OpenWrt permanently modifies MAC address source code

*
* Flash MAC
* Copyright (C) 2014 Wrtnode machine team.
* This are free software; You can redistribute it and/or modify
*
* Cross-compile with Cross-gcc-i/path/to/cross-kernel/include
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <unistd.h>
#include <stdint.h>
#define Memerase _iow (' M ', 2, struct erase_info_user)

struct Erase_info_user {
uint32_t start;
uint32_t length;
};

int main (int argc,char *argv[])
{
int fd,sz,i,offset=0x04;
int mac[6];
SZ = 0x10000;
unsigned char *buf;
BUF = (unsigned char *) malloc (SZ);
for (i=0;i<6;i++) {
Mac[i] = Strtol (argv[i+1], NULL, 16);
}
if (mac[0]%4!=0)
{
printf ("Mac[0]%4==0,please input a Effective Mac again\n");
return-1;
}
FD = open ("/dev/mtd2", O_RDWR | O_sync);
if (FD < 0) {
fprintf (stderr, "failed to open mtd2\n");
Free (BUF);
return-1;
}
Read-----------
Lseek (FD, 0, Seek_set);
Backup
If Read (FD, buf, SZ)!= sz) {
fprintf (stderr, "failed to read%d bytes from mtd2\n",
SZ);
Free (BUF);
Close (FD);
return-1;
}
Erase
struct Erase_info_user ei;
Lseek (FD, 0, Seek_set);
Ei.start = 0;
Ei.length = sz;
if (IOCTL (FD, Memerase, &ei) < 0) {
fprintf (stderr, "failed to erase mtd2\n");
Free (BUF);
Close (FD);
return-1;
}
for (i=0;i<6;i++) {
* (buf + (offset) + i) = Mac[i];
}
Write
Lseek (FD, 0, Seek_set);
If write (FD, buf, sz) = = 1) {
fprintf (stderr, "failed to write mtd%d\n", i);
Free (BUF);
Close (FD);
return-1;
}
Free (BUF);
Close (FD);
return 0;
}