diff --git a/libc/include/net/if.h b/libc/include/net/if.h
index 0efbf7f..aa4c19e 100644
--- a/libc/include/net/if.h
+++ b/libc/include/net/if.h
@@ -39,11 +39,15 @@
 
 __BEGIN_DECLS
 
-/*
- * Map an interface name into its corresponding index.
- */
-extern unsigned int if_nametoindex(const char *);
-extern char*        if_indextoname(unsigned ifindex, char *ifname);
+struct if_nameindex {
+  unsigned if_index;
+  char* if_name;
+};
+
+char* if_indextoname(unsigned, char*);
+unsigned if_nametoindex(const char*);
+struct if_nameindex* if_nameindex(void);
+void if_freenameindex(struct if_nameindex*);
 
 __END_DECLS