Getting MAC address from a network interface

Simple sample of getting MAC address information

#include <stdio.h>

#include <string.h> /* for strncpy */

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <netinet/in.h>
#include <net/if.h>

int
main()
{
 int fd;
 struct ifreq ifr;

 fd = socket(AF_INET, SOCK_DGRAM, 0);

 ifr.ifr_addr.sa_family = AF_INET;
 strncpy(ifr.ifr_name, "eth0", IFNAMSIZ-1);

 ioctl(fd, SIOCGIFHWADDR, &ifr);

 close(fd);

 /* display result */
 printf("%.2x:%.2x:%.2x:%.2x:%.2x:%.2x\n",
         (unsigned char)ifr.ifr_hwaddr.sa_data[0],
         (unsigned char)ifr.ifr_hwaddr.sa_data[1],
         (unsigned char)ifr.ifr_hwaddr.sa_data[2],
         (unsigned char)ifr.ifr_hwaddr.sa_data[3],
         (unsigned char)ifr.ifr_hwaddr.sa_data[4],
         (unsigned char)ifr.ifr_hwaddr.sa_data[5]);

 return 0;
}

On Linux platform, you can use ioctl to obtain the MAC address information. To use ioctl, you must create a socket. The important thing is that the socket family used is AF_INET. You can use either TCP(SOCK_STREAM) or UDP(SOCK_DGRAM) socket. This sample uses an UDP socket.

The socket used to get the MAC address information can be closed after obtaining the MAC address information. You can use it as a normal socket to communicate too.