Re: how to get interface information

[Miika Komu <miika@xxxxxx>]

On Wed, 9 Feb 2005, Jochen Witte wrote:

> Hello,
>
> I would like to get a list of all my current ip-adresses in a C program.
> How do I do this? Do I really have to use ioctl? Or is there something
> simple/portable out there?

Something like this:

#include <sys/types.h>
#include <sys/socket.h>
#include <ifaddrs.h>
#include <net/if.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include "libinet6/debug.h"

int debug_sockaddr(int family, const struct sockaddr *sockaddr) {
      int maxlen;
      void *addr;
      char addr_str[INET6_ADDRSTRLEN+1];

      switch (family) {
      case AF_INET:
        maxlen = INET_ADDRSTRLEN;
        addr = &(((struct sockaddr_in *) sockaddr)->sin_addr);
        break;
      case AF_INET6:
        maxlen = INET6_ADDRSTRLEN;
        addr = &(((struct sockaddr_in6 *) sockaddr)->sin6_addr);
        break;
      default:
        maxlen = 0;
      }

      if (!inet_ntop(family, addr, addr_str, maxlen)) {
        printf(stderr, "inet_ntop");
        return -1;
      }

      printf("%s\n", addr_str);

      return 0;
}

int main(int argc,char *argv[]) {
  struct ifaddrs *g_ifaces = NULL, *g_iface;
  struct if_nameindex *i_ifaces = NULL, *i_iface;
  int err = 0;
  char *default_str = "<unknown>";
  char addr_str[INET6_ADDRSTRLEN+1]; /* Segfault? Alloc this dynamically?x
*/

  /* getifaddrs */

  err = getifaddrs(&g_ifaces);
  if (err) {
    fprintf(stderr,"getifaddr failed\n");
    goto out;
  }

  printf("===getifaddrs===\n");
  for (g_iface = g_ifaces; g_iface; g_iface = g_iface->ifa_next) {
    sa_family_t family = g_iface->ifa_addr->sa_family;
    printf("name: %s, family: %d, address: ", g_iface->ifa_name, family);
    debug_sockaddr("", family, g_iface->ifa_addr);
  }

  /* if_nameindex */

  printf("===nameindex===\n");
  i_ifaces = if_nameindex();
  for (i_iface = i_ifaces; i_iface->if_index; i_iface++) {
    printf("name: %s index: %d\n", i_iface->if_name, i_iface->if_index);
  }

 out:

  if (g_ifaces)
    freeifaddrs(g_ifaces);
  if (i_ifaces)
    if_freenameindex(i_ifaces);
}

-- 
Miika Komu              miika@xxxxxx          http://www.iki.fi/miika/
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