1 files changed, 101 insertions, 107 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 16d0040de34..9da9f19ece8 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3429,6 +3429,22 @@ 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().
  */
@@ -3440,16 +3456,8 @@ 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;
@@ -4148,6 +4156,18 @@ 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
@@ -4165,11 +4185,7 @@ 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;
 		}
 
@@ -4233,11 +4249,7 @@ 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)
@@ -4678,6 +4690,67 @@ 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.
  *
@@ -4705,6 +4778,7 @@ 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.
@@ -4743,19 +4817,10 @@ 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;
@@ -4886,51 +4951,12 @@ 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)
@@ -5212,6 +5238,7 @@ 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;
 
@@ -5264,42 +5291,9 @@ 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) {