If including vnet.h one has to include opt_route.h as well. This is

because struct vnet_net holds the rt_tables[][] for MRT and array size
is compile time dependent.  If you had ROUTETABLES set to >1 after
r192011 V_loif was pointing into nonsense leading to strange results
or even panics for some people.

Reviewed by:	mz

sys/netinet/in.c

@@ -34,6 +34,7 @@
 __FBSDID("$FreeBSD$");
 
 #include "opt_carp.h"
+#include "opt_route.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>