1 files changed, 170 insertions, 162 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 67ccce2..d77c0d2 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -979,6 +979,39 @@ static void tcp_update_reordering(struct sock *sk, const int metric,
 	}
 }
 
+/* This must be called before lost_out is incremented */
+static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb)
+{
+	if ((tp->retransmit_skb_hint == NULL) ||
+	    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;
+}
+
+static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb)
+{
+	if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {
+		tcp_verify_retransmit_hint(tp, skb);
+
+		tp->lost_out += tcp_skb_pcount(skb);
+		TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
+	}
+}
+
+void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, struct sk_buff *skb)
+{
+	tcp_verify_retransmit_hint(tp, skb);
+
+	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;
+	}
+}
+
 /* This procedure tags the retransmission queue when SACKs arrive.
  *
  * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
@@ -1155,13 +1188,7 @@ static void tcp_mark_lost_retrans(struct sock *sk)
 			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;
-			}
+			tcp_skb_mark_lost_uncond_verify(tp, skb);
 			NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT);
 		} else {
 			if (before(ack_seq, new_low_seq))
@@ -1271,9 +1298,6 @@ static int tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,
 					~(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)) {
@@ -1292,9 +1316,6 @@ static int tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,
 			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;
 			}
 		}
 
@@ -1324,7 +1345,6 @@ static int tcp_sacktag_one(struct sk_buff *skb, struct sock *sk,
 	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;
@@ -1726,6 +1746,8 @@ int tcp_use_frto(struct sock *sk)
 		return 0;
 
 	skb = tcp_write_queue_head(sk);
+	if (tcp_skb_is_last(sk, skb))
+		return 1;
 	skb = tcp_write_queue_next(sk, skb);	/* Skips head */
 	tcp_for_write_queue_from(skb, sk) {
 		if (skb == tcp_send_head(sk))
@@ -1867,6 +1889,7 @@ static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
 		if (!(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);
@@ -1883,7 +1906,7 @@ static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag)
 	tp->high_seq = tp->snd_nxt;
 	TCP_ECN_queue_cwr(tp);
 
-	tcp_clear_retrans_hints_partial(tp);
+	tcp_clear_all_retrans_hints(tp);
 }
 
 static void tcp_clear_retrans_partial(struct tcp_sock *tp)
@@ -1934,12 +1957,11 @@ void tcp_enter_loss(struct sock *sk, int 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_clear_all_retrans_hints(tp);
 
 	tcp_for_write_queue(skb, sk) {
 		if (skb == tcp_send_head(sk))
@@ -1952,6 +1974,7 @@ 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);
+			tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;
 		}
 	}
 	tcp_verify_left_out(tp);
@@ -2157,19 +2180,6 @@ static int tcp_time_to_recover(struct sock *sk)
 	return 0;
 }
 
-/* RFC: This is from the original, I doubt that this is necessary at all:
- * clear xmit_retrans hint if seq of this skb is beyond hint. How could we
- * retransmitted past LOST markings in the first place? I'm not fully sure
- * about undo and end of connection cases, which can cause R without L?
- */
-static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb)
-{
-	if ((tp->retransmit_skb_hint != NULL) &&
-	    before(TCP_SKB_CB(skb)->seq,
-		   TCP_SKB_CB(tp->retransmit_skb_hint)->seq))
-		tp->retransmit_skb_hint = NULL;
-}
-
 /* Mark head of queue up as lost. With RFC3517 SACK, the packets is
  * is against sacked "cnt", otherwise it's against facked "cnt"
  */
@@ -2217,11 +2227,7 @@ static void tcp_mark_head_lost(struct sock *sk, int packets)
 			cnt = packets;
 		}
 
-		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);
-		}
+		tcp_skb_mark_lost(tp, skb);
 	}
 	tcp_verify_left_out(tp);
 }
@@ -2263,11 +2269,7 @@ static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit)
 			if (!tcp_skb_timedout(sk, skb))
 				break;
 
-			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);
-			}
+			tcp_skb_mark_lost(tp, skb);
 		}
 
 		tp->scoreboard_skb_hint = skb;
@@ -2378,10 +2380,6 @@ static void tcp_undo_cwr(struct sock *sk, const int undo)
 	}
 	tcp_moderate_cwnd(tp);
 	tp->snd_cwnd_stamp = tcp_time_stamp;
-
-	/* There is something screwy going on with the retrans hints after
-	   an undo */
-	tcp_clear_all_retrans_hints(tp);
 }
 
 static inline int tcp_may_undo(struct tcp_sock *tp)
@@ -2838,7 +2836,8 @@ static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb)
  * is before the ack sequence we can discard it as it's confirmed to have
  * arrived at the other end.
  */
-static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
+static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
+			       u32 prior_snd_una)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 	const struct inet_connection_sock *icsk = inet_csk(sk);
@@ -2848,6 +2847,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
 	int flag = 0;
 	u32 pkts_acked = 0;
 	u32 reord = tp->packets_out;
+	u32 prior_sacked = tp->sacked_out;
 	s32 seq_rtt = -1;
 	s32 ca_seq_rtt = -1;
 	ktime_t last_ackt = net_invalid_timestamp();
@@ -2904,9 +2904,6 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
 		if (sacked & TCPCB_LOST)
 			tp->lost_out -= acked_pcount;
 
-		if (unlikely(tp->urg_mode && !before(end_seq, tp->snd_up)))
-			tp->urg_mode = 0;
-
 		tp->packets_out -= acked_pcount;
 		pkts_acked += acked_pcount;
 
@@ -2929,9 +2926,16 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
 
 		tcp_unlink_write_queue(skb, sk);
 		sk_wmem_free_skb(sk, skb);
-		tcp_clear_all_retrans_hints(tp);
+		tp->scoreboard_skb_hint = NULL;
+		if (skb == tp->retransmit_skb_hint)
+			tp->retransmit_skb_hint = NULL;
+		if (skb == tp->lost_skb_hint)
+			tp->lost_skb_hint = NULL;
 	}
 
+	if (likely(between(tp->snd_up, prior_snd_una, tp->snd_una)))
+		tp->snd_up = tp->snd_una;
+
 	if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))
 		flag |= FLAG_SACK_RENEGING;
 
@@ -2948,6 +2952,15 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets)
 			/* Non-retransmitted hole got filled? That's reordering */
 			if (reord < prior_fackets)
 				tcp_update_reordering(sk, tp->fackets_out - reord, 0);
+
+			/* No need to care for underflows here because
+			 * the lost_skb_hint gets NULLed if we're past it
+			 * (or something non-trivial happened)
+			 */
+			if (tcp_is_fack(tp))
+				tp->lost_cnt_hint -= pkts_acked;
+			else
+				tp->lost_cnt_hint -= prior_sacked - tp->sacked_out;
 		}
 
 		tp->fackets_out -= min(pkts_acked, tp->fackets_out);
@@ -3299,7 +3312,7 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
 		goto no_queue;
 
 	/* See if we can take anything off of the retransmit queue. */
-	flag |= tcp_clean_rtx_queue(sk, prior_fackets);
+	flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una);
 
 	if (tp->frto_counter)
 		frto_cwnd = tcp_process_frto(sk, flag);
@@ -3442,6 +3455,22 @@ void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx,
 	}
 }
 
+static int tcp_parse_aligned_timestamp(struct tcp_sock *tp, struct tcphdr *th)
+{
+	__be32 *ptr = (__be32 *)(th + 1);
+
+	if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
+			  | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
+		tp->rx_opt.saw_tstamp = 1;
+		++ptr;
+		tp->rx_opt.rcv_tsval = ntohl(*ptr);
+		++ptr;
+		tp->rx_opt.rcv_tsecr = ntohl(*ptr);
+		return 1;
+	}
+	return 0;
+}
+
 /* Fast parse options. This hopes to only see timestamps.
  * If it is wrong it falls back on tcp_parse_options().
  */
@@ -3453,16 +3482,8 @@ static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
 		return 0;
 	} else if (tp->rx_opt.tstamp_ok &&
 		   th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) {
-		__be32 *ptr = (__be32 *)(th + 1);
-		if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
-				  | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
-			tp->rx_opt.saw_tstamp = 1;
-			++ptr;
-			tp->rx_opt.rcv_tsval = ntohl(*ptr);
-			++ptr;
-			tp->rx_opt.rcv_tsecr = ntohl(*ptr);
+		if (tcp_parse_aligned_timestamp(tp, th))
 			return 1;
-		}
 	}
 	tcp_parse_options(skb, &tp->rx_opt, 1);
 	return 1;
@@ -4138,7 +4159,7 @@ drop:
 				skb1 = skb1->prev;
 			}
 		}
-		__skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue);
+		__skb_queue_after(&tp->out_of_order_queue, skb1, skb);
 
 		/* And clean segments covered by new one as whole. */
 		while ((skb1 = skb->next) !=
@@ -4161,6 +4182,18 @@ add_sack:
 	}
 }
 
+static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb,
+					struct sk_buff_head *list)
+{
+	struct sk_buff *next = skb->next;
+
+	__skb_unlink(skb, list);
+	__kfree_skb(skb);
+	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED);
+
+	return next;
+}
+
 /* Collapse contiguous sequence of skbs head..tail with
  * sequence numbers start..end.
  * Segments with FIN/SYN are not collapsed (only because this
@@ -4178,11 +4211,7 @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list,
 	for (skb = head; skb != tail;) {
 		/* No new bits? It is possible on ofo queue. */
 		if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
-			struct sk_buff *next = skb->next;
-			__skb_unlink(skb, list);
-			__kfree_skb(skb);
-			NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED);
-			skb = next;
+			skb = tcp_collapse_one(sk, skb, list);
 			continue;
 		}
 
@@ -4228,7 +4257,7 @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list,
 		memcpy(nskb->head, skb->head, header);
 		memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
 		TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
-		__skb_insert(nskb, skb->prev, skb, list);
+		__skb_queue_before(list, skb, nskb);
 		skb_set_owner_r(nskb, sk);
 
 		/* Copy data, releasing collapsed skbs. */
@@ -4246,11 +4275,7 @@ tcp_collapse(struct sock *sk, struct sk_buff_head *list,
 				start += size;
 			}
 			if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
-				struct sk_buff *next = skb->next;
-				__skb_unlink(skb, list);
-				__kfree_skb(skb);
-				NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED);
-				skb = next;
+				skb = tcp_collapse_one(sk, skb, list);
 				if (skb == tail ||
 				    tcp_hdr(skb)->syn ||
 				    tcp_hdr(skb)->fin)
@@ -4436,8 +4461,8 @@ static void tcp_new_space(struct sock *sk)
 
 	if (tcp_should_expand_sndbuf(sk)) {
 		int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) +
-			MAX_TCP_HEADER + 16 + sizeof(struct sk_buff),
-		    demanded = max_t(unsigned int, tp->snd_cwnd,
+			MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
+		int demanded = max_t(unsigned int, tp->snd_cwnd,
 				     tp->reordering + 1);
 		sndmem *= 2 * demanded;
 		if (sndmem > sk->sk_sndbuf)
@@ -4691,6 +4716,67 @@ out:
 }
 #endif /* CONFIG_NET_DMA */
 
+/* Does PAWS and seqno based validation of an incoming segment, flags will
+ * play significant role here.
+ */
+static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
+			      struct tcphdr *th, int syn_inerr)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	/* RFC1323: H1. Apply PAWS check first. */
+	if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
+	    tcp_paws_discard(sk, skb)) {
+		if (!th->rst) {
+			NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
+			tcp_send_dupack(sk, skb);
+			goto discard;
+		}
+		/* Reset is accepted even if it did not pass PAWS. */
+	}
+
+	/* Step 1: check sequence number */
+	if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
+		/* RFC793, page 37: "In all states except SYN-SENT, all reset
+		 * (RST) segments are validated by checking their SEQ-fields."
+		 * And page 69: "If an incoming segment is not acceptable,
+		 * an acknowledgment should be sent in reply (unless the RST
+		 * bit is set, if so drop the segment and return)".
+		 */
+		if (!th->rst)
+			tcp_send_dupack(sk, skb);
+		goto discard;
+	}
+
+	/* Step 2: check RST bit */
+	if (th->rst) {
+		tcp_reset(sk);
+		goto discard;
+	}
+
+	/* ts_recent update must be made after we are sure that the packet
+	 * is in window.
+	 */
+	tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
+
+	/* step 3: check security and precedence [ignored] */
+
+	/* step 4: Check for a SYN in window. */
+	if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
+		if (syn_inerr)
+			TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
+		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN);
+		tcp_reset(sk);
+		return -1;
+	}
+
+	return 1;
+
+discard:
+	__kfree_skb(skb);
+	return 0;
+}
+
 /*
  *	TCP receive function for the ESTABLISHED state.
  *
@@ -4718,6 +4804,7 @@ int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
 			struct tcphdr *th, unsigned len)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
+	int res;
 
 	/*
 	 *	Header prediction.
@@ -4756,19 +4843,10 @@ int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
 
 		/* Check timestamp */
 		if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
-			__be32 *ptr = (__be32 *)(th + 1);
-
 			/* No? Slow path! */
-			if (*ptr != htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
-					  | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP))
+			if (!tcp_parse_aligned_timestamp(tp, th))
 				goto slow_path;
 
-			tp->rx_opt.saw_tstamp = 1;
-			++ptr;
-			tp->rx_opt.rcv_tsval = ntohl(*ptr);
-			++ptr;
-			tp->rx_opt.rcv_tsecr = ntohl(*ptr);
-
 			/* If PAWS failed, check it more carefully in slow path */
 			if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
 				goto slow_path;
@@ -4879,7 +4957,8 @@ int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
 					goto no_ack;
 			}
 
-			__tcp_ack_snd_check(sk, 0);
+			if (!copied_early || tp->rcv_nxt != tp->rcv_wup)
+				__tcp_ack_snd_check(sk, 0);
 no_ack:
 #ifdef CONFIG_NET_DMA
 			if (copied_early)
@@ -4899,51 +4978,12 @@ slow_path:
 		goto csum_error;
 
 	/*
-	 * RFC1323: H1. Apply PAWS check first.
-	 */
-	if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
-	    tcp_paws_discard(sk, skb)) {
-		if (!th->rst) {
-			NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
-			tcp_send_dupack(sk, skb);
-			goto discard;
-		}
-		/* Resets are accepted even if PAWS failed.
-
-		   ts_recent update must be made after we are sure
-		   that the packet is in window.
-		 */
-	}
-
-	/*
 	 *	Standard slow path.
 	 */
 
-	if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
-		/* RFC793, page 37: "In all states except SYN-SENT, all reset
-		 * (RST) segments are validated by checking their SEQ-fields."
-		 * And page 69: "If an incoming segment is not acceptable,
-		 * an acknowledgment should be sent in reply (unless the RST bit
-		 * is set, if so drop the segment and return)".
-		 */
-		if (!th->rst)
-			tcp_send_dupack(sk, skb);
-		goto discard;
-	}
-
-	if (th->rst) {
-		tcp_reset(sk);
-		goto discard;
-	}
-
-	tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
-
-	if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
-		TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
-		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN);
-		tcp_reset(sk);
-		return 1;
-	}
+	res = tcp_validate_incoming(sk, skb, th, 1);
+	if (res <= 0)
+		return -res;
 
 step5:
 	if (th->ack)
@@ -5225,6 +5265,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 	struct tcp_sock *tp = tcp_sk(sk);
 	struct inet_connection_sock *icsk = inet_csk(sk);
 	int queued = 0;
+	int res;
 
 	tp->rx_opt.saw_tstamp = 0;
 
@@ -5277,42 +5318,9 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 		return 0;
 	}
 
-	if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
-	    tcp_paws_discard(sk, skb)) {
-		if (!th->rst) {
-			NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED);
-			tcp_send_dupack(sk, skb);
-			goto discard;
-		}
-		/* Reset is accepted even if it did not pass PAWS. */
-	}
-
-	/* step 1: check sequence number */
-	if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
-		if (!th->rst)
-			tcp_send_dupack(sk, skb);
-		goto discard;
-	}
-
-	/* step 2: check RST bit */
-	if (th->rst) {
-		tcp_reset(sk);
-		goto discard;
-	}
-
-	tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
-
-	/* step 3: check security and precedence [ignored] */
-
-	/*	step 4:
-	 *
-	 *	Check for a SYN in window.
-	 */
-	if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
-		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN);
-		tcp_reset(sk);
-		return 1;
-	}
+	res = tcp_validate_incoming(sk, skb, th, 0);
+	if (res <= 0)
+		return -res;
 
 	/* step 5: check the ACK field */
 	if (th->ack) {