Index: sys/net/if.c
===================================================================
--- sys/net/if.c
+++ sys/net/if.c
@@ -615,6 +615,8 @@
 	struct ifnet *ifp;
 
 	ifp = __containerof(ctx, struct ifnet, if_epoch_ctx);
+	if (ifp->if_cleanup != NULL)
+		ifp->if_cleanup(ifp);
 	if_free_internal(ifp);
 }
 
Index: sys/net/if_lagg.c
===================================================================
--- sys/net/if_lagg.c
+++ sys/net/if_lagg.c
@@ -129,6 +129,7 @@
 static void	lagg_init(void *);
 static void	lagg_stop(struct lagg_softc *);
 static int	lagg_ioctl(struct ifnet *, u_long, caddr_t);
+static void	lagg_cleanup(struct ifnet *);
 #ifdef RATELIMIT
 static int	lagg_snd_tag_alloc(struct ifnet *,
 		    union if_snd_tag_alloc_params *,
@@ -511,6 +512,7 @@
 	ifp->if_init = lagg_init;
 	ifp->if_ioctl = lagg_ioctl;
 	ifp->if_get_counter = lagg_get_counter;
+	ifp->if_cleanup = lagg_cleanup;
 	ifp->if_flags = IFF_SIMPLEX | IFF_BROADCAST | IFF_MULTICAST;
 #ifdef RATELIMIT
 	ifp->if_snd_tag_alloc = lagg_snd_tag_alloc;
@@ -568,6 +570,12 @@
 	LAGG_LIST_LOCK();
 	SLIST_REMOVE(&V_lagg_list, sc, lagg_softc, sc_entries);
 	LAGG_LIST_UNLOCK();
+}
+
+static void
+lagg_cleanup(struct ifnet *ifp)
+{
+	struct lagg_softc *sc = ifp->if_softc;
 
 	LAGG_SX_DESTROY(sc);
 	free(sc, M_DEVBUF);
Index: sys/net/if_var.h
===================================================================
--- sys/net/if_var.h
+++ sys/net/if_var.h
@@ -133,6 +133,7 @@
 typedef void (*if_qflush_fn_t)(if_t);
 typedef int (*if_transmit_fn_t)(if_t, struct mbuf *);
 typedef	uint64_t (*if_get_counter_t)(if_t, ift_counter);
+typedef void (*if_cleanup_fn_t)(if_t);
 
 struct ifnet_hw_tsomax {
 	u_int	tsomaxbytes;	/* TSO total burst length limit in bytes */
@@ -331,7 +332,8 @@
 	int	(*if_resolvemulti)	/* validate/resolve multicast */
 		(struct ifnet *, struct sockaddr **, struct sockaddr *);
 	if_qflush_fn_t	if_qflush;	/* flush any queue */	
-	if_transmit_fn_t if_transmit;   /* initiate output routine */
+	if_transmit_fn_t if_transmit;	/* initiate output routine */
+	if_cleanup_fn_t	if_cleanup;	/* clean up and free softc */
 
 	void	(*if_reassign)		/* reassign to vnet routine */
 		(struct ifnet *, struct vnet *, char *);