diff --git a/sys/netinet/cc/cc.c b/sys/netinet/cc/cc.c
--- a/sys/netinet/cc/cc.c
+++ b/sys/netinet/cc/cc.c
@@ -500,13 +500,7 @@
 		break;
 	case CC_RTO:
 		if (CCV(ccv, t_rxtshift) == 1) {
-			if (V_tcp_do_newsack) {
-				pipe = tcp_compute_pipe(ccv->tp);
-			} else {
-				pipe = CCV(ccv, snd_max) -
-					CCV(ccv, snd_fack) +
-					CCV(ccv, sackhint.sack_bytes_rexmit);
-			}
+			pipe = tcp_compute_pipe(ccv->tp);
 			CCV(ccv, snd_ssthresh) = max(2,
 				min(CCV(ccv, snd_wnd), pipe) / 2 / mss) * mss;
 		}
diff --git a/sys/netinet/cc/cc_cubic.c b/sys/netinet/cc/cc_cubic.c
--- a/sys/netinet/cc/cc_cubic.c
+++ b/sys/netinet/cc/cc_cubic.c
@@ -470,13 +470,7 @@
 			cubic_data->undo_cwnd_epoch = cubic_data->cwnd_epoch;
 			cubic_data->undo_W_max = cubic_data->W_max;
 			cubic_data->undo_K = cubic_data->K;
-			if (V_tcp_do_newsack) {
-				pipe = tcp_compute_pipe(ccv->tp);
-			} else {
-				pipe = CCV(ccv, snd_max) -
-					CCV(ccv, snd_fack) +
-					CCV(ccv, sackhint.sack_bytes_rexmit);
-			}
+			pipe = tcp_compute_pipe(ccv->tp);
 			CCV(ccv, snd_ssthresh) = max(2,
 				(((uint64_t)min(CCV(ccv, snd_wnd), pipe) *
 				CUBIC_BETA) >> CUBIC_SHIFT) / mss) * mss;
diff --git a/sys/netinet/cc/cc_dctcp.c b/sys/netinet/cc/cc_dctcp.c
--- a/sys/netinet/cc/cc_dctcp.c
+++ b/sys/netinet/cc/cc_dctcp.c
@@ -294,13 +294,7 @@
 			break;
 		case CC_RTO:
 			if (CCV(ccv, t_rxtshift) == 1) {
-				if (V_tcp_do_newsack) {
-					pipe = tcp_compute_pipe(ccv->tp);
-				} else {
-					pipe = CCV(ccv, snd_max) -
-						CCV(ccv, snd_fack) +
-						CCV(ccv, sackhint.sack_bytes_rexmit);
-				}
+				pipe = tcp_compute_pipe(ccv->tp);
 				CCV(ccv, snd_ssthresh) = max(2,
 					min(CCV(ccv, snd_wnd), pipe) / 2 / mss) * mss;
 			}
diff --git a/sys/netinet/cc/cc_htcp.c b/sys/netinet/cc/cc_htcp.c
--- a/sys/netinet/cc/cc_htcp.c
+++ b/sys/netinet/cc/cc_htcp.c
@@ -325,13 +325,7 @@
 
 	case CC_RTO:
 		if (CCV(ccv, t_rxtshift) == 1) {
-			if (V_tcp_do_newsack) {
-				pipe = tcp_compute_pipe(ccv->tp);
-			} else {
-				pipe = CCV(ccv, snd_max) -
-					CCV(ccv, snd_fack) +
-					CCV(ccv, sackhint.sack_bytes_rexmit);
-			}
+			pipe = tcp_compute_pipe(ccv->tp);
 			CCV(ccv, snd_ssthresh) = max(2,
 				min(CCV(ccv, snd_wnd), pipe) / 2 / mss) * mss;
 		}
diff --git a/sys/netinet/cc/cc_newreno.c b/sys/netinet/cc/cc_newreno.c
--- a/sys/netinet/cc/cc_newreno.c
+++ b/sys/netinet/cc/cc_newreno.c
@@ -428,13 +428,7 @@
 		break;
 	case CC_RTO:
 		if (CCV(ccv, t_rxtshift) == 1) {
-			if (V_tcp_do_newsack) {
-				pipe = tcp_compute_pipe(ccv->tp);
-			} else {
-				pipe = CCV(ccv, snd_max) -
-					CCV(ccv, snd_fack) +
-					CCV(ccv, sackhint.sack_bytes_rexmit);
-			}
+			pipe = tcp_compute_pipe(ccv->tp);
 			CCV(ccv, snd_ssthresh) = max(2,
 				((uint64_t)min(CCV(ccv, snd_wnd), pipe) *
 				    (uint64_t)factor) /
diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -2660,12 +2660,7 @@
 						 * we have less than ssthresh
 						 * worth of data in flight.
 						 */
-						if (V_tcp_do_newsack) {
-							awnd = tcp_compute_pipe(tp);
-						} else {
-							awnd = (tp->snd_nxt - tp->snd_fack) +
-								tp->sackhint.sack_bytes_rexmit;
-						}
+						awnd = tcp_compute_pipe(tp);
 						if (awnd < tp->snd_ssthresh) {
 							tp->snd_cwnd += imax(maxseg,
 							    imin(2 * maxseg,
@@ -4098,11 +4093,7 @@
 	    (IN_CONGRECOVERY(tp->t_flags) &&
 	     !IN_FASTRECOVERY(tp->t_flags))) {
 		del_data = tp->sackhint.delivered_data;
-		if (V_tcp_do_newsack)
-			pipe = tcp_compute_pipe(tp);
-		else
-			pipe = (tp->snd_nxt - tp->snd_fack) +
-				tp->sackhint.sack_bytes_rexmit;
+		pipe = tcp_compute_pipe(tp);
 	} else {
 		if (tp->sackhint.prr_delivered < (tcprexmtthresh * maxseg +
 					     tp->snd_recover - tp->snd_una)) {
@@ -4206,14 +4197,19 @@
 int
 tcp_compute_pipe(struct tcpcb *tp)
 {
-	if (tp->t_fb->tfb_compute_pipe == NULL) {
-		return (tp->snd_max - tp->snd_una +
+	int pipe;
+
+	if (tp->t_fb->tfb_compute_pipe != NULL) {
+		pipe = (*tp->t_fb->tfb_compute_pipe)(tp);
+	} else if (V_tcp_do_newsack) {
+		pipe = tp->snd_max - tp->snd_una +
 			tp->sackhint.sack_bytes_rexmit -
 			tp->sackhint.sacked_bytes -
-			tp->sackhint.lost_bytes);
+			tp->sackhint.lost_bytes;
 	} else {
-		return((*tp->t_fb->tfb_compute_pipe)(tp));
+		pipe = tp->snd_nxt - tp->snd_fack + tp->sackhint.sack_bytes_rexmit;
 	}
+	return (imax(pipe, 0));
 }
 
 uint32_t