Having a problem figuring out how to get Ethernet interface info on Mac OS X using ioctl/SIOCGIFADDR/SIOCGIFCONF?

Question

Are you having a problem figuring out how to get interface info on Mac OS X using ioctl/SIOCGIFADDR/SIOCGIFCONF?

I had a lot of trouble getting code that worked fine on Linux to work on Mac OS X today.

Answer 1

Copy-paste to main.c and gcc main.c && ./a.out should work (lists all network interfaces, their ipv4/6 address, netmask and MAC address if associated):

Works fine on Mac OSX and iOS iPad/iPhone:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <net/if.h>
#include <net/if_dl.h>
#include <ifaddrs.h>
#include <errno.h>

int main() {
  struct ifaddrs *if_addrs = NULL;
  struct ifaddrs *if_addr = NULL;
  void *tmp = NULL;
  char buf[INET6_ADDRSTRLEN];
  if (0 == getifaddrs(&if_addrs)) {    
    for (if_addr = if_addrs; if_addr != NULL; if_addr = if_addr->ifa_next) {

      printf("name : %s\n", if_addr->ifa_name);

      // Address
      if (if_addr->ifa_addr->sa_family == AF_INET) {
        tmp = &((struct sockaddr_in *)if_addr->ifa_addr)->sin_addr;
      } else {
        tmp = &((struct sockaddr_in6 *)if_addr->ifa_addr)->sin6_addr;
      }
      printf("addr : %s\n",
             inet_ntop(if_addr->ifa_addr->sa_family,
                       tmp,
                       buf,
                       sizeof(buf)));

      // Mask
      if (if_addr->ifa_netmask != NULL) {
        if (if_addr->ifa_netmask->sa_family == AF_INET) {
          tmp = &((struct sockaddr_in *)if_addr->ifa_netmask)->sin_addr;
        } else {
          tmp = &((struct sockaddr_in6 *)if_addr->ifa_netmask)->sin6_addr;
        }
        printf("mask : %s\n",
               inet_ntop(if_addr->ifa_netmask->sa_family,
                         tmp,
                         buf,
                         sizeof(buf)));
      }

      // MAC address
      if (if_addr->ifa_addr != NULL && if_addr->ifa_addr->sa_family == AF_LINK) {
        struct sockaddr_dl* sdl = (struct sockaddr_dl *)if_addr->ifa_addr;
        unsigned char mac[6];
        if (6 == sdl->sdl_alen) {
          memcpy(mac, LLADDR(sdl), sdl->sdl_alen);
          printf("mac  : %02x:%02x:%02x:%02x:%02x:%02x\n", mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
        }
      }

      printf("\n");
    }
    freeifaddrs(if_addrs);
    if_addrs = NULL;
  } else {
    printf("getifaddrs() failed with errno =  %i %s\n", errno, strerror(errno));
    return -1;
  }
}