--- /dev/null
+#define _GNU_SOURCE
+#include <net/if.h>
+#include <stdlib.h>
+#include <sys/socket.h>
+#include <sys/ioctl.h>
+#include <errno.h>
+#include "syscall.h"
+
+#include <stdio.h>
+
+static void *do_nameindex(int s, size_t n)
+{
+ size_t i, len;
+ struct ifconf conf;
+ struct if_nameindex *idx;
+
+ idx = malloc(n * (sizeof(struct if_nameindex)+sizeof(struct ifreq)));
+ if (!idx) return 0;
+
+ conf.ifc_buf = (void *)&idx[n];
+ conf.ifc_len = len = n * sizeof(struct ifreq);
+ if (ioctl(s, SIOCGIFCONF, &conf) < 0) {
+ free(idx);
+ return 0;
+ }
+ if (conf.ifc_len == len) {
+ free(idx);
+ return (void *)-1;
+ }
+
+ n = conf.ifc_len / sizeof(struct ifreq);
+ for (i=0; i<n; i++) {
+ if (ioctl(s, SIOCGIFINDEX, &conf.ifc_req[i]) < 0) {
+ i--;
+ n--;
+ continue;
+ }
+ idx[i].if_index = conf.ifc_req[i].ifr_ifindex;
+ idx[i].if_name = conf.ifc_req[i].ifr_name;
+ }
+ idx[i].if_name = 0;
+ idx[i].if_index = 0;
+
+ return idx;
+}
+
+struct if_nameindex *if_nameindex()
+{
+ size_t n;
+ void *p = 0;
+ int s = socket(AF_UNIX, SOCK_DGRAM, 0);
+ if (s>=0) {
+ for (n=0; (p=do_nameindex(s, n)) == (void *)-1; n++);
+ __syscall(SYS_close, s);
+ }
+ errno = ENOBUFS;
+ return p;
+}