UDP实现简单的ifconfig查询功能

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一 代码

#include <net/if.h>       /* for ifconf */  
#include <linux/sockios.h>    /* for net status mask */  
#include <netinet/in.h>       /* for sockaddr_in */  
#include <sys/socket.h>  
#include <sys/types.h>  
#include <sys/ioctl.h>  
#include <stdio.h>  
#include <unistd.h> //for close
#include <arpa/inet.h>
#include <string.h>
#define MAX_INTERFACE   (16)  
      
void port_status(unsigned int flags);  
      

int get_if_info(int fd)  
{  
    struct ifreq buf[MAX_INTERFACE];      
    struct ifconf ifc;  
    int ret = 0;  
    int if_num = 0;  
      
    ifc.ifc_len = sizeof(buf);  
    ifc.ifc_buf = (caddr_t) buf;  
          
    ret = ioctl(fd, SIOCGIFCONF, (char*)&ifc);  
    if (ret)  
    {  
        printf("get if config info failed");  
        return -1;  
    }  
    /* 网口总数 ifc.ifc_len 应该是一个出入参数 */      
    if_num = ifc.ifc_len / sizeof(struct ifreq);  
    printf("interface num is interface = %d\n", if_num);  
    while (if_num-- > 0)  
    {  
        printf("net device: %s\n", buf[if_num].ifr_name);     
        /* 获取第n个网口信息 */  
        ret = ioctl(fd, SIOCGIFFLAGS, (char*)&buf[if_num]);  
        if (ret)  
            continue;  
      
        /* 获取网口状态 */  
        port_status(buf[if_num].ifr_flags);  
              
        /* 获取当前网卡的ip地址 */  
        ret = ioctl(fd, SIOCGIFADDR, (char*)&buf[if_num]);  
        if (ret)  
            continue;  
        printf("IP address is: \n%s\n", inet_ntoa(((struct sockaddr_in *)(&buf[if_num].ifr_addr))->sin_addr));  
      
        /* 获取当前网卡的mac */  
        ret = ioctl(fd, SIOCGIFHWADDR, (char*)&buf[if_num]);  
        if (ret)  
            continue;  
      
        printf("%02x:%02x:%02x:%02x:%02x:%02x\n\n",  
            (unsigned char)buf[if_num].ifr_hwaddr.sa_data[0],  
            (unsigned char)buf[if_num].ifr_hwaddr.sa_data[1],  
            (unsigned char)buf[if_num].ifr_hwaddr.sa_data[2],  
            (unsigned char)buf[if_num].ifr_hwaddr.sa_data[3],  
            (unsigned char)buf[if_num].ifr_hwaddr.sa_data[4],  
            (unsigned char)buf[if_num].ifr_hwaddr.sa_data[5]);  
    }  
}  
      
void port_status(unsigned int flags)  
{  
    if (flags & IFF_UP)    
    {  
        printf("is up\n");        
    }  
    if (flags & IFF_BROADCAST)     
    {  
        printf("is broadcast\n");     
    }  
    if (flags & IFF_LOOPBACK)      
    {  
        printf("is loop back\n");     
    }  
    if (flags & IFF_POINTOPOINT)   
    {  
        printf("is point to point\n");    
    }  
    if (flags & IFF_RUNNING)   
    {  
        printf("is running\n");   
    }  
    if (flags & IFF_PROMISC)   
    {  
        printf("is promisc\n");   
    }  
}  
      
int main()  
{  
    int fd;  
      
    fd = socket(AF_INET, SOCK_DGRAM, 0);  
    if (fd > 0)  
    {  
        get_if_info(fd);  
        close(fd);  
    }  
      
    return 0;  
}  

二 运行

[root@localhost test]# g++ test.cpp -o test
[root@localhost test]# ./test
interface num is interface = 2
net device: enp0s3
is up
is broadcast
is running
IP address is:
192.168.0.120
08:00:27:0c:3b:d3

net device: lo
is up
is loop back
is running
IP address is:
127.0.0.1
00:00:00:00:00:00

三 说明

1 网络相关的ioctl请求的request参数及arg地址必须指向的数据类型如下表所示：

接口

SIOCGIFCONF SIOCSIFADDR SIOCGIFADDR SIOCSIFBRDADDR SIOCGIFBRDADDR SIOCSIFNETMASK SIOCGIFNETMASK

获取所有接口列表 设置接口地址 获取接口地址 设置广播地址 获取广播地址 设置子网掩码 获取子网掩码

Struct  ifconf Struct  ifreq Struct  ifreq Struct  ifreq Struct  ifreq Struct  ifreq Struct  ifreq

2  ifconf定义如下：

struct ifconf{
lint ifc_len;
union{
    caddr_t  ifcu_buf
    Struct   ifreq *ifcu_req;
}ifc_ifcu
}
#define    ifc_buf    ifc_ifcu.ifcu_buf
#define    ifc_req    ifc_ifcu.ifcu_req

3 本机所有的网卡信息都列举出来了，效果和ifconfig命令类似。