DNS请求响应

问题背景：在无线网络可用，而有线网络不可用的场景下，依靠第三方接口解析域名，或者udp，tcp接口内部解析域名，会默认阻塞10秒钟

办法：自行定制dns请求及响应

BOOL 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 RecvDNSResponse(sockaddr_in sockAddrDNSServer, ULONG ulTimeout, std::vector<ULONG> *pveculIPList, std::vector<std::string> *pvecstrCNameList, ULONG *pulTimeSpent)
{