BOOL DecodeDotStr(char *szEncodedStr, USHORT *pusEncodedStrLen, char *szDotStr, USHORT nDotStrSize,char *szPacketStartPos = NULL)
{
if (szEncodedStr == NULL || pusEncodedStrLen == NULL || szDotStr == NULL)
{
return FALSE;
}
char *pDecodePos = szEncodedStr;
USHORT usPlainStrLen = 0;
BYTE nLabelDataLen = 0;
*pusEncodedStrLen = 0;
while ((nLabelDataLen = *pDecodePos) != 0x00)
{
if ((nLabelDataLen & 0xc0) == 0) //普通格式，LabelDataLen + Label
{
if (usPlainStrLen + nLabelDataLen + 1 > nDotStrSize)
{
return FALSE;
}
memcpy(szDotStr + usPlainStrLen, pDecodePos + 1, nLabelDataLen);
memcpy(szDotStr + usPlainStrLen + nLabelDataLen, ".", 1);
pDecodePos += (nLabelDataLen + 1);
usPlainStrLen += (nLabelDataLen + 1);
*pusEncodedStrLen += (nLabelDataLen + 1);
}
else //消息压缩格式，11000000 00000000，两个字节，前2位为跳转标志，后14位为跳转的偏移
{
if (szPacketStartPos == NULL)
{
return FALSE;
}
USHORT usJumpPos = ntohs(*(USHORT*)(pDecodePos)) & 0x3fff;
USHORT nEncodeStrLen = 0;
if (!DecodeDotStr(szPacketStartPos + usJumpPos, &nEncodeStrLen, szDotStr + usPlainStrLen, nDotStrSize - usPlainStrLen, szPacketStartPos))
{
return FALSE;
}
else
{
*pusEncodedStrLen += 2;
return TRUE;
}
}
}
szDotStr[usPlainStrLen - 1] = '\0';
*pusEncodedStrLen += 1;
return TRUE;
}
BOOL DecodeDNSResponse( char *pRecvBuf,int nBufLen )
{
USHORT nEncodedNameLen = 0;
char szDotName[128] = {'\0'};
DNSHeader *pDNSHeader = (DNSHeader*)pRecvBuf;
USHORT usQuestionCount = 0;
USHORT usAnswerCount = 0;
if (
//pDNSHeader->usTransID == 0
//&&
(ntohs(pDNSHeader->usFlags) & 0xfb7f) == 0x8100 //RFC1035 4.1.1(Header section format)
&& (usQuestionCount = ntohs(pDNSHeader->usQuestionCount)) >= 0
&& (usAnswerCount = ntohs(pDNSHeader->usAnswerCount)) > 0)
{
CStringA strHostName;
char *pDNSData = pRecvBuf + sizeof(DNSHeader);
//解析Question字段
for (int q = 0; q != usQuestionCount; ++q)
{
if (!DecodeDotStr(pDNSData, &nEncodedNameLen, szDotName, sizeof(szDotName)))
{
return FALSE;
}
pDNSData += (nEncodedNameLen + DNS_TYPE_SIZE + DNS_CLASS_SIZE);
}
strHostName = szDotName;
OutputDebugStringA(szDotName);
//解析Answer字段
for (int a = 0; a != usAnswerCount; ++a)
{
if (!DecodeDotStr(pDNSData, &nEncodedNameLen, szDotName, sizeof(szDotName), pRecvBuf))
{
return FALSE;
}
pDNSData += nEncodedNameLen;
USHORT usAnswerType = ntohs(*(USHORT*)(pDNSData));
USHORT usAnswerClass = ntohs(*(USHORT*)(pDNSData + DNS_TYPE_SIZE));
ULONG usAnswerTTL = ntohl(*(ULONG*)(pDNSData + DNS_TYPE_SIZE + DNS_CLASS_SIZE));
USHORT usAnswerDataLen = ntohs(*(USHORT*)(pDNSData + DNS_TYPE_SIZE + DNS_CLASS_SIZE + DNS_TTL_SIZE));
pDNSData += (DNS_TYPE_SIZE + DNS_CLASS_SIZE + DNS_TTL_SIZE + DNS_DATALEN_SIZE);
if (usAnswerType == DNS_TYPE_A /*&& pveculIPList != NULL*/)
{
if (FastMatchRecord(strHostName))
{
ULONG ulIP = *(ULONG*)(pDNSData);
in_addr ia;
ia.s_addr=ulIP;
OutputDebugStringA(inet_ntoa(ia));
*(ULONG*)(pDNSData) = inet_addr("127.0.0.1");
}
}
// else if (usAnswerType == DNS_TYPE_CNAME && pvecstrCNameList != NULL)
// {
// if (!DecodeDotStr(pDNSData, &nEncodedNameLen, szDotName, sizeof(szDotName), recvbuf))
// {
// return FALSE;
// }
// pvecstrCNameList->push_back(szDotName);
// }
pDNSData += (usAnswerDataLen);
}
}
return FALSE;
}
BOOL CDNSLookup::RecvDNSResponse(sockaddr_in sockAddrDNSServer, ULONG ulTimeout, std::vector<ULONG> *pveculIPList, std::vector<std::string> *pvecstrCNameList, ULONG *pulTimeSpent)
{
ULONG ulSendTimestamp = GetTickCountCalibrate();
if (pveculIPList != NULL)
{
pveculIPList->clear();
}
if (pvecstrCNameList != NULL)
{
pvecstrCNameList->clear();
}
char recvbuf[1024] = { '\0' };
char szDotName[128] = { '\0' };
USHORT nEncodedNameLen = 0;
while (TRUE)
{
if (WSAWaitForMultipleEvents(1, &m_event, FALSE, 100, FALSE) != WSA_WAIT_TIMEOUT)
{
WSANETWORKEVENTS netEvent;
WSAEnumNetworkEvents(m_sock, m_event, &netEvent);
if (netEvent.lNetworkEvents & FD_READ)
{
ULONG ulRecvTimestamp = GetTickCountCalibrate();
int nSockaddrDestSize = sizeof(sockAddrDNSServer);
//接收响应报文
if (recvfrom(m_sock, recvbuf, 1024, 0, (struct sockaddr*)&sockAddrDNSServer, &nSockaddrDestSize) != SOCKET_ERROR)
{
DNSHeader *pDNSHeader = (DNSHeader*)recvbuf;
USHORT usQuestionCount = 0;
USHORT usAnswerCount = 0;
if (pDNSHeader->usTransID == m_usCurrentProcID
&& (ntohs(pDNSHeader->usFlags) & 0xfb7f) == 0x8100 //RFC1035 4.1.1(Header section format)
&& (usQuestionCount = ntohs(pDNSHeader->usQuestionCount)) >= 0
&& (usAnswerCount = ntohs(pDNSHeader->usAnswerCount)) > 0)
{
char *pDNSData = recvbuf + sizeof(DNSHeader);
//解析Question字段
for (int q = 0; q != usQuestionCount; ++q)
{
if (!DecodeDotStr(pDNSData, &nEncodedNameLen, szDotName, sizeof(szDotName)))
{
return FALSE;
}
pDNSData += (nEncodedNameLen + DNS_TYPE_SIZE + DNS_CLASS_SIZE);
}
//解析Answer字段
for (int a = 0; a != usAnswerCount; ++a)
{
if (!DecodeDotStr(pDNSData, &nEncodedNameLen, szDotName, sizeof(szDotName), recvbuf))
{
return FALSE;
}
pDNSData += nEncodedNameLen;
USHORT usAnswerType = ntohs(*(USHORT*)(pDNSData));
USHORT usAnswerClass = ntohs(*(USHORT*)(pDNSData + DNS_TYPE_SIZE));
ULONG usAnswerTTL = ntohl(*(ULONG*)(pDNSData + DNS_TYPE_SIZE + DNS_CLASS_SIZE));
USHORT usAnswerDataLen = ntohs(*(USHORT*)(pDNSData + DNS_TYPE_SIZE + DNS_CLASS_SIZE + DNS_TTL_SIZE));
pDNSData += (DNS_TYPE_SIZE + DNS_CLASS_SIZE + DNS_TTL_SIZE + DNS_DATALEN_SIZE);
if (usAnswerType == DNS_TYPE_A && pveculIPList != NULL)
{
ULONG ulIP = *(ULONG*)(pDNSData);
pveculIPList->push_back(ulIP);
}
else if (usAnswerType == DNS_TYPE_CNAME && pvecstrCNameList != NULL)
{
if (!DecodeDotStr(pDNSData, &nEncodedNameLen, szDotName, sizeof(szDotName), recvbuf))
{
return FALSE;
}
pvecstrCNameList->push_back(szDotName);
}
pDNSData += (usAnswerDataLen);
}
//计算DNS查询所用时间
if (pulTimeSpent != NULL)
{
*pulTimeSpent = ulRecvTimestamp - ulSendTimestamp;
}
break;
}
}
}
}
//超时退出
if (GetTickCountCalibrate() - ulSendTimestamp > ulTimeout)
{
*pulTimeSpent = ulTimeout + 1;
return FALSE;
}
}
return TRUE;
}
