Index: head/sys/netinet/cc/cc_cdg.c
===================================================================
--- head/sys/netinet/cc/cc_cdg.c
+++ head/sys/netinet/cc/cc_cdg.c
@@ -431,6 +431,11 @@
 cdg_cong_signal(struct cc_var *ccv, uint32_t signal_type)
 {
 	struct cdg *cdg_data = ccv->cc_data;
+	uint32_t cwin;
+	u_int mss;
+
+	cwin = CCV(ccv, snd_cwnd);
+	mss = CCV(ccv, t_maxseg);
 
 	switch(signal_type) {
 	case CC_CDG_DELAY:
@@ -448,7 +453,7 @@
 		 */
 		if (IN_CONGRECOVERY(CCV(ccv, t_flags)) ||
 		    cdg_data->queue_state < CDG_Q_FULL) {
-			CCV(ccv, snd_ssthresh) = CCV(ccv, snd_cwnd);
+			CCV(ccv, snd_ssthresh) = cwin;
 			CCV(ccv, snd_recover) = CCV(ccv, snd_max);
 		} else {
 			/*
@@ -461,13 +466,17 @@
 				    cdg_data->shadow_w, RENO_BETA);
 
 			CCV(ccv, snd_ssthresh) = max(cdg_data->shadow_w,
-			    cdg_window_decrease(ccv, CCV(ccv, snd_cwnd),
-			    V_cdg_beta_loss));
+			    cdg_window_decrease(ccv, cwin, V_cdg_beta_loss));
+			CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh);
 
 			cdg_data->window_incr = cdg_data->rtt_count = 0;
 		}
 		ENTER_RECOVERY(CCV(ccv, t_flags));
 		break;
+	case CC_RTO:
+		CCV(ccv, snd_ssthresh) = max(2*mss, cwin/2);
+		CCV(ccv, snd_cwnd) = mss;
+		break;
 	default:
 		newreno_cc_algo.cong_signal(ccv, signal_type);
 		break;
Index: head/sys/netinet/cc/cc_chd.c
===================================================================
--- head/sys/netinet/cc/cc_chd.c
+++ head/sys/netinet/cc/cc_chd.c
@@ -330,10 +330,14 @@
 	struct ertt *e_t;
 	struct chd *chd_data;
 	int qdly;
+	uint32_t cwin;
+	u_int mss;
 
 	e_t = khelp_get_osd(CCV(ccv, osd), ertt_id);
 	chd_data = ccv->cc_data;
 	qdly = imax(e_t->rtt, chd_data->maxrtt_in_rtt) - e_t->minrtt;
+	cwin = CCV(ccv, snd_cwnd);
+	mss = CCV(ccv, t_maxseg);
 
 	switch(signal_type) {
 	case CC_CHD_DELAY:
@@ -373,6 +377,10 @@
 		}
 		ENTER_FASTRECOVERY(CCV(ccv, t_flags));
 		break;
+	case CC_RTO:
+		CCV(ccv, snd_ssthresh) = max(2*mss, cwin/2);
+		CCV(ccv, snd_cwnd) = mss;
+		break;
 
 	default:
 		newreno_cc_algo.cong_signal(ccv, signal_type);
Index: head/sys/netinet/cc/cc_cubic.c
===================================================================
--- head/sys/netinet/cc/cc_cubic.c
+++ head/sys/netinet/cc/cc_cubic.c
@@ -225,8 +225,12 @@
 cubic_cong_signal(struct cc_var *ccv, uint32_t type)
 {
 	struct cubic *cubic_data;
+	uint32_t cwin;
+	u_int mss;
 
 	cubic_data = ccv->cc_data;
+	cwin = CCV(ccv, snd_cwnd);
+	mss = CCV(ccv, t_maxseg);
 
 	switch (type) {
 	case CC_NDUPACK:
@@ -235,7 +239,8 @@
 				cubic_ssthresh_update(ccv);
 				cubic_data->num_cong_events++;
 				cubic_data->prev_max_cwnd = cubic_data->max_cwnd;
-				cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
+				cubic_data->max_cwnd = cwin;
+				CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh);
 			}
 			ENTER_RECOVERY(CCV(ccv, t_flags));
 		}
@@ -246,7 +251,7 @@
 			cubic_ssthresh_update(ccv);
 			cubic_data->num_cong_events++;
 			cubic_data->prev_max_cwnd = cubic_data->max_cwnd;
-			cubic_data->max_cwnd = CCV(ccv, snd_cwnd);
+			cubic_data->max_cwnd = cwin;
 			cubic_data->t_last_cong = ticks;
 			CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh);
 			ENTER_CONGRECOVERY(CCV(ccv, t_flags));
@@ -261,9 +266,13 @@
 		 * chance the first one is a false alarm and may not indicate
 		 * congestion.
 		 */
-		if (CCV(ccv, t_rxtshift) >= 2)
+		if (CCV(ccv, t_rxtshift) >= 2) {
 			cubic_data->num_cong_events++;
 			cubic_data->t_last_cong = ticks;
+			cubic_ssthresh_update(ccv);
+			cubic_data->max_cwnd = cwin;
+			CCV(ccv, snd_cwnd) = mss;
+		}
 		break;
 	}
 }
Index: head/sys/netinet/cc/cc_dctcp.c
===================================================================
--- head/sys/netinet/cc/cc_dctcp.c
+++ head/sys/netinet/cc/cc_dctcp.c
@@ -230,10 +230,11 @@
 dctcp_cong_signal(struct cc_var *ccv, uint32_t type)
 {
 	struct dctcp *dctcp_data;
-	u_int win, mss;
+	uint32_t cwin;
+	u_int mss;
 
 	dctcp_data = ccv->cc_data;
-	win = CCV(ccv, snd_cwnd);
+	cwin = CCV(ccv, snd_cwnd);
 	mss = CCV(ccv, t_maxseg);
 
 	switch (type) {
@@ -241,16 +242,16 @@
 		if (!IN_FASTRECOVERY(CCV(ccv, t_flags))) {
 			if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
 				CCV(ccv, snd_ssthresh) = mss *
-				    max(win / 2 / mss, 2);
+				    max(cwin / 2 / mss, 2);
 				dctcp_data->num_cong_events++;
 			} else {
 				/* cwnd has already updated as congestion
 				 * recovery. Reverse cwnd value using
 				 * snd_cwnd_prev and recalculate snd_ssthresh
 				 */
-				win = CCV(ccv, snd_cwnd_prev);
+				cwin = CCV(ccv, snd_cwnd_prev);
 				CCV(ccv, snd_ssthresh) =
-				    max(win / 2 / mss, 2) * mss;
+				    max(cwin / 2 / mss, 2) * mss;
 			}
 			ENTER_RECOVERY(CCV(ccv, t_flags));
 		}
@@ -260,18 +261,18 @@
 		 * Save current snd_cwnd when the host encounters both
 		 * congestion recovery and fast recovery.
 		 */
-		CCV(ccv, snd_cwnd_prev) = win;
+		CCV(ccv, snd_cwnd_prev) = cwin;
 		if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
 			if (V_dctcp_slowstart &&
 			    dctcp_data->num_cong_events++ == 0) {
 				CCV(ccv, snd_ssthresh) =
-				    mss * max(win / 2 / mss, 2);
+				    mss * max(cwin / 2 / mss, 2);
 				dctcp_data->alpha = MAX_ALPHA_VALUE;
 				dctcp_data->bytes_ecn = 0;
 				dctcp_data->bytes_total = 0;
 				dctcp_data->save_sndnxt = CCV(ccv, snd_nxt);
 			} else
-				CCV(ccv, snd_ssthresh) = max((win - ((win *
+				CCV(ccv, snd_ssthresh) = max((cwin - ((cwin *
 				    dctcp_data->alpha) >> 11)) / mss, 2) * mss;
 			CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh);
 			ENTER_CONGRECOVERY(CCV(ccv, t_flags));
@@ -284,6 +285,8 @@
 			dctcp_update_alpha(ccv);
 			dctcp_data->save_sndnxt += CCV(ccv, t_maxseg);
 			dctcp_data->num_cong_events++;
+			CCV(ccv, snd_ssthresh) = max(2 * mss, cwin / 2);
+			CCV(ccv, snd_cwnd) = mss;
 		}
 		break;
 	}
Index: head/sys/netinet/cc/cc_htcp.c
===================================================================
--- head/sys/netinet/cc/cc_htcp.c
+++ head/sys/netinet/cc/cc_htcp.c
@@ -271,8 +271,12 @@
 htcp_cong_signal(struct cc_var *ccv, uint32_t type)
 {
 	struct htcp *htcp_data;
+	uint32_t cwin;
+	u_int mss;
 
 	htcp_data = ccv->cc_data;
+	cwin = CCV(ccv, snd_cwnd);
+	mss = CCV(ccv, t_maxseg);
 
 	switch (type) {
 	case CC_NDUPACK:
@@ -287,8 +291,9 @@
 				    (htcp_data->maxrtt - htcp_data->minrtt) *
 				    95) / 100;
 				htcp_ssthresh_update(ccv);
+				CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh);
 				htcp_data->t_last_cong = ticks;
-				htcp_data->prev_cwnd = CCV(ccv, snd_cwnd);
+				htcp_data->prev_cwnd = cwin;
 			}
 			ENTER_RECOVERY(CCV(ccv, t_flags));
 		}
@@ -305,7 +310,7 @@
 			htcp_ssthresh_update(ccv);
 			CCV(ccv, snd_cwnd) = CCV(ccv, snd_ssthresh);
 			htcp_data->t_last_cong = ticks;
-			htcp_data->prev_cwnd = CCV(ccv, snd_cwnd);
+			htcp_data->prev_cwnd = cwin;
 			ENTER_CONGRECOVERY(CCV(ccv, t_flags));
 		}
 		break;
@@ -320,6 +325,8 @@
 		 */
 		if (CCV(ccv, t_rxtshift) >= 2)
 			htcp_data->t_last_cong = ticks;
+		CCV(ccv, snd_ssthresh) = max(2 * mss, cwin / 2);
+		CCV(ccv, snd_cwnd) = mss;
 		break;
 	}
 }
Index: head/sys/netinet/cc/cc_newreno.c
===================================================================
--- head/sys/netinet/cc/cc_newreno.c
+++ head/sys/netinet/cc/cc_newreno.c
@@ -182,30 +182,39 @@
 static void
 newreno_cong_signal(struct cc_var *ccv, uint32_t type)
 {
-	u_int win;
+	uint32_t cwin;
+	u_int mss;
+
+	cwin = CCV(ccv, snd_cwnd);
+	mss = CCV(ccv, t_maxseg);
 
 	/* Catch algos which mistakenly leak private signal types. */
 	KASSERT((type & CC_SIGPRIVMASK) == 0,
 	    ("%s: congestion signal type 0x%08x is private\n", __func__, type));
 
-	win = max(CCV(ccv, snd_cwnd) / 2 / CCV(ccv, t_maxseg), 2) *
-	    CCV(ccv, t_maxseg);
+	cwin = max(2*mss, cwin/2);
 
 	switch (type) {
 	case CC_NDUPACK:
 		if (!IN_FASTRECOVERY(CCV(ccv, t_flags))) {
-			if (!IN_CONGRECOVERY(CCV(ccv, t_flags)))
-				CCV(ccv, snd_ssthresh) = win;
+			if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
+				CCV(ccv, snd_ssthresh) = cwin;
+				CCV(ccv, snd_cwnd) = cwin;
+			}
 			ENTER_RECOVERY(CCV(ccv, t_flags));
 		}
 		break;
 	case CC_ECN:
 		if (!IN_CONGRECOVERY(CCV(ccv, t_flags))) {
-			CCV(ccv, snd_ssthresh) = win;
-			CCV(ccv, snd_cwnd) = win;
+			CCV(ccv, snd_ssthresh) = cwin;
+			CCV(ccv, snd_cwnd) = cwin;
 			ENTER_CONGRECOVERY(CCV(ccv, t_flags));
 		}
 		break;
+	case CC_RTO:
+		CCV(ccv, snd_ssthresh) = cwin;
+		CCV(ccv, snd_cwnd) = mss;
+		break;
 	}
 }
 
Index: head/sys/netinet/tcp_input.c
===================================================================
--- head/sys/netinet/tcp_input.c
+++ head/sys/netinet/tcp_input.c
@@ -438,9 +438,15 @@
 		tp->t_dupacks = 0;
 		tp->t_bytes_acked = 0;
 		EXIT_RECOVERY(tp->t_flags);
-		tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 /
-		    maxseg) * maxseg;
-		tp->snd_cwnd = maxseg;
+		if (CC_ALGO(tp)->cong_signal == NULL) {
+			/*
+			 * RFC5681 Section 3.1 
+			 * ssthresh = max (FlightSize / 2, 2*SMSS) eq (4)
+			 */
+			tp->snd_ssthresh =
+			    max((tp->snd_max - tp->snd_una) / 2, 2 * maxseg);
+			tp->snd_cwnd = maxseg;
+		}
 		break;
 	case CC_RTO_ERR:
 		TCPSTAT_INC(tcps_sndrexmitbad);
@@ -2613,6 +2619,15 @@
 
 						if (awnd < tp->snd_ssthresh) {
 							tp->snd_cwnd += maxseg;
+							/*
+							 * RFC5681 Section 3.2 talks about cwnd
+							 * inflation on additional dupacks and
+							 * deflation on recovering from loss.
+							 *
+							 * We keep cwnd into check so that
+							 * we don't have to 'deflate' it when we
+							 * get out of recovery.
+							 */
 							if (tp->snd_cwnd > tp->snd_ssthresh)
 								tp->snd_cwnd = tp->snd_ssthresh;
 						}
@@ -2652,19 +2667,22 @@
 						TCPSTAT_INC(
 						    tcps_sack_recovery_episode);
 						tp->sack_newdata = tp->snd_nxt;
-						tp->snd_cwnd = maxseg;
+						if (CC_ALGO(tp)->cong_signal == NULL)
+							tp->snd_cwnd = maxseg;
 						(void) tp->t_fb->tfb_tcp_output(tp);
 						goto drop;
 					}
 					tp->snd_nxt = th->th_ack;
-					tp->snd_cwnd = maxseg;
+					if (CC_ALGO(tp)->cong_signal == NULL)
+						tp->snd_cwnd = maxseg;
 					(void) tp->t_fb->tfb_tcp_output(tp);
 					KASSERT(tp->snd_limited <= 2,
 					    ("%s: tp->snd_limited too big",
 					    __func__));
-					tp->snd_cwnd = tp->snd_ssthresh +
-					     maxseg *
-					     (tp->t_dupacks - tp->snd_limited);
+					if (CC_ALGO(tp)->cong_signal == NULL)
+						tp->snd_cwnd = tp->snd_ssthresh +
+						    maxseg *
+						    (tp->t_dupacks - tp->snd_limited);
 					if (SEQ_GT(onxt, tp->snd_nxt))
 						tp->snd_nxt = onxt;
 					goto drop;