X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;ds=sidebyside;f=net%2Fipv4%2Ftcp_input.c;h=ca9590f4f520a4b08a2913659a1a48b374d341d9;hb=487350e4434610e31b71eac5d6a9714b72fa32f6;hp=0feb10935be16bb5f675a194b0e3436de93b5d40;hpb=009a2e3e4ec395a290b9e4c7c9ff99296fd6b7d8;p=linux-2.6

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 0feb10935b..ca9590f4f5 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -85,7 +85,7 @@ int sysctl_tcp_adv_win_scale __read_mostly = 2;
 int sysctl_tcp_stdurg __read_mostly;
 int sysctl_tcp_rfc1337 __read_mostly;
 int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
-int sysctl_tcp_frto __read_mostly;
+int sysctl_tcp_frto __read_mostly = 2;
 int sysctl_tcp_frto_response __read_mostly;
 int sysctl_tcp_nometrics_save __read_mostly;
 
@@ -103,7 +103,7 @@ int sysctl_tcp_abc __read_mostly;
 #define FLAG_SLOWPATH		0x100 /* Do not skip RFC checks for window update.*/
 #define FLAG_ONLY_ORIG_SACKED	0x200 /* SACKs only non-rexmit sent before RTO */
 #define FLAG_SND_UNA_ADVANCED	0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
-#define FLAG_DSACKING_ACK	0x800 /* SACK blocks contained DSACK info */
+#define FLAG_DSACKING_ACK	0x800 /* SACK blocks contained D-SACK info */
 #define FLAG_NONHEAD_RETRANS_ACKED	0x1000 /* Non-head rexmitted data was ACKed */
 
 #define FLAG_ACKED		(FLAG_DATA_ACKED|FLAG_SYN_ACKED)
@@ -866,7 +866,7 @@ static void tcp_disable_fack(struct tcp_sock *tp)
 	tp->rx_opt.sack_ok &= ~2;
 }
 
-/* Take a notice that peer is sending DSACKs */
+/* Take a notice that peer is sending D-SACKs */
 static void tcp_dsack_seen(struct tcp_sock *tp)
 {
 	tp->rx_opt.sack_ok |= 4;
@@ -1027,8 +1027,15 @@ static void tcp_update_reordering(struct sock *sk, const int metric,
  * SACK block range validation checks that the received SACK block fits to
  * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
  * Note that SND.UNA is not included to the range though being valid because
- * it means that the receiver is rather inconsistent with itself (reports
- * SACK reneging when it should advance SND.UNA).
+ * it means that the receiver is rather inconsistent with itself reporting
+ * SACK reneging when it should advance SND.UNA. Such SACK block this is
+ * perfectly valid, however, in light of RFC2018 which explicitly states
+ * that "SACK block MUST reflect the newest segment.  Even if the newest
+ * segment is going to be discarded ...", not that it looks very clever
+ * in case of head skb. Due to potentional receiver driven attacks, we
+ * choose to avoid immediate execution of a walk in write queue due to
+ * reneging and defer head skb's loss recovery to standard loss recovery
+ * procedure that will eventually trigger (nothing forbids us doing this).
  *
  * Implements also blockage to start_seq wrap-around. Problem lies in the
  * fact that though start_seq (s) is before end_seq (i.e., not reversed),
@@ -1051,7 +1058,7 @@ static void tcp_update_reordering(struct sock *sk, const int metric,
  *
  * With D-SACK the lower bound is extended to cover sequence space below
  * SND.UNA down to undo_marker, which is the last point of interest. Yet
- * again, DSACK block must not to go across snd_una (for the same reason as
+ * again, D-SACK block must not to go across snd_una (for the same reason as
  * for the normal SACK blocks, explained above). But there all simplicity
  * ends, TCP might receive valid D-SACKs below that. As long as they reside
  * fully below undo_marker they do not affect behavior in anyway and can
@@ -1073,7 +1080,7 @@ static int tcp_is_sackblock_valid(struct tcp_sock *tp, int is_dsack,
 	if (!before(start_seq, tp->snd_nxt))
 		return 0;
 
-	/* In outstanding window? ...This is valid exit for DSACKs too.
+	/* In outstanding window? ...This is valid exit for D-SACKs too.
 	 * start_seq == snd_una is non-sensical (see comments above)
 	 */
 	if (after(start_seq, tp->snd_una))
@@ -1099,6 +1106,64 @@ static int tcp_is_sackblock_valid(struct tcp_sock *tp, int is_dsack,
 	return !before(start_seq, end_seq - tp->max_window);
 }
 
+/* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
+ * Event "C". Later note: FACK people cheated me again 8), we have to account
+ * for reordering! Ugly, but should help.
+ *
+ * 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.
+ */
+static int tcp_mark_lost_retrans(struct sock *sk, u32 received_upto)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct sk_buff *skb;
+	int flag = 0;
+	int cnt = 0;
+	u32 new_low_seq = tp->snd_nxt;
+
+	tcp_for_write_queue(skb, sk) {
+		u32 ack_seq = TCP_SKB_CB(skb)->ack_seq;
+
+		if (skb == tcp_send_head(sk))
+			break;
+		if (cnt == tp->retrans_out)
+			break;
+		if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
+			continue;
+
+		if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS))
+			continue;
+
+		if (after(received_upto, ack_seq) &&
+		    (tcp_is_fack(tp) ||
+		     !before(received_upto,
+			     ack_seq + tp->reordering * tp->mss_cache))) {
+			TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
+			tp->retrans_out -= tcp_skb_pcount(skb);
+
+			/* clear lost hint */
+			tp->retransmit_skb_hint = NULL;
+
+			if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
+				tp->lost_out += tcp_skb_pcount(skb);
+				TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
+				flag |= FLAG_DATA_SACKED;
+				NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT);
+			}
+		} else {
+			if (before(ack_seq, new_low_seq))
+				new_low_seq = ack_seq;
+			cnt += tcp_skb_pcount(skb);
+		}
+	}
+
+	if (tp->retrans_out)
+		tp->lost_retrans_low = new_low_seq;
+
+	return flag;
+}
 
 static int tcp_check_dsack(struct tcp_sock *tp, struct sk_buff *ack_skb,
 			   struct tcp_sack_block_wire *sp, int num_sacks,
@@ -1133,6 +1198,38 @@ static int tcp_check_dsack(struct tcp_sock *tp, struct sk_buff *ack_skb,
 	return dup_sack;
 }
 
+/* Check if skb is fully within the SACK block. In presence of GSO skbs,
+ * the incoming SACK may not exactly match but we can find smaller MSS
+ * aligned portion of it that matches. Therefore we might need to fragment
+ * which may fail and creates some hassle (caller must handle error case
+ * returns).
+ */
+static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb,
+				 u32 start_seq, u32 end_seq)
+{
+	int in_sack, err;
+	unsigned int pkt_len;
+
+	in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
+		  !before(end_seq, TCP_SKB_CB(skb)->end_seq);
+
+	if (tcp_skb_pcount(skb) > 1 && !in_sack &&
+	    after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
+
+		in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq);
+
+		if (!in_sack)
+			pkt_len = start_seq - TCP_SKB_CB(skb)->seq;
+		else
+			pkt_len = end_seq - TCP_SKB_CB(skb)->seq;
+		err = tcp_fragment(sk, skb, pkt_len, skb_shinfo(skb)->gso_size);
+		if (err < 0)
+			return err;
+	}
+
+	return in_sack;
+}
+
 static int
 tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una)
 {
@@ -1145,15 +1242,17 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 	int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3;
 	int reord = tp->packets_out;
 	int prior_fackets;
-	u32 lost_retrans = 0;
+	u32 highest_sack_end_seq = tp->lost_retrans_low;
 	int flag = 0;
 	int found_dup_sack = 0;
 	int cached_fack_count;
 	int i;
 	int first_sack_index;
+	int force_one_sack;
 
 	if (!tp->sacked_out) {
-		tp->fackets_out = 0;
+		if (WARN_ON(tp->fackets_out))
+			tp->fackets_out = 0;
 		tp->highest_sack = tp->snd_una;
 	}
 	prior_fackets = tp->fackets_out;
@@ -1174,18 +1273,18 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 	 * if the only SACK change is the increase of the end_seq of
 	 * the first block then only apply that SACK block
 	 * and use retrans queue hinting otherwise slowpath */
-	flag = 1;
+	force_one_sack = 1;
 	for (i = 0; i < num_sacks; i++) {
 		__be32 start_seq = sp[i].start_seq;
 		__be32 end_seq = sp[i].end_seq;
 
 		if (i == 0) {
 			if (tp->recv_sack_cache[i].start_seq != start_seq)
-				flag = 0;
+				force_one_sack = 0;
 		} else {
 			if ((tp->recv_sack_cache[i].start_seq != start_seq) ||
 			    (tp->recv_sack_cache[i].end_seq != end_seq))
-				flag = 0;
+				force_one_sack = 0;
 		}
 		tp->recv_sack_cache[i].start_seq = start_seq;
 		tp->recv_sack_cache[i].end_seq = end_seq;
@@ -1197,7 +1296,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 	}
 
 	first_sack_index = 0;
-	if (flag)
+	if (force_one_sack)
 		num_sacks = 1;
 	else {
 		int j;
@@ -1223,9 +1322,6 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 		}
 	}
 
-	/* clear flag as used for different purpose in following code */
-	flag = 0;
-
 	/* Use SACK fastpath hint if valid */
 	cached_skb = tp->fastpath_skb_hint;
 	cached_fack_count = tp->fastpath_cnt_hint;
@@ -1234,12 +1330,15 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 		cached_fack_count = 0;
 	}
 
-	for (i=0; i<num_sacks; i++, sp++) {
+	for (i = 0; i < num_sacks; i++) {
 		struct sk_buff *skb;
 		__u32 start_seq = ntohl(sp->start_seq);
 		__u32 end_seq = ntohl(sp->end_seq);
 		int fack_count;
 		int dup_sack = (found_dup_sack && (i == first_sack_index));
+		int next_dup = (found_dup_sack && (i+1 == first_sack_index));
+
+		sp++;
 
 		if (!tcp_is_sackblock_valid(tp, dup_sack, start_seq, end_seq)) {
 			if (dup_sack) {
@@ -1247,8 +1346,13 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 					NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDNOUNDO);
 				else
 					NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDOLD);
-			} else
+			} else {
+				/* Don't count olds caused by ACK reordering */
+				if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) &&
+				    !after(end_seq, tp->snd_una))
+					continue;
 				NET_INC_STATS_BH(LINUX_MIB_TCPSACKDISCARD);
+			}
 			continue;
 		}
 
@@ -1260,7 +1364,7 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 			flag |= FLAG_DATA_LOST;
 
 		tcp_for_write_queue_from(skb, sk) {
-			int in_sack, pcount;
+			int in_sack = 0;
 			u8 sacked;
 
 			if (skb == tcp_send_head(sk))
@@ -1279,30 +1383,27 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 			if (!before(TCP_SKB_CB(skb)->seq, end_seq))
 				break;
 
-			in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
-				!before(end_seq, TCP_SKB_CB(skb)->end_seq);
+			dup_sack = (found_dup_sack && (i == first_sack_index));
 
-			pcount = tcp_skb_pcount(skb);
+			/* Due to sorting DSACK may reside within this SACK block! */
+			if (next_dup) {
+				u32 dup_start = ntohl(sp->start_seq);
+				u32 dup_end = ntohl(sp->end_seq);
 
-			if (pcount > 1 && !in_sack &&
-			    after(TCP_SKB_CB(skb)->end_seq, start_seq)) {
-				unsigned int pkt_len;
-
-				in_sack = !after(start_seq,
-						 TCP_SKB_CB(skb)->seq);
-
-				if (!in_sack)
-					pkt_len = (start_seq -
-						   TCP_SKB_CB(skb)->seq);
-				else
-					pkt_len = (end_seq -
-						   TCP_SKB_CB(skb)->seq);
-				if (tcp_fragment(sk, skb, pkt_len, skb_shinfo(skb)->gso_size))
-					break;
-				pcount = tcp_skb_pcount(skb);
+				if (before(TCP_SKB_CB(skb)->seq, dup_end)) {
+					in_sack = tcp_match_skb_to_sack(sk, skb, dup_start, dup_end);
+					if (in_sack > 0)
+						dup_sack = 1;
+				}
 			}
 
-			fack_count += pcount;
+			/* DSACK info lost if out-of-mem, try SACK still */
+			if (in_sack <= 0)
+				in_sack = tcp_match_skb_to_sack(sk, skb, start_seq, end_seq);
+			if (in_sack < 0)
+				break;
+
+			fack_count += tcp_skb_pcount(skb);
 
 			sacked = TCP_SKB_CB(skb)->sacked;
 
@@ -1329,11 +1430,6 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 				continue;
 			}
 
-			if ((sacked&TCPCB_SACKED_RETRANS) &&
-			    after(end_seq, TCP_SKB_CB(skb)->ack_seq) &&
-			    (!lost_retrans || after(end_seq, lost_retrans)))
-				lost_retrans = end_seq;
-
 			if (!in_sack)
 				continue;
 
@@ -1387,9 +1483,10 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 				if (fack_count > tp->fackets_out)
 					tp->fackets_out = fack_count;
 
-				if (after(TCP_SKB_CB(skb)->seq,
-				    tp->highest_sack))
+				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);
@@ -1409,43 +1506,10 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 		}
 	}
 
-	/* Check for lost retransmit. This superb idea is
-	 * borrowed from "ratehalving". Event "C".
-	 * Later note: FACK people cheated me again 8),
-	 * we have to account for reordering! Ugly,
-	 * but should help.
-	 */
-	if (lost_retrans && icsk->icsk_ca_state == TCP_CA_Recovery) {
-		struct sk_buff *skb;
-
-		tcp_for_write_queue(skb, sk) {
-			if (skb == tcp_send_head(sk))
-				break;
-			if (after(TCP_SKB_CB(skb)->seq, lost_retrans))
-				break;
-			if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
-				continue;
-			if ((TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) &&
-			    after(lost_retrans, TCP_SKB_CB(skb)->ack_seq) &&
-			    (tcp_is_fack(tp) ||
-			     !before(lost_retrans,
-				     TCP_SKB_CB(skb)->ack_seq + tp->reordering *
-				     tp->mss_cache))) {
-				TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
-				tp->retrans_out -= tcp_skb_pcount(skb);
-
-				/* clear lost hint */
-				tp->retransmit_skb_hint = NULL;
-
-				if (!(TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_SACKED_ACKED))) {
-					tp->lost_out += tcp_skb_pcount(skb);
-					TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
-					flag |= FLAG_DATA_SACKED;
-					NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT);
-				}
-			}
-		}
-	}
+	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);
 
 	tcp_verify_left_out(tp);
 
@@ -1462,8 +1526,9 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_
 	return flag;
 }
 
-/* F-RTO can only be used if TCP has never retransmitted anything other than
- * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
+/* If we receive more dupacks than we expected counting segments
+ * in assumption of absent reordering, interpret this as reordering.
+ * The only another reason could be bug in receiver TCP.
  */
 static void tcp_check_reno_reordering(struct sock *sk, const int addend)
 {
@@ -1511,6 +1576,9 @@ static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
 	tp->sacked_out = 0;
 }
 
+/* F-RTO can only be used if TCP has never retransmitted anything other than
+ * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
+ */
 int tcp_use_frto(struct sock *sk)
 {
 	const struct tcp_sock *tp = tcp_sk(sk);
@@ -1564,7 +1632,7 @@ void tcp_enter_frto(struct sock *sk)
 	     !icsk->icsk_retransmits)) {
 		tp->prior_ssthresh = tcp_current_ssthresh(sk);
 		/* Our state is too optimistic in ssthresh() call because cwnd
-		 * is not reduced until tcp_enter_frto_loss() when previous FRTO
+		 * is not reduced until tcp_enter_frto_loss() when previous F-RTO
 		 * recovery has not yet completed. Pattern would be this: RTO,
 		 * Cumulative ACK, RTO (2xRTO for the same segment does not end
 		 * up here twice).
@@ -1664,6 +1732,7 @@ static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
 	tp->snd_cwnd_cnt = 0;
 	tp->snd_cwnd_stamp = tcp_time_stamp;
 	tp->frto_counter = 0;
+	tp->bytes_acked = 0;
 
 	tp->reordering = min_t(unsigned int, tp->reordering,
 					     sysctl_tcp_reordering);
@@ -1671,21 +1740,26 @@ static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
 	tp->high_seq = tp->frto_highmark;
 	TCP_ECN_queue_cwr(tp);
 
-	tcp_clear_all_retrans_hints(tp);
+	tcp_clear_retrans_hints_partial(tp);
 }
 
-void tcp_clear_retrans(struct tcp_sock *tp)
+static void tcp_clear_retrans_partial(struct tcp_sock *tp)
 {
 	tp->retrans_out = 0;
-
-	tp->fackets_out = 0;
-	tp->sacked_out = 0;
 	tp->lost_out = 0;
 
 	tp->undo_marker = 0;
 	tp->undo_retrans = 0;
 }
 
+void tcp_clear_retrans(struct tcp_sock *tp)
+{
+	tcp_clear_retrans_partial(tp);
+
+	tp->fackets_out = 0;
+	tp->sacked_out = 0;
+}
+
 /* Enter Loss state. If "how" is not zero, forget all SACK information
  * and reset tags completely, otherwise preserve SACKs. If receiver
  * dropped its ofo queue, we will know this due to reneging detection.
@@ -1695,7 +1769,6 @@ void tcp_enter_loss(struct sock *sk, int how)
 	const struct inet_connection_sock *icsk = inet_csk(sk);
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct sk_buff *skb;
-	int cnt = 0;
 
 	/* Reduce ssthresh if it has not yet been made inside this window. */
 	if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq ||
@@ -1709,17 +1782,26 @@ void tcp_enter_loss(struct sock *sk, int how)
 	tp->snd_cwnd_stamp = tcp_time_stamp;
 
 	tp->bytes_acked = 0;
-	tcp_clear_retrans(tp);
+	tcp_clear_retrans_partial(tp);
 
-	/* Push undo marker, if it was plain RTO and nothing
-	 * was retransmitted. */
-	if (!how)
+	if (tcp_is_reno(tp))
+		tcp_reset_reno_sack(tp);
+
+	if (!how) {
+		/* Push undo marker, if it was plain RTO and nothing
+		 * was retransmitted. */
 		tp->undo_marker = tp->snd_una;
+		tcp_clear_retrans_hints_partial(tp);
+	} else {
+		tp->sacked_out = 0;
+		tp->fackets_out = 0;
+		tcp_clear_all_retrans_hints(tp);
+	}
 
 	tcp_for_write_queue(skb, sk) {
 		if (skb == tcp_send_head(sk))
 			break;
-		cnt += tcp_skb_pcount(skb);
+
 		if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS)
 			tp->undo_marker = 0;
 		TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
@@ -1727,9 +1809,6 @@ void tcp_enter_loss(struct sock *sk, int how)
 			TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
 			TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
 			tp->lost_out += tcp_skb_pcount(skb);
-		} else {
-			tp->sacked_out += tcp_skb_pcount(skb);
-			tp->fackets_out = cnt;
 		}
 	}
 	tcp_verify_left_out(tp);
@@ -1739,10 +1818,8 @@ void tcp_enter_loss(struct sock *sk, int how)
 	tcp_set_ca_state(sk, TCP_CA_Loss);
 	tp->high_seq = tp->snd_nxt;
 	TCP_ECN_queue_cwr(tp);
-	/* Abort FRTO algorithm if one is in progress */
+	/* Abort F-RTO algorithm if one is in progress */
 	tp->frto_counter = 0;
-
-	tcp_clear_all_retrans_hints(tp);
 }
 
 static int tcp_check_sack_reneging(struct sock *sk)
@@ -1886,7 +1963,7 @@ static int tcp_time_to_recover(struct sock *sk)
 	struct tcp_sock *tp = tcp_sk(sk);
 	__u32 packets_out;
 
-	/* Do not perform any recovery during FRTO algorithm */
+	/* Do not perform any recovery during F-RTO algorithm */
 	if (tp->frto_counter)
 		return 0;
 
@@ -1935,8 +2012,7 @@ static void tcp_verify_retransmit_hint(struct tcp_sock *tp,
 }
 
 /* Mark head of queue up as lost. */
-static void tcp_mark_head_lost(struct sock *sk,
-			       int packets, u32 high_seq)
+static void tcp_mark_head_lost(struct sock *sk, int packets)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct sk_buff *skb;
@@ -1959,9 +2035,9 @@ static void tcp_mark_head_lost(struct sock *sk,
 		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, high_seq))
+		if (cnt > packets || after(TCP_SKB_CB(skb)->end_seq, tp->high_seq))
 			break;
-		if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
+		if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_SACKED_ACKED|TCPCB_LOST))) {
 			TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
 			tp->lost_out += tcp_skb_pcount(skb);
 			tcp_verify_retransmit_hint(tp, skb);
@@ -1980,9 +2056,9 @@ static void tcp_update_scoreboard(struct sock *sk)
 		int lost = tp->fackets_out - tp->reordering;
 		if (lost <= 0)
 			lost = 1;
-		tcp_mark_head_lost(sk, lost, tp->high_seq);
+		tcp_mark_head_lost(sk, lost);
 	} else {
-		tcp_mark_head_lost(sk, 1, tp->high_seq);
+		tcp_mark_head_lost(sk, 1);
 	}
 
 	/* New heuristics: it is possible only after we switched
@@ -2002,7 +2078,7 @@ static void tcp_update_scoreboard(struct sock *sk)
 			if (!tcp_skb_timedout(sk, skb))
 				break;
 
-			if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
+			if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_SACKED_ACKED|TCPCB_LOST))) {
 				TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
 				tp->lost_out += tcp_skb_pcount(skb);
 				tcp_verify_retransmit_hint(tp, skb);
@@ -2321,7 +2397,7 @@ tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)
 	    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, tp->high_seq);
+		tcp_mark_head_lost(sk, tp->fackets_out - tp->reordering);
 		NET_INC_STATS_BH(LINUX_MIB_TCPLOSS);
 	}
 
@@ -2685,7 +2761,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, s32 *seq_rtt_p)
 	BUG_TRAP((int)tp->lost_out >= 0);
 	BUG_TRAP((int)tp->retrans_out >= 0);
 	if (!tp->packets_out && tcp_is_sack(tp)) {
-		const struct inet_connection_sock *icsk = inet_csk(sk);
+		icsk = inet_csk(sk);
 		if (tp->lost_out) {
 			printk(KERN_DEBUG "Leak l=%u %d\n",
 			       tp->lost_out, icsk->icsk_ca_state);
@@ -2799,6 +2875,7 @@ static void tcp_conservative_spur_to_response(struct tcp_sock *tp)
 {
 	tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
 	tp->snd_cwnd_cnt = 0;
+	tp->bytes_acked = 0;
 	TCP_ECN_queue_cwr(tp);
 	tcp_moderate_cwnd(tp);
 }
@@ -2902,7 +2979,7 @@ 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 FRTO */
+		/* 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)) {
@@ -2928,6 +3005,7 @@ static int tcp_process_frto(struct sock *sk, int flag)
 		}
 		tp->frto_counter = 0;
 		tp->undo_marker = 0;
+		NET_INC_STATS_BH(LINUX_MIB_TCPSPURIOUSRTOS);
 	}
 	return 0;
 }
@@ -3008,6 +3086,9 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
 	/* See if we can take anything off of the retransmit queue. */
 	flag |= tcp_clean_rtx_queue(sk, &seq_rtt);
 
+	/* 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);
 
@@ -3845,7 +3926,7 @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list,
 
 	while (before(start, end)) {
 		struct sk_buff *nskb;
-		int header = skb_headroom(skb);
+		unsigned int header = skb_headroom(skb);
 		int copy = SKB_MAX_ORDER(header, 0);
 
 		/* Too big header? This can happen with IPv6. */