Finding original MAC address from Hardware itself

Is this possible to read MAC address form NIC directly ? I have below code but it just read from above layer but not the card itself !!!

I'm trying to figure out how to find the original MAC address of an ethernet NIC on my linux box. I understand how to find the current MAC address using ifconfig, but if the address has been changed, say by using 'ifconfig eth0 hw ether uu:vv:ww:yy:xx:zz',or I set "permanent" it using vi /etc/sysconfig/network-scripts/ifcfg-eth0.this file...I can successfully UP it in REBOOT also. how do I find the original? There must be a way to find it, because it is still burned permanently into the card, but I can't find a tool to read the burned in address. is there any utility for it or command for it? I suppose to write C code for it. but don't know how to do this in above case.

** below code gives my current MAC but not original MAC

#include <stdio.h>              /* Standard I/O */
#include <stdlib.h>             /* Standard Library */
#include <errno.h>              /* Error number and related */


#define ENUMS
#include <sys/socket.h>
#include <net/route.h>
#include <net/if.h>
#include <features.h>           /* for the glibc version number */
#if __GLIBC__ >= 2 && __GLIBC_MINOR >= 1
#include <netpacket/packet.h>
#include <net/ethernet.h>       /* the L2 protocols */
#else
#include <asm/types.h>
#include <linux/if_packet.h>
#include <linux/if_ether.h>     /* The L2 protocols */
#endif
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/un.h>
#include <sys/ioctl.h>
#include <netdb.h>


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

unsigned char  mac[IFHWADDRLEN];
int i;
    get_local_hwaddr( argv[1], mac );
    for( i = 0; i < IFHWADDRLEN; i++ ){
        printf( "%02X:", (unsigned int)(mac[i]) );
    }

}


int get_local_hwaddr(const char *ifname, unsigned char *mac)
{
    struct ifreq ifr;
    int fd;
    int rv;                     // return value - error value from df or ioctl call

    /* determine the local MAC address */
    strcpy(ifr.ifr_name, ifname);
    fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
    if (fd < 0)
        rv = fd;
    else {
        rv = ioctl(fd, SIOCGIFHWADDR, &ifr);
        if (rv >= 0)            /* worked okay */
            memcpy(mac, ifr.ifr_hwaddr.sa_data, IFHWADDRLEN);
    }

    return rv;
}

Answers;-

Well, the old ethernet address remains in the first bytes of the card eeprom (at least for some types of cards), so it is possible to extract it using ethtool
bash$ sudo ethtool -e eth1
Offset      Values
------      ------
0x0000      tt uu ww xx yy zz 79 03 
0x....
where tt:uu:ww:xx:yy:zz is old mac address

Posted in: Embedded System