+++ b/sysdeps/unix/sysv/linux/if_index.c
@@ -38,12 +38,19 @@ __if_nametoindex (const char *ifname)
   return 0;
 #else
   struct ifreq ifr;
+  if (strlen (ifname) >= IFNAMSIZ)
+    {
+      __set_errno (ENODEV);
+      return 0;
+    }
+
+  strncpy (ifr.ifr_name, ifname, sizeof (ifr.ifr_name));
+
   int fd = __opensock ();
 
   if (fd < 0)
     return 0;