Index: sys/netinet/tcp_input.c
===================================================================
--- sys/netinet/tcp_input.c
+++ sys/netinet/tcp_input.c
@@ -1762,7 +1762,7 @@
 						tp->t_rttlow = t;
 					tcp_xmit_timer(tp,
 					    TCP_TS_TO_TICKS(t) + 1);
-				} else if (tp->t_rtttime &&
+				} else if (tp->t_rtseq &&
 				    SEQ_GT(th->th_ack, tp->t_rtseq)) {
 					if (!tp->t_rttlow ||
 					    tp->t_rttlow > ticks - tp->t_rtttime)
@@ -2581,6 +2581,7 @@
 					    CC_DUPACK);
 					tcp_timer_activate(tp, TT_REXMT, 0);
 					tp->t_rtttime = 0;
+					tp->t_rtseq = 0;
 					if (tp->t_flags & TF_SACK_PERMIT) {
 						TCPSTAT_INC(
 						    tcps_sack_recovery_episode);
@@ -2761,7 +2762,7 @@
 			if (!tp->t_rttlow || tp->t_rttlow > t)
 				tp->t_rttlow = t;
 			tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1);
-		} else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
+		} else if (tp->t_rtseq && SEQ_GT(th->th_ack, tp->t_rtseq)) {
 			if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime)
 				tp->t_rttlow = ticks - tp->t_rtttime;
 			tcp_xmit_timer(tp, ticks - tp->t_rtttime);
@@ -3481,7 +3482,16 @@
 		tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
 		tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
 	}
-	tp->t_rtttime = 0;
+	/*
+	 * For the after-idle check, exclude the last RTT and
+	 * set rtttime to the current time. The RTT sample
+	 * is being collected when t_rtseq != 0, so we clear
+	 * t_rtseq instead of t_rtttime.
+	 */
+	tp->t_rtttime = ticks;
+	if (tp->t_rtttime == 0)
+		tp->t_rtttime--;
+	tp->t_rtseq = 0;
 	tp->t_rxtshift = 0;
 
 	/*
@@ -3810,6 +3820,7 @@
 
 	tcp_timer_activate(tp, TT_REXMT, 0);
 	tp->t_rtttime = 0;
+	tp->t_rtseq = 0;
 	tp->snd_nxt = th->th_ack;
 	/*
 	 * Set snd_cwnd to one segment beyond acknowledged offset.
Index: sys/netinet/tcp_output.c
===================================================================
--- sys/netinet/tcp_output.c
+++ sys/netinet/tcp_output.c
@@ -260,7 +260,8 @@
 	 * to send, then transmit; otherwise, investigate further.
 	 */
 	idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
-	if (idle && ticks - tp->t_rcvtime >= tp->t_rxtcur)
+	if (idle && (((ticks - tp->t_rcvtime) >= tp->t_rxtcur) ||
+	    (tp->t_rtttime && ((ticks - tp->t_rtttime) >= tp->t_rxtcur))))
 		cc_after_idle(tp);
 	tp->t_flags &= ~TF_LASTIDLE;
 	if (idle) {
@@ -1499,9 +1500,13 @@
 			 * Time this transmission if not a retransmission and
 			 * not currently timing anything.
 			 */
-			if (tp->t_rtttime == 0) {
+			if (tp->t_rtseq ==0) {
 				tp->t_rtttime = ticks;
+				if (tp->t_rtttime == 0)
+					tp->t_rtttime--;
 				tp->t_rtseq = startseq;
+				if (tp->t_rtseq == 0)
+					tp->t_rtseq++;
 				TCPSTAT_INC(tcps_segstimed);
 			}
 #ifdef STATS
Index: sys/netinet/tcp_sack.c
===================================================================
--- sys/netinet/tcp_sack.c
+++ sys/netinet/tcp_sack.c
@@ -777,6 +777,7 @@
 	INP_WLOCK_ASSERT(tp->t_inpcb);
 	tcp_timer_activate(tp, TT_REXMT, 0);
 	tp->t_rtttime = 0;
+	tp->t_rtseq = 0;
 	/* Send one or 2 segments based on how much new data was acked. */
 	if ((BYTES_THIS_ACK(tp, th) / tp->t_maxseg) >= 2)
 		num_segs = 2;
Index: sys/netinet/tcp_stacks/bbr.c
===================================================================
--- sys/netinet/tcp_stacks/bbr.c
+++ sys/netinet/tcp_stacks/bbr.c
@@ -5213,6 +5213,7 @@
 	tp->snd_recover = tp->snd_max;
 	tp->t_flags |= TF_ACKNOW;
 	tp->t_rtttime = 0;
+	tp->t_rtseq = 0;
 out:
 	return (retval);
 }
Index: sys/netinet/tcp_stacks/rack.c
===================================================================
--- sys/netinet/tcp_stacks/rack.c
+++ sys/netinet/tcp_stacks/rack.c
@@ -5886,6 +5886,7 @@
 	tp->snd_recover = tp->snd_max;
 	tp->t_flags |= TF_ACKNOW;
 	tp->t_rtttime = 0;
+	tp->t_rtseq = 0;
 	rack_cong_signal(tp, NULL, CC_RTO);
 out:
 	return (retval);
@@ -10993,7 +10994,8 @@
 	 */
 	if  (tp->t_idle_reduce &&
 	     (tp->snd_max == tp->snd_una) &&
-	     ((ticks - tp->t_rcvtime) >= tp->t_rxtcur)) {
+	     (((ticks - tp->t_rcvtime) >= tp->t_rxtcur) ||
+	      (tp->t_rtttime && ((ticks - tp->t_rtttime) >= tp->t_rxtcur)))) {
 		counter_u64_add(rack_input_idle_reduces, 1);
 		rack_cc_after_idle(rack, tp);
 	}
@@ -12146,7 +12148,8 @@
 	 */
 	idle = (tp->t_flags & TF_LASTIDLE) || (tp->snd_max == tp->snd_una);
 	if (tp->t_idle_reduce) {
-		if (idle && ((ticks - tp->t_rcvtime) >= tp->t_rxtcur))
+		if (idle && (((ticks - tp->t_rcvtime) >= tp->t_rxtcur) ||
+		    (tp->t_rtttime && ((ticks - tp->t_rtttime) >= tp->t_rxtcur))))
 			rack_cc_after_idle(rack, tp);
 	}
 	tp->t_flags &= ~TF_LASTIDLE;
@@ -14044,9 +14047,13 @@
 			 * This is only relevant in case of switching back to
 			 * the base stack.
 			 */
-			if (tp->t_rtttime == 0) {
+			if (tp->t_rtseq == 0) {
 				tp->t_rtttime = ticks;
+				if (tp->t_rtttime == 0)
+					tp->t_rtttime--;
 				tp->t_rtseq = startseq;
+				if (tp->t_rtseq == 0)
+					tp->t_rtseq++;
 				KMOD_TCPSTAT_INC(tcps_segstimed);
 			}
 			if (len &&
Index: sys/netinet/tcp_subr.c
===================================================================
--- sys/netinet/tcp_subr.c
+++ sys/netinet/tcp_subr.c
@@ -2902,6 +2902,7 @@
 
 	TCPSTAT_INC(tcps_mturesent);
 	tp->t_rtttime = 0;
+	tp->t_rtseq = 0;
 	tp->snd_nxt = tp->snd_una;
 	tcp_free_sackholes(tp);
 	tp->snd_recover = tp->snd_max;
Index: sys/netinet/tcp_timer.c
===================================================================
--- sys/netinet/tcp_timer.c
+++ sys/netinet/tcp_timer.c
@@ -873,6 +873,7 @@
 	 * If timing a segment in this window, stop the timer.
 	 */
 	tp->t_rtttime = 0;
+	tp->t_rtseq = 0;
 
 	cc_cong_signal(tp, NULL, CC_RTO);
 	NET_EPOCH_ENTER(et);