From df5c4cbd8f6fc9eaccd140ad298df6bce9ede98d Mon Sep 17 00:00:00 2001
From: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
Date: Sun, 25 Aug 2024 10:27:50 +0200
Subject: [PATCH] Update

---
 include/linux/tcp.h  |  3 ++-
 net/ipv4/tcp.c       |  1 +
 net/ipv4/tcp_input.c | 12 +++++++++---
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index af509652f59d..94e9ee76a024 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -389,7 +389,8 @@ struct tcp_sock {
 	u8	dup_ack_counter:2,
 		tlp_retrans:1,	/* TLP is a retransmission */
 		syn_ect_snt:2,	/* AccECN ECT memory, only */
-		syn_ect_rcv:2;	/* ... needed durign 3WHS + first seqno */
+		syn_ect_rcv:2,	/* ... needed durign 3WHS + first seqno */
+		wait_third_ack:1; /* Need 3rd ack in simultaneous ope nfor AccECN */
 	u8	accecn_fail_mode:4,     /* AccECN failure handling */
 		saw_accecn_opt:2,	/* An AccECN option was seen */
 		first_data_ack:1;	/* Check for first data ack */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index fa8882e0eda3..723a7295c608 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3079,6 +3079,7 @@ int tcp_disconnect(struct sock *sk, int flags)
 	tp->window_clamp = 0;
 	tp->delivered = 0;
 	tp->delivered_ce = 0;
+	tp->wait_third_ack = 0;
 	tp->accecn_fail_mode = 0;
 	tp->saw_accecn_opt = TCP_ACCECN_OPT_NOT_SEEN;
 	tp->first_data_ack = 0;
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 0ddb0099eac9..5a236cc57e44 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -6492,8 +6492,10 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
 		    TCP_SKB_CB(skb)->seq + 1 == TCP_SKB_CB(skb)->end_seq &&
 		    TCP_SKB_CB(skb)->seq + 1 == tp->rcv_nxt &&
 		    TCP_SKB_CB(skb)->ack_seq == tp->snd_nxt) {
-			if (!tcp_ecn_disabled(tp))
+			if (!tcp_ecn_disabled(tp)) {
+				tp->wait_third_ack = true;
 				__tcp_send_ack(sk, tp->rcv_nxt, tcp_accecn_reflector_flags(tp->syn_ect_rcv));
+			}
 			goto pass;
 		}
 
@@ -6712,6 +6714,10 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb)
 		return;
 
 step5:
+	if (tcp_ecn_mode_accecn(tp) && tp->wait_third_ack) {
+		tp->wait_third_ack = false;
+		tcp_accecn_third_ack(sk, skb, tp->syn_ect_snt);
+	}
 	tcp_ecn_received_counters(sk, skb, len - th->doff * 4);
 
 	reason = tcp_ack(sk, skb, FLAG_SLOWPATH | FLAG_UPDATE_TS_RECENT);
@@ -7322,13 +7328,13 @@ tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 		tp->lsndtime = tcp_jiffies32;
 
 		tcp_initialize_rcv_mss(sk);
-		if (tcp_ecn_mode_accecn(tp))
+		if (tcp_ecn_mode_accecn(tp) && !tp->wait_third_ack)
 			tcp_accecn_third_ack(sk, skb, tp->syn_ect_snt);
 		tcp_fast_path_on(tp);
 		if (sk->sk_shutdown & SEND_SHUTDOWN)
 			tcp_shutdown(sk, SEND_SHUTDOWN);
 
-		if (sk->sk_socket)
+		if (sk->sk_socket && !tp->wait_third_ack)
 			goto consume;
 		break;