Index: head/sys/netinet/tcp_syncache.c
===================================================================
--- head/sys/netinet/tcp_syncache.c
+++ head/sys/netinet/tcp_syncache.c
@@ -127,7 +127,8 @@
 static void	 syncache_drop(struct syncache *, struct syncache_head *);
 static void	 syncache_free(struct syncache *);
 static void	 syncache_insert(struct syncache *, struct syncache_head *);
-static int	 syncache_respond(struct syncache *, struct syncache_head *, int);
+static int	 syncache_respond(struct syncache *, struct syncache_head *, int,
+		    const struct mbuf *);
 static struct	 socket *syncache_socket(struct syncache *, struct socket *,
 		    struct mbuf *m);
 static void	 syncache_timeout(struct syncache *sc, struct syncache_head *sch,
@@ -457,7 +458,7 @@
 			free(s, M_TCPLOG);
 		}
 
-		syncache_respond(sc, sch, 1);
+		syncache_respond(sc, sch, 1, NULL);
 		TCPSTAT_INC(tcps_sc_retransmitted);
 		syncache_timeout(sc, sch, 0);
 	}
@@ -1307,7 +1308,7 @@
 			    s, __func__);
 			free(s, M_TCPLOG);
 		}
-		if (syncache_respond(sc, sch, 1) == 0) {
+		if (syncache_respond(sc, sch, 1, m) == 0) {
 			sc->sc_rxmits = 0;
 			syncache_timeout(sc, sch, 1);
 			TCPSTAT_INC(tcps_sndacks);
@@ -1474,7 +1475,7 @@
 	/*
 	 * Do a standard 3-way handshake.
 	 */
-	if (syncache_respond(sc, sch, 0) == 0) {
+	if (syncache_respond(sc, sch, 0, m) == 0) {
 		if (V_tcp_syncookies && V_tcp_syncookiesonly && sc != &scs)
 			syncache_free(sc);
 		else if (sc != &scs)
@@ -1505,7 +1506,8 @@
 }
 
 static int
-syncache_respond(struct syncache *sc, struct syncache_head *sch, int locked)
+syncache_respond(struct syncache *sc, struct syncache_head *sch, int locked,
+    const struct mbuf *m0)
 {
 	struct ip *ip = NULL;
 	struct mbuf *m;
@@ -1686,6 +1688,10 @@
 
 	M_SETFIB(m, sc->sc_inc.inc_fibnum);
 	m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
+	if (m0 != NULL && M_HASHTYPE_GET(m0) != M_HASHTYPE_NONE) {
+		m->m_pkthdr.flowid = m0->m_pkthdr.flowid;
+		M_HASHTYPE_SET(m, M_HASHTYPE_GET(m0));
+	}
 #ifdef INET6
 	if (sc->sc_inc.inc_flags & INC_ISIPV6) {
 		m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;