The iptunnel applet belongs in /sbin not /bin to match other systems
as well as the full version from net-tools.
Index: busybox-1.18.4/include/applets.src.h
===================================================================
--- busybox-1.18.4.orig/include/applets.src.h
+++ busybox-1.18.4/include/applets.src.h
@@ -249,7 +249,7 @@ IF_IPCS(APPLET(ipcs, _BB_DIR_USR_BIN, _B
 IF_IPLINK(APPLET(iplink, _BB_DIR_BIN, _BB_SUID_DROP))
 IF_IPROUTE(APPLET(iproute, _BB_DIR_BIN, _BB_SUID_DROP))
 IF_IPRULE(APPLET(iprule, _BB_DIR_BIN, _BB_SUID_DROP))
-IF_IPTUNNEL(APPLET(iptunnel, _BB_DIR_BIN, _BB_SUID_DROP))
+IF_IPTUNNEL(APPLET(iptunnel, _BB_DIR_SBIN, _BB_SUID_DROP))
 IF_KBD_MODE(APPLET(kbd_mode, _BB_DIR_USR_BIN, _BB_SUID_DROP))
 IF_KILL(APPLET(kill, _BB_DIR_BIN, _BB_SUID_DROP))
 IF_KILLALL(APPLET_ODDNAME(killall, kill, _BB_DIR_USR_BIN, _BB_SUID_DROP, killall))