X-Git-Url: http://pilppa.org/gitweb/?a=blobdiff_plain;f=net%2Fipv4%2Ftcp_input.c;h=a62e0f90f566eda8df48bee60ca9b4c7d8501bfc;hb=9e10c47cb9fe3154416787523f7a0df02133063f;hp=b59da5308ac0ed35c135162fbfcc54cac32c8bd6;hpb=746aa32d280084dbd520249170852e4616799928;p=linux-2.6-omap-h63xx.git

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index b59da5308ac..a62e0f90f56 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -863,6 +863,9 @@ void tcp_enter_cwr(struct sock *sk, const int set_ssthresh)
  */
 static void tcp_disable_fack(struct tcp_sock *tp)
 {
+	/* RFC3517 uses different metric in lost marker => reset on change */
+	if (tcp_is_fack(tp))
+		tp->lost_skb_hint = NULL;
 	tp->rx_opt.sack_ok &= ~2;
 }
 
@@ -923,7 +926,7 @@ static void tcp_init_metrics(struct sock *sk)
 	}
 	if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) {
 		tp->mdev = dst_metric(dst, RTAX_RTTVAR);
-		tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
+		tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk));
 	}
 	tcp_set_rto(sk);
 	tcp_bound_rto(sk);
@@ -1112,16 +1115,23 @@ static int tcp_is_sackblock_valid(struct tcp_sock *tp, int is_dsack,
  *
  * Search retransmitted skbs from write_queue that were sent when snd_nxt was
  * less than what is now known to be received by the other end (derived from
- * SACK blocks by the caller). Also calculate the lowest snd_nxt among the
- * remaining retransmitted skbs to avoid some costly processing per ACKs.
+ * highest SACK block). Also calculate the lowest snd_nxt among the remaining
+ * retransmitted skbs to avoid some costly processing per ACKs.
  */
-static int tcp_mark_lost_retrans(struct sock *sk, u32 received_upto)
+static int tcp_mark_lost_retrans(struct sock *sk)
 {
+	const struct inet_connection_sock *icsk = inet_csk(sk);
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct sk_buff *skb;
 	int flag = 0;
 	int cnt = 0;
 	u32 new_low_seq = tp->snd_nxt;
+	u32 received_upto = TCP_SKB_CB(tp->highest_sack)->end_seq;
+
+	if (!tcp_is_fack(tp) || !tp->retrans_out ||
+	    !after(received_upto, tp->lost_retrans_low) ||
+	    icsk->icsk_ca_state != TCP_CA_Recovery)
+		return flag;
 
 	tcp_for_write_queue(skb, sk) {
 		u32 ack_seq = TCP_SKB_CB(skb)->ack_seq;
@@ -1230,6 +1240,99 @@ static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
 	return in_sack;
 }
 
+static int tcp_sacktag_one(struct sk_buff *skb, struct tcp_sock *tp,
+			   int *reord, int dup_sack, int fack_count)
+{
+	u8 sacked = TCP_SKB_CB(skb)->sacked;
+	int flag = 0;
+
+	/* Account D-SACK for retransmitted packet. */
+	if (dup_sack && (sacked & TCPCB_RETRANS)) {
+		if (after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
+			tp->undo_retrans--;
+		if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una) &&
+		    (sacked & TCPCB_SACKED_ACKED))
+			*reord = min(fack_count, *reord);
+	}
+
+	/* Nothing to do; acked frame is about to be dropped (was ACKed). */
+	if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
+		return flag;
+
+	if (!(sacked & TCPCB_SACKED_ACKED)) {
+		if (sacked & TCPCB_SACKED_RETRANS) {
+			/* If the segment is not tagged as lost,
+			 * we do not clear RETRANS, believing
+			 * that retransmission is still in flight.
+			 */
+			if (sacked & TCPCB_LOST) {
+				TCP_SKB_CB(skb)->sacked &=
+					~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
+				tp->lost_out -= tcp_skb_pcount(skb);
+				tp->retrans_out -= tcp_skb_pcount(skb);
+
+				/* clear lost hint */
+				tp->retransmit_skb_hint = NULL;
+			}
+		} else {
+			if (!(sacked & TCPCB_RETRANS)) {
+				/* New sack for not retransmitted frame,
+				 * which was in hole. It is reordering.
+				 */
+				if (before(TCP_SKB_CB(skb)->seq,
+					   tcp_highest_sack_seq(tp)))
+					*reord = min(fack_count, *reord);
+
+				/* SACK enhanced F-RTO (RFC4138; Appendix B) */
+				if (!after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark))
+					flag |= FLAG_ONLY_ORIG_SACKED;
+			}
+
+			if (sacked & TCPCB_LOST) {
+				TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
+				tp->lost_out -= tcp_skb_pcount(skb);
+
+				/* clear lost hint */
+				tp->retransmit_skb_hint = NULL;
+			}
+		}
+
+		TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
+		flag |= FLAG_DATA_SACKED;
+		tp->sacked_out += tcp_skb_pcount(skb);
+
+		fack_count += tcp_skb_pcount(skb);
+
+		/* Lost marker hint past SACKed? Tweak RFC3517 cnt */
+		if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) &&
+		    before(TCP_SKB_CB(skb)->seq,
+			   TCP_SKB_CB(tp->lost_skb_hint)->seq))
+			tp->lost_cnt_hint += tcp_skb_pcount(skb);
+
+		if (fack_count > tp->fackets_out)
+			tp->fackets_out = fack_count;
+
+		if (after(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
+			tp->highest_sack = skb;
+
+	} else {
+		if (dup_sack && (sacked & TCPCB_RETRANS))
+			*reord = min(fack_count, *reord);
+	}
+
+	/* D-SACK. We can detect redundant retransmission in S|R and plain R
+	 * frames and clear it. undo_retrans is decreased above, L|R frames
+	 * are accounted above as well.
+	 */
+	if (dup_sack && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)) {
+		TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
+		tp->retrans_out -= tcp_skb_pcount(skb);
+		tp->retransmit_skb_hint = NULL;
+	}
+
+	return flag;
+}
+
 static int
 tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una)
 {
@@ -1241,8 +1344,6 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 	struct sk_buff *cached_skb;
 	int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3;
 	int reord = tp->packets_out;
-	int prior_fackets;
-	u32 highest_sack_end_seq = tp->lost_retrans_low;
 	int flag = 0;
 	int found_dup_sack = 0;
 	int cached_fack_count;
@@ -1253,9 +1354,8 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 	if (!tp->sacked_out) {
 		if (WARN_ON(tp->fackets_out))
 			tp->fackets_out = 0;
-		tp->highest_sack = tp->snd_una;
+		tp->highest_sack = tcp_write_queue_head(sk);
 	}
-	prior_fackets = tp->fackets_out;
 
 	found_dup_sack = tcp_check_dsack(tp, ack_skb, sp,
 					 num_sacks, prior_snd_una);
@@ -1269,6 +1369,9 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 	if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window))
 		return 0;
 
+	if (!tp->packets_out)
+		goto out;
+
 	/* SACK fastpath:
 	 * if the only SACK change is the increase of the end_seq of
 	 * the first block then only apply that SACK block
@@ -1365,7 +1468,6 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 
 		tcp_for_write_queue_from(skb, sk) {
 			int in_sack = 0;
-			u8 sacked;
 
 			if (skb == tcp_send_head(sk))
 				break;
@@ -1403,98 +1505,10 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 			if (unlikely(in_sack < 0))
 				break;
 
-			sacked = TCP_SKB_CB(skb)->sacked;
-
-			/* Account D-SACK for retransmitted packet. */
-			if ((dup_sack && in_sack) &&
-			    (sacked & TCPCB_RETRANS) &&
-			    after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
-				tp->undo_retrans--;
+			if (in_sack)
+				flag |= tcp_sacktag_one(skb, tp, &reord, dup_sack, fack_count);
 
-			/* The frame is ACKed. */
-			if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) {
-				if (sacked&TCPCB_RETRANS) {
-					if ((dup_sack && in_sack) &&
-					    (sacked&TCPCB_SACKED_ACKED))
-						reord = min(fack_count, reord);
-				}
-
-				/* Nothing to do; acked frame is about to be dropped. */
-				fack_count += tcp_skb_pcount(skb);
-				continue;
-			}
-
-			if (!in_sack) {
-				fack_count += tcp_skb_pcount(skb);
-				continue;
-			}
-
-			if (!(sacked&TCPCB_SACKED_ACKED)) {
-				if (sacked & TCPCB_SACKED_RETRANS) {
-					/* If the segment is not tagged as lost,
-					 * we do not clear RETRANS, believing
-					 * that retransmission is still in flight.
-					 */
-					if (sacked & TCPCB_LOST) {
-						TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
-						tp->lost_out -= tcp_skb_pcount(skb);
-						tp->retrans_out -= tcp_skb_pcount(skb);
-
-						/* clear lost hint */
-						tp->retransmit_skb_hint = NULL;
-					}
-				} else {
-					if (!(sacked & TCPCB_RETRANS)) {
-						/* New sack for not retransmitted frame,
-						 * which was in hole. It is reordering.
-						 */
-						if (fack_count < prior_fackets)
-							reord = min(fack_count, reord);
-
-						/* SACK enhanced F-RTO (RFC4138; Appendix B) */
-						if (!after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark))
-							flag |= FLAG_ONLY_ORIG_SACKED;
-					}
-
-					if (sacked & TCPCB_LOST) {
-						TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
-						tp->lost_out -= tcp_skb_pcount(skb);
-
-						/* clear lost hint */
-						tp->retransmit_skb_hint = NULL;
-					}
-				}
-
-				TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
-				flag |= FLAG_DATA_SACKED;
-				tp->sacked_out += tcp_skb_pcount(skb);
-
-				fack_count += tcp_skb_pcount(skb);
-				if (fack_count > tp->fackets_out)
-					tp->fackets_out = fack_count;
-
-				if (after(TCP_SKB_CB(skb)->seq, tp->highest_sack)) {
-					tp->highest_sack = TCP_SKB_CB(skb)->seq;
-					highest_sack_end_seq = TCP_SKB_CB(skb)->end_seq;
-				}
-			} else {
-				if (dup_sack && (sacked&TCPCB_RETRANS))
-					reord = min(fack_count, reord);
-
-				fack_count += tcp_skb_pcount(skb);
-			}
-
-			/* D-SACK. We can detect redundant retransmission
-			 * in S|R and plain R frames and clear it.
-			 * undo_retrans is decreased above, L|R frames
-			 * are accounted above as well.
-			 */
-			if (dup_sack &&
-			    (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) {
-				TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
-				tp->retrans_out -= tcp_skb_pcount(skb);
-				tp->retransmit_skb_hint = NULL;
-			}
+			fack_count += tcp_skb_pcount(skb);
 		}
 
 		/* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct
@@ -1504,17 +1518,17 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 			flag &= ~FLAG_ONLY_ORIG_SACKED;
 	}
 
-	if (tp->retrans_out &&
-	    after(highest_sack_end_seq, tp->lost_retrans_low) &&
-	    icsk->icsk_ca_state == TCP_CA_Recovery)
-		flag |= tcp_mark_lost_retrans(sk, highest_sack_end_seq);
+	flag |= tcp_mark_lost_retrans(sk);
 
 	tcp_verify_left_out(tp);
 
-	if ((reord < tp->fackets_out) && icsk->icsk_ca_state != TCP_CA_Loss &&
+	if ((reord < tp->fackets_out) &&
+	    ((icsk->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker) &&
 	    (!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark)))
 		tcp_update_reordering(sk, tp->fackets_out - reord, 0);
 
+out:
+
 #if FASTRETRANS_DEBUG > 0
 	BUG_TRAP((int)tp->sacked_out >= 0);
 	BUG_TRAP((int)tp->lost_out >= 0);
@@ -1704,6 +1718,8 @@ static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
 	tcp_for_write_queue(skb, sk) {
 		if (skb == tcp_send_head(sk))
 			break;
+
+		TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
 		/*
 		 * Count the retransmission made on RTO correctly (only when
 		 * waiting for the first ACK and did not get it)...
@@ -1717,7 +1733,7 @@ static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
 		} else {
 			if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS)
 				tp->undo_marker = 0;
-			TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
+			TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
 		}
 
 		/* Don't lost mark skbs that were fwd transmitted after RTO */
@@ -1853,6 +1869,26 @@ static inline int tcp_fackets_out(struct tcp_sock *tp)
 	return tcp_is_reno(tp) ? tp->sacked_out+1 : tp->fackets_out;
 }
 
+/* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
+ * counter when SACK is enabled (without SACK, sacked_out is used for
+ * that purpose).
+ *
+ * Instead, with FACK TCP uses fackets_out that includes both SACKed
+ * segments up to the highest received SACK block so far and holes in
+ * between them.
+ *
+ * With reordering, holes may still be in flight, so RFC3517 recovery
+ * uses pure sacked_out (total number of SACKed segments) even though
+ * it violates the RFC that uses duplicate ACKs, often these are equal
+ * but when e.g. out-of-window ACKs or packet duplication occurs,
+ * they differ. Since neither occurs due to loss, TCP should really
+ * ignore them.
+ */
+static inline int tcp_dupack_heurestics(struct tcp_sock *tp)
+{
+	return tcp_is_fack(tp) ? tp->fackets_out : tp->sacked_out + 1;
+}
+
 static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb)
 {
 	return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto);
@@ -1973,13 +2009,13 @@ static int tcp_time_to_recover(struct sock *sk)
 		return 1;
 
 	/* Not-A-Trick#2 : Classic rule... */
-	if (tcp_fackets_out(tp) > tp->reordering)
+	if (tcp_dupack_heurestics(tp) > tp->reordering)
 		return 1;
 
 	/* Trick#3 : when we use RFC2988 timer restart, fast
 	 * retransmit can be triggered by timeout of queue head.
 	 */
-	if (tcp_head_timedout(sk))
+	if (tcp_is_fack(tp) && tcp_head_timedout(sk))
 		return 1;
 
 	/* Trick#4: It is still not OK... But will it be useful to delay
@@ -2012,8 +2048,10 @@ static void tcp_verify_retransmit_hint(struct tcp_sock *tp,
 		tp->retransmit_skb_hint = NULL;
 }
 
-/* Mark head of queue up as lost. */
-static void tcp_mark_head_lost(struct sock *sk, int packets)
+/* Mark head of queue up as lost. With RFC3517 SACK, the packets is
+ * is against sacked "cnt", otherwise it's against facked "cnt"
+ */
+static void tcp_mark_head_lost(struct sock *sk, int packets, int fast_rexmit)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct sk_buff *skb;
@@ -2035,8 +2073,13 @@ static void tcp_mark_head_lost(struct sock *sk, int packets)
 		/* this is not the most efficient way to do this... */
 		tp->lost_skb_hint = skb;
 		tp->lost_cnt_hint = cnt;
-		cnt += tcp_skb_pcount(skb);
-		if (cnt > packets || after(TCP_SKB_CB(skb)->end_seq, tp->high_seq))
+
+		if (tcp_is_fack(tp) ||
+		    (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
+			cnt += tcp_skb_pcount(skb);
+
+		if (((!fast_rexmit || (tp->lost_out > 0)) && (cnt > packets)) ||
+		     after(TCP_SKB_CB(skb)->end_seq, tp->high_seq))
 			break;
 		if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_SACKED_ACKED|TCPCB_LOST))) {
 			TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
@@ -2049,17 +2092,22 @@ static void tcp_mark_head_lost(struct sock *sk, int packets)
 
 /* Account newly detected lost packet(s) */
 
-static void tcp_update_scoreboard(struct sock *sk)
+static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 
-	if (tcp_is_fack(tp)) {
+	if (tcp_is_reno(tp)) {
+		tcp_mark_head_lost(sk, 1, fast_rexmit);
+	} else if (tcp_is_fack(tp)) {
 		int lost = tp->fackets_out - tp->reordering;
 		if (lost <= 0)
 			lost = 1;
-		tcp_mark_head_lost(sk, lost);
+		tcp_mark_head_lost(sk, lost, fast_rexmit);
 	} else {
-		tcp_mark_head_lost(sk, 1);
+		int sacked_upto = tp->sacked_out - tp->reordering;
+		if (sacked_upto < 0)
+			sacked_upto = 0;
+		tcp_mark_head_lost(sk, sacked_upto, fast_rexmit);
 	}
 
 	/* New heuristics: it is possible only after we switched
@@ -2067,7 +2115,7 @@ static void tcp_update_scoreboard(struct sock *sk)
 	 * Hence, we can detect timed out packets during fast
 	 * retransmit without falling to slow start.
 	 */
-	if (!tcp_is_reno(tp) && tcp_head_timedout(sk)) {
+	if (tcp_is_fack(tp) && tcp_head_timedout(sk)) {
 		struct sk_buff *skb;
 
 		skb = tp->scoreboard_skb_hint ? tp->scoreboard_skb_hint
@@ -2240,7 +2288,7 @@ static int tcp_try_undo_partial(struct sock *sk, int acked)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	/* Partial ACK arrived. Force Hoe's retransmit. */
-	int failed = tcp_is_reno(tp) || tp->fackets_out>tp->reordering;
+	int failed = tcp_is_reno(tp) || (tcp_fackets_out(tp) > tp->reordering);
 
 	if (tcp_may_undo(tp)) {
 		/* Plain luck! Hole if filled with delayed
@@ -2374,7 +2422,8 @@ tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
 	struct tcp_sock *tp = tcp_sk(sk);
 	int is_dupack = !(flag&(FLAG_SND_UNA_ADVANCED|FLAG_NOT_DUP));
 	int do_lost = is_dupack || ((flag&FLAG_DATA_SACKED) &&
-				    (tp->fackets_out > tp->reordering));
+				    (tcp_fackets_out(tp) > tp->reordering));
+	int fast_rexmit = 0;
 
 	/* Some technical things:
 	 * 1. Reno does not count dupacks (sacked_out) automatically. */
@@ -2394,11 +2443,11 @@ tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
 		return;
 
 	/* C. Process data loss notification, provided it is valid. */
-	if ((flag&FLAG_DATA_LOST) &&
+	if (tcp_is_fack(tp) && (flag & FLAG_DATA_LOST) &&
 	    before(tp->snd_una, tp->high_seq) &&
 	    icsk->icsk_ca_state != TCP_CA_Open &&
 	    tp->fackets_out > tp->reordering) {
-		tcp_mark_head_lost(sk, tp->fackets_out - tp->reordering);
+		tcp_mark_head_lost(sk, tp->fackets_out-tp->reordering, 0);
 		NET_INC_STATS_BH(LINUX_MIB_TCPLOSS);
 	}
 
@@ -2517,10 +2566,11 @@ tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
 		tp->bytes_acked = 0;
 		tp->snd_cwnd_cnt = 0;
 		tcp_set_ca_state(sk, TCP_CA_Recovery);
+		fast_rexmit = 1;
 	}
 
-	if (do_lost || tcp_head_timedout(sk))
-		tcp_update_scoreboard(sk);
+	if (do_lost || (tcp_is_fack(tp) && tcp_head_timedout(sk)))
+		tcp_update_scoreboard(sk, fast_rexmit);
 	tcp_cwnd_down(sk, flag);
 	tcp_xmit_retransmit_queue(sk);
 }
@@ -2644,6 +2694,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, s32 *seq_rtt_p,
 	u32 cnt = 0;
 	u32 reord = tp->packets_out;
 	s32 seq_rtt = -1;
+	s32 ca_seq_rtt = -1;
 	ktime_t last_ackt = net_invalid_timestamp();
 
 	while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) {
@@ -2652,6 +2703,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, s32 *seq_rtt_p,
 		u32 packets_acked;
 		u8 sacked = scb->sacked;
 
+		/* Determine how many packets and what bytes were acked, tso and else */
 		if (after(scb->end_seq, tp->snd_una)) {
 			if (tcp_skb_pcount(skb) == 1 ||
 			    !after(tp->snd_una, scb->seq))
@@ -2679,15 +2731,16 @@ static int tcp_clean_rtx_queue(struct sock *sk, s32 *seq_rtt_p,
 				if (sacked & TCPCB_SACKED_RETRANS)
 					tp->retrans_out -= packets_acked;
 				flag |= FLAG_RETRANS_DATA_ACKED;
+				ca_seq_rtt = -1;
 				seq_rtt = -1;
 				if ((flag & FLAG_DATA_ACKED) ||
 				    (packets_acked > 1))
 					flag |= FLAG_NONHEAD_RETRANS_ACKED;
 			} else {
+				ca_seq_rtt = now - scb->when;
+				last_ackt = skb->tstamp;
 				if (seq_rtt < 0) {
-					seq_rtt = now - scb->when;
-					if (fully_acked)
-						last_ackt = skb->tstamp;
+					seq_rtt = ca_seq_rtt;
 				}
 				if (!(sacked & TCPCB_SACKED_ACKED))
 					reord = min(cnt, reord);
@@ -2702,10 +2755,10 @@ static int tcp_clean_rtx_queue(struct sock *sk, s32 *seq_rtt_p,
 			    !before(end_seq, tp->snd_up))
 				tp->urg_mode = 0;
 		} else {
+			ca_seq_rtt = now - scb->when;
+			last_ackt = skb->tstamp;
 			if (seq_rtt < 0) {
-				seq_rtt = now - scb->when;
-				if (fully_acked)
-					last_ackt = skb->tstamp;
+				seq_rtt = ca_seq_rtt;
 			}
 			reord = min(cnt, reord);
 		}
@@ -2765,8 +2818,8 @@ static int tcp_clean_rtx_queue(struct sock *sk, s32 *seq_rtt_p,
 						 net_invalid_timestamp()))
 					rtt_us = ktime_us_delta(ktime_get_real(),
 								last_ackt);
-				else if (seq_rtt > 0)
-					rtt_us = jiffies_to_usecs(seq_rtt);
+				else if (ca_seq_rtt > 0)
+					rtt_us = jiffies_to_usecs(ca_seq_rtt);
 			}
 
 			ca_ops->pkts_acked(sk, pkts_acked, rtt_us);
@@ -2996,17 +3049,13 @@ static int tcp_process_frto(struct sock *sk, int flag)
 	}
 
 	if (tp->frto_counter == 1) {
-		/* Sending of the next skb must be allowed or no F-RTO */
-		if (!tcp_send_head(sk) ||
-		    after(TCP_SKB_CB(tcp_send_head(sk))->end_seq,
-				     tp->snd_una + tp->snd_wnd)) {
-			tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3),
-					    flag);
-			return 1;
-		}
-
+		/* tcp_may_send_now needs to see updated state */
 		tp->snd_cwnd = tcp_packets_in_flight(tp) + 2;
 		tp->frto_counter = 2;
+
+		if (!tcp_may_send_now(sk))
+			tcp_enter_frto_loss(sk, 2, flag);
+
 		return 1;
 	} else {
 		switch (sysctl_tcp_frto_response) {
@@ -3062,6 +3111,7 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
 	}
 
 	prior_fackets = tp->fackets_out;
+	prior_in_flight = tcp_packets_in_flight(tp);
 
 	if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
 		/* Window is constant, pure forward advance.
@@ -3101,16 +3151,14 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
 	if (!prior_packets)
 		goto no_queue;
 
-	prior_in_flight = tcp_packets_in_flight(tp);
-
 	/* See if we can take anything off of the retransmit queue. */
 	flag |= tcp_clean_rtx_queue(sk, &seq_rtt, prior_fackets);
 
+	if (tp->frto_counter)
+		frto_cwnd = tcp_process_frto(sk, flag);
 	/* Guarantee sacktag reordering detection against wrap-arounds */
 	if (before(tp->frto_highmark, tp->snd_una))
 		tp->frto_highmark = 0;
-	if (tp->frto_counter)
-		frto_cwnd = tcp_process_frto(sk, flag);
 
 	if (tcp_ack_is_dubious(sk, flag)) {
 		/* Advance CWND, if state allows this. */