Knowledge Base

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <net/if_dl.h>
#include <ifaddrs.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char ** argv)
{
struct ifaddrs *ifaphead;
unsigned char * if_mac;
int found = 0;
struct ifaddrs *ifap;
struct sockaddr_dl *sdl = NULL;

if (argc < 2)
{
fprintf(stderr,"usage:\n");
fprintf(stderr,"\t %s <interface name>\n",argv[0]);
exit(1);
}

if (getifaddrs(&ifaphead) != 0)
{
perror("get_if_name: getifaddrs() failed");
exit(1);
}

for (ifap = ifaphead; ifap && !found; ifap = ifap->ifa_next)
{
if ((ifap->ifa_addr->sa_family == AF_LINK))
{
if (strlen(ifap->ifa_name) == strlen(argv[1]))
if (strcmp(ifap->ifa_name,argv[1]) == 0)
{
found = 1;
sdl = (struct sockaddr_dl *)ifap->ifa_addr;
if (sdl)
{
/* I was returning this from a function before converting
* this snippet, which is why I make a copy here on the heap */
if_mac = malloc(sdl->sdl_alen);
memcpy(if_mac, LLADDR(sdl), sdl->sdl_alen);
}
}
}
}
if (!found)
{
fprintf (stderr,"Can't find interface %s.\n",argv[1]);
if(ifaphead)
freeifaddrs(ifaphead);
exit(1);
}

fprintf (stdout, "%02X%02X%02X%02X%02X%02X\n",
if_mac[0] , if_mac[1] , if_mac[2] ,
if_mac[3] , if_mac[4] , if_mac[5] );

if(ifaphead)
freeifaddrs(ifaphead);

exit(0);
}