset : Word;
ip_ttl : Byte;
ip_protocol : Byte;
ip_checksum : Word;
ip_srcaddr : LongWord;
ip_destaddr : LongWord;
end;
// Заголово?TCP пакета
type
T_TCP_Header = record
src_portno : Word;
dst_portno : Word;
turn_num:longword;
conf_num:longword;
data_offset:byte;
tcp_flags:byte;
tcp_window:word;
tcp_checksum:word;
tcp_priority:word;
end;
type
TPseudo= record
saddr:longword;
daddr:longword;
mbz:Byte;
proto:Byte;
tcplength:word;
end;
// Некоторы?об?влен? типо?для Winsock 2
u_char = Char;
u_short = Word;
u_int = Integer;
u_long = Longint;
SunB = packed record
s_b1, s_b2, s_b3, s_b4: u_char;
end;
SunW = packed record
s_w1, s_w2: u_short;
end;
in_addr = record
case integer of
0: (S_un_b: SunB);
1: (S_un_w: SunW);
2: (S_addr: u_long);
end;
TInAddr = in_addr;
Sockaddr_in = record
case Integer of
0: (sin_family: u_short;
sin_port: u_short;
sin_addr: TInAddr;
sin_zero: array[0..7] of Char);
1: (sa_family: u_short;
sa_data: array[0..13] of Char)
end;
TSockAddr = Sockaddr_in;
TSocket = u_int;
const
WSADESCRIPTION_LEN = 256;
WSASYS_STATUS_LEN = 128;
type
PWSAData = ^TWSAData;
WSAData = record // !!! also WSDATA
wVersion: Word;
wHighVersion: Word;
szDescription: array[0..WSADESCRIPTION_LEN] of Char;
szSystemStatus: array[0..WSASYS_STATUS_LEN] of Char;
iMaxSockets: Word;
lpVendorInfo: PChar;
end;
TWSAData = WSAData;
// Опреде?ем необходимы?функци?winsock 2
function closesocket(s: TSocket): Integer; stdcall;
function socket(af, Struct, protocol: Integer): TSocket; stdcall;
function sendto(s: TSocket; var Buf; len, flags: Integer; var addrto:
TSockAddr;
tolen: Integer): Integer; stdcall;{}
function setsockopt(s: TSocket; level, optname: Integer; optval: PChar;
optlen: Integer): Integer; stdcall;
function inet_addr(cp: PChar): u_long; stdcall; {PInAddr;} { TInAddr }
function htons(hostshort: u_short): u_short; stdcall;
function WSAGetLastError: Integer; stdcall;
function WSAStartup(wVersionRequired: word; var WSData: TWSAData): Integer;
stdcall;
function WSACleanup: Integer; stdcall;
const
AF_INET = 2; // internetwork: UDP, TCP, etc.
IP_HDRINCL = 2; // включаем заголово?IP пакета
SOCK_RAW = 3; // интерфей?raw-протокол?
IPPROTO_IP = 0; // dummy for IP
IPPROTO_TCP = 6; // tcp
IPPROTO_UDP = 17; // user datagram protocol
IPPROTO_RAW = 255; // raw IP паке?
INVALID_SOCKET = TSocket(not(0));
SOCKET_ERROR = -1;
var
Form1: TForm1;
implementation
// Импортируе?функци?Winsock 2
const WinSocket = 'WS2_32.DLL';
function closesocket; external winsocket name 'closesocket';
function socket; external winsocket name 'socket';
function sendto; external winsocket name 'sendto';
function setsockopt; external winsocket name 'setsockopt';
function inet_addr; external winsocket name 'inet_addr';
function htons; external winsocket name 'htons';
function WSAGetLastError; external winsocket name 'WSAGetLastError';
function WSAStartup; external winsocket name 'WSAStartup';
function WSACleanup; external winsocket name 'WSACleanup';
{$R *.DFM}
//
// Function: checksum
//
// Description:
// This function calculates the 16-bit one's complement sum
// for the supplied buffer
//
function CheckSum(var Buffer; Size : integer) : Word;
type
TWordArray = array[0..1] of Word;
var
ChkSum : LongWord;
i : Integer;
begin
ChkSum := 0;
i := 0;
while Size>1 do
begin
ChkSum := ChkSum + TWordArray(Buffer)[i];
inc(i);
Size := Size - SizeOf(Word);
end;
if Size=1 then
ChkSum := ChkSum + Byte(TWordArray(Buffer)[i]);
ChkSum := (ChkSum shr 16) + (ChkSum and $FFFF);
ChkSum := ChkSum + (Chksum shr 16);
Result := Word(ChkSum);
end;
procedure BuildHeaders(FromIP : string; iFromPort : Word; ToIP : string;
iToPort : Word; StrMessage : string; var Buf : TPacketBuffer;
var remote : TSockAddr; var iTotalSize: Word);
var
dwFromIP : LongWord;
dwToIP : LongWord;
iIPVersion : Word;
iIPSize : Word;
ipHdr : T_IP_Header;
tcpHdr : T_TCP_Header;
pHdr:TPseudo;
iTcpSize : Word;
iTcpChecksumSize : Word;
cksum : Word;
Ptr : ^Byte;
procedure IncPtr(Value : Integer);
begin
ptr := pointer(integer(ptr) + Value);
end;
begin
// преобразуе?ip адреса
dwFromIP := inet_Addr(PChar(FromIP));
dwToIP := inet_Addr(PChar(ToIP));
// Инициализируем заголово?IP пакета
//
iTotalSize := sizeof(ipHdr) + sizeof(tcpHdr) + length(strMessage);
iIPVersion := 4;
iIPSize := sizeof(ipHdr) div sizeof(LongWord);
//
// IP version goes in the high order 4 bits of ip_verlen. The
// IP header length (in 32-bit words) goes in the lower 4 bits.
//
ipHdr.ip_verlen := (iIPVersion shl 4) or iIPSize;
ipHdr.ip_tos := 0; // IP type of service
ipHdr.ip_totallength := htons(iTotalSize); // Total packet len
ipHdr.ip_id := 0; // Unique identifier: set to 0
ipHdr.ip_offset := htons($4000); // Fragment offset field
ipHdr.ip_ttl := 128; // время жизн?пакета
ipHdr.ip_protocol := $06; // Protocol(TCP)
ipHdr.ip_checksum := 0 ; // IP checksum
ipHdr.ip_srcaddr := dwFromIP; // Source address
ipHdr.ip_destaddr := dwToIP; // Destination address
//
// Инициализируем заголово?TCP пакета
//
iTcpSize := sizeof(tcpHdr) + length(strMessage);
tcpHdr.src_portno := htons(iFromPort) ;
tcpHdr.dst_portno := htons(iToPort) ;
tcpHdr.turn_num:= random($FFFFFFFF);
tcpHdr.conf_num:= random($FFFFFFFF);
tcpHdr.data_offset:=$50;
tcpHdr.tcp_flags:=$18;
tcpHdr.tcp_window:=$F0FA;
tcpHdr.tcp_checksum:={$A2B6}0;
tcpHdr.tcp_priority:=0;
//
pHdr.saddr:=ipHdr.ip_srcaddr;
pHdr.daddr:=ipHdr.ip_destaddr;
pHdr.mbz:=0;
pHdr.proto:=IPPROTO_TCP;
pHdr.tcplength:=htons(iTcpSize);
//
ptr := @buf[0];
FillChar(Buf, SizeOf(Buf), 0);
Move(pHdr,ptr^,SizeOf(pHdr)); IncPtr(SizeOf(pHdr));
{ Move(ipHdr, ptr^, SizeOf(ipHdr)); IncPtr(SizeOf(ipHdr));}
Move(tcpHdr, ptr^, SizeOf(tcpHdr)); IncPtr(SizeOf(tcpHdr));
Move(StrMessage[1], ptr^, length(StrMessage));
cksum := checksum(buf, Sizeof(pHdr)+SizeOf(tcpHdr)+Length(strMessage));
tcpHdr.tcp_checksum:= cksum;
//
//
FillChar(Buf, SizeOf(Buf), 0);
Ptr := @Buf[0];
Move(ipHdr, ptr^, SizeOf(ipHdr)); IncPtr(SizeOf(ipHdr));
Move(tcpHdr, ptr^, SizeOf(tcpHdr)); IncPtr(SizeOf(tcpHdr));
Move(StrMessage[1], ptr^, length(StrMessage));
// Apparently, this SOCKADDR_IN structure makes no difference.
// Whatever we put as the destination IP addr in the IP header
// is what goes. Specifying a different destination in remote
// will be ignored.
//
remote.sin_family := AF_INET;
remote.sin_port := htons(iToPort);
remote.sin_addr.s_addr := dwToIP;
end;
procedure TForm1.SendIt;
var
sh : TSocket;
bOpt : Integer;
ret : Integer;
Buf : TPacketBuffer;
Remote : TSockAddr;
Local : TSockAddr;
iTotalSize : Word;
wsdata : TWSAdata;
begin
// Startup Winsock 2
ret := WSAStartup($0002, wsdata);
if ret<>0 then
begin
memo1.lines.add('WSA Startup failed.');
exit;
end;
with memo1.lines do
begin
add('WSA Startup:');
add('Desc.: '+wsData.szDescription);
add('Status: '+wsData.szSystemStatus);
end;
try
// Создаё?соке?
sh := Socket(AF_INET, SOCK_RAW, IPPROTO_UDP);
if (sh = INVALID_SOCKET) then
begin
memo1.lines.add('Socket() failed: '+IntToStr(WSAGetLastError));
exit;
end;
Memo1.lines.add('Socket Handle = '+IntToStr(sh));
// Option: Header Include
bOpt := 1;
ret := SetSockOpt(sh, IPPROTO_IP, IP_HDRINCL, @bOpt, SizeOf(bOpt));
if ret = SOCKET_ERROR then
begin
Memo1.lines.add('setsockopt(IP_HDRINCL) failed:
'+IntToStr(WSAGetLastError));
exit;
end;
// строим паке?
BuildHeaders( SrcIP, SrcPort,
DestIP, DestPort,
'Test',
Buf, Remote, iTotalSize );
// Отправ?ем паке?
ret := SendTo(sh, buf, iTotalSize, 0, Remote, SizeOf(Remote));
if ret = SOCKET_ERROR then
Memo1.Lines.Add('sendto() failed: '+IntToStr(WSAGetLastError))
else
Memo1.Lines.Add('send '+IntToStr(ret)+' bytes.');
// Закрывае?соке?
CloseSocket(sh);
finally
// Закрывае?Winsock 2
WSACleanup;
end;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
SendIt;
end;
end.