Unix Programming - How to read the MAC Address out of /proc or /sys

Author

How to read the MAC Address out of /proc or /sys

Niko Schwarz

2005-01-23, 8:58 pm

Hello,

I'm writing a little obstacle for users to mass-copy programs my
university wrote.
It works fine already, I do it through the MAC address, which I read
from /sbin/ifconfig.

But: How can I read the MAC Address out of /proc? I s

ed it a
little, but the file put out in the manual, /proc/net/socket doesn't
exist.
In /sys I don't find anything either. The only useful thing I found
was the ip6 address, which seems to contain the MAC Address.

Please don't tell me how unsafe all this is - I know it perfectly. And
I don't care much, it's not for me, I'd probably just rely on the
user's honesty.

Thanks in advance,

niko

Average Joe

2005-01-28, 8:57 am

Niko Schwarz wrote:
> Hello,
>
> I'm writing a little obstacle for users to mass-copy programs my
> university wrote. It works fine already, I do it through the MAC
> address, which I read from /sbin/ifconfig.

This isn't through /proc, but it's just another way to do it without:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <net/if.h>
#include <arpa/inet.h>

int main(void)
{
int sfd;
unsigned char *u;
struct ifreq ifr;
struct sockaddr_in *sin = (struct sockaddr_in *) &ifr.ifr_addr;

memset(&ifr, 0, sizeof ifr);

if (0 > (sfd = socket(AF_INET, SOCK_STREAM, 0))) {
perror("socket()");
exit(EXIT_FAILURE);
}

strcpy(ifr.ifr_name, "eth0");
sin->sin_family = AF_INET;

if (0 == ioctl(sfd, SIOCGIFADDR, &ifr)) {
printf("%s: %s\n", ifr.ifr_name, inet_ntoa(sin->sin_addr));
}

if (0 > ioctl(sfd, SIOCGIFHWADDR, &ifr)) {
return EXIT_FAILURE;
}

u = (unsigned char *) &ifr.ifr_addr.sa_data;

if (u[0] + u[1] + u[2] + u[3] + u[4] + u[5]) {
printf("HW Address: %2.2x:%2.2x:%2.2x:%2.2x:%2.2x:%2.2x\n",
u[0], u[1], u[2], u[3], u[4], u[5]);
}

return EXIT_SUCCESS;
}

--
Average Joe

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