Index: netinet/tcp_subr.c
===================================================================
--- netinet/tcp_subr.c	(revision 212549)
+++ netinet/tcp_subr.c	(working copy)
@@ -876,6 +876,27 @@
 }
 
 /*
+ * Remove the fusion of two socket buffer to let TCP
+ * handle the remainder of the connection shutdown
+ * phase.
+ */
+void
+tcp_defuse(struct socket *so, struct inpcb *inp)
+{
+	struct inpcb *finp = (struct inpcb *)inp->inp_pspare[0];
+
+	INP_WLOCK(finp);
+	if (finp->inp_socket != NULL)
+		finp->inp_socket->so_snd.sb_cc = 0;
+	so->so_snd.sb_cc = 0;
+	finp->inp_flags &= ~INP_FUSED;
+	inp->inp_flags &= ~INP_FUSED;
+	finp->inp_pspare[0] = NULL;
+	inp->inp_pspare[0] = NULL;
+	INP_WUNLOCK(finp);
+}
+
+/*
  * Attempt to close a TCP control block, marking it as dropped, and freeing
  * the socket if we hold the only reference.
  */
@@ -896,6 +917,10 @@
 	KASSERT(inp->inp_socket != NULL, ("tcp_close: inp_socket NULL"));
 	so = inp->inp_socket;
 	soisdisconnected(so);
+
+	if (inp->inp_flags & INP_FUSED)
+		tcp_defuse(so, inp);
+
 	if (inp->inp_flags & INP_SOCKREF) {
 		KASSERT(so->so_state & SS_PROTOREF,
 		    ("tcp_close: !SS_PROTOREF"));
Index: netinet/in_pcb.h
===================================================================
--- netinet/in_pcb.h	(revision 212549)
+++ netinet/in_pcb.h	(working copy)
@@ -414,6 +414,7 @@
 #define	INP_DONTFRAG		0x00000800 /* don't fragment packet */
 #define	INP_BINDANY		0x00001000 /* allow bind to any address */
 #define	INP_INHASHLIST		0x00002000 /* in_pcbinshash() has been called */
+#define	INP_FUSED		0x00004000 /* inp's fused together for IPC */
 #define	IN6P_IPV6_V6ONLY	0x00008000 /* restrict AF_INET6 socket for v6 */
 #define	IN6P_PKTINFO		0x00010000 /* receive IP6 dst and I/F */
 #define	IN6P_HOPLIMIT		0x00020000 /* receive hoplimit */
Index: netinet/tcp_var.h
===================================================================
--- netinet/tcp_var.h	(revision 212549)
+++ netinet/tcp_var.h	(working copy)
@@ -595,6 +595,7 @@
 int	 tcp_addoptions(struct tcpopt *, u_char *);
 struct tcpcb *
 	 tcp_close(struct tcpcb *);
+void	 tcp_defuse(struct socket *, struct inpcb *);
 void	 tcp_discardcb(struct tcpcb *);
 void	 tcp_twstart(struct tcpcb *);
 #if 0
Index: netinet/tcp_syncache.c
===================================================================
--- netinet/tcp_syncache.c	(revision 212549)
+++ netinet/tcp_syncache.c	(working copy)
@@ -109,6 +109,10 @@
     &VNET_NAME(tcp_syncookiesonly), 0,
     "Use only TCP SYN cookies");
 
+static int	tcp_loopfuse = 1;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, loopfuse, CTLFLAG_RW,
+    &tcp_loopfuse, 0, "Allow looped back connections to fuse sockets");
+
 #ifdef TCP_OFFLOAD_DISABLE
 #define TOEPCB_ISSET(sc) (0)
 #else
@@ -829,6 +833,31 @@
 		tp->snd_cwnd = tp->t_maxseg;
 	tcp_timer_activate(tp, TT_KEEP, tcp_keepinit);
 
+	/*
+	 * For connections that go are looped back the socket
+	 * buffers can be directly merged together instead of
+	 * sending TCP segments through the loopback interface.
+	 * Perform a lookup on the other INP and if found, set
+	 * up crossover pointers to the sockets and set the flag.
+	 */
+	if (tcp_loopfuse && in_localaddr(sc->sc_inc.inc_faddr)) {
+		struct inpcb *finp;
+
+		finp = in_pcblookup_hash(&V_tcbinfo,
+			   sc->sc_inc.inc_laddr, sc->sc_inc.inc_lport,
+			   sc->sc_inc.inc_faddr, sc->sc_inc.inc_fport,
+			   0, m->m_pkthdr.rcvif);
+
+		if (finp != NULL) {
+			INP_WLOCK(finp);
+			finp->inp_pspare[0] = (void *)inp;
+			inp->inp_pspare[0] = (void *)finp;
+			finp->inp_flags |= INP_FUSED;
+			inp->inp_flags |= INP_FUSED;
+			INP_WUNLOCK(finp);
+		}
+	}
+
 	INP_WUNLOCK(inp);
 
 	TCPSTAT_INC(tcps_accepts);
Index: netinet/tcp_usrreq.c
===================================================================
--- netinet/tcp_usrreq.c	(revision 212549)
+++ netinet/tcp_usrreq.c	(working copy)
@@ -718,8 +718,21 @@
 	}
 	tp = intotcpcb(inp);
 	TCPDEBUG1();
+
+	/*
+	 * When fused directly inform the other socket buffer
+	 * that we dequeued some data.
+	 */
+	if (inp->inp_flags & INP_FUSED) {
+		struct inpcb *finp = (struct inpcb *)inp->inp_pspare[0];
+
+		SOCKBUF_LOCK(&finp->inp_socket->so_snd);
+		finp->inp_socket->so_snd.sb_cc = so->so_rcv.sb_cc;
+		sowwakeup_locked(finp->inp_socket);
+		goto out;
+	}
+
 	tcp_output_rcvd(tp);
-
 out:
 	TCPDEBUG2(PRU_RCVD);
 	INP_WUNLOCK(inp);
@@ -774,6 +787,20 @@
 	isipv6 = nam && nam->sa_family == AF_INET6;
 #endif /* INET6 */
 	tp = intotcpcb(inp);
+
+	/*
+	 * Drop it directly into the receive buffer on the other side.
+	 */
+	if (inp->inp_flags & INP_FUSED) {
+		struct inpcb *finp = (struct inpcb *)inp->inp_pspare[0];
+
+		SOCKBUF_LOCK(&finp->inp_socket->so_rcv);
+		sbappendstream_locked(&finp->inp_socket->so_rcv, m);
+		inp->inp_socket->so_snd.sb_cc = finp->inp_socket->so_rcv.sb_cc;
+		sorwakeup_locked(finp->inp_socket);
+		goto out;
+	}
+
 	TCPDEBUG1();
 	if (control) {
 		/* TCP doesn't do control messages (rights, creds, etc) */
@@ -1327,7 +1354,8 @@
 				tp->t_flags |= TF_NOPUSH;
 			else {
 				tp->t_flags &= ~TF_NOPUSH;
-				error = tcp_output(tp);
+				if (!(inp->inp_flags & INP_FUSED))
+					error = tcp_output(tp);
 			}
 			INP_WUNLOCK(inp);
 			break;
@@ -1499,8 +1527,11 @@
 		soisdisconnecting(so);
 		sbflush(&so->so_rcv);
 		tcp_usrclosed(tp);
-		if (!(inp->inp_flags & INP_DROPPED))
+		if (!(inp->inp_flags & INP_DROPPED)) {
+			if (inp->inp_flags & INP_FUSED)
+				tcp_defuse(so, inp);
 			tcp_output_disconnect(tp);
+		}
 	}
 }