diff --git a/sys/dev/netmap/netmap_freebsd.c b/sys/dev/netmap/netmap_freebsd.c
--- a/sys/dev/netmap/netmap_freebsd.c
+++ b/sys/dev/netmap/netmap_freebsd.c
@@ -403,15 +403,20 @@
  * addr and len identify the netmap buffer, m is the (preallocated)
  * mbuf to use for transmissions.
  *
- * We should add a reference to the mbuf so the m_freem() at the end
- * of the transmission does not consume resources.
+ * Zero-copy transmission is possible if netmap is attached directly to a
+ * hardware interface: when cleaning we simply wait for the mbuf cluster
+ * refcount to decrement to 1, indicating that the driver has completed
+ * transmission and is done with the buffer.  However, this approach can
+ * lead to queue deadlocks when attaching to software interfaces (e.g.,
+ * if_bridge) since we cannot rely on member ports to promptly reclaim
+ * transmitted mbufs.  Since there is no easy way to distinguish these
+ * cases, we currently always copy the buffer.
  *
- * On FreeBSD, and on multiqueue cards, we can force the queue using
+ * On multiqueue cards, we can force the queue using
  *      if (M_HASHTYPE_GET(m) != M_HASHTYPE_NONE)
  *              i = m->m_pkthdr.flowid % adapter->num_queues;
  *      else
  *              i = curcpu % adapter->num_queues;
- *
  */
 int
 nm_os_generic_xmit_frame(struct nm_os_gen_arg *a)
@@ -421,16 +426,18 @@
 	if_t ifp = a->ifp;
 	struct mbuf *m = a->m;
 
-	/* Link the external storage to
-	 * the netmap buffer, so that no copy is necessary. */
-	m->m_ext.ext_buf = m->m_data = a->addr;
-	m->m_ext.ext_size = len;
+	if (MBUF_REFCNT(m) != 1) {
+		nm_prerr("invalid refcnt %d for %p", MBUF_REFCNT(m), m);
+		panic("in generic_xmit_frame");
+	}
+	if (unlikely(m->m_ext.ext_size < len)) {
+		nm_prlim(2, "size %d < len %d", m->m_ext.ext_size, len);
+		len = m->m_ext.ext_size;
+	}
+	m_copyback(m, 0, len, a->addr);
 
 	m->m_flags |= M_PKTHDR;
 	m->m_len = m->m_pkthdr.len = len;
-
-	/* mbuf refcnt is not contended, no need to use atomic
-	 * (a memory barrier is enough). */
 	SET_MBUF_REFCNT(m, 2);
 	M_HASHTYPE_SET(m, M_HASHTYPE_OPAQUE);
 	m->m_pkthdr.flowid = a->ring_nr;
@@ -438,10 +445,11 @@
 	CURVNET_SET(if_getvnet(ifp));
 	ret = NA(ifp)->if_transmit(ifp, m);
 	CURVNET_RESTORE();
+	if (ret != 0)
+		if_inc_counter(ifp, IFCOUNTER_OQDROPS, 1);
 	return ret ? -1 : 0;
 }
 
-
 struct netmap_adapter *
 netmap_getna(if_t ifp)
 {
diff --git a/sys/dev/netmap/netmap_generic.c b/sys/dev/netmap/netmap_generic.c
--- a/sys/dev/netmap/netmap_generic.c
+++ b/sys/dev/netmap/netmap_generic.c
@@ -424,6 +424,7 @@
 	return error;
 }
 
+#ifndef __FreeBSD__
 /*
  * Callback invoked when the device driver frees an mbuf used
  * by netmap to transmit a packet. This usually happens when
@@ -481,10 +482,8 @@
 	/* Second, wake up clients. They will reclaim the event through
 	 * txsync. */
 	netmap_generic_irq(na, r, NULL);
-#ifdef __FreeBSD__
-	void_mbuf_dtor(m);
-#endif
 }
+#endif
 
 /* Record completed transmissions and update hwtail.
  *
@@ -537,10 +536,12 @@
 				}
 				/* The event has been consumed, we can go
 				 * ahead. */
-
 			} else if (MBUF_REFCNT(m) != 1) {
-				/* This mbuf is still busy: its refcnt is 2. */
-				break;
+				/* This mbuf has been submitted but is still busy
+				 * (refcount is 2).
+				 * Leave it to the driver and replenish. */
+				m_freem(m);
+				tx_pool[nm_i] = NULL;
 			}
 		}
 
@@ -577,6 +578,13 @@
 	return e;
 }
 
+#ifdef __FreeBSD__
+static void
+generic_set_tx_event(struct netmap_kring *kring __unused, u_int hwcur __unused)
+{
+	netmap_common_irq(kring->na, kring->ring_id, NULL);
+}
+#else
 static void
 generic_set_tx_event(struct netmap_kring *kring, u_int hwcur)
 {
@@ -631,9 +639,8 @@
 	/* Decrement the refcount. This will free it if we lose the race
 	 * with the driver. */
 	m_freem(m);
-	smp_mb();
 }
-
+#endif
 
 /*
  * generic_netmap_txsync() transforms netmap buffers into mbufs
@@ -698,7 +705,7 @@
 			/* Tale a mbuf from the tx pool (replenishing the pool
 			 * entry if necessary) and copy in the user packet. */
 			m = kring->tx_pool[nm_i];
-			if (unlikely(m == NULL)) {
+			if (m == NULL) {
 				kring->tx_pool[nm_i] = m =
 					nm_os_get_mbuf(ifp, NETMAP_BUF_SIZE(na));
 				if (m == NULL) {
diff --git a/sys/dev/netmap/netmap_kern.h b/sys/dev/netmap/netmap_kern.h
--- a/sys/dev/netmap/netmap_kern.h
+++ b/sys/dev/netmap/netmap_kern.h
@@ -2394,7 +2394,7 @@
  * has a KASSERT(), checking that the mbuf dtor function is not NULL.
  */
 
-static void void_mbuf_dtor(struct mbuf *m) { }
+static inline void void_mbuf_dtor(struct mbuf *m) { }
 
 #define SET_MBUF_DESTRUCTOR(m, fn)	do {		\
 	(m)->m_ext.ext_free = (fn != NULL) ?		\
@@ -2402,22 +2402,9 @@
 } while (0)
 
 static inline struct mbuf *
-nm_os_get_mbuf(if_t ifp, int len)
+nm_os_get_mbuf(if_t ifp __unused, int len)
 {
-	struct mbuf *m;
-
-	(void)ifp;
-	(void)len;
-
-	m = m_gethdr(M_NOWAIT, MT_DATA);
-	if (m == NULL) {
-		return m;
-	}
-
-	m_extadd(m, NULL /* buf */, 0 /* size */, void_mbuf_dtor,
-		 NULL, NULL, 0, EXT_NET_DRV);
-
-	return m;
+	return (m_getjcl(M_NOWAIT, MT_DATA, M_PKTHDR, len));
 }
 
 #endif /* __FreeBSD__ */