[嵌入式开发模块]DNS客户端模块(基于wiz/W5500官方io库)

刺骨的言语ヽ痛彻心扉 2023-06-01 05:53 43阅读 0赞

### 文章目录 ###

*  前言
 *  代码
 *   *  DNSClient.h
     *  DNSClient.c
 *  使用示例
 *  更新历史

# 前言 #

出于同样的项目需要的原因，我把我的DNS模块也进一步进行了封装。基于W5500官方IO库，提供完成一次域名解析IPv4的整个过程的接口。

先复制黏贴好DNS模块的代码：  
https://blog.csdn.net/lin\_strong/article/details/101915670

代码中遇到的依赖之类的问题都可以在NTPClient模块中找到：  
https://blog.csdn.net/lin\_strong/article/details/100807679

接下来直接上源码：

# 代码 #

## DNSClient.h ##

/*
    ******************************************************************************************
    *
    *                                   DNS CLIENT MODULE
    *
    * File : DNSClient.h
    * By   : Lin Shijun(http://blog.csdn.net/lin_strong)
    * Date:  2019/10/15
    * Version: V1.1
    * History: 2019/09/16  V1.0
    *          2019/10/15  V1.1 add bufSize parameter to DnsClient_QueryIPv4 interface
    *                           fix serverPort parameter from uint8_t to uint16_t
    * NOTE(s): the module is to provide DNS client function based on wiznet io-library.
    ******************************************************************************************
    */
    
    #ifndef _DNSCLIENT_H
    #define _DNSCLIENT_H
    
    /*
    *******************************************************************************************
    *                                       INCLUDE
    *******************************************************************************************
    */
    
    #include "DNS.h"
    
    /*
    *******************************************************************************************
    *                                     CONFIGURATION
    *******************************************************************************************
    */
    
    // to enable debug message
    //#define DNSC_DEBUG
    
    // set the wait time of a request
    #ifndef DNSC_TIMEOUT_TIME_MS
    #define DNSC_TIMEOUT_TIME_MS   1000
    #endif
    
    /*
    *******************************************************************************************
    *                                    PUBLIC INTERFACES
    *******************************************************************************************
    */
    
    // description: launch a dns ipv4 standard query(A record) on given socketNum and return the respond if any.
    // parameter  : socketNum   the socket number for dns client
    //              buf         the buffer for dns client.
    //              bufSize     the size of buffer. Should be bigger enough to hold the request
    //                          and respond message, or it will fail.
    //              serverIp    ip of the dns server.
    //              serverPort  udp port of the dns server. 0 if default port(i.e. DNSS_PORT)
    //              DName       domain name to query
    //              ret         to return the result if success, uint8_t[4]
    // return     : TRUE        if success
    //              FALSE       if fail
    // note       : 
    BOOL DnsClient_QueryIPv4(uint8_t socketNum, uint8_t *buf, uint16_t bufSize, uint8_t serverIp[4], 
                      uint16_t serverPort, const char *DName,uint8_t *ret);
    
    #endif

## DNSClient.c ##

/*
    ******************************************************************************************
    *
    *                                   DNS CLIENT MODULE
    *
    * File : DNSClient.c
    * By   : Lin Shijun(http://blog.csdn.net/lin_strong)
    * Date:  2019/10/15
    * Version: V1.1
    * History: 
    * NOTE(s): 
    ******************************************************************************************
    */
    
    
    /*
    *******************************************************************************************
    *                                       INCLUDES
    *******************************************************************************************
    */
    #include <string.h>
    #include "DNSClient.h"
    #include "socket.h"
    #include "MyOS.h"
    
    #ifndef DNSC_DEBUG
    #undef _DEBUG
    #endif
    
    #include "DebugMsg.h"
     
    /*
    *******************************************************************************************
    *                                     CONFIGURATION
    *******************************************************************************************
    */
    
    #ifndef DNSC_POLL_INTERVAL_MS
    #define DNSC_POLL_INTERVAL_MS  10
    #endif
    #define DNSC_POLL_CNT ((DNSC_TIMEOUT_TIME_MS) / (DNSC_POLL_INTERVAL_MS))
    
    #define ANYNUM   0x3453
    
    /*
    *******************************************************************************************
    *                                 LOCAL FUNCTION DECLARATION
    *******************************************************************************************
    */
    
    #define socketNum_valid(socketNum)  ((socketNum) < _WIZCHIP_SOCK_NUM_)
    
    /*
    *******************************************************************************************
    *                                 LOCAL VARIABLE DECLARATION
    *******************************************************************************************
    */
    
    static uint16_t _id = ANYNUM;
    
    /*
    *******************************************************************************************
    *                                       DEBUG STRINGS
    *******************************************************************************************
    */
    
    static const char *_str_DNSCErrFormat = "DNSC Err: %s.\r\n";
    
    /*
    *******************************************************************************************
    *                             PUBLIC INTERFACE IMPLEMENTATIONS
    *******************************************************************************************
    */
    
    BOOL DnsClient_QueryIPv4(uint8_t socketNum, uint8_t *buf, uint16_t bufSize, uint8_t serverIp[4],
                  uint16_t serverPort, const char *DName,uint8_t *ret){
        
      int32_t len;
      uint8_t dip[4];
      uint16_t dport;
      uint16_t id;
      DNSHdr hdr;
      DNSRR QueOrRR;
      const uint8_t *p;
      int i;
      BOOL rst = FALSE;
      int remainPollCnt = DNSC_POLL_CNT;
      id = ++_id;
      if(serverIp == NULL || ret == NULL || buf == NULL || DName == NULL || !socketNum_valid(socketNum)){
        
        _dbg_printf1(_str_DNSCErrFormat, "bad param");
        return FALSE;
      }
      serverPort = (serverPort != 0)? serverPort: DNSS_PORT;
      if(getSn_SR(socketNum) != SOCK_UDP)
        if(socketNum != socket(socketNum, Sn_MR_UDP, 0, 0x00)){
        
          _dbg_printf1(_str_DNSCErrFormat, "Open socket");
          goto bail;
        };
      len = (int32_t)DnsMsg_printStandardQueryIPv4Message(buf, bufSize, id, DName);
      if(len <= 0){
        
        _dbg_printf1(_str_DNSCErrFormat, "printf query");
        goto bail;
      }
      len = sendto(socketNum, buf, (uint16_t)len, serverIp, serverPort);
      if(len < 0){
        
        _dbg_printf1(_str_DNSCErrFormat, "sendto");
        goto bail;
      }
      _dbg_printf0("DNSC :wating for respond\r\n");
      do{
        
        MyOS_DlyHMSM(0,0,0,DNSC_POLL_INTERVAL_MS);
        if(getSn_RX_RSR(socketNum) <= 0)
          continue;
        len = recvfrom(socketNum, buf, bufSize, dip, &dport);
        if(len <= 0){
        
          _dbg_printf1(_str_DNSCErrFormat, "socket mode");
          goto bail;
        }
        // intentionly only check server ip. considering the situation that respond with another port;
        if(*(uint32_t *)dip != *(uint32_t *)serverIp)
          continue;
        p = DNSMsg_scanHeader(buf, (uint16_t)len, &hdr);
        if(p == NULL || hdr.QR != 1 || id != hdr.TransID)
          continue;
        // we have confirm that this message is the response, so stop loop in this time.
        // jumpoff query section
        for(i = 0; i < hdr.Questions; i++){
        
          if((p = DNSMsg_scanQuery(buf, (uint16_t)len, p, (DNSQue *)&QueOrRR)) == NULL){
        
            _dbg_printf1(_str_DNSCErrFormat, "resolve query");
            goto bail;
          }
          DNSMsg_freeQueReturnByScan((DNSQue *)&QueOrRR);
        }
        for(i = 0; i < hdr.AnswerRRs; i++){
        
          if((p = DNSMsg_scanRR(buf, (uint16_t)len, p, (DNSRR *)&QueOrRR)) == NULL){
        
            _dbg_printf1(_str_DNSCErrFormat, "resolve RR");
            goto bail;
          }
          // id对上了就默认回答的A记录一定是那个域名的了。就不浪费时间核对域名了。因为有的时候有别名就特麻烦。
          if(QueOrRR.Type == DNSQT_A){
        
            rst = TRUE;
            (void)memcpy(ret, QueOrRR.RData.A.addr, 4);
            DNSMsg_freeRRReturnByScan((DNSRR *)&QueOrRR);
            _dbg_printf4("DNSC :got IPv4 addr %u.%u.%u.%u\r\n", ret[0], ret[1], ret[2], ret[3]);
            goto bail;
          }
          DNSMsg_freeRRReturnByScan((DNSRR *)&QueOrRR);
        }
        _dbg_printf1(_str_DNSCErrFormat, "no answer");
        goto bail;
      }while(remainPollCnt-- > 0);
      // timeout
      _dbg_printf1(_str_DNSCErrFormat, "timeout");
    bail:
      close(socketNum);
      return rst;
    }

# 使用示例 #

如下就可以从192.168.1.1处的DNS服务器处要到www.baidu.com的IP地址：

static uint8_t dnsBuf[200];
    static uint8_t dnsServerIP[] = {
        192,168,1,1};
    static const char * dnameForQuery = "www.baidu.com";
    void DnsTask(void *p_arg){
        
      uint8_t ip[4];
      // 已省去不重要的代码
      ...
      printf("launch dns query for %s to %u.%u.%u.%u on socket %u\r\n", dnameForQuery, 
            dnsServerIP[0], dnsServerIP[1], dnsServerIP[2], dnsServerIP[3],DNS_SOCKET);
      if(DnsClient_QueryIPv4(DNS_SOCKET, dnsBuf, sizeof(dnsBuf), (uint8_t *)dnsServerIP, 0, dnameForQuery,ip) == TRUE){
        
        printf("%s's ip is %u.%u.%u.%u\r\n", dnameForQuery, ip[0], ip[1], ip[2], ip[3]);
      }else{
        
        printf("query dns fail\r\n");
      }
      ...
    }

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2xpbl9zdHJvbmc_size_16_color_FFFFFF_t_70][]

# 更新历史 #

2020/06/04 更新到V1.1 修复V1.0中端口号使用uint8\_t的问题，应该使用uint16\_t；为接口添加bufSize参数以避免超出缓冲区；

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