C++实现DNS域名解析

#pragma once#include <WinSock2.h>#pragma comment(lib, "Ws2_32.lib")#include <windows.h>#include <string>#include <vector>#define MAX_DOMAINNAME_LEN  255#define DNS_PORT            53#define DNS_TYPE_SIZE       2#define DNS_CLASS_SIZE      2#define DNS_TTL_SIZE        4#define DNS_DATALEN_SIZE    2#define DNS_TYPE_A          0x0001 //1 a host address#define DNS_TYPE_CNAME      0x0005 //5 the canonical name for an alias#define DNS_PACKET_MAX_SIZE (sizeof(DNSHeader) + MAX_DOMAINNAME_LEN + DNS_TYPE_SIZE + DNS_CLASS_SIZE)struct DNSHeader{USHORT usTransID; //标识符USHORT usFlags; //各种标志位USHORT usQuestionCount; //Question字段个数 USHORT usAnswerCount; //Answer字段个数USHORT usAuthorityCount; //Authority字段个数USHORT usAdditionalCount; //Additional字段个数};class CDNSLookup{public:CDNSLookup();~CDNSLookup();BOOL DNSLookup(ULONG ulDNSServerIP, char *szDomainName, std::vector<ULONG> *pveculIPList = NULL, std::vector<std::string> *pvecstrCNameList = NULL, ULONG ulTimeout = 1000, ULONG *pulTimeSpent = NULL);BOOL DNSLookup(ULONG ulDNSServerIP, char *szDomainName, std::vector<std::string> *pvecstrIPList = NULL, std::vector<std::string> *pvecstrCNameList = NULL, ULONG ulTimeout = 1000, ULONG *pulTimeSpent = NULL);private:BOOL Init();BOOL UnInit();BOOL DNSLookupCore(ULONG ulDNSServerIP, char *szDomainName, std::vector<ULONG> *pveculIPList, std::vector<std::string> *pvecstrCNameList, ULONG ulTimeout, ULONG *pulTimeSpent);BOOL SendDNSRequest(sockaddr_in sockAddrDNSServer, char *szDomainName);BOOL RecvDNSResponse(sockaddr_in sockAddrDNSServer, ULONG ulTimeout, std::vector<ULONG> *pveculIPList, std::vector<std::string> *pvecstrCNameList, ULONG *pulTimeSpent);BOOL EncodeDotStr(char *szDotStr, char *szEncodedStr, USHORT nEncodedStrSize);BOOL DecodeDotStr(char *szEncodedStr, USHORT *pusEncodedStrLen, char *szDotStr, USHORT nDotStrSize, char *szPacketStartPos = NULL);ULONG GetTickCountCalibrate();private:BOOL m_bIsInitOK;SOCKET m_sock;WSAEVENT m_event;USHORT m_usCurrentProcID;char *m_szDNSPacket;};

#include "DNSLookup.h"#include <stdio.h>#include <string.h>CDNSLookup::CDNSLookup() :m_bIsInitOK(FALSE),m_sock(INVALID_SOCKET),m_szDNSPacket(NULL){m_bIsInitOK = Init();}CDNSLookup::~CDNSLookup(){UnInit();}BOOL CDNSLookup::DNSLookup(ULONG ulDNSServerIP, char *szDomainName, std::vector<ULONG> *pveculIPList, std::vector<std::string> *pvecstrCNameList, ULONG ulTimeout, ULONG *pulTimeSpent){return DNSLookupCore(ulDNSServerIP, szDomainName, pveculIPList, pvecstrCNameList, ulTimeout, pulTimeSpent);}BOOL CDNSLookup::DNSLookup(ULONG ulDNSServerIP, char *szDomainName, std::vector<std::string> *pvecstrIPList, std::vector<std::string> *pvecstrCNameList, ULONG ulTimeout, ULONG *pulTimeSpent){std::vector<ULONG> *pveculIPList = NULL;if (pvecstrIPList != NULL){std::vector<ULONG> veculIPList;pveculIPList = new std::vector<ULONG>;}BOOL bRet = DNSLookupCore(ulDNSServerIP, szDomainName, pveculIPList, pvecstrCNameList, ulTimeout, pulTimeSpent);if (bRet){pvecstrIPList->clear();char szIP[16] = { '\0' };for (std::vector<ULONG>::iterator iter = pveculIPList->begin(); iter != pveculIPList->end(); ++iter){BYTE *pbyIPSegment = (BYTE*)(&(*iter));//sprintf_s(szIP, 16, "%d.%d.%d.%d", pbyIPSegment[0], pbyIPSegment[1], pbyIPSegment[2], pbyIPSegment[3]);sprintf(szIP, "%d.%d.%d.%d", pbyIPSegment[0], pbyIPSegment[1], pbyIPSegment[2], pbyIPSegment[3]);pvecstrIPList->push_back(szIP);}}return bRet;}BOOL CDNSLookup::Init(){WSADATA wsaData;if (WSAStartup(MAKEWORD(2, 2), &wsaData) == SOCKET_ERROR){return FALSE;}if ((m_sock = socket(AF_INET, SOCK_DGRAM, 0)) == INVALID_SOCKET){return FALSE;}m_event = WSACreateEvent();WSAEventSelect(m_sock, m_event, FD_READ);m_szDNSPacket = new (std::nothrow) char[DNS_PACKET_MAX_SIZE];if (m_szDNSPacket == NULL){return FALSE;}m_usCurrentProcID = (USHORT)GetCurrentProcessId();return TRUE;}BOOL CDNSLookup::UnInit(){WSACleanup();if (m_szDNSPacket != NULL){delete[] m_szDNSPacket;}return TRUE;}BOOL CDNSLookup::DNSLookupCore(ULONG ulDNSServerIP, char *szDomainName, std::vector<ULONG> *pveculIPList, std::vector<std::string> *pvecstrCNameList, ULONG ulTimeout, ULONG *pulTimeSpent){if (m_bIsInitOK == FALSE || szDomainName == NULL){return FALSE;}//配置SOCKETsockaddr_in sockAddrDNSServer;sockAddrDNSServer.sin_family = AF_INET;sockAddrDNSServer.sin_addr.s_addr = ulDNSServerIP;sockAddrDNSServer.sin_port = htons(DNS_PORT);//DNS查询与解析if (!SendDNSRequest(sockAddrDNSServer, szDomainName)|| !RecvDNSResponse(sockAddrDNSServer, ulTimeout, pveculIPList, pvecstrCNameList, pulTimeSpent)){return FALSE;}return TRUE;}BOOL CDNSLookup::SendDNSRequest(sockaddr_in sockAddrDNSServer, char *szDomainName){char *pWriteDNSPacket = m_szDNSPacket;memset(pWriteDNSPacket, 0, DNS_PACKET_MAX_SIZE);//填充DNS查询报文头部DNSHeader *pDNSHeader = (DNSHeader*)pWriteDNSPacket;pDNSHeader->usTransID = m_usCurrentProcID;pDNSHeader->usFlags = htons(0x0100);pDNSHeader->usQuestionCount = htons(0x0001);pDNSHeader->usAnswerCount = 0x0000;pDNSHeader->usAuthorityCount = 0x0000;pDNSHeader->usAdditionalCount = 0x0000;//设置DNS查询报文内容USHORT usQType = htons(0x0001);USHORT usQClass = htons(0x0001);USHORT nDomainNameLen = strlen(szDomainName);char *szEncodedDomainName = (char *)malloc(nDomainNameLen + 2);if (szEncodedDomainName == NULL){return FALSE;}if (!EncodeDotStr(szDomainName, szEncodedDomainName, nDomainNameLen + 2)){return FALSE;}//填充DNS查询报文内容USHORT nEncodedDomainNameLen = strlen(szEncodedDomainName) + 1;memcpy(pWriteDNSPacket += sizeof(DNSHeader), szEncodedDomainName, nEncodedDomainNameLen);memcpy(pWriteDNSPacket += nEncodedDomainNameLen, (char*)(&usQType), DNS_TYPE_SIZE);memcpy(pWriteDNSPacket += DNS_TYPE_SIZE, (char*)(&usQClass), DNS_CLASS_SIZE);free(szEncodedDomainName);//发送DNS查询报文USHORT nDNSPacketSize = sizeof(DNSHeader) + nEncodedDomainNameLen + DNS_TYPE_SIZE + DNS_CLASS_SIZE;if (sendto(m_sock, m_szDNSPacket, nDNSPacketSize, 0, (sockaddr*)&sockAddrDNSServer, sizeof(sockAddrDNSServer)) == SOCKET_ERROR){return FALSE;}return TRUE;}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;}/** convert "www.baidu.com" to "\x03www\x05baidu\x03com"* 0x0000 03 77 77 77 05 62 61 69 64 75 03 63 6f 6d 00 ff*/BOOL CDNSLookup::EncodeDotStr(char *szDotStr, char *szEncodedStr, USHORT nEncodedStrSize){USHORT nDotStrLen = strlen(szDotStr);if (szDotStr == NULL || szEncodedStr == NULL || nEncodedStrSize < nDotStrLen + 2){return FALSE;}char *szDotStrCopy = new char[nDotStrLen + 1];//strcpy_s(szDotStrCopy, nDotStrLen + 1, szDotStr);strcpy(szDotStrCopy, szDotStr);char *pNextToken = NULL;//char *pLabel = strtok_s(szDotStrCopy, ".", &pNextToken);char *pLabel = strtok(szDotStrCopy, ".");USHORT nLabelLen = 0;USHORT nEncodedStrLen = 0;while (pLabel != NULL){if ((nLabelLen = strlen(pLabel)) != 0){//sprintf_s(szEncodedStr + nEncodedStrLen, nEncodedStrSize - nEncodedStrLen, "%c%s", nLabelLen, pLabel);sprintf(szEncodedStr + nEncodedStrLen, "%c%s", nLabelLen, pLabel);nEncodedStrLen += (nLabelLen + 1);}//pLabel = strtok_s(NULL, ".", &pNextToken);pLabel = strtok(NULL, ".");}delete[] szDotStrCopy;return TRUE;}/** convert "\x03www\x05baidu\x03com\x00" to "www.baidu.com"* 0x0000 03 77 77 77 05 62 61 69 64 75 03 63 6f 6d 00 ff* convert "\x03www\x05baidu\xc0\x13" to "www.baidu.com"* 0x0000 03 77 77 77 05 62 61 69 64 75 c0 13 ff ff ff ff* 0x0010 ff ff ff 03 63 6f 6d 00 ff ff ff ff ff ff ff ff*/BOOL CDNSLookup::DecodeDotStr(char *szEncodedStr, USHORT *pusEncodedStrLen, char *szDotStr, USHORT nDotStrSize, char *szPacketStartPos){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;}ULONG CDNSLookup::GetTickCountCalibrate(){static ULONG s_ulFirstCallTick = 0;static LONGLONG s_ullFirstCallTickMS = 0;SYSTEMTIME systemtime;FILETIME filetime;GetLocalTime(&systemtime);SystemTimeToFileTime(&systemtime, &filetime);LARGE_INTEGER liCurrentTime;liCurrentTime.HighPart = filetime.dwHighDateTime;liCurrentTime.LowPart = filetime.dwLowDateTime;LONGLONG llCurrentTimeMS = liCurrentTime.QuadPart / 10000;if (s_ulFirstCallTick == 0){s_ulFirstCallTick = GetTickCount();}if (s_ullFirstCallTickMS == 0){s_ullFirstCallTickMS = llCurrentTimeMS;}return s_ulFirstCallTick + (ULONG)(llCurrentTimeMS - s_ullFirstCallTickMS);}

#include <stdio.h>#include "DNSLookup.h"int main(void){char szDomainName[] = "www.baidu.com";std::vector<ULONG> veculIPList;std::vector<std::string> vecstrIPList;std::vector<std::string> vecCNameList;ULONG ulTimeSpent = 0;CDNSLookup dnslookup;BOOL bRet = dnslookup.DNSLookup(inet_addr("218.85.152.99"), szDomainName, &vecstrIPList, &vecCNameList, 1000, &ulTimeSpent);printf("DNSLookup result (%s):\n", szDomainName);if (!bRet){printf("timeout!\n");return -1;}for (int i = 0; i != veculIPList.size(); ++i){printf("IP%d(ULONG) = %u\n", i + 1, veculIPList[i]);}for (int i = 0; i != vecstrIPList.size(); ++i){printf("IP%d(string) = %s\n", i + 1, vecstrIPList[i].c_str());}for (int i = 0; i != vecCNameList.size(); ++i){printf("CName%d = %s\n", i + 1, vecCNameList[i].c_str());}printf("time spent = %ums\n", ulTimeSpent);return 0;}