linux下检测网卡与网线连通状态

Linux下检测网卡与网线连接状态，使用ioctl向socket发送SIOCETHTOOL命令字。

link_stat.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <fcntl.h>
#include <errno.h>
#include <sys/ioctl.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <linux/if.h>
#include <linux/sockios.h>
#include <linux/ethtool.h>

int get_netlink_status(const char *if_name);

int main()
{
    if(getuid() != 0)
    {
        fprintf(stderr, "Netlink Status Check Need Root Power.\n");
        return 1;
    }
    
    printf("Net link status: %d\n", get_netlink_status("eth0"));

    return 0;
}

// if_name like "ath0", "eth0". Notice: call this function
// need root privilege.
// return value:
// -1 -- error , details can check errno
// 1 -- interface link up
// 0 -- interface link down.
int get_netlink_status(const char *if_name)
{
    int skfd;
    struct ifreq ifr;
    struct ethtool_value edata;

    edata.cmd = ETHTOOL_GLINK;
    edata.data = 0;

    memset(&ifr, 0, sizeof(ifr));
    strncpy(ifr.ifr_name, if_name, sizeof(ifr.ifr_name) - 1);
    ifr.ifr_data = (char *) &edata;

    if (( skfd = socket( AF_INET, SOCK_DGRAM, 0 )) < 0)
        return -1;

    if(ioctl( skfd, SIOCETHTOOL, &ifr ) == -1)
    {
        close(skfd);
        return -1;
    }

    close(skfd);
    return edata.data;
}

参考：
http://noliper.spaces.live.com/blog/cns!920E150C4B69A294!605.entry