--- //depot/vendor/freebsd/src/sys/dev/em/if_em.c	2005/06/10 16:51:34
+++ //depot/user/rwatson/ifnet/src/sys/dev/em/if_em.c	2005/06/12 16:49:13
@@ -650,6 +650,68 @@
 	return;
 }
 
+static void
+em_startmbuf_locked(struct ifnet *ifp)
+{
+        struct mbuf    *m_head;
+        struct adapter *adapter = ifp->if_softc;
+	struct ifqueue *ifq = (struct ifqueue *)&ifp->if_snd;
+
+	mtx_assert(&adapter->mtx, MA_OWNED);
+
+	while (_IF_QLEN(ifq) != 0) {
+
+		_IF_DEQUEUE(ifq, m_head);
+
+                if (m_head == NULL) break;
+
+		/*
+		 * em_encap() can modify our pointer, and or make it NULL on
+		 * failure.  In that event, we can't requeue.
+		 */
+		if (em_encap(adapter, &m_head)) { 
+			if (m_head == NULL)
+				break;
+			ifp->if_flags |= IFF_OACTIVE;
+			_IF_PREPEND(ifq, m_head);
+			break;
+                }
+
+		/* Send a copy of the frame to the BPF listener */
+		BPF_MTAP(ifp, m_head);
+        
+                /* Set timeout in case hardware has problems transmitting */
+                ifp->if_timer = EM_TX_TIMEOUT;
+        
+        }
+        return;
+}
+
+static int
+em_startmbuf(struct ifnet *ifp, struct mbuf *m, int adjust)
+{
+	struct adapter *adapter = ifp->if_softc;
+	struct ifqueue *ifq = (struct ifqueue *)&ifp->if_snd;
+	int ret;
+
+	if (!adapter->link_active) {
+		m_freem(m);
+		return (1);		/* Emulate success case. */
+	}
+
+	/*
+	 * XXXRW: We could fast path the queue length zero case, but for now
+	 * insert into the driver-locked queue and then try to proceed
+	 * normally.
+	 */
+	EM_LOCK(adapter);
+	ret = if_startmbuf_enqueue(ifq, m, ifp, adjust);
+	if (ret == 1)
+		em_startmbuf_locked(ifp);
+	EM_UNLOCK(adapter);
+	return (ret);
+}
+
 /*********************************************************************
  *  Ioctl entry point
  *
@@ -1940,6 +2002,7 @@
 	ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
 	ifp->if_ioctl = em_ioctl;
 	ifp->if_start = em_start;
+	ifp->if_startmbuf = em_startmbuf;
 	ifp->if_watchdog = em_watchdog;
 	IFQ_SET_MAXLEN(&ifp->if_snd, adapter->num_tx_desc - 1);
 	ifp->if_snd.ifq_drv_maxlen = adapter->num_tx_desc - 1;
--- //depot/vendor/freebsd/src/sys/net/if.c	2005/06/12 00:55:43
+++ //depot/user/rwatson/ifnet/src/sys/net/if.c	2005/06/12 15:49:54
@@ -2127,11 +2127,18 @@
 	(ifp->if_start)(ifp);
 }
 
+static int	startmbuf_enabled;
+SYSCTL_INT(_net, OID_AUTO, startmbuf_enabled, CTLFLAG_RW, &startmbuf_enabled,
+    0, "");
+
 int
 if_handoff(struct ifqueue *ifq, struct mbuf *m, struct ifnet *ifp, int adjust)
 {
 	int active = 0;
 
+	if (startmbuf_enabled && ifp != NULL && ifp->if_startmbuf != NULL)
+		return ((ifp->if_startmbuf)(ifp, m, adjust));
+
 	IF_LOCK(ifq);
 	if (_IF_QFULL(ifq)) {
 		_IF_DROP(ifq);
@@ -2152,6 +2159,23 @@
 	return (1);
 }
 
+int
+if_startmbuf_enqueue(struct ifqueue *ifq, struct mbuf *m, struct ifnet *ifp,
+    int adjust)
+{
+
+	if (_IF_QFULL(ifq)) {
+		_IF_DROP(ifq);
+		m_freem(m);
+		return (0);
+	}
+	ifp->if_obytes += m->m_pkthdr.len + adjust;
+	if (m->m_flags & (M_BCAST|M_MCAST))
+		ifp->if_omcasts++;
+	_IF_ENQUEUE(ifq, m);
+	return (1);
+}
+
 void
 if_register_com_alloc(u_char type,
     if_com_alloc_t *a, if_com_free_t *f)
--- //depot/vendor/freebsd/src/sys/net/if_var.h	2005/06/10 16:51:34
+++ //depot/user/rwatson/ifnet/src/sys/net/if_var.h	2005/06/12 08:07:53
@@ -158,7 +158,8 @@
 		(void *);
 	int	(*if_resolvemulti)	/* validate/resolve multicast */
 		(struct ifnet *, struct sockaddr **, struct sockaddr *);
-	void	*if_spare1;		/* spare pointer 1 */
+	int	(*if_startmbuf)		/* enqueue and start output */
+		(struct ifnet *, struct mbuf *, int adjust);
 	void	*if_spare2;		/* spare pointer 2 */
 	void	*if_spare3;		/* spare pointer 3 */
 	u_int	if_spare_flags1;	/* spare flags 1 */
@@ -324,6 +325,9 @@
 
 int	if_handoff(struct ifqueue *ifq, struct mbuf *m, struct ifnet *ifp,
 	    int adjust);
+int	if_startmbuf_enqueue(struct ifqueue *ifq, struct mbuf *m,
+	    struct ifnet *ifp, int adjust);
+
 #define	IF_HANDOFF(ifq, m, ifp)			\
 	if_handoff((struct ifqueue *)ifq, m, ifp, 0)
 #define	IF_HANDOFF_ADJ(ifq, m, ifp, adj)	\