Finding original MAC address from Hardware itself

Question

Os:REDHAT LINUX Linux manage: 2.6.18.8-1 #

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;
}

Just because it is burned there, does not mean it HAS to be available. I don't know how linux and the cards work, but it would be entirely plausible if the MAC was only restored on a power cycle when the cards' firmware does initialization. — Prof. Falken
I just want to UP my machine with SPOOFED MAC and I can do it successfully . but during that I want my original MAC for my application. that is my issue. — Jatin Bodarya
I think @AmigableClarkKant is suggesting that a full power cycle might make the NIC initialize from firmware. Don't just restart; shutdown, wait, power on. That might restart the NIC with its original MAC address. Then you could retrieve and store the original MAC address before you change it at run time. — Mike Sherrill 'Cat Recall'
ohh.... I have no Idea How to do that Pragmatically.. There is no other way that I can get it whenever I want in my application... using C code (without storing it somewhere) — Jatin Bodarya
It is a matter of "how do you get that information", assuming it is available. All the drivers for the network cards will know how to do this, but like I describe below, the information is read then stored, and if that gets overwritten later, then that's it - gone. You could add some code to each driver, but that would be a lot of work, and almost certain not to get into the Linux kernel, so you'd forever carry a patch for every network driver available - that would be rather a lot of effort to maintain... — Mats Petersson

Jason M Jason M · Accepted Answer · 2013-12-19T16:26:19

Certainly in ethtool 3.1 you can just print the address: ethtool -P|--show-permaddr DEVNAME Show permanent hardware address

e.g.

ethtool -P eth0

Permanent address: 94:de:80:6a:21:25

Finding original MAC address from Hardware itself

7 Answers