1 files changed, 30 insertions, 21 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index ff10be8c76cf..a140d9f7a0a3 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1164,7 +1164,7 @@ static void tcp_count_delivered(struct tcp_sock *tp, u32 delivered,
  * L|R	1		- orig is lost, retransmit is in flight.
  * S|R  1		- orig reached receiver, retrans is still in flight.
  * (L|S|R is logically valid, it could occur when L|R is sacked,
- *  but it is equivalent to plain S and code short-curcuits it to S.
+ *  but it is equivalent to plain S and code short-circuits it to S.
  *  L|S is logically invalid, it would mean -1 packet in flight 8))
  *
  * These 6 states form finite state machine, controlled by the following events:
@@ -6361,6 +6361,7 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
 				inet_csk_reset_xmit_timer(sk,
 						ICSK_TIME_RETRANS,
 						TCP_TIMEOUT_MIN, TCP_RTO_MAX);
+			SKB_DR_SET(reason, TCP_INVALID_ACK_SEQUENCE);
 			goto reset_and_undo;
 		}
 
@@ -6369,6 +6370,7 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
 			     tcp_time_stamp_ts(tp))) {
 			NET_INC_STATS(sock_net(sk),
 					LINUX_MIB_PAWSACTIVEREJECTED);
+			SKB_DR_SET(reason, TCP_RFC7323_PAWS);
 			goto reset_and_undo;
 		}
 
@@ -6572,7 +6574,8 @@ discard_and_undo:
 reset_and_undo:
 	tcp_clear_options(&tp->rx_opt);
 	tp->rx_opt.mss_clamp = saved_clamp;
-	return 1;
+	/* we can reuse/return @reason to its caller to handle the exception */
+	return reason;
 }
 
 static void tcp_rcv_synrecv_state_fastopen(struct sock *sk)
@@ -6616,14 +6619,14 @@ static void tcp_rcv_synrecv_state_fastopen(struct sock *sk)
  *	address independent.
  */
 
-int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
+enum skb_drop_reason
+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);
 	const struct tcphdr *th = tcp_hdr(skb);
 	struct request_sock *req;
 	int queued = 0;
-	bool acceptable;
 	SKB_DR(reason);
 
 	switch (sk->sk_state) {
@@ -6633,7 +6636,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 
 	case TCP_LISTEN:
 		if (th->ack)
-			return 1;
+			return SKB_DROP_REASON_TCP_FLAGS;
 
 		if (th->rst) {
 			SKB_DR_SET(reason, TCP_RESET);
@@ -6649,12 +6652,10 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 			 */
 			rcu_read_lock();
 			local_bh_disable();
-			acceptable = icsk->icsk_af_ops->conn_request(sk, skb) >= 0;
+			icsk->icsk_af_ops->conn_request(sk, skb);
 			local_bh_enable();
 			rcu_read_unlock();
 
-			if (!acceptable)
-				return 1;
 			consume_skb(skb);
 			return 0;
 		}
@@ -6699,17 +6700,25 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 		return 0;
 
 	/* step 5: check the ACK field */
-	acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH |
-				      FLAG_UPDATE_TS_RECENT |
-				      FLAG_NO_CHALLENGE_ACK) > 0;
-
-	if (!acceptable) {
-		if (sk->sk_state == TCP_SYN_RECV)
-			return 1;	/* send one RST */
-		tcp_send_challenge_ack(sk);
-		SKB_DR_SET(reason, TCP_OLD_ACK);
-		goto discard;
+	reason = tcp_ack(sk, skb, FLAG_SLOWPATH |
+				  FLAG_UPDATE_TS_RECENT |
+				  FLAG_NO_CHALLENGE_ACK);
+
+	if ((int)reason <= 0) {
+		if (sk->sk_state == TCP_SYN_RECV) {
+			/* send one RST */
+			if (!reason)
+				return SKB_DROP_REASON_TCP_OLD_ACK;
+			return -reason;
+		}
+		/* accept old ack during closing */
+		if ((int)reason < 0) {
+			tcp_send_challenge_ack(sk);
+			reason = -reason;
+			goto discard;
+		}
 	}
+	SKB_DR_SET(reason, NOT_SPECIFIED);
 	switch (sk->sk_state) {
 	case TCP_SYN_RECV:
 		tp->delivered++; /* SYN-ACK delivery isn't tracked in tcp_ack */
@@ -6779,7 +6788,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 		if (READ_ONCE(tp->linger2) < 0) {
 			tcp_done(sk);
 			NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
-			return 1;
+			return SKB_DROP_REASON_TCP_ABORT_ON_DATA;
 		}
 		if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
 		    after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
@@ -6788,7 +6797,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 				tcp_fastopen_active_disable(sk);
 			tcp_done(sk);
 			NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
-			return 1;
+			return SKB_DROP_REASON_TCP_ABORT_ON_DATA;
 		}
 
 		tmo = tcp_fin_time(sk);
@@ -6853,7 +6862,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 			    after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
 				NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONDATA);
 				tcp_reset(sk, skb);
-				return 1;
+				return SKB_DROP_REASON_TCP_ABORT_ON_DATA;
 			}
 		}
 		fallthrough;