Index: sys/netinet/cc/cc_newreno.c
===================================================================
--- sys/netinet/cc/cc_newreno.c
+++ sys/netinet/cc/cc_newreno.c
@@ -134,7 +134,7 @@
 	if (type == CC_ACK && !IN_RECOVERY(CCV(ccv, t_flags)) &&
 	    (ccv->flags & CCF_CWND_LIMITED)) {
 		u_int cw = CCV(ccv, snd_cwnd);
-		u_int incr = CCV(ccv, t_maxseg);
+		u_int incr = 0;
 
 		/*
 		 * Regular in-order ACK, open the congestion window.
@@ -169,7 +169,7 @@
 					ccv->flags &= ~CCF_ABC_SENTAWND;
 				else
 					incr = 0;
-			} else
+			} else if (ccv->bytes_this_ack > 0)
 				incr = max((incr * incr / cw), 1);
 		} else if (V_tcp_do_rfc3465) {
 			/*
@@ -188,7 +188,8 @@
 				    CCV(ccv, t_maxseg));
 			else
 				incr = min(ccv->bytes_this_ack, CCV(ccv, t_maxseg));
-		}
+		} else if (ccv->bytes_this_ack > 0)
+			incr = CCV(ccv, t_maxseg);
 		/* ABC is on by default, so incr equals 0 frequently. */
 		if (incr > 0)
 			CCV(ccv, snd_cwnd) = min(cw + incr,
Index: sys/netinet/tcp_input.c
===================================================================
--- sys/netinet/tcp_input.c
+++ sys/netinet/tcp_input.c
@@ -2396,12 +2396,6 @@
 		if (IS_FASTOPEN(tp->t_flags) && tp->t_tfo_pending) {
 			tcp_fastopen_decrement_counter(tp->t_tfo_pending);
 			tp->t_tfo_pending = NULL;
-
-			/*
-			 * Account for the ACK of our SYN prior to
-			 * regular ACK processing below.
-			 */ 
-			tp->snd_una++;
 		}
 		if (tp->t_flags & TF_NEEDFIN) {
 			tcp_state_change(tp, TCPS_FIN_WAIT_1);
@@ -2421,6 +2415,12 @@
 				cc_conn_init(tp);
 			tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
 		}
+		if (SEQ_GT(th->th_ack, tp->snd_una))
+			/*
+			 * Account for the ACK of our SYN prior to
+			 * regular ACK processing below.
+			 */
+			tp->snd_una++;
 		/*
 		 * If segment contains data or ACK, will call tcp_reass()
 		 * later; if not, do so now to pass queued data to user.
Index: sys/netinet/tcp_stacks/rack.c
===================================================================
--- sys/netinet/tcp_stacks/rack.c
+++ sys/netinet/tcp_stacks/rack.c
@@ -5433,6 +5433,7 @@
 		tp->ts_recent_age = tcp_ts_getticks();
 		tp->ts_recent = to->to_tsval;
 	}
+	tp->snd_wnd = tiwin;
 	/*
 	 * If the ACK bit is off:  if in SYN-RECEIVED state or SENDSYN flag
 	 * is on (half-synchronized state), then queue data for later
@@ -5440,7 +5441,6 @@
 	 */
 	if ((thflags & TH_ACK) == 0) {
 		if (IS_FASTOPEN(tp->t_flags)) {
-			tp->snd_wnd = tiwin;
 			cc_conn_init(tp);
 		}
 		return (rack_process_data(m, th, so, tp, drop_hdrlen, tlen,
@@ -5452,7 +5452,6 @@
 	if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) ==
 	    (TF_RCVD_SCALE | TF_REQ_SCALE)) {
 		tp->rcv_scale = tp->request_r_scale;
-		tp->snd_wnd = tiwin;
 	}
 	/*
 	 * Make transitions: SYN-RECEIVED  -> ESTABLISHED SYN-RECEIVED* ->
@@ -5462,12 +5461,6 @@
 	if (IS_FASTOPEN(tp->t_flags) && tp->t_tfo_pending) {
 		tcp_fastopen_decrement_counter(tp->t_tfo_pending);
 		tp->t_tfo_pending = NULL;
-
-		/*
-		 * Account for the ACK of our SYN prior to
-		 * regular ACK processing below.
-		 */ 
-		tp->snd_una++;
 	}
 	if (tp->t_flags & TF_NEEDFIN) {
 		tcp_state_change(tp, TCPS_FIN_WAIT_1);
@@ -5485,6 +5478,12 @@
 		if (!IS_FASTOPEN(tp->t_flags))
 			cc_conn_init(tp);
 	}
+	if (SEQ_GT(th->th_ack, tp->snd_una))
+		/*
+		 * Account for the ACK of our SYN prior to
+		 * regular ACK processing below.
+		 */
+		tp->snd_una++;
 	/*
 	 * If segment contains data or ACK, will call tcp_reass() later; if
 	 * not, do so now to pass queued data to user.