Index: head/sys/netinet/in_pcb.h
===================================================================
--- head/sys/netinet/in_pcb.h
+++ head/sys/netinet/in_pcb.h
@@ -832,7 +832,7 @@
 	    u_short *, struct ucred *);
 int	in_pcbconnect(struct inpcb *, struct sockaddr *, struct ucred *);
 int	in_pcbconnect_mbuf(struct inpcb *, struct sockaddr *, struct ucred *,
-	    struct mbuf *);
+	    struct mbuf *, bool);
 int	in_pcbconnect_setup(struct inpcb *, struct sockaddr *, in_addr_t *,
 	    u_short *, in_addr_t *, u_short *, struct inpcb **,
 	    struct ucred *);
@@ -841,7 +841,7 @@
 void	in_pcbdrop(struct inpcb *);
 void	in_pcbfree(struct inpcb *);
 int	in_pcbinshash(struct inpcb *);
-int	in_pcbinshash_nopcbgroup(struct inpcb *);
+int	in_pcbinshash_mbuf(struct inpcb *, struct mbuf *);
 int	in_pcbladdr(struct inpcb *, struct in_addr *, struct in_addr *,
 	    struct ucred *);
 struct inpcb *
Index: head/sys/netinet/in_pcb.c
===================================================================
--- head/sys/netinet/in_pcb.c
+++ head/sys/netinet/in_pcb.c
@@ -972,7 +972,7 @@
  */
 int
 in_pcbconnect_mbuf(struct inpcb *inp, struct sockaddr *nam,
-    struct ucred *cred, struct mbuf *m)
+    struct ucred *cred, struct mbuf *m, bool rehash)
 {
 	u_short lport, fport;
 	in_addr_t laddr, faddr;
@@ -991,6 +991,8 @@
 
 	/* Do the initial binding of the local address if required. */
 	if (inp->inp_laddr.s_addr == INADDR_ANY && inp->inp_lport == 0) {
+		KASSERT(rehash == true,
+		    ("Rehashing required for unbound inps"));
 		inp->inp_lport = lport;
 		inp->inp_laddr.s_addr = laddr;
 		if (in_pcbinshash(inp) != 0) {
@@ -1005,7 +1007,11 @@
 	inp->inp_laddr.s_addr = laddr;
 	inp->inp_faddr.s_addr = faddr;
 	inp->inp_fport = fport;
-	in_pcbrehash_mbuf(inp, m);
+	if (rehash) {
+		in_pcbrehash_mbuf(inp, m);
+	} else {
+		in_pcbinshash_mbuf(inp, m);
+	}
 
 	if (anonport)
 		inp->inp_flags |= INP_ANONPORT;
@@ -1016,7 +1022,7 @@
 in_pcbconnect(struct inpcb *inp, struct sockaddr *nam, struct ucred *cred)
 {
 
-	return (in_pcbconnect_mbuf(inp, nam, cred, NULL));
+	return (in_pcbconnect_mbuf(inp, nam, cred, NULL, true));
 }
 
 /*
@@ -2500,7 +2506,7 @@
  * Insert PCB onto various hash lists.
  */
 static int
-in_pcbinshash_internal(struct inpcb *inp, int do_pcbgroup_update)
+in_pcbinshash_internal(struct inpcb *inp, struct mbuf *m)
 {
 	struct inpcbhead *pcbhash;
 	struct inpcbporthead *pcbporthash;
@@ -2566,35 +2572,27 @@
 	CK_LIST_INSERT_HEAD(pcbhash, inp, inp_hash);
 	inp->inp_flags |= INP_INHASHLIST;
 #ifdef PCBGROUP
-	if (do_pcbgroup_update)
+	if (m != NULL) {
+		in_pcbgroup_update_mbuf(inp, m);
+	} else {
 		in_pcbgroup_update(inp);
+	}
 #endif
 	return (0);
 }
 
-/*
- * For now, there are two public interfaces to insert an inpcb into the hash
- * lists -- one that does update pcbgroups, and one that doesn't.  The latter
- * is used only in the TCP syncache, where in_pcbinshash is called before the
- * full 4-tuple is set for the inpcb, and we don't want to install in the
- * pcbgroup until later.
- *
- * XXXRW: This seems like a misfeature.  in_pcbinshash should always update
- * connection groups, and partially initialised inpcbs should not be exposed
- * to either reservation hash tables or pcbgroups.
- */
 int
 in_pcbinshash(struct inpcb *inp)
 {
 
-	return (in_pcbinshash_internal(inp, 1));
+	return (in_pcbinshash_internal(inp, NULL));
 }
 
 int
-in_pcbinshash_nopcbgroup(struct inpcb *inp)
+in_pcbinshash_mbuf(struct inpcb *inp, struct mbuf *m)
 {
 
-	return (in_pcbinshash_internal(inp, 0));
+	return (in_pcbinshash_internal(inp, m));
 }
 
 /*
Index: head/sys/netinet/tcp_syncache.c
===================================================================
--- head/sys/netinet/tcp_syncache.c
+++ head/sys/netinet/tcp_syncache.c
@@ -841,34 +841,8 @@
 #endif
 	}
 
-	/*
-	 * Install in the reservation hash table for now, but don't yet
-	 * install a connection group since the full 4-tuple isn't yet
-	 * configured.
-	 */
 	inp->inp_lport = sc->sc_inc.inc_lport;
-	if ((error = in_pcbinshash_nopcbgroup(inp)) != 0) {
-		/*
-		 * Undo the assignments above if we failed to
-		 * put the PCB on the hash lists.
-		 */
 #ifdef INET6
-		if (sc->sc_inc.inc_flags & INC_ISIPV6)
-			inp->in6p_laddr = in6addr_any;
-		else
-#endif
-			inp->inp_laddr.s_addr = INADDR_ANY;
-		inp->inp_lport = 0;
-		if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
-			log(LOG_DEBUG, "%s; %s: in_pcbinshash failed "
-			    "with error %i\n",
-			    s, __func__, error);
-			free(s, M_TCPLOG);
-		}
-		INP_HASH_WUNLOCK(&V_tcbinfo);
-		goto abort;
-	}
-#ifdef INET6
 	if (inp->inp_vflag & INP_IPV6PROTO) {
 		struct inpcb *oinp = sotoinpcb(lso);
 
@@ -900,7 +874,7 @@
 		if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr))
 			inp->in6p_laddr = sc->sc_inc.inc6_laddr;
 		if ((error = in6_pcbconnect_mbuf(inp, (struct sockaddr *)&sin6,
-		    thread0.td_ucred, m)) != 0) {
+		    thread0.td_ucred, m, false)) != 0) {
 			inp->in6p_laddr = laddr6;
 			if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
 				log(LOG_DEBUG, "%s; %s: in6_pcbconnect failed "
@@ -940,7 +914,7 @@
 		if (inp->inp_laddr.s_addr == INADDR_ANY)
 			inp->inp_laddr = sc->sc_inc.inc_laddr;
 		if ((error = in_pcbconnect_mbuf(inp, (struct sockaddr *)&sin,
-		    thread0.td_ucred, m)) != 0) {
+		    thread0.td_ucred, m, false)) != 0) {
 			inp->inp_laddr = laddr;
 			if ((s = tcp_log_addrs(&sc->sc_inc, NULL, NULL, NULL))) {
 				log(LOG_DEBUG, "%s; %s: in_pcbconnect failed "
Index: head/sys/netinet6/in6_pcb.h
===================================================================
--- head/sys/netinet6/in6_pcb.h
+++ head/sys/netinet6/in6_pcb.h
@@ -86,7 +86,7 @@
 int	in6_pcbbind(struct inpcb *, struct sockaddr *, struct ucred *);
 int	in6_pcbconnect(struct inpcb *, struct sockaddr *, struct ucred *);
 int	in6_pcbconnect_mbuf(struct inpcb *, struct sockaddr *,
-	    struct ucred *, struct mbuf *);
+	    struct ucred *, struct mbuf *, bool);
 void	in6_pcbdisconnect(struct inpcb *);
 struct	inpcb *
 	in6_pcblookup_local(struct inpcbinfo *,
Index: head/sys/netinet6/in6_pcb.c
===================================================================
--- head/sys/netinet6/in6_pcb.c
+++ head/sys/netinet6/in6_pcb.c
@@ -411,7 +411,7 @@
  */
 int
 in6_pcbconnect_mbuf(struct inpcb *inp, struct sockaddr *nam,
-    struct ucred *cred, struct mbuf *m)
+    struct ucred *cred, struct mbuf *m, bool rehash)
 {
 	struct inpcbinfo *pcbinfo = inp->inp_pcbinfo;
 	struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)nam;
@@ -437,6 +437,8 @@
 	}
 	if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) {
 		if (inp->inp_lport == 0) {
+			KASSERT(rehash == true,
+			    ("Rehashing required for unbound inps"));
 			error = in6_pcbbind(inp, (struct sockaddr *)0, cred);
 			if (error)
 				return (error);
@@ -451,7 +453,11 @@
 		inp->inp_flow |=
 		    (htonl(ip6_randomflowlabel()) & IPV6_FLOWLABEL_MASK);
 
-	in_pcbrehash_mbuf(inp, m);
+	if (rehash) {
+		in_pcbrehash_mbuf(inp, m);
+	} else {
+		in_pcbinshash_mbuf(inp, m);
+	}
 
 	return (0);
 }
@@ -460,7 +466,7 @@
 in6_pcbconnect(struct inpcb *inp, struct sockaddr *nam, struct ucred *cred)
 {
 
-	return (in6_pcbconnect_mbuf(inp, nam, cred, NULL));
+	return (in6_pcbconnect_mbuf(inp, nam, cred, NULL, true));
 }
 
 void