C实现网卡状态检测

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <linux/sockios.h>
#include <linux/types.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

struct mii_data
{
        __u16 phy_id;
        __u16 reg_num;
        __u16 val_in;
        __u16 val_out;
};

int main(int argc, char *argv[])
{
        struct mii_data *mii = NULL;
        int sockfd;
        struct ifreq ifr;

        if(argc != 2)
        {
                printf( "Useage: argv[0] ethX.\n" );
                return 0;
        }

        if((sockfd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1)
        {
                perror("socket");
                return -1;
        }

        memset(&ifr, '\0', sizeof(ifr));
        strncpy(ifr.ifr_name, argv[1], IFNAMSIZ - 1);
        if(ioctl(sockfd, SIOCGMIIPHY, &ifr) == -1)
        {
                perror("ioct SIOCGMIIPHY");
                return -1;
        }

        mii = (struct mii_data*)&ifr.ifr_data;
        mii->reg_num = 0x01;
        if(ioctl(sockfd, SIOCGMIIREG, &ifr) == -1)
        {
                perror("ioctl SIOCGMIIREG");
                return -1;
        }

        if(mii->val_out & 0x0004)
                printf("link up\n");
        else
                printf("link down\n");

        close(sockfd);

        return 0;
}