我可以构建一个原始 IP 数据包，其中包含一个包含有用数据(DNS 请求)的 UDP 数据包。 我可以发送它，并看到它是在 Wireshark 中发送的。 Wireshark 将其解析为合法的 DNS 请求，因此除了 DNS 答案之外，一切看起来都很顺利 - 我没有得到任何答案，什么也没有。
我的代码(抱歉，它与产品级代码相去甚远):
var
D:WSAData;
SendSocket, ReceiveSocket: TSocket;
bytes: Integer;
bOpt : Integer;
Buf : TPacketBuffer;
SendAddrIn : TSockAddrIn;
RecvAddIn: TSockAddrIn;
sockAddrSize: Integer;
iTotalSize : Word;
begin
try
if WSAStartup($202, D)<>0 then
begin
writeln('error..');
exit;
end;
SendSocket:=socket(AF_INET, SOCK_RAW, IPPROTO_RAW);
if SendSocket=INVALID_SOCKET then
writeln(WSAGetLastError);
// Option: Header Include
bOpt := 1;
bytes := SetSockOpt(SendSocket, IPPROTO_IP, IP_HDRINCL, @bOpt, SizeOf(bOpt));
if bytes = SOCKET_ERROR then
begin
Writeln('setsockopt(IP_HDRINCL) failed: '+IntToStr(WSAGetLastError));
exit;
end;
BuildHeaders(SrcIP, SrcPort,
DestIP, DestPort,
dns,
Buf, SendAddrIn, iTotalSize);
Writeln(inttostr(iTotalSize) + ' bytes to send');
bytes := SendTo(SendSocket, buf, iTotalSize, 0, @SendAddrIn, SizeOf(SendAddrIn));
if bytes = SOCKET_ERROR then
writeln('sendto() failed: '+IntToStr(WSAGetLastError))
else
writeln('send '+IntToStr(bytes)+' bytes.');
ReceiveSocket:=socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
RecvAddIn.sin_addr.s_addr := htonl(0);
RecvAddIn.sin_family := AF_INET;
RecvAddIn.sin_port := htons(SrcPort);
if bind(ReceiveSocket, TSockAddr(RecvAddIn), sizeof(RecvAddIn)) = SOCKET_ERROR then
begin
writeln('bind() failed: '+IntToStr(WSAGetLastError));
exit;
end;
FillChar(buf, SizeOf(buf), 0);
sockAddrSize := sizeof(RecvAddIn);
bytes := RecvFrom(ReceiveSocket, buf, SizeOf(buf), 0, TSockAddr(RecvAddIn), sockAddrSize);
if bytes = SOCKET_ERROR then
writeln('RecvFrom() failed: '+IntToStr(WSAGetLastError))
else
writeln('RecvFrom '+IntToStr(bytes)+' bytes.');
CloseSocket(SendSocket);
CloseSocket(ReceiveSocket);
WSACleanup;
except
on E: Exception do
Writeln(E.ClassName, ': ', E.Message);
end;
end.
Wireshark 显示此数据包为:
我尝试创建两个具有相同本地端口的套接字来发送和接收数据，每个套接字都有自己的类型。怎么了？..
更新:
谢谢你们的想法。 事实上，接收套接字必须在发送之前完全初始化。 但正如我发现的，主要问题在于 UDP 数据包校验和计算。我发现一个简单的“ping”工具生成的校验和不等于我的代码生成的校验和(当然，对于相同的输入值)。当我刚刚使用它们的值时(同样，所有输入值都被保留)- DNS 服务器返回了响应! 为了生成校验和，我使用以下代码:
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 : TBytes; var Buf: TPacketBuffer;
var remote : TSockAddrIn; var iTotalSize: Word);
var
dwFromIP : LongWord;
dwToIP : LongWord;
iIPVersion : Word;
iIPSize : Word;
ipHdr : T_IP_Header;
udpHdr : T_UDP_Header;
iUdpSize : Word;
iUdpChecksumSize : Word;
cksum : Word;
Ptr : ^Byte;
procedure IncPtr(Value : Integer);
begin
ptr := pointer(integer(ptr) + Value);
end;
begin
dwFromIP := inet_Addr(PAnsiChar(AnsiString(FromIP)));
dwToIP := inet_Addr(PAnsiChar(AnsiString(ToIP)));
iTotalSize := sizeof(ipHdr) + sizeof(udpHdr) + 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 := $1545; // Unique identifier: set to 0
ipHdr.ip_offset := 0; // Fragment offset field
ipHdr.ip_ttl := 128;
ipHdr.ip_protocol := $11; // Protocol(UDP)
ipHdr.ip_checksum := 0 ; // IP checksum
ipHdr.ip_srcaddr := dwFromIP; // Source address
ipHdr.ip_destaddr := dwToIP; // Destination address
iUdpSize := sizeof(udpHdr) + length(strMessage);
udpHdr.src_portno := htons(iFromPort) ;
udpHdr.dst_portno := htons(iToPort) ;
udpHdr.udp_length := htons(iUdpSize) ;
udpHdr.udp_checksum := 0 ;
//
// Build the UDP pseudo-header for calculating the UDP checksum.
// The pseudo-header consists of the 32-bit source IP address,
// the 32-bit destination IP address, a zero byte, the 8-bit
// IP protocol field, the 16-bit UDP length, and the UDP
// header itself along with its data (padded with a 0 if
// the data is odd length).
//
iUdpChecksumSize := 0;
ptr := @buf[0];
FillChar(Buf, SizeOf(Buf), 0);
Move(ipHdr.ip_srcaddr, ptr^, SizeOf(ipHdr.ip_srcaddr));
IncPtr(SizeOf(ipHdr.ip_srcaddr));
iUdpChecksumSize := iUdpChecksumSize + sizeof(ipHdr.ip_srcaddr);
Move(ipHdr.ip_destaddr, ptr^, SizeOf(ipHdr.ip_destaddr));
IncPtr(SizeOf(ipHdr.ip_destaddr));
iUdpChecksumSize := iUdpChecksumSize + sizeof(ipHdr.ip_destaddr);
IncPtr(1);
Inc(iUdpChecksumSize);
Move(ipHdr.ip_protocol, ptr^, sizeof(ipHdr.ip_protocol));
IncPtr(sizeof(ipHdr.ip_protocol));
iUdpChecksumSize := iUdpChecksumSize + sizeof(ipHdr.ip_protocol);
Move(udpHdr.udp_length, ptr^, sizeof(udpHdr.udp_length));
IncPtr(sizeof(udpHdr.udp_length));
iUdpChecksumSize := iUdpChecksumSize + sizeof(udpHdr.udp_length);
move(udpHdr, ptr^, sizeof(udpHdr));
IncPtr(sizeof(udpHdr));
iUdpChecksumSize := iUdpCheckSumSize + sizeof(udpHdr);
Move(StrMessage[1], ptr^, Length(strMessage));
IncPtr(Length(StrMessage));
iUdpChecksumSize := iUdpChecksumSize + length(strMessage);
cksum := checksum(buf, iUdpChecksumSize);
udpHdr.udp_checksum := $FA8B;//cksum;
//
// Now assemble the IP and UDP headers along with the data
// so we can send it
//
FillChar(Buf, SizeOf(Buf), 0);
Ptr := @Buf[0];
Move(ipHdr, ptr^, SizeOf(ipHdr)); IncPtr(SizeOf(ipHdr));
Move(udpHdr, ptr^, SizeOf(udpHdr)); IncPtr(SizeOf(udpHdr));
Move(StrMessage[0], ptr^, length(StrMessage));
remote.sin_family := AF_INET;
remote.sin_port := htons(iToPort);
remote.sin_addr.s_addr := dwToIP;
end;
如果有人有另一个运行良好的实现，请分享...
最佳答案
您正在创建单独的套接字来发送和接收 DNS 数据包，但您是在发送请求之后创建接收套接字。响应有可能在接收套接字准备好之前到达(使用 Wireshark 来确认)，在这种情况下，响应将被操作系统丢弃。
在发送请求之前，您需要完全准备好接收套接字。
关于delphi - Delphi 上通过 Winsock2 的原始 UDP 数据包，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/71694805/