Linux下檢測網卡與網線連接狀態

Linux下檢測網卡與網線連接狀態：

方法一：使用ioctl向socket發送SIOCETHTOOL命令字


#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(constchar *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(constchar *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;

}

方法二： 使用ifconfigl命令能很方便的查看網卡與網線是否連通：

# ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 00:25:35:68:CC:D6 
          inet addr:192.168.1.168  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::215:c5ff:fe18:ccd6/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:130722 errors:0 dropped:0 overruns:0 frame:0
          TX packets:112560 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:104371099 (99.5 MiB)  TX bytes:20518584 (19.5 MiB)
          Interrupt:16 

其中的RUNNING就表示網卡與網線正常鏈接，拔掉網線再運行此命令就會發現RUNNING不在了。

    linux系統提供了popen/pclose進程管道讓C和shell很方便的交互，下面C代碼結合shell命令檢測網卡與網線連通狀況：

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

int GetNetStat( )
{
    char    buffer[BUFSIZ];
    FILE    *read_fp;
    int        chars_read;
    int        ret;
   
    memset( buffer, 0, BUFSIZ );
    read_fp = popen("ifconfig eth0 | grep RUNNING", "r");
    if ( read_fp != NULL )
    {
        chars_read = fread(buffer, sizeof(char), BUFSIZ-1, read_fp);
        if (chars_read > 0)
        {
            ret = 1;
        }
        else
        {
            ret = -1;
        }
        pclose(read_fp);
    }
    else
    {
        ret = -1;
    }

    return ret;
}


int main()
{
    int i=0;
    i = GetNetStat();
    printf( "\nNetStat = %d\n", i );
    return 0;
}