The macro versions of htonl et al don't require them, but POSIX says

<arpa/inet.h> needs to provide uint16_t and uint32_t.
ok millert@ krw@ naddy@

src/include/arpa/inet.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: inet.h,v 1.20 2017/02/04 02:54:33 guenther Exp $	*/
+/*	$OpenBSD: inet.h,v 1.21 2017/02/04 19:16:25 guenther Exp $	*/
 
 /*
  * ++Copyright++ 1983, 1993
@@ -71,6 +71,16 @@
 #define ntohl(x)	__htobe32(x)
 #endif
 
+#ifndef	_UINT16_T_DEFINED_
+#define	_UINT16_T_DEFINED_
+typedef	__uint16_t	uint16_t;
+#endif
+
+#ifndef	_UINT32_T_DEFINED_
+#define	_UINT32_T_DEFINED_
+typedef	__uint32_t	uint32_t;
+#endif
+
 #ifndef	_SOCKLEN_T_DEFINED_
 #define	_SOCKLEN_T_DEFINED_
 typedef	__socklen_t	socklen_t;	/* length type for network syscalls */