The following sample program returns the Ethernet adapter's MAC address from its interface name.
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <net/if.h> /* declares IFNAMSIZ */
#include <net/if_arp.h> /* declares types of link, such as, APRHRD_ETHER */
#include <net/ethernet.h> /* declares ETH_ALEN */
#include <netinet/ip.h> /* declares IPPROTO_IP */
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
int main(int argc, char *argv[])
{
int sockfd, i, addrlen;
struct ifreq ifr;
if (argc < 2) {
fprintf(stderr, "Usage: %s IFNAME\n", argv[0]);
exit(1);
}
/* many network sockets would do, here are 3 examples. */
/* sockfd = socket(AF_PACKET, SOCK_RAW, 0); */
/* sockfd = socket(AF_UNIX, SOCK_DGRAM, 0); */
sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
if (sockfd == -1) {
fprintf(stderr, "Error: calling socket(AF_PACKET, SOCK_DGRAM, 0): %s\n",
strerror(errno));
exit(1);
}
ifr.ifr_name[IFNAMSIZ-1] = '\0';
strncpy(ifr.ifr_name, argv[1], IFNAMSIZ-1);
if (ioctl(sockfd, SIOCGIFHWADDR, &ifr) == -1) {
fprintf(stderr, "Error: calling ioctl(sockfd, SIOCGIFHWADDR, ...): %s\n",
strerror(errno));
exit(1);
}
switch(ifr.ifr_hwaddr.sa_family) {
case ARPHRD_ETHER:
addrlen = ETH_ALEN;
break;
default:
fprintf(stderr, "Warn: not Ethernet, give up ...\n");
exit(1);
}
for (i=0; i<addrlen-1; i++)
printf("%02x:", (unsigned char)ifr.ifr_hwaddr.sa_data[i]);
printf("%02x\n", (unsigned char)ifr.ifr_hwaddr.sa_data[addrlen-1]);
close(sockfd);
return 0;
}
