Index: ifq.c
===================================================================
RCS file: /cvs/src/sys/net/ifq.c,v
retrieving revision 1.6
diff -u -p -r1.6 ifq.c
--- ifq.c	24 Jan 2017 03:57:35 -0000	1.6
+++ ifq.c	2 Mar 2017 00:31:53 -0000
@@ -29,7 +29,7 @@
  * priq glue
  */
 unsigned int	 priq_idx(unsigned int, const struct mbuf *);
-int		 priq_enq(struct ifqueue *, struct mbuf *);
+struct mbuf	*priq_enq(struct ifqueue *, struct mbuf *);
 struct mbuf	*priq_deq_begin(struct ifqueue *, void **);
 void		 priq_deq_commit(struct ifqueue *, struct mbuf *, void *);
 void		 priq_purge(struct ifqueue *, struct mbuf_list *);
@@ -225,7 +225,8 @@ ifq_attach(struct ifqueue *ifq, const st
 	ifq->ifq_q = newq;
 
 	while ((m = ml_dequeue(&ml)) != NULL) {
-		if (ifq->ifq_ops->ifqop_enq(ifq, m) != 0) {
+		m = ifq->ifq_ops->ifqop_enq(ifq, m);
+		if (m != NULL) {
 			ifq->ifq_qdrops++;
 			ml_enqueue(&free_ml, m);
 		} else
@@ -252,13 +253,14 @@ ifq_destroy(struct ifqueue *ifq)
 }
 
 int
-ifq_enqueue_try(struct ifqueue *ifq, struct mbuf *m)
+ifq_enqueue(struct ifqueue *ifq, struct mbuf *m)
 {
+	struct mbuf *dm;
 	int rv;
 
 	mtx_enter(&ifq->ifq_mtx);
-	rv = ifq->ifq_ops->ifqop_enq(ifq, m);
-	if (rv == 0) {
+	dm = ifq->ifq_ops->ifqop_enq(ifq, m);
+	if (dm == NULL) {
 		ifq->ifq_len++;
 
 		ifq->ifq_packets++;
@@ -269,19 +271,14 @@ ifq_enqueue_try(struct ifqueue *ifq, str
 		ifq->ifq_qdrops++;
 	mtx_leave(&ifq->ifq_mtx);
 
-	return (rv);
-}
-
-int
-ifq_enqueue(struct ifqueue *ifq, struct mbuf *m)
-{
-	int err;
-
-	err = ifq_enqueue_try(ifq, m);
-	if (err != 0)
-		m_freem(m);
+	if (dm == NULL)
+		rv = 0;
+	else {
+		m_freem(dm);
+		rv = ENOBUFS;
+	}
 
-	return (err);
+	return (rv);
 }
 
 struct mbuf *
@@ -403,14 +400,14 @@ priq_free(unsigned int idx, void *pq)
 	free(pq, M_DEVBUF, sizeof(struct priq));
 }
 
-int
+struct mbuf *
 priq_enq(struct ifqueue *ifq, struct mbuf *m)
 {
 	struct priq *pq;
 	struct priq_list *pl;
 
 	if (ifq_len(ifq) >= ifq->ifq_maxlen)
-		return (ENOBUFS);
+		return (m);
 
 	pq = ifq->ifq_q;
 	KASSERT(m->m_pkthdr.pf.prio <= IFQ_MAXPRIO);
@@ -423,7 +420,7 @@ priq_enq(struct ifqueue *ifq, struct mbu
 		pl->tail->m_nextpkt = m;
 	pl->tail = m;
 
-	return (0);
+	return (NULL);
 }
 
 struct mbuf *
Index: ifq.h
===================================================================
RCS file: /cvs/src/sys/net/ifq.h,v
retrieving revision 1.9
diff -u -p -r1.9 ifq.h
--- ifq.h	24 Jan 2017 10:08:30 -0000	1.9
+++ ifq.h	2 Mar 2017 00:31:53 -0000
@@ -117,25 +117,21 @@ struct ifqueue {
  * the ifqueue. All the pending mbufs are removed from the previous
  * conditioner and requeued on the new.
  *
- * === ifq_enqueue() and ifq_enqueue_try()
+ * === ifq_enqueue()
  *
- * ifq_enqueue() and ifq_enqueue_try() attempt to fit an mbuf onto the
- * ifqueue. If the current traffic conditioner rejects the packet it
- * wont be queued and will be counted as a drop. ifq_enqueue() will
- * free the mbuf on the callers behalf if the packet is rejected.
- * ifq_enqueue_try() does not free the mbuf, allowing the caller to
- * reuse it.
+ * ifq_enqueue() attempts to fit an mbuf onto the ifqueue. The
+ * current traffic conditioner may drop a packet to make space on the
+ * queue.
  *
  * === ifq_start()
  *
- * Once a packet has been successfully queued with ifq_enqueue() or
- * ifq_enqueue_try(), the network card is notified with a call to
- * if_start(). If an interface is marked with IFXF_MPSAFE in its
- * if_xflags field, if_start() calls ifq_start() to dispatch the
- * interfaces start routine. Calls to ifq_start() run in the ifqueue
- * serialisation context, guaranteeing that only one instance of
- * ifp->if_start() will be running in the system at any point in time.
- *
+ * Once a packet has been successfully queued with ifq_enqueue(),
+ * the network card is notified with a call to if_start(). If an
+ * interface is marked with IFXF_MPSAFE in its if_xflags field,
+ * if_start() calls ifq_start() to dispatch the interfaces start
+ * routine. Calls to ifq_start() run in the ifqueue serialisation
+ * context, guaranteeing that only one instance of ifp->if_start()
+ * will be running in the system at any point in time.
  *
  * == Traffic conditioners API
  *
@@ -324,7 +320,7 @@ struct ifqueue {
 struct ifq_ops {
 	unsigned int		 (*ifqop_idx)(unsigned int,
 				    const struct mbuf *);
-	int			 (*ifqop_enq)(struct ifqueue *, struct mbuf *);
+	struct mbuf		*(*ifqop_enq)(struct ifqueue *, struct mbuf *);
 	struct mbuf		*(*ifqop_deq_begin)(struct ifqueue *, void **);
 	void			 (*ifqop_deq_commit)(struct ifqueue *,
 				    struct mbuf *, void *);
@@ -341,7 +337,6 @@ struct ifq_ops {
 void		 ifq_init(struct ifqueue *, struct ifnet *, unsigned int);
 void		 ifq_attach(struct ifqueue *, const struct ifq_ops *, void *);
 void		 ifq_destroy(struct ifqueue *);
-int		 ifq_enqueue_try(struct ifqueue *, struct mbuf *);
 int		 ifq_enqueue(struct ifqueue *, struct mbuf *);
 struct mbuf	*ifq_deq_begin(struct ifqueue *);
 void		 ifq_deq_commit(struct ifqueue *, struct mbuf *);
Index: hfsc.c
===================================================================
RCS file: /cvs/src/sys/net/hfsc.c,v
retrieving revision 1.35
diff -u -p -r1.35 hfsc.c
--- hfsc.c	24 Jan 2017 03:57:35 -0000	1.35
+++ hfsc.c	2 Mar 2017 00:31:53 -0000
@@ -260,7 +260,7 @@ struct pool	hfsc_class_pl, hfsc_internal
  */
 
 unsigned int	 hfsc_idx(unsigned int, const struct mbuf *);
-int		 hfsc_enq(struct ifqueue *, struct mbuf *);
+struct mbuf	*hfsc_enq(struct ifqueue *, struct mbuf *);
 struct mbuf	*hfsc_deq_begin(struct ifqueue *, void **);
 void		 hfsc_deq_commit(struct ifqueue *, struct mbuf *, void *);
 void		 hfsc_purge(struct ifqueue *, struct mbuf_list *);
@@ -650,7 +650,7 @@ hfsc_nextclass(struct hfsc_class *cl)
 	return (cl);
 }
 
-int
+struct mbuf *
 hfsc_enq(struct ifqueue *ifq, struct mbuf *m)
 {
 	struct hfsc_if *hif = ifq->ifq_q;
@@ -660,14 +660,14 @@ hfsc_enq(struct ifqueue *ifq, struct mbu
 	    cl->cl_children != NULL) {
 		cl = hif->hif_defaultclass;
 		if (cl == NULL)
-			return (ENOBUFS);
+			return (m);
 		cl->cl_pktattr = NULL;
 	}
 
 	if (ml_len(&cl->cl_q.q) >= cl->cl_q.qlimit) {
 		/* drop occurred.  mbuf needs to be freed */
 		PKTCNTR_INC(&cl->cl_stats.drop_cnt, m->m_pkthdr.len);
-		return (ENOBUFS);
+		return (m);
 	}
 
 	ml_enqueue(&cl->cl_q.q, m);
@@ -677,7 +677,7 @@ hfsc_enq(struct ifqueue *ifq, struct mbu
 	if (ml_len(&cl->cl_q.q) == 1)
 		hfsc_set_active(hif, cl, m->m_pkthdr.len);
 
-	return (0);
+	return (NULL);
 }
 
 struct mbuf *