1 files changed, 119 insertions, 152 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 41dcbd568cbe..2c0ff327b6df 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -79,7 +79,7 @@
 int sysctl_tcp_timestamps __read_mostly = 1;
 int sysctl_tcp_window_scaling __read_mostly = 1;
 int sysctl_tcp_sack __read_mostly = 1;
-int sysctl_tcp_fack __read_mostly = 1;
+int sysctl_tcp_fack __read_mostly;
 int sysctl_tcp_max_reordering __read_mostly = 300;
 int sysctl_tcp_dsack __read_mostly = 1;
 int sysctl_tcp_app_win __read_mostly = 31;
@@ -95,9 +95,6 @@ int sysctl_tcp_rfc1337 __read_mostly;
 int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
 int sysctl_tcp_frto __read_mostly = 2;
 int sysctl_tcp_min_rtt_wlen __read_mostly = 300;
-
-int sysctl_tcp_thin_dupack __read_mostly;
-
 int sysctl_tcp_moderate_rcvbuf __read_mostly = 1;
 int sysctl_tcp_early_retrans __read_mostly = 3;
 int sysctl_tcp_invalid_ratelimit __read_mostly = HZ/2;
@@ -904,8 +901,6 @@ static void tcp_update_reordering(struct sock *sk, const int metric,
 		tcp_disable_fack(tp);
 	}
 
-	if (metric > 0)
-		tcp_disable_early_retrans(tp);
 	tp->rack.reord = 1;
 }
 
@@ -916,10 +911,6 @@ static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb)
 	    before(TCP_SKB_CB(skb)->seq,
 		   TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
 		tp->retransmit_skb_hint = skb;
-
-	if (!tp->lost_out ||
-	    after(TCP_SKB_CB(skb)->end_seq, tp->retransmit_high))
-		tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
 }
 
 /* Sum the number of packets on the wire we have marked as lost.
@@ -1135,6 +1126,7 @@ struct tcp_sacktag_state {
 	 */
 	struct skb_mstamp first_sackt;
 	struct skb_mstamp last_sackt;
+	struct skb_mstamp ack_time; /* Timestamp when the S/ACK was received */
 	struct rate_sample *rate;
 	int	flag;
 };
@@ -1217,7 +1209,8 @@ static u8 tcp_sacktag_one(struct sock *sk,
 		return sacked;
 
 	if (!(sacked & TCPCB_SACKED_ACKED)) {
-		tcp_rack_advance(tp, xmit_time, sacked);
+		tcp_rack_advance(tp, sacked, end_seq,
+				 xmit_time, &state->ack_time);
 
 		if (sacked & TCPCB_SACKED_RETRANS) {
 			/* If the segment is not tagged as lost,
@@ -1937,7 +1930,6 @@ void tcp_enter_loss(struct sock *sk)
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct net *net = sock_net(sk);
 	struct sk_buff *skb;
-	bool new_recovery = icsk->icsk_ca_state < TCP_CA_Recovery;
 	bool is_reneg;			/* is receiver reneging on SACKs? */
 	bool mark_lost;
 
@@ -1982,7 +1974,6 @@ void tcp_enter_loss(struct sock *sk)
 			TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
 			TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
 			tp->lost_out += tcp_skb_pcount(skb);
-			tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
 		}
 	}
 	tcp_verify_left_out(tp);
@@ -1998,13 +1989,15 @@ void tcp_enter_loss(struct sock *sk)
 	tp->high_seq = tp->snd_nxt;
 	tcp_ecn_queue_cwr(tp);
 
-	/* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous
-	 * loss recovery is underway except recurring timeout(s) on
-	 * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing
+	/* F-RTO RFC5682 sec 3.1 step 1 mandates to disable F-RTO
+	 * if a previous recovery is underway, otherwise it may incorrectly
+	 * call a timeout spurious if some previously retransmitted packets
+	 * are s/acked (sec 3.2). We do not apply that retriction since
+	 * retransmitted skbs are permanently tagged with TCPCB_EVER_RETRANS
+	 * so FLAG_ORIG_SACK_ACKED is always correct. But we do disable F-RTO
+	 * on PTMU discovery to avoid sending new data.
 	 */
-	tp->frto = sysctl_tcp_frto &&
-		   (new_recovery || icsk->icsk_retransmits) &&
-		   !inet_csk(sk)->icsk_mtup.probe_size;
+	tp->frto = sysctl_tcp_frto && !inet_csk(sk)->icsk_mtup.probe_size;
 }
 
 /* If ACK arrived pointing to a remembered SACK, it means that our
@@ -2056,30 +2049,6 @@ static inline int tcp_dupack_heuristics(const struct tcp_sock *tp)
 	return tcp_is_fack(tp) ? tp->fackets_out : tp->sacked_out + 1;
 }
 
-static bool tcp_pause_early_retransmit(struct sock *sk, int flag)
-{
-	struct tcp_sock *tp = tcp_sk(sk);
-	unsigned long delay;
-
-	/* Delay early retransmit and entering fast recovery for
-	 * max(RTT/4, 2msec) unless ack has ECE mark, no RTT samples
-	 * available, or RTO is scheduled to fire first.
-	 */
-	if (sysctl_tcp_early_retrans < 2 || sysctl_tcp_early_retrans > 3 ||
-	    (flag & FLAG_ECE) || !tp->srtt_us)
-		return false;
-
-	delay = max(usecs_to_jiffies(tp->srtt_us >> 5),
-		    msecs_to_jiffies(2));
-
-	if (!time_after(inet_csk(sk)->icsk_timeout, (jiffies + delay)))
-		return false;
-
-	inet_csk_reset_xmit_timer(sk, ICSK_TIME_EARLY_RETRANS, delay,
-				  TCP_RTO_MAX);
-	return true;
-}
-
 /* Linux NewReno/SACK/FACK/ECN state machine.
  * --------------------------------------
  *
@@ -2127,10 +2096,26 @@ static bool tcp_pause_early_retransmit(struct sock *sk, int flag)
  *	F.e. after RTO, when all the queue is considered as lost,
  *	lost_out = packets_out and in_flight = retrans_out.
  *
- *		Essentially, we have now two algorithms counting
+ *		Essentially, we have now a few algorithms detecting
  *		lost packets.
  *
- *		FACK: It is the simplest heuristics. As soon as we decided
+ *		If the receiver supports SACK:
+ *
+ *		RFC6675/3517: It is the conventional algorithm. A packet is
+ *		considered lost if the number of higher sequence packets
+ *		SACKed is greater than or equal the DUPACK thoreshold
+ *		(reordering). This is implemented in tcp_mark_head_lost and
+ *		tcp_update_scoreboard.
+ *
+ *		RACK (draft-ietf-tcpm-rack-01): it is a newer algorithm
+ *		(2017-) that checks timing instead of counting DUPACKs.
+ *		Essentially a packet is considered lost if it's not S/ACKed
+ *		after RTT + reordering_window, where both metrics are
+ *		dynamically measured and adjusted. This is implemented in
+ *		tcp_rack_mark_lost.
+ *
+ *		FACK (Disabled by default. Subsumbed by RACK):
+ *		It is the simplest heuristics. As soon as we decided
  *		that something is lost, we decide that _all_ not SACKed
  *		packets until the most forward SACK are lost. I.e.
  *		lost_out = fackets_out - sacked_out and left_out = fackets_out.
@@ -2139,16 +2124,14 @@ static bool tcp_pause_early_retransmit(struct sock *sk, int flag)
  *		takes place. We use FACK by default until reordering
  *		is suspected on the path to this destination.
  *
- *		NewReno: when Recovery is entered, we assume that one segment
+ *		If the receiver does not support SACK:
+ *
+ *		NewReno (RFC6582): in Recovery we assume that one segment
  *		is lost (classic Reno). While we are in Recovery and
  *		a partial ACK arrives, we assume that one more packet
  *		is lost (NewReno). This heuristics are the same in NewReno
  *		and SACK.
  *
- *  Imagine, that's all! Forget about all this shamanism about CWND inflation
- *  deflation etc. CWND is real congestion window, never inflated, changes
- *  only according to classic VJ rules.
- *
  * Really tricky (and requiring careful tuning) part of algorithm
  * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
  * The first determines the moment _when_ we should reduce CWND and,
@@ -2176,8 +2159,6 @@ static bool tcp_pause_early_retransmit(struct sock *sk, int flag)
 static bool tcp_time_to_recover(struct sock *sk, int flag)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
-	__u32 packets_out;
-	int tcp_reordering = sock_net(sk)->ipv4.sysctl_tcp_reordering;
 
 	/* Trick#1: The loss is proven. */
 	if (tp->lost_out)
@@ -2187,39 +2168,6 @@ static bool tcp_time_to_recover(struct sock *sk, int flag)
 	if (tcp_dupack_heuristics(tp) > tp->reordering)
 		return true;
 
-	/* Trick#4: It is still not OK... But will it be useful to delay
-	 * recovery more?
-	 */
-	packets_out = tp->packets_out;
-	if (packets_out <= tp->reordering &&
-	    tp->sacked_out >= max_t(__u32, packets_out/2, tcp_reordering) &&
-	    !tcp_may_send_now(sk)) {
-		/* We have nothing to send. This connection is limited
-		 * either by receiver window or by application.
-		 */
-		return true;
-	}
-
-	/* If a thin stream is detected, retransmit after first
-	 * received dupack. Employ only if SACK is supported in order
-	 * to avoid possible corner-case series of spurious retransmissions
-	 * Use only if there are no unsent data.
-	 */
-	if ((tp->thin_dupack || sysctl_tcp_thin_dupack) &&
-	    tcp_stream_is_thin(tp) && tcp_dupack_heuristics(tp) > 1 &&
-	    tcp_is_sack(tp) && !tcp_send_head(sk))
-		return true;
-
-	/* Trick#6: TCP early retransmit, per RFC5827.  To avoid spurious
-	 * retransmissions due to small network reorderings, we implement
-	 * Mitigation A.3 in the RFC and delay the retransmission for a short
-	 * interval if appropriate.
-	 */
-	if (tp->do_early_retrans && !tp->retrans_out && tp->sacked_out &&
-	    (tp->packets_out >= (tp->sacked_out + 1) && tp->packets_out < 4) &&
-	    !tcp_may_send_now(sk))
-		return !tcp_pause_early_retransmit(sk, flag);
-
 	return false;
 }
 
@@ -2521,8 +2469,7 @@ static void tcp_init_cwnd_reduction(struct sock *sk)
 	tcp_ecn_queue_cwr(tp);
 }
 
-static void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked,
-			       int flag)
+void tcp_cwnd_reduction(struct sock *sk, int newly_acked_sacked, int flag)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	int sndcnt = 0;
@@ -2690,7 +2637,7 @@ void tcp_simple_retransmit(struct sock *sk)
 }
 EXPORT_SYMBOL(tcp_simple_retransmit);
 
-static void tcp_enter_recovery(struct sock *sk, bool ece_ack)
+void tcp_enter_recovery(struct sock *sk, bool ece_ack)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	int mib_idx;
@@ -2726,14 +2673,18 @@ static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack,
 	    tcp_try_undo_loss(sk, false))
 		return;
 
-	if (tp->frto) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
-		/* Step 3.b. A timeout is spurious if not all data are
-		 * lost, i.e., never-retransmitted data are (s)acked.
-		 */
-		if ((flag & FLAG_ORIG_SACK_ACKED) &&
-		    tcp_try_undo_loss(sk, true))
-			return;
+	/* The ACK (s)acks some never-retransmitted data meaning not all
+	 * the data packets before the timeout were lost. Therefore we
+	 * undo the congestion window and state. This is essentially
+	 * the operation in F-RTO (RFC5682 section 3.1 step 3.b). Since
+	 * a retransmitted skb is permantly marked, we can apply such an
+	 * operation even if F-RTO was not used.
+	 */
+	if ((flag & FLAG_ORIG_SACK_ACKED) &&
+	    tcp_try_undo_loss(sk, tp->undo_marker))
+		return;
 
+	if (tp->frto) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
 		if (after(tp->snd_nxt, tp->high_seq)) {
 			if (flag & FLAG_DATA_SACKED || is_dupack)
 				tp->frto = 0; /* Step 3.a. loss was real */
@@ -2800,6 +2751,21 @@ static bool tcp_try_undo_partial(struct sock *sk, const int acked)
 	return false;
 }
 
+static void tcp_rack_identify_loss(struct sock *sk, int *ack_flag,
+				   const struct skb_mstamp *ack_time)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	/* Use RACK to detect loss */
+	if (sysctl_tcp_recovery & TCP_RACK_LOSS_DETECTION) {
+		u32 prior_retrans = tp->retrans_out;
+
+		tcp_rack_mark_lost(sk, ack_time);
+		if (prior_retrans > tp->retrans_out)
+			*ack_flag |= FLAG_LOST_RETRANS;
+	}
+}
+
 /* Process an event, which can update packets-in-flight not trivially.
  * Main goal of this function is to calculate new estimate for left_out,
  * taking into account both packets sitting in receiver's buffer and
@@ -2813,7 +2779,8 @@ static bool tcp_try_undo_partial(struct sock *sk, const int acked)
  * tcp_xmit_retransmit_queue().
  */
 static void tcp_fastretrans_alert(struct sock *sk, const int acked,
-				  bool is_dupack, int *ack_flag, int *rexmit)
+				  bool is_dupack, int *ack_flag, int *rexmit,
+				  const struct skb_mstamp *ack_time)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
 	struct tcp_sock *tp = tcp_sk(sk);
@@ -2864,13 +2831,6 @@ static void tcp_fastretrans_alert(struct sock *sk, const int acked,
 		}
 	}
 
-	/* Use RACK to detect loss */
-	if (sysctl_tcp_recovery & TCP_RACK_LOST_RETRANS &&
-	    tcp_rack_mark_lost(sk)) {
-		flag |= FLAG_LOST_RETRANS;
-		*ack_flag |= FLAG_LOST_RETRANS;
-	}
-
 	/* E. Process state. */
 	switch (icsk->icsk_ca_state) {
 	case TCP_CA_Recovery:
@@ -2888,11 +2848,13 @@ static void tcp_fastretrans_alert(struct sock *sk, const int acked,
 			tcp_try_keep_open(sk);
 			return;
 		}
+		tcp_rack_identify_loss(sk, ack_flag, ack_time);
 		break;
 	case TCP_CA_Loss:
 		tcp_process_loss(sk, flag, is_dupack, rexmit);
-		if (icsk->icsk_ca_state != TCP_CA_Open &&
-		    !(flag & FLAG_LOST_RETRANS))
+		tcp_rack_identify_loss(sk, ack_flag, ack_time);
+		if (!(icsk->icsk_ca_state == TCP_CA_Open ||
+		      (*ack_flag & FLAG_LOST_RETRANS)))
 			return;
 		/* Change state if cwnd is undone or retransmits are lost */
 	default:
@@ -2906,6 +2868,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const int acked,
 		if (icsk->icsk_ca_state <= TCP_CA_Disorder)
 			tcp_try_undo_dsack(sk);
 
+		tcp_rack_identify_loss(sk, ack_flag, ack_time);
 		if (!tcp_time_to_recover(sk, flag)) {
 			tcp_try_to_open(sk, flag);
 			return;
@@ -3024,7 +2987,7 @@ void tcp_rearm_rto(struct sock *sk)
 	} else {
 		u32 rto = inet_csk(sk)->icsk_rto;
 		/* Offset the time elapsed after installing regular RTO */
-		if (icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
+		if (icsk->icsk_pending == ICSK_TIME_REO_TIMEOUT ||
 		    icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
 			struct sk_buff *skb = tcp_write_queue_head(sk);
 			const u32 rto_time_stamp =
@@ -3041,24 +3004,6 @@ void tcp_rearm_rto(struct sock *sk)
 	}
 }
 
-/* This function is called when the delayed ER timer fires. TCP enters
- * fast recovery and performs fast-retransmit.
- */
-void tcp_resume_early_retransmit(struct sock *sk)
-{
-	struct tcp_sock *tp = tcp_sk(sk);
-
-	tcp_rearm_rto(sk);
-
-	/* Stop if ER is disabled after the delayed ER timer is scheduled */
-	if (!tp->do_early_retrans)
-		return;
-
-	tcp_enter_recovery(sk, false);
-	tcp_update_scoreboard(sk, 1);
-	tcp_xmit_retransmit_queue(sk);
-}
-
 /* If we get here, the whole TSO packet has not been acked. */
 static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb)
 {
@@ -3101,11 +3046,11 @@ static void tcp_ack_tstamp(struct sock *sk, struct sk_buff *skb,
  */
 static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 			       u32 prior_snd_una, int *acked,
-			       struct tcp_sacktag_state *sack,
-			       struct skb_mstamp *now)
+			       struct tcp_sacktag_state *sack)
 {
 	const struct inet_connection_sock *icsk = inet_csk(sk);
 	struct skb_mstamp first_ackt, last_ackt;
+	struct skb_mstamp *now = &sack->ack_time;
 	struct tcp_sock *tp = tcp_sk(sk);
 	u32 prior_sacked = tp->sacked_out;
 	u32 reord = tp->packets_out;
@@ -3165,7 +3110,9 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 		} else if (tcp_is_sack(tp)) {
 			tp->delivered += acked_pcount;
 			if (!tcp_skb_spurious_retrans(tp, skb))
-				tcp_rack_advance(tp, &skb->skb_mstamp, sacked);
+				tcp_rack_advance(tp, sacked, scb->end_seq,
+						 &skb->skb_mstamp,
+						 &sack->ack_time);
 		}
 		if (sacked & TCPCB_LOST)
 			tp->lost_out -= acked_pcount;
@@ -3595,7 +3542,6 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 	u32 lost = tp->lost;
 	int acked = 0; /* Number of packets newly acked */
 	int rexmit = REXMIT_NONE; /* Flag to (re)transmit to recover losses */
-	struct skb_mstamp now;
 
 	sack_state.first_sackt.v64 = 0;
 	sack_state.rate = &rs;
@@ -3621,10 +3567,9 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 	if (after(ack, tp->snd_nxt))
 		goto invalid_ack;
 
-	skb_mstamp_get(&now);
+	skb_mstamp_get(&sack_state.ack_time);
 
-	if (icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
-	    icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
+	if (icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
 		tcp_rearm_rto(sk);
 
 	if (after(ack, prior_snd_una)) {
@@ -3689,34 +3634,34 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 
 	/* See if we can take anything off of the retransmit queue. */
 	flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una, &acked,
-				    &sack_state, &now);
+				    &sack_state);
 
 	if (tcp_ack_is_dubious(sk, flag)) {
 		is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP));
-		tcp_fastretrans_alert(sk, acked, is_dupack, &flag, &rexmit);
+		tcp_fastretrans_alert(sk, acked, is_dupack, &flag, &rexmit,
+				      &sack_state.ack_time);
 	}
 	if (tp->tlp_high_seq)
 		tcp_process_tlp_ack(sk, ack, flag);
 
-	if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP)) {
-		struct dst_entry *dst = __sk_dst_get(sk);
-		if (dst)
-			dst_confirm(dst);
-	}
+	if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP))
+		sk_dst_confirm(sk);
 
 	if (icsk->icsk_pending == ICSK_TIME_RETRANS)
 		tcp_schedule_loss_probe(sk);
 	delivered = tp->delivered - delivered;	/* freshly ACKed or SACKed */
 	lost = tp->lost - lost;			/* freshly marked lost */
-	tcp_rate_gen(sk, delivered, lost, &now, &rs);
-	tcp_cong_control(sk, ack, delivered, flag, &rs);
+	tcp_rate_gen(sk, delivered, lost, &sack_state.ack_time,
+		     sack_state.rate);
+	tcp_cong_control(sk, ack, delivered, flag, sack_state.rate);
 	tcp_xmit_recovery(sk, rexmit);
 	return 1;
 
 no_queue:
 	/* If data was DSACKed, see if we can undo a cwnd reduction. */
 	if (flag & FLAG_DSACKING_ACK)
-		tcp_fastretrans_alert(sk, acked, is_dupack, &flag, &rexmit);
+		tcp_fastretrans_alert(sk, acked, is_dupack, &flag, &rexmit,
+				      &sack_state.ack_time);
 	/* If this ack opens up a zero window, clear backoff.  It was
 	 * being used to time the probes, and is probably far higher than
 	 * it needs to be for normal retransmission.
@@ -3737,9 +3682,11 @@ old_ack:
 	 * If data was DSACKed, see if we can undo a cwnd reduction.
 	 */
 	if (TCP_SKB_CB(skb)->sacked) {
+		skb_mstamp_get(&sack_state.ack_time);
 		flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una,
 						&sack_state);
-		tcp_fastretrans_alert(sk, acked, is_dupack, &flag, &rexmit);
+		tcp_fastretrans_alert(sk, acked, is_dupack, &flag, &rexmit,
+				      &sack_state.ack_time);
 		tcp_xmit_recovery(sk, rexmit);
 	}
 
@@ -4557,6 +4504,7 @@ add_sack:
 end:
 	if (skb) {
 		tcp_grow_window(sk, skb);
+		skb_condense(skb);
 		skb_set_owner_r(skb, sk);
 	}
 }
@@ -5249,6 +5197,23 @@ static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
 	return err;
 }
 
+/* Accept RST for rcv_nxt - 1 after a FIN.
+ * When tcp connections are abruptly terminated from Mac OSX (via ^C), a
+ * FIN is sent followed by a RST packet. The RST is sent with the same
+ * sequence number as the FIN, and thus according to RFC 5961 a challenge
+ * ACK should be sent. However, Mac OSX rate limits replies to challenge
+ * ACKs on the closed socket. In addition middleboxes can drop either the
+ * challenge ACK or a subsequent RST.
+ */
+static bool tcp_reset_check(const struct sock *sk, const struct sk_buff *skb)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	return unlikely(TCP_SKB_CB(skb)->seq == (tp->rcv_nxt - 1) &&
+			(1 << sk->sk_state) & (TCPF_CLOSE_WAIT | TCPF_LAST_ACK |
+					       TCPF_CLOSING));
+}
+
 /* Does PAWS and seqno based validation of an incoming segment, flags will
  * play significant role here.
  */
@@ -5287,20 +5252,25 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
 						  LINUX_MIB_TCPACKSKIPPEDSEQ,
 						  &tp->last_oow_ack_time))
 				tcp_send_dupack(sk, skb);
+		} else if (tcp_reset_check(sk, skb)) {
+			tcp_reset(sk);
 		}
 		goto discard;
 	}
 
 	/* Step 2: check RST bit */
 	if (th->rst) {
-		/* RFC 5961 3.2 (extend to match against SACK too if available):
-		 * If seq num matches RCV.NXT or the right-most SACK block,
+		/* RFC 5961 3.2 (extend to match against (RCV.NXT - 1) after a
+		 * FIN and SACK too if available):
+		 * If seq num matches RCV.NXT or (RCV.NXT - 1) after a FIN, or
+		 * the right-most SACK block,
 		 * then
 		 *     RESET the connection
 		 * else
 		 *     Send a challenge ACK
 		 */
-		if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
+		if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt ||
+		    tcp_reset_check(sk, skb)) {
 			rst_seq_match = true;
 		} else if (tcp_is_sack(tp) && tp->rx_opt.num_sacks > 0) {
 			struct tcp_sack_block *sp = &tp->selective_acks[0];
@@ -6022,7 +5992,6 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 		break;
 
 	case TCP_FIN_WAIT1: {
-		struct dst_entry *dst;
 		int tmo;
 
 		/* If we enter the TCP_FIN_WAIT1 state and we are a
@@ -6049,9 +6018,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 		tcp_set_state(sk, TCP_FIN_WAIT2);
 		sk->sk_shutdown |= SEND_SHUTDOWN;
 
-		dst = __sk_dst_get(sk);
-		if (dst)
-			dst_confirm(dst);
+		sk_dst_confirm(sk);
 
 		if (!sock_flag(sk, SOCK_DEAD)) {
 			/* Wake up lingering close() */
@@ -6363,7 +6330,7 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
 		 * timewait bucket, so that all the necessary checks
 		 * are made in the function processing timewait state.
 		 */
-		if (tcp_death_row.sysctl_tw_recycle) {
+		if (net->ipv4.tcp_death_row.sysctl_tw_recycle) {
 			bool strict;
 
 			dst = af_ops->route_req(sk, &fl, req, &strict);
@@ -6377,8 +6344,8 @@ int tcp_conn_request(struct request_sock_ops *rsk_ops,
 		}
 		/* Kill the following clause, if you dislike this way. */
 		else if (!net->ipv4.sysctl_tcp_syncookies &&
-			 (sysctl_max_syn_backlog - inet_csk_reqsk_queue_len(sk) <
-			  (sysctl_max_syn_backlog >> 2)) &&
+			 (net->ipv4.sysctl_max_syn_backlog - inet_csk_reqsk_queue_len(sk) <
+			  (net->ipv4.sysctl_max_syn_backlog >> 2)) &&
 			 !tcp_peer_is_proven(req, dst, false,
 					     tmp_opt.saw_tstamp)) {
 			/* Without syncookies last quarter of