Thread: ioctl request to get the HW address

hi heres my sample code

Code:

#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <sys/ioctl.h>

int main (void)
{
    int sockfd;
    int io;
    char buffer[1024];
    
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if(sockfd < 0){
	perror("socket");
	exit(1);
    }
    
    io = ioctl(sockfd, SIOCGIFHWADDR, (char *)buffer);
    if(io < 0){
	perror("ioctl");
	exit(1);
    }
    
    printf("fetched HW address with ioctl on sockfd.\n");
    printf("HW address of interface is: %s\n", buffer);

    exit(0);
}

why am i getting a "bad address" error with ioctl?
i found the constant used with the ioctl in bits/ioctls.h.

sockfd is obviously a socket but why isnt it working?

thanks

ok i figured out what the third argument must be when requesting the hw address of an interface.

heres the fixed code, with this code i still get an error message: no such device.

why isnt this working out?
do i have to fill something in the ifreq structure?

Code:

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

int main (void)
{
    int sockfd;
    int io;
    struct ifreq *interf;
    /* SIOCGIFHWADDR
    Gets the interface hardware address. argp points to an ifreq structure.
   */
    interf = (struct ifreq *)malloc(sizeof(struct ifreq));
    
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if(sockfd < 0){
	perror("socket");
	exit(1);
    }
    
    io = ioctl(sockfd, SIOCGIFHWADDR, interf);
    if(io < 0){
	perror("ioctl");
	exit(1);
    }

    exit(0);
}

Try this programe.

Code:

#include <sys/ioctl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <net/if.h>
#include <arpa/inet.h>

#include <unistd.h>
#include <stdio.h>
#define MAX_IFS 64

int main()
{
    struct ifreq *ifr, *ifend;
    struct ifreq ifreq;
    struct ifconf ifc;
    struct ifreq ifs[MAX_IFS];
    int SockFD;


    SockFD = socket(AF_INET, SOCK_DGRAM, 0);


    ifc.ifc_len = sizeof(ifs);
    ifc.ifc_req = ifs;
    if (ioctl(SockFD, SIOCGIFCONF, &ifc) < 0)
    {
        printf("ioctl(SIOCGIFCONF): %m\n");
        return 0;
    }


    ifend = ifs + (ifc.ifc_len / sizeof(struct ifreq));
    for (ifr = ifc.ifc_req; ifr < ifend; ifr++)
    {
        if (ifr->ifr_addr.sa_family == AF_INET)
        {
            strncpy(ifreq.ifr_name, ifr->ifr_name,sizeof(ifreq.ifr_name));
            if (ioctl (SockFD, SIOCGIFHWADDR, &ifreq) < 0)
            {
              printf("SIOCGIFHWADDR(%s): %m\n", ifreq.ifr_name);
              return 0;
            }


      printf("Device %s -> Ethernet %02x:%02x:%02x:%02x:%02x:%02x\n", ifreq.ifr_name,
      (int) ((unsigned char *) &ifreq.ifr_hwaddr.sa_data)[0],
      (int) ((unsigned char *) &ifreq.ifr_hwaddr.sa_data)[1],
      (int) ((unsigned char *) &ifreq.ifr_hwaddr.sa_data)[2],
      (int) ((unsigned char *) &ifreq.ifr_hwaddr.sa_data)[3],
      (int) ((unsigned char *) &ifreq.ifr_hwaddr.sa_data)[4],
      (int) ((unsigned char *) &ifreq.ifr_hwaddr.sa_data)[5]);
 }
    }

    return 0;
}

Code:

#include <sys/ioctl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <net/if.h>
#include <arpa/inet.h>

#include <unistd.h>
#include <stdio.h>
#define MAX_IFS 64

int main()
{
    struct ifreq *ifr, *ifend;
    struct ifreq ifreq;
    struct ifconf ifc;
    struct ifreq ifs[MAX_IFS];
    int SockFD;


    SockFD = socket(AF_INET, SOCK_DGRAM, 0);


    ifc.ifc_len = sizeof(ifs);
    ifc.ifc_req = ifs;
    if (ioctl(SockFD, SIOCGIFCONF, &ifc) < 0)
    {
        printf("ioctl(SIOCGIFCONF): %m\n");
        return 0;
    }


    ifend = ifs + (ifc.ifc_len / sizeof(struct ifreq));
    for (ifr = ifc.ifc_req; ifr < ifend; ifr++)
    {
        if (ifr->ifr_addr.sa_family == AF_INET)
        {
            strncpy(ifreq.ifr_name, ifr->ifr_name,sizeof(ifreq.ifr_name));
            if (ioctl (SockFD, SIOCGIFHWADDR, &ifreq) < 0)
            {
              printf("SIOCGIFHWADDR(%s): %m\n", ifreq.ifr_name);
              return 0;
            }

printf("Ip Address %s\n", inet_ntoa( ( (struct sockaddr_in *)  &ifr->ifr_addr)->sin_addr)); 
      printf("Device %s -> Ethernet %02x:%02x:%02x:%02x:%02x:%02x\n", ifreq.ifr_name,
      (int) ((unsigned char *) &ifreq.ifr_hwaddr.sa_data)[0],
      (int) ((unsigned char *) &ifreq.ifr_hwaddr.sa_data)[1],
      (int) ((unsigned char *) &ifreq.ifr_hwaddr.sa_data)[2],
      (int) ((unsigned char *) &ifreq.ifr_hwaddr.sa_data)[3],
      (int) ((unsigned char *) &ifreq.ifr_hwaddr.sa_data)[4],
      (int) ((unsigned char *) &ifreq.ifr_hwaddr.sa_data)[5]);
 }
    }

    return 0;
}

see man page netdevice(7)

thanks

Hello,

I fixed your code. You will need to include the net/if.h and use the struct ifreq to pass the request info (fill in the eth0 for IF name first), and get the result in the same structure.

Code:

#include <sys/types.h> 
#include <sys/socket.h> 
#include <stdio.h> 
#include <sys/ioctl.h> 
#include <net/if.h>

int main (void)  
{ 
  int sockfd; 
  int io; 
  char buffer[1024]; 
  struct ifreq ifr;

  sprintf(ifr.ifr_name, "eth0");
 
  sockfd = socket(AF_INET, SOCK_STREAM, 0); 
  if(sockfd < 0){ 
    perror("socket"); 
    exit(1); 
  } 
 
  io = ioctl(sockfd, SIOCGIFHWADDR, (char *)&ifr); 
  if(io < 0){ 
    perror("ioctl"); 
    exit(1); 
  } 
 
  printf("fetched HW address with ioctl on sockfd.\n"); 
  printf("HW address of interface is: %02X:%02X:%02X:%02X:%02X:%02X\n", 
    (unsigned char)ifr.ifr_ifru.ifru_hwaddr.sa_data[0],
    (unsigned char)ifr.ifr_ifru.ifru_hwaddr.sa_data[1],
    (unsigned char)ifr.ifr_ifru.ifru_hwaddr.sa_data[2],
    (unsigned char)ifr.ifr_ifru.ifru_hwaddr.sa_data[3],
    (unsigned char)ifr.ifr_ifru.ifru_hwaddr.sa_data[4],
    (unsigned char)ifr.ifr_ifru.ifru_hwaddr.sa_data[5]
  ); 
 
  exit(0); 
}

TuomasKK