Index: sys/netinet/tcp_stacks/rack.c
===================================================================
--- sys/netinet/tcp_stacks/rack.c
+++ sys/netinet/tcp_stacks/rack.c
@@ -12508,6 +12508,7 @@
 				  ip6, rack->r_ctl.fsb.th);
 	} else
 #endif				/* INET6 */
+#ifdef INET
 	{
 		rack->r_ctl.fsb.tcp_ip_hdr_len = sizeof(struct tcpiphdr);
 		ip = (struct ip *)rack->r_ctl.fsb.tcp_ip_hdr;
@@ -12527,9 +12528,38 @@
 				  tp->t_port,
 				  ip, rack->r_ctl.fsb.th);
 	}
+#endif
 	rack->r_fsb_inited = 1;
 }
 
+static void
+rack_update_fsb_codepoint(struct tcpcb *tp, struct tcp_rack *rack)
+{
+#ifdef INET6
+	struct ip6_hdr *ip6 = NULL;
+#endif
+#ifdef INET
+	struct ip *ip = NULL;
+#endif
+	/*
+	 * A socket option changed the outgoing TOS/TCLASS update
+	 * the fast send block.
+	 */
+#ifdef INET6
+	if (rack->r_is_v6) {
+		ip6 = (struct ip6_hdr *)rack->r_ctl.fsb.tcp_ip_hdr;
+		ip6->ip6_flow = (ip6->ip6_flow & ~IPV6_FLOWINFO_MASK) |
+			(rack->rc_inp->inp_flow & IPV6_FLOWINFO_MASK);
+	}
+#endif
+#ifdef INET
+	else {
+		ip = (struct ip *)rack->r_ctl.fsb.tcp_ip_hdr;
+		ip->ip_tos = rack->rc_inp->inp_ip_tos;
+	}
+#endif
+}
+
 static int
 rack_init_fsb(struct tcpcb *tp, struct tcp_rack *rack)
 {
@@ -16873,6 +16903,11 @@
 		}
 		idle = 0;
 	}
+	if (tp->t_flags2 & TF2_CODEPOINT_CHANGED) {
+		if (rack->r_fsb_inited)
+			rack_update_fsb_codepoint(tp, rack);
+		tp->t_flags2 &= ~TF2_CODEPOINT_CHANGED;
+	}
 	if (rack_use_fsb && (rack->r_fsb_inited == 0) && (rack->r_state != TCPS_CLOSED))
 		rack_init_fsb_block(tp, rack);
 again:
Index: sys/netinet/tcp_subr.c
===================================================================
--- sys/netinet/tcp_subr.c
+++ sys/netinet/tcp_subr.c
@@ -4129,3 +4129,19 @@
 		}
 	}
 }
+
+void
+tcp_codepoint_changed(struct inpcb *inp)
+{
+	struct tcpcb *tp = intotcpcb(inp);	
+
+	/*
+	 * This is used by IP stacks to announce a
+	 * change in the IP DSCP codepoint. Stacks
+	 * like rack can use the flag to realize their
+	 * fastpath may need an update.
+	 */
+	INP_WLOCK(inp);
+	tp->t_flags2 |= TF2_CODEPOINT_CHANGED;
+	INP_WUNLOCK(inp);
+}
Index: sys/netinet/tcp_usrreq.c
===================================================================
--- sys/netinet/tcp_usrreq.c
+++ sys/netinet/tcp_usrreq.c
@@ -1745,6 +1745,15 @@
 #ifdef INET6
 		if (inp->inp_vflag & INP_IPV6PROTO) {
 			error = ip6_ctloutput(so, sopt);
+			/*
+			 * If the TCLASS changes we need to 
+			 * notify tcp stacks that care.
+			 */
+			if ((sopt->sopt_level == IPPROTO_IPV6) &&
+			    (sopt->sopt_name == IPV6_TCLASS) &&
+			    (error == 0)) {
+				tcp_codepoint_changed(inp);
+			}
 			/*
 			 * In case of the IPV6_USE_MIN_MTU socket option,
 			 * the INC_IPV6MINMTU flag to announce a corresponding
@@ -1788,7 +1797,17 @@
 #endif
 #ifdef INET
 		{
+			/*
+			 * If the TOS changes we need to 
+			 * notify tcp stacks that care.
+			 */
 			error = ip_ctloutput(so, sopt);
+			if ((sopt->sopt_level == IPPROTO_IP) &&
+			    (sopt->sopt_name == IP_TOS) &&
+			    (error == 0)) {
+				tcp_codepoint_changed(inp);
+			}
+
 		}
 #endif
 		return (error);
Index: sys/netinet/tcp_var.h
===================================================================
--- sys/netinet/tcp_var.h
+++ sys/netinet/tcp_var.h
@@ -462,6 +462,7 @@
 #define	TF2_ECN_SND_ECE		0x00000080 /* ECN ECE in queue */
 #define	TF2_ACE_PERMIT		0x00000100 /* Accurate ECN mode */
 #define TF2_FBYTES_COMPLETE	0x00000400 /* We have first bytes in and out */
+#define TF2_CODEPOINT_CHANGED	0x00020000 /* An ip option changed the DSCP codepoint */
 /*
  * Structure to hold TCP options that are only used during segment
  * processing (in tcp_input), but not held in the tcpcb.
@@ -1124,6 +1125,7 @@
     size_t seed_len);
 int tcp_can_enable_pacing(void);
 void tcp_decrement_paced_conn(void);
+void tcp_codepoint_changed(struct inpcb *);
 
 struct mbuf *
 	 tcp_m_copym(struct mbuf *m, int32_t off0, int32_t *plen,