南宁彩票网站开发,工业软件开发技术,宠物发布网站模板,怎么把几个网站做互通C如何实现DNS域名解析 这片文章介绍了C如何实现DNS域名解析#xff0c;还有对相关技术的介绍#xff0c;代码很详细,需要的朋友可以参考下一、概述 现在来搞定DNS域名解析#xff0c;其实这是前面一篇文章C实现Ping里面的遗留问题#xff0c;要干的活是ping的过程中画红线的…C如何实现DNS域名解析 这片文章介绍了C如何实现DNS域名解析还有对相关技术的介绍代码很详细,需要的朋友可以参考下 一、概述 现在来搞定DNS域名解析其实这是前面一篇文章C实现Ping里面的遗留问题要干的活是ping的过程中画红线的部分 cmd下域名解析的命令是nslookup比如“nslookup www.baidu.com”的结果如下 其中Address返回的就是www.baidu.com对应的IP地址这个可能有多个 Alias指别名也就是说www.baidu.com是www.a.shifen.com的别名而www.a.shifen.com则是www.baidu.com的规范名(Canonical NameCName)具体参考RFC1035 3.2.2 wikipedia 二、实现结果预览 先看一下最终搞成了什么样子 输入域名字符串 输出IP列表、CName列表、DNS查询所用时间 三、相关技术 3.1、UDP or TCP ? (RFC1035 4.2) UDPDNS查询和回复采用低开销高性能的UDP端口号为53。 TCP辅助DNS服务器从主DNS服务器拉取最新数据时采用可靠的TCP传输端口号也为53。 我们这里做DNS查询采用UDP53端口。 3.2、DNS查询/回复包头部解析 (RFC1035 4.1.1) 重点介绍一下我们关心的部分 ID(16bits)标识符一般填入本进程的标识符 QR(1bits)标志位查询包为0回复包为1 Opcode(4bits)查询的种类标准查询为0 QDCOUNT(16bits)DNS查询/回复包数据部分Question字段的个数 ANCOUNT(16bits)DNS查询/回复包数据部分Answer字段的个数 3.2、DNS查询/回复包数据部分解析 (RFC1035 4.1.2 4.1.3) 查询/回复包的数据部分依次为QDCOUNT个Question字段、ANCOUNT个Answer字段.... 对于任意字段其格式如下 Name(不定长)域名这部分的格式比较复杂后面单独说。 TYPE(16bits)查询类型/回复包RDATA类型比如TYPE1表示主机IP地址、TYPE5表示CNAME详见RFC1035 3.2.2 CLASS(16bits)类一般情况下CLASS1表示Internet详见RFC1035 3.2.4 TTL(32bits仅回复包)生存时间 RDLENGTH(16bits仅回复包)RDATA部分的字节数 RDATA(不定长仅回复包)资源数据具体格式取决于TYPE和CLASS比如TYPE1、CLASS1时RDATA为四个字节的IP地址 3.3、Name解析消息压缩 3.3.1、一般格式 (RFC1035 4.1.2) 标签内容长度(1个字节) 标签内容以标签内容长度0作为Name的结束符例如 3.3.2、消息压缩格式 (RFC1035 4.1.4) 如果标签内容长度的二进制前两位是11则表示消息压缩。 此时标签内容长度1个字节后面的1个字节一共16位后14位表示相对DNS包起始地址的偏移(Byte)例如 上述例子中DNS包起始地址为0x0000c0 13的二进制为11000000 00010003即跳转偏移为0x13个字节对应的数据为03 63 6f 6d 00。 RFC1035中规定支持的消息压缩规则为 ①以内容长度0结尾的标签序列 ②偏移指针 ③标签序列偏移指针 也就是说Name的消息压缩要求偏移指针必须在Name的尾部且不支持同一级存在多个偏移指针(偏移指针序列) 但Name的消息压缩支持嵌套的偏移指针即指针指向的偏移位置仍然是以偏移指针结尾的数据 四、代码实现 #pragma once//这里需要导入库 Ws2_32.lib在不同的IDE下可能不太一样
//#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::vectorULONG *pveculIPList NULL, std::vectorstd::string *pvecstrCNameList NULL, ULONG ulTimeout 1000, ULONG *pulTimeSpent NULL);BOOL DNSLookup(ULONG ulDNSServerIP, char *szDomainName, std::vectorstd::string *pvecstrIPList NULL, std::vectorstd::string *pvecstrCNameList NULL, ULONG ulTimeout 1000, ULONG *pulTimeSpent NULL);private:BOOL Init();BOOL UnInit();BOOL DNSLookupCore(ULONG ulDNSServerIP, char *szDomainName, std::vectorULONG *pveculIPList, std::vectorstd::string *pvecstrCNameList, ULONG ulTimeout, ULONG *pulTimeSpent);BOOL SendDNSRequest(sockaddr_in sockAddrDNSServer, char *szDomainName);BOOL RecvDNSResponse(sockaddr_in sockAddrDNSServer, ULONG ulTimeout, std::vectorULONG *pveculIPList, std::vectorstd::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;
};[DNSLookup.h]#include DNSLookup.h
#include stdio.h
#include string.hCDNSLookup::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::vectorULONG *pveculIPList, std::vectorstd::string *pvecstrCNameList, ULONG ulTimeout, ULONG *pulTimeSpent)
{return DNSLookupCore(ulDNSServerIP, szDomainName, pveculIPList, pvecstrCNameList, ulTimeout, pulTimeSpent);
}BOOL CDNSLookup::DNSLookup(ULONG ulDNSServerIP, char *szDomainName, std::vectorstd::string *pvecstrIPList, std::vectorstd::string *pvecstrCNameList, ULONG ulTimeout, ULONG *pulTimeSpent)
{std::vectorULONG *pveculIPList NULL;if (pvecstrIPList){return FALSE;} std::vectorULONG veculIPList; pveculIPList veculIPList; BOOL bRet DNSLookupCore(ulDNSServerIP, szDomainName, pveculIPList, pvecstrCNameList, ulTimeout, pulTimeSpent);if (bRet){pvecstrIPList-clear();char szIP[16] {\0};for (std::vectorULONG::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::vectorULONG *pveculIPList, std::vectorstd::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::vectorULONG *pveculIPList, std::vectorstd::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);
}[DNSLookup.cpp]#include stdio.h
#include windows.h
#include DNSLookup.hint main(void)
{char szDomainName[] www.baidu.com;std::vectorULONG veculIPList;std::vectorstd::string vecstrIPList;std::vectorstd::string vecCNameList;ULONG ulTimeSpent 0;CDNSLookup dnslookup;BOOL bRet dnslookup.DNSLookup(inet_addr(114.114.114.114), 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;
} http://www.jb51.net/article/70359.htm 转载于:https://www.cnblogs.com/wainiwann/p/8087035.html
