Question

我正在尝试将DNS标头和问题发送到UDP套接字。我已经调用了以下命令来建立连接：button.accordions { max-height: 0; transition: max-height 0.5s ease; } button.accordions:hover { max-height: 75px; }，socket(PF_INET, SOCK_DGRAM, 0)使用端口53和inet_aton(temp, &servAddr.sin_addr)。

我遇到的问题是编写包含标题和DNS查询问题的消息。到目前为止，我的DNS标头结构看起来像这样：

connect(sock, (const sockaddr*) &servAddr, sizeof(servAddr))

我创建DNS查询标题：

struct DNS_Header {
            uint16_t id;
            struct {
                uint8_t rd: 1;      // recursion desired
                uint8_t tc: 1;      // message was truncated
                uint8_t aa: 1;      // authoritative answer
                uint8_t opcode: 4;  // query type
                // 0 a standard query (QUERY); 1 an inverse query (IQUERY);
                // 2 a server status request (STATUS);
                // 3 - 15 reserved for futre use
                uint8_t qr: 1;      // query(0) or response (1)

                uint8_t rcode: 4;   // response code
                // 0: No error condition; 1:Format error; 2:Server failure;
                // 3: Name Error (authoritative server, name doesn't exist)
                // 4: Not implemented; 5: Refused
                uint8_t z: 3;       // reserved for future use. Must be zero
                uint8_t ra: 1;      // recursion
                } flags;
            uint16_t gdcount;
            uint16_t ancount;
            uint16_t nscount;
            uint16_t arcount;
        };

我知道我需要将DNS问题的名称部分的主机名更改为标签/数据格式。我这样做是这样的：

   packetHeader.id = htons(1337);   
    packetHeader.flags.rd = 0;          
    packetHeader.flags.tc = 0;          
    packetHeader.flags.aa = 0;          
    packetHeader.flags.opcode = htons(0);       
    packetHeader.flags.qr = 0;          
    packetHeader.flags.rcode = htons(0);    
    packetHeader.flags.z = htons(0);        
    packetHeader.flags.ra = 0;          
    packetHeader.gdcount = htons(1);        
    packetHeader.ancount = htons(0);        
    packetHeader.nscount = htons(0);        
    packetHeader.arcount = htons(0);

我使用DNS_Question结构将所有关于DNS查询问题的内容组合在一起。该结构不包括DNS查询问题名称。我将名称存储在变量static const char* const hex = "0123456789ABCDEF"; hostname.push_back(' '); int len = hostname.length(); int segCount = 0; std::vector<std::string> storage; std::string temp = ""; for (int i = 0; i < len; i++) { if (hostname[i] == '.' || hostname[i] == ' ') { storage.push_back(std::to_string(0)); storage.push_back(std::to_string(segCount)); storage.push_back(temp); // reset segCount = 0; temp = ""; continue; } const unsigned char c = hostname[i]; std::cout << c << " : " << hex[c >> 4] << " " << hex[c & 15] << std::endl; temp.push_back(hex[c >> 4]); temp.push_back(hex[c & 15]); segCount ++; continue; } storage.push_back(std::to_string(0)); storage.push_back(std::to_string(0)); for (int i = 0; i < storage.size(); i++) { qname_labelFormat.append(storage[i]); } std::cout << "The hex representation of qname TOTAL: " << qname_labelFormat << std::endl中。查看下面的DNS查询问题结构：

qname_lableFormat

要填充结构DNS_Question，我已经这样做：

struct DNS_Question {
            uint16_t qtype;
            uint16_t qclass;
        };

完成所有这些操作后，我使用套接字int queryTypeNum = 0; if (queryType == "A") { queryTypeNum = 1; } if (queryType == "NS") { queryTypeNum = 2; } if (queryType == "CNAME") { queryTypeNum = 5; } if (queryType == "SOA") { queryTypeNum = 6; } if (queryType == "WKS") { queryTypeNum = 11; } if (queryType == "PTR") { queryTypeNum = 12; } if (queryType == "MX") { queryTypeNum = 15; } if (queryType == "SRV") { queryTypeNum = 33; } if (queryType == "AAAA") { queryTypeNum = 28; } if (queryType == "") { queryTypeNum = 1; } packetQuestion.qtype = htons(queryTypeNum); std::cout << "QType value set to: " << queryTypeNum << std::endl; packetQuestion.qclass = htons(1);，我相信这是发生错误的地方。没有报告错误消息，但是当我调用write(int fd, const void *buf, size_t count);命令时，什么都没有收到。我的写命令如下。

read(int fd, void *buf, size_t count);

如果有人能够提供帮助，我将非常感谢。

DNS UDP套接字write（）问题

0 个答案: