修改MAC地址的方法（未测试）

用ioctl控制，通过SIOCGIFHWADDR获取MAC地址，SIOCSIFHWADDR设置MAC地址，不过在设

置MAC地址之前，要先把网卡down掉，设置好了以后，再UP起来。

#include <sys/types.h>  /* for socket(2) and related bits and pieces */
#include <sys/socket.h> /* for socket(2) */
#include <net/if.h>     /* for struct ifreq */
#include <net/if_arp.h> /* for ARPHRD_ETHER */
#include <sys/ioctl.h>  /* for IOCTL's */
#include <stdio.h>      /* for fprintf etc */
#include <unistd.h>     /* for close */

int main(int argc,char **argv)
{

    struct ifreq ifr;
    int skfd;

    if (argc<3) 
　{

        fprintf(stderr,"usage:/n%s interface hwaddr/n",argv[1]);

        return 1;

    }

    /* Fill in the structure */

    snprintf(ifr.ifr_name, IFNAMSIZ, "%s", argv[1]);

    ifr.ifr_hwaddr.sa_family = ARPHRD_ETHER;

    /* TODO: write some code to parse argv[2] into ifr.ifr_hwaddr.sa_data */

    /* memcpy(&ifr.ifr_hwaddr.sa_data, argv[2], sizeof(ether.address)); */

    /* Create a socket fd */

    skfd = socket(PF_INET,SOCK_STREAM,0);

    /* call the IOCTL */

    if (ioctl(skfd, SIOCSIFHWADDR, &ifr) < 0) {

        perror("ioctl(SIOCSIFHWADDR)");

        return 1;

    }