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;
}
