实现域名解析

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编写程序，使用gethostbyname，getaddrinfo。

//不过你必须保证自己设备板子的DNS配置部分是正常的。

////////代码不一定完全正确，我简单测试了一下，可以用。主要是：bool TE_GetRealIP(char *HostName,char *strRealIP)，输入的HostName可以是IP，也可以是域名，strRealIP得到真正的IP

#include <netdb.h>#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <netdb.h>#include <time.h>#include <ifaddrs.h>#include <string.h>#include <errno.h>#include <string>#include <iostream>#include <poll.h>#include <pthread.h>#include <signal.h>#include <fcntl.h>#include <libgen.h>#include <dirent.h>#include <ifaddrs.h>#include <netinet/in.h>#include <netinet/in_systm.h>#include <netinet/ip.h>#include <netinet/ip_icmp.h>#include <netinet/tcp.h>#include <netinet/if_ether.h>#include <asm/types.h>#include <linux/netlink.h>#include <linux/rtnetlink.h>#include <linux/neighbour.h>#include <linux/if_addr.h> #include <sys/sysinfo.h>#include <net/if.h>#include <net/if_arp.h>#include <net/route.h>#include <error.h>#include <math.h>#include <sys/socket.h>#include <sys/signal.h>#include <sys/time.h>#include <sys/vfs.h>#include <sys/statvfs.h>#include <sys/types.h>#include <sys/ioctl.h>#include <sys/stat.h>#include <sys/utsname.h>#include <arpa/inet.h>using namespace std;#include <netdb.h>bool TE_CheckIfRealIp(char *IP){        if(!IP)                return false;        int nlen=strlen(IP);        //长度不能小于7不能大于15        if(nlen<7||nlen>15)                return false;        //不能有非0-9以外的字母        for(int i=0;i<nlen;i++){                if((char)IP[i]=='.')                        continue;                if((char)IP[i]<'0'||(char)IP[i]>'9')                        return false;        }        return true;}DWORD platform_domain2ipEx(const char *szDomain, char *szDotNumIP){        char szAddr[32] = {0};        struct hostent *pHost;        if((pHost = gethostbyname(szDomain)) == NULL)                return -1;        DWORD dwIP = inet_addr( inet_ntoa(*(struct in_addr *)*pHost->h_addr_list) );        strcpy(szAddr, inet_ntoa(*((struct in_addr *)pHost->h_addr)));        if(TE_CheckIfRealIp(szAddr)){                strcpy(szDotNumIP, szAddr);                return dwIP;        }        return 0;}bool TE_GetRealIP(char *HostName,char *strRealIP){        if(!HostName||!strRealIP)                return false;        struct addrinfo hints;        struct addrinfo *result, *result_pointer;        int ret;        bool bGetIP=false;        memset(&hints, 0, sizeof(struct addrinfo));        hints.ai_family = AF_UNSPEC;        hints.ai_socktype = SOCK_STREAM;        hints.ai_flags = AI_CANONNAME;        hints.ai_protocol = 0;        ret = getaddrinfo(HostName, NULL, &hints, &result);        if (ret != 0)                return false;        DebugInf("getnameinfo:%s int \n",HostName);        for (result_pointer = result; result_pointer != NULL; result_pointer = result_pointer->ai_next)        {                char hostname[1025] = "";                ret = getnameinfo(result_pointer->ai_addr, result_pointer->ai_addrlen, hostname, sizeof(hostname), NULL, 0, NI_NUMERICHOST);                if (ret != 0)                        continue;                else                {                   DebugInf("getnameinfo:%s IP: %s \n",HostName,hostname);                   if(strlen(hostname)>0&&TE_CheckIfRealIp(hostname)){                           printf("HostName:%s IP: %s \n",HostName,hostname);                           sprintf(strRealIP,"%s",hostname);                           bGetIP=true;                           break;                   }                }        }        freeaddrinfo(result);        DebugInf("getnameinfo:%s in 2 \n",HostName);        //没有获取到        if(!bGetIP){                DebugInf("platform_domain2ipEx:%s int \n",HostName);                if(platform_domain2ipEx(HostName,strRealIP)!=-1)                        bGetIP=true;        }        ////////////////////////////////////////////////        if(bGetIP)                return true;        else                return false;}

手动写一个或者直接用没办法的代码：

void WriteNewDNS(char *_strNewDNS){        char strCMD[128];        memset(strCMD,0,sizeof strCMD);        ////////删除系统的DNS文件        printf("WriteNewDNS   delete resolv.conf \n");        sprintf(strCMD,"/bin/rm /etc/resolv.conf");        system(strCMD);        ////////////////////        printf("WriteNewDNS   recreate resolv.conf \n");        sprintf(strCMD,"echo \"nameserver %s \">> /etc/resolv.conf",_strNewDNS);        system(strCMD);}

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