diff --git a/sys/net/if_clone.h b/sys/net/if_clone.h
--- a/sys/net/if_clone.h
+++ b/sys/net/if_clone.h
@@ -101,6 +101,11 @@
 #define	IFC_F_SYSSPACE	0x04	/* Cloner callback: params pointer is in kernel memory */
 #define	IFC_F_FORCE	0x08	/* Deletion flag: force interface deletion */
 #define	IFC_F_CREATE	0x10	/* Creation flag: indicate creation request */
+#define	IFC_F_LIMITUNIT	0x20	/* Creation flag: the unit number is limited */
+
+_Static_assert(offsetof(struct if_clone_addreq, destroy_f) ==
+    offsetof(struct if_clone_addreq_v2, destroy_f),
+    "destroy_f in if_clone_addreq and if_clone_addreq_v2 are at different offset");
 
 struct if_clone	*ifc_attach_cloner(const char *name, struct if_clone_addreq *req);
 void ifc_detach_cloner(struct if_clone *ifc);
diff --git a/sys/net/if_clone.c b/sys/net/if_clone.c
--- a/sys/net/if_clone.c
+++ b/sys/net/if_clone.c
@@ -483,12 +483,13 @@
 	struct if_clone *ifc;
 
 	KASSERT(name != NULL, ("%s: no name\n", __func__));
+	MPASS(maxunit >= 0);
 
 	ifc = malloc(sizeof(struct if_clone), M_CLONE, M_WAITOK | M_ZERO);
 	strncpy(ifc->ifc_name, name, IFCLOSIZ-1);
 	IF_CLONE_LOCK_INIT(ifc);
 	IF_CLONE_ADDREF(ifc);
-	ifc->ifc_maxunit = maxunit ? maxunit : IF_MAXUNIT;
+	ifc->ifc_maxunit = maxunit;
 	ifc->ifc_unrhdr = new_unrhdr(0, ifc->ifc_maxunit, &ifc->ifc_mtx);
 	LIST_INIT(&ifc->ifc_iflist);
 
@@ -521,12 +522,16 @@
 struct if_clone *
 ifc_attach_cloner(const char *name, struct if_clone_addreq *req)
 {
+	int maxunit;
+	struct if_clone *ifc;
+
 	if (req->create_f == NULL || req->destroy_f == NULL)
 		return (NULL);
 	if (strnlen(name, IFCLOSIZ) >= (IFCLOSIZ - 1))
 		return (NULL);
 
-	struct if_clone *ifc = if_clone_alloc(name, req->maxunit);
+	maxunit = (req->flags & IFC_F_LIMITUNIT) ? req->maxunit : IF_MAXUNIT;
+	ifc = if_clone_alloc(name, maxunit);
 	ifc->ifc_match = req->match_f != NULL ? req->match_f : ifc_simple_match;
 	ifc->ifc_create = req->create_f;
 	ifc->ifc_destroy = req->destroy_f;
@@ -584,7 +589,7 @@
 {
 	struct if_clone *ifc;
 
-	ifc = if_clone_alloc(name, maxunit);
+	ifc = if_clone_alloc(name, maxunit ? maxunit : IF_MAXUNIT);
 	ifc->ifc_match = match;
 	ifc->ifc_create = ifc_advanced_create_wrapper;
 	ifc->ifc_destroy = ifc_advanced_destroy_wrapper;
@@ -629,7 +634,7 @@
 	struct if_clone *ifc;
 	u_int unit;
 
-	ifc = if_clone_alloc(name, 0);
+	ifc = if_clone_alloc(name, IF_MAXUNIT);
 	ifc->ifc_match = ifc_simple_match;
 	ifc->ifc_create = ifc_simple_create_wrapper;
 	ifc->ifc_destroy = ifc_simple_destroy_wrapper;