busybox分析--7.whois

1.简介
whois:用于查询域名是否被注册，以及注册域名的详细信息
a.例如查百度的域名信息

cong@msi:/work/busybox$ ./_install/busybox whois -h whois.dns.com.cn   www.baidu.com

Whois Server Version 2.0

Domain names in the .com and .net domains can now be registered
with many different competing registrars. Go to http://www.internic.net
for detailed information.

   Server Name: WWW.BAIDU.COM.CN
   Registrar: XIN NET TECHNOLOGY CORPORATION     -->Registrar说明己被注册
   Whois Server: whois.paycenter.com.cn
   Referral URL: http://www.xinnet.com

>>> Last update of whois database: Thu, 16 Jul 2015 02:53:39 GMT <<<
...一堆NOTICE信息，不关注

b.再随便查一个

cong@msi:/work/test/busytest/4whois$ ./whois www.tnnd.com
whois.c:str2sockaddr[34]: inaddr=119.254.72.20
whois.c:str2sockaddr[36]: inaddr=119.254.72.20
whois.c:main[89]: inaddr=119.254.72.20

Whois Server Version 2.0

Domain names in the .com and .net domains can now be registered
with many different competing registrars. Go to http://www.internic.net
for detailed information.

No match for "".                -->no match 说明没有注册

2. 源码
whois的原理就是向域名服务器发送一个命令，然后将回应的信息打印出来。
a.下面的代码将域名服务器写死了,固定为"whois.dns.com.cn"
b. 向域名服务器发送的命令就是要查的域名,比如查百度,就将"\r\n"发送即可
c. 最后将收到的信息打印

cong@msi:/work/test/busytest/4whois$ cat whois.c
#include "utils.h"

int str2sockaddr(const char *host, struct sockaddr_in* servaddr)
{
    struct in_addr inaddr;
    struct addrinfo hint, *result, *used_res;
    int ret;
    //1.convert numbers-and-dots notation into binary
    if(inet_aton(host, &inaddr) != 0)    //a.把点分十进制字符串转为socket的格式
    {
        //servaddr->sin_addr = inaddr;
        memcpy(&servaddr->sin_addr, &inaddr, sizeof(inaddr));
        dbmsg("inaddr=%s", inet_ntoa(servaddr->sin_addr));
        return 0;
    }
    //2.convert www.baidu.com to binary
    memset(&hint, 0, sizeof(hint));
    hint.ai_family = AF_UNSPEC;
    hint.ai_socktype = SOCK_STREAM;
    hint.ai_flags = AI_CANONNAME;   //b.如果上述a不成功，则把字符串域名串转为socket的格式
    ret = getaddrinfo(host, NULL, &hint, &result);
    if(ret || !result)
    {
        dbmsg("%s",strerror(errno));
        return -1;
    }
    used_res = result;

    do{
        if(used_res->ai_family == AF_INET)
            break;
    }while( (used_res= used_res->ai_next) != NULL);

    dbmsg("inaddr=%s", inet_ntoa(((struct sockaddr_in*)used_res->ai_addr)->sin_addr));
    memcpy(servaddr, used_res->ai_addr, used_res->ai_addrlen);
    dbmsg("inaddr=%s", inet_ntoa(servaddr->sin_addr));

    freeaddrinfo(result);
    return 0;
}

int pipe_out(int fd)
{
    FILE *fp;
    char buf[1024];
    fp = fdopen(fd, "r");
    if(!fp)
    {
        dbmsg("%s",strerror(errno));
        return -1;
    }

    while (fgets(buf, sizeof(buf), fp)) {
        char *p = strpbrk(buf, "\r\n");
        if (p)
            *p = '\0';
        puts(buf);
    }
    return 0;
}

int main ( int argc, char *argv[] )
{
    int sockfd;
    int port = 43;
    int ret;
    const char* host = "whois.dns.com.cn";
    char cmdbuf[1024];
    //const char* host = "119.254.72.20";
    struct sockaddr_in servaddr;
    if(argc < 2)
    {
        dbmsg("usage: arping ");
        dbmsg("eg: ./arping ");
        return -1;
    }
    //1. create socket
    if( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
    {
        dbmsg("%s",strerror(errno));
        return -1;
    }
    //2. set reuse addr
    ret = 1;
    setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &ret, sizeof(int));

    //3.1 turn string host to socket host
    str2sockaddr(host, &servaddr);
    dbmsg("inaddr=%s", inet_ntoa(servaddr.sin_addr));
    //3.2 connect to server
    servaddr.sin_family =AF_INET;
    servaddr.sin_port = htons(port);
    ret = connect(sockfd, (const struct sockaddr*)&servaddr, sizeof(servaddr));
    if(ret<0)
    {
        dbmsg("ret=%d,err=%s", ret, strerror(errno));
        return -1;
    }
    //4.send cmd to server
    snprintf(cmdbuf, sizeof(cmdbuf), "%s\r\n", argv[1]);
    write(sockfd, cmdbuf, strlen(cmdbuf)+1);

    //5.get info from server
    pipe_out(sockfd);
    return EXIT_SUCCESS;
}

注: str2sockaddr即可把点分十进制字符串119.254.72.20转为sockaddr_in
也可以将whois.dns.com.cn这将的转为sockaddr_in
3.运行结果

cong@msi:/work/test/busytest/4whois$ ./whois www.baidu.com
whois.c:str2sockaddr[34]: inaddr=119.254.72.20
whois.c:str2sockaddr[36]: inaddr=119.254.72.20
whois.c:main[89]: inaddr=119.254.72.20

Whois Server Version 2.0

Domain names in the .com and .net domains can now be registered
with many different competing registrars. Go to http://www.internic.net
for detailed information.

   Server Name: WWW.BAIDU.COM.CN
   Registrar: XIN NET TECHNOLOGY CORPORATION
   Whois Server: whois.paycenter.com.cn
   Referral URL: http://www.xinnet.com

>>> Last update of whois database: Thu, 16 Jul 2015 08:52:26 GMT <<<
...一堆NOTICE信息，不关注

4. 代码包
4whois.rar (下载后改名为4whois.tar.gz)