4-7 インターフェース一覧を取得する

#include <stdio.h>
#include <string.h>
#include <ifaddrs.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

int
main()
{
  struct ifaddrs *ifa_list;
  struct ifaddrs *ifa;
  int n;
  char addrstr[256], netmaskstr[256];

  n = getifaddrs(&ifa_list);
  if (n != 0) {
    return 1;
  }

  for(ifa = ifa_list; ifa != NULL; ifa=ifa->ifa_next) {
    printf("%s\n", ifa->ifa_name);
    printf(" 0x%.8x\n", ifa->ifa_flags);

    memset(addrstr, 0, sizeof(addrstr));
    memset(netmaskstr, 0, sizeof(netmaskstr));
    if (ifa->ifa_addr->sa_family == AF_INET) {
      inet_ntop(AF_INET,
        &((struct sockaddr_in *)ifa->ifa_addr)->sin_addr,
        addrstr, sizeof(addrstr));
      inet_ntop(AF_INET,
        &((struct sockaddr_in *)ifa->ifa_netmask)->sin_addr,
        netmaskstr, sizeof(netmaskstr));

       printf(" IPv4: %s netmask %s\n", addrstr, netmaskstr);
    } else if (ifa->ifa_addr->sa_family == AF_INET6) {
      inet_ntop(AF_INET6,
        &((struct sockaddr_in6 *)ifa->ifa_addr)->sin6_addr,
        addrstr, sizeof(addrstr));
      inet_ntop(AF_INET6,
        &((struct sockaddr_in6 *)ifa->ifa_netmask)->sin6_addr,
       netmaskstr, sizeof(netmaskstr));

      printf(" IPv6: %s netmask %s\n", addrstr, netmaskstr);
    } else if (ifa->ifa_addr->sa_family == AF_PACKET) {
      printf(" af_packet:%d\n", ifa->ifa_addr->sa_family);
    } else {
      printf(" else:%d\n", ifa->ifa_addr->sa_family);
    }

    printf("\n");
  }

  freeifaddrs(ifa_list);

  return 0;
}

拙著「Linuxネットワークプログラミング」の紹介