Build if_stf(4) module only when both INET and INET6 support are enabled.

sys/modules/Makefile

@@ -149,7 +149,7 @@ SUBDIR=	\
 	${_if_me} \
 	if_lagg \
 	${_if_ndis} \
-	if_stf \
+	${_if_stf} \
 	if_tap \
 	if_tun \
 	if_vlan \
@@ -411,6 +411,11 @@ _if_gif=	if_gif
 _if_gre=	if_gre
 .endif
 
+.if (${MK_INET_SUPPORT} != "no" && ${MK_INET6_SUPPORT} != "no") || \
+	defined(ALL_MODULES)
+_if_stf=	if_stf
+.endif
+
 .if ${MK_INET_SUPPORT} != "no" || defined(ALL_MODULES)
 _if_me=		if_me
 _ipdivert=	ipdivert

sys/modules/if_stf/Makefile

@@ -3,6 +3,6 @@
 .PATH: ${.CURDIR}/../../net
 
 KMOD=	if_stf
-SRCS=	if_stf.c opt_inet.h opt_inet6.h
+SRCS=	if_stf.c
 
 .include <bsd.kmod.mk>

sys/net/if_stf.c

@@ -74,9 +74,6 @@
  * Note that there is no way to be 100% secure.
  */
 
-#include "opt_inet.h"
-#include "opt_inet6.h"
-
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/socket.h>