Linux下利用ioctl函数获取网卡信息

linux下的ioctl函数原型如下：

#include <sys/ioctl.h>

int ioctl(int handle, int cmd, [int *argc, int argv])

函数成功返回0，失败返回-1.

其相关命令接口如下：

在这里我们需要用到的结构体

#include<netinet/in.h>

#include <net/if.h>

struct ifreq
{
#define IFHWADDRLEN 6
union
{
charifrn_name[IFNAMSIZ]; 
} ifr_ifrn;

union {
structsockaddr ifru_addr;
structsockaddr ifru_dstaddr;
structsockaddr ifru_broadaddr;
structsockaddr ifru_netmask;
struct sockaddr ifru_hwaddr;
shortifru_flags;
intifru_ivalue;
intifru_mtu;
struct ifmap ifru_map;
charifru_slave[IFNAMSIZ]; 
charifru_newname[IFNAMSIZ];
void __user * ifru_data;
structif_settings ifru_settings;
} ifr_ifru;
};

#define ifr_name ifr_ifrn.ifrn_name 
#define ifr_hwaddr ifr_ifru.ifru_hwaddr 
#defineifr_addr ifr_ifru.ifru_addr 
#defineifr_dstaddr ifr_ifru.ifru_dstaddr 
#defineifr_broadaddr ifr_ifru.ifru_broadaddr 
#defineifr_netmask ifr_ifru.ifru_netmask
#defineifr_flags ifr_ifru.ifru_flags 
#defineifr_metric ifr_ifru.ifru_ivalue
#defineifr_mtu ifr_ifru.ifru_mtu
#define ifr_map ifr_ifru.ifru_map
#define ifr_slave ifr_ifru.ifru_slave
#defineifr_data ifr_ifru.ifru_data 
#define ifr_ifindex ifr_ifru.ifru_ivalue
#define ifr_bandwidth ifr_ifru.ifru_ivalue 
#define ifr_qlen ifr_ifru.ifru_ivalue
#define ifr_newname ifr_ifru.ifru_newname
#define ifr_settings ifr_ifru.ifru_setting

ioctl函数能获取到IP地址、子网掩码、广播地址、硬件MAC地址等信息，至于网关及路由表比较复杂，在此不讨论。

具体代码如下：（测试通过）

#include <stdio.h>

#include <stdlib.h>

#include <net/if.h>

#include <unistd.h>

#include <sys/ioctl.h>

#include <arpa/inet.h>

#include <sys/stat.h>

#include <sys/types.h>

#include <errno.h>

#include <fcntl.h>

#include <netinet/in.h>

#include <net/route.h>

#include <string.h>

#include <net/if_arp.h>

int main()

{

   struct sockaddr_in *sin;

   struct ifreq ifr;

   FILE *dns;

   FILE *gw;

   char *ip = new char(16);

   char *netmask = new char(16);

   char *broadcast = new char(16);

   //char *ip = (char *)malloc(16);

   char *mac = new  char(32);

   //char *mac = (char *)malloc(32);

   int socket_fd;

       if((socket_fd = socket(AF_INET, SOCK_DGRAM, 0)) < 0){

               perror("socket");

               exit(1);

       }

       memset(&ifr, 0, sizeof(ifr));

       strcpy(ifr.ifr_name, "eth0");

       memset(&sin, 0, sizeof(sin));

//获取IP地址

       if(ioctl(socket_fd, SIOCGIFADDR, &ifr) != -1){

               sin = (struct sockaddr_in *)&ifr.ifr_addr;

               strcpy(ip, inet_ntoa(sin->sin_addr));

               printf("IP address is %s\n", ip);

       }

//获取广播地址

       if(ioctl(socket_fd, SIOCGIFBRDADDR, &ifr) != -1){

               sin = (struct sockaddr_in *)&ifr.ifr_broadaddr;

               strcpy(broadcast, inet_ntoa(sin->sin_addr));

               printf("Broadcast is %s\n", broadcast);

       }

//获取子网掩码

       if(ioctl(socket_fd, SIOCGIFNETMASK, &ifr) != -1){

               sin = (struct sockaddr_in *)&ifr.ifr_broadaddr;

               strcpy(netmask, inet_ntoa(sin->sin_addr));

               printf("Net-mask is %s\n", netmask);

       }

//获取硬件MAC地址

       if(ioctl(socket_fd, SIOCGIFHWADDR, &ifr) != -1){

               sin = (struct sockaddr_in *)&ifr.ifr_netmask;

               sprintf(mac, "%02x:%02x:%02x:%02x:%02x:%02x",

               (unsigned char)ifr.ifr_netmask.sa_data[0],

               (unsigned char)ifr.ifr_netmask.sa_data[1],

               (unsigned char)ifr.ifr_netmask.sa_data[2],

               (unsigned char)ifr.ifr_netmask.sa_data[3],

               (unsigned char)ifr.ifr_netmask.sa_data[4],

               (unsigned char)ifr.ifr_netmask.sa_data[5]);

               printf("Mac address is %s\n", mac);

       }

   return 0;

}

至于获取网关以及DNS，我是通过相关命令获得的。

主要代码如下：

//获取网关，利用route -n 命令可以看到相关的网关。连接标志是‘UG’

if(gw_fd = popen("route -n | grep ‘UG‘", "r")){

   fread(temp,1,128, gw_fd);

   sscanf(temp, "%*s%s", szNetGate);

   printf("Gateway is %s\n", szNetGate);

}

//获取DNS；一般DNS保存在/etc/reslov.conf文件中。具体获得方法要根据实际情况而定。

我的配置文件中是这样的

root@nill:/home/arm-none-linux# cat /etc/resolv.conf

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)

#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN

nameserver 202.96.134.133  

上面的202.96.134.133就是我需要获取的主DNS，没有备用DNS

if(dns_fd = popen("cat /etc/reslov.conf | grep ‘nameserver‘", "r")){

   fread(temp,1,128, gw_fd);

   sscanf(temp, "%*s%s%*s%s", szDNS1,szDNS2);

   printf("DNS1 is %s",szDNS1);

   printf("DNS2is %s", szDNS2);

}