Index: head/sys/net/if.c
===================================================================
--- head/sys/net/if.c
+++ head/sys/net/if.c
@@ -172,8 +172,8 @@
 static int	if_getgroup(struct ifgroupreq *, struct ifnet *);
 static int	if_getgroupmembers(struct ifgroupreq *);
 static void	if_delgroups(struct ifnet *);
-static void	if_attach_internal(struct ifnet *, int);
-static void	if_detach_internal(struct ifnet *, int);
+static void	if_attach_internal(struct ifnet *, int, struct if_clone *);
+static void	if_detach_internal(struct ifnet *, int, struct if_clone **);
 
 #ifdef INET6
 /*
@@ -558,6 +558,15 @@
  * tasks, given that we are moving from one vnet to another an ifnet which
  * has already been fully initialized.
  *
+ * Note that if_detach_internal() removes group membership unconditionally
+ * even when vmove flag is set, and if_attach_internal() adds only IFG_ALL.
+ * Thus, when if_vmove() is applied to a cloned interface, group membership
+ * is lost while a cloned one always joins a group whose name is
+ * ifc->ifc_name.  To recover this after if_detach_internal() and
+ * if_attach_internal(), the cloner should be specified to
+ * if_attach_internal() via ifc.  If it is non-NULL, if_attach_internal()
+ * attempts to join a group whose name is ifc->ifc_name.
+ *
  * XXX:
  *  - The decision to return void and thus require this function to
  *    succeed is questionable.
@@ -568,7 +577,7 @@
 if_attach(struct ifnet *ifp)
 {
 
-	if_attach_internal(ifp, 0);
+	if_attach_internal(ifp, 0, NULL);
 }
 
 /*
@@ -623,7 +632,7 @@
 }
 
 static void
-if_attach_internal(struct ifnet *ifp, int vmove)
+if_attach_internal(struct ifnet *ifp, int vmove, struct if_clone *ifc)
 {
 	unsigned socksize, ifasize;
 	int namelen, masklen;
@@ -642,6 +651,10 @@
 
 	if_addgroup(ifp, IFG_ALL);
 
+	/* Restore group membership for cloned interfaces. */
+	if (vmove && ifc != NULL)
+		if_clone_addgroup(ifp, ifc);
+
 	getmicrotime(&ifp->if_lastchange);
 	ifp->if_epoch = time_uptime;
 
@@ -860,12 +873,12 @@
 {
 
 	CURVNET_SET_QUIET(ifp->if_vnet);
-	if_detach_internal(ifp, 0);
+	if_detach_internal(ifp, 0, NULL);
 	CURVNET_RESTORE();
 }
 
 static void
-if_detach_internal(struct ifnet *ifp, int vmove)
+if_detach_internal(struct ifnet *ifp, int vmove, struct if_clone **ifcp)
 {
 	struct ifaddr *ifa;
 	struct radix_node_head	*rnh;
@@ -894,6 +907,10 @@
 			return; /* XXX this should panic as well? */
 	}
 
+	/* Check if this is a cloned interface or not. */
+	if (vmove && ifcp != NULL)
+		*ifcp = if_clone_findifc(ifp);
+
 	/*
 	 * Remove/wait for pending events.
 	 */
@@ -999,12 +1016,13 @@
 void
 if_vmove(struct ifnet *ifp, struct vnet *new_vnet)
 {
+	struct if_clone *ifc;
 
 	/*
 	 * Detach from current vnet, but preserve LLADDR info, do not
 	 * mark as dead etc. so that the ifnet can be reattached later.
 	 */
-	if_detach_internal(ifp, 1);
+	if_detach_internal(ifp, 1, &ifc);
 
 	/*
 	 * Unlink the ifnet from ifindex_table[] in current vnet, and shrink
@@ -1034,7 +1052,7 @@
 	ifnet_setbyindex_locked(ifp->if_index, ifp);
 	IFNET_WUNLOCK();
 
-	if_attach_internal(ifp, 1);
+	if_attach_internal(ifp, 1, ifc);
 
 	CURVNET_RESTORE();
 }
Index: head/sys/net/if_clone.h
===================================================================
--- head/sys/net/if_clone.h
+++ head/sys/net/if_clone.h
@@ -69,6 +69,8 @@
 int	if_clone_create(char *, size_t, caddr_t);
 int	if_clone_destroy(const char *);
 int	if_clone_list(struct if_clonereq *);
+struct if_clone *if_clone_findifc(struct ifnet *);
+void	if_clone_addgroup(struct ifnet *, struct if_clone *);
 
 /* The below interface used only by epair(4). */
 int	if_clone_destroyif(struct if_clone *, struct ifnet *);
Index: head/sys/net/if_clone.c
===================================================================
--- head/sys/net/if_clone.c
+++ head/sys/net/if_clone.c
@@ -518,6 +518,49 @@
 }
 
 /*
+ * if_clone_findifc() looks up ifnet from the current
+ * cloner list, and returns ifc if found.  Note that ifc_refcnt
+ * is incremented.
+ */
+struct if_clone *
+if_clone_findifc(struct ifnet *ifp)
+{
+	struct if_clone *ifc, *ifc0;
+	struct ifnet *ifcifp;
+
+	ifc0 = NULL;
+	IF_CLONERS_LOCK();
+	LIST_FOREACH(ifc, &V_if_cloners, ifc_list) {
+		IF_CLONE_LOCK(ifc);
+		LIST_FOREACH(ifcifp, &ifc->ifc_iflist, if_clones) {
+			if (ifp == ifcifp) {
+				ifc0 = ifc;
+				IF_CLONE_ADDREF_LOCKED(ifc);
+				break;
+			}
+		}
+		IF_CLONE_UNLOCK(ifc);
+		if (ifc0 != NULL)
+			break;
+	}
+	IF_CLONERS_UNLOCK();
+
+	return (ifc0);
+}
+
+/*
+ * if_clone_addgroup() decrements ifc_refcnt because it is called after
+ * if_clone_findifc().
+ */
+void
+if_clone_addgroup(struct ifnet *ifp, struct if_clone *ifc)
+{
+
+	if_addgroup(ifp, ifc->ifc_name);
+	IF_CLONE_REMREF(ifc);
+}
+
+/*
  * A utility function to extract unit numbers from interface names of
  * the form name###.
  *