Merge branch 'tcp-accecn'

Chia-Yu Chang says:

====================
AccECN protocol preparation patch series

Please find the v7

v7 (03-Mar-2025)
- Move 2 new patches added in v6 to the next AccECN patch series

v6 (27-Dec-2024)
- Avoid removing removing the potential CA_ACK_WIN_UPDATE in ack_ev_flags of patch #1 (Eric Dumazet <edumazet@google.com>)
- Add reviewed-by tag in patches #2, #3, #4, #5, #6, #7, #8, #12, #14
- Foloiwng 2 new pathces are added after patch #9 (Patch that adds SKB_GSO_TCP_ACCECN)
  * New patch #10 to replace exisiting SKB_GSO_TCP_ECN with SKB_GSO_TCP_ACCECN in the driver to avoid CWR flag corruption
  * New patch #11 adds AccECN for virtio by adding new negotiation flag (VIRTIO_NET_F_HOST/GUEST_ACCECN) in feature handshake and translating Accurate ECN GSO flag between virtio_net_hdr (VIRTIO_NET_HDR_GSO_ACCECN) and skb header (SKB_GSO_TCP_ACCECN)
- Add detailed changelog and comments in #13 (Eric Dumazet <edumazet@google.com>)
- Move patch #14 to the next AccECN patch series (Eric Dumazet <edumazet@google.com>)

v5 (5-Nov-2024)
- Add helper function "tcp_flags_ntohs" to preserve last 2 bytes of TCP flags of patch #4 (Paolo Abeni <pabeni@redhat.com>)
- Fix reverse X-max tree order of patches #4, #11 (Paolo Abeni <pabeni@redhat.com>)
- Rename variable "delta" as "timestamp_delta" of patch #2 fo clariety
- Remove patch #14 in this series (Paolo Abeni <pabeni@redhat.com>, Joel Granados <joel.granados@kernel.org>)

v4 (21-Oct-2024)
- Fix line length warning of patches #2, #4, #8, #10, #11, #14
- Fix spaces preferred around '|' (ctx:VxV) warning of patch #7
- Add missing CC'ed of patches #4, #12, #14

v3 (19-Oct-2024)
- Fix build error in v2

v2 (18-Oct-2024)
- Fix warning caused by NETIF_F_GSO_ACCECN_BIT in patch #9 (Jakub Kicinski <kuba@kernel.org>)

The full patch series can be found in
https://github.com/L4STeam/linux-net-next/commits/upstream_l4steam/

The Accurate ECN draft can be found in
https://datatracker.ietf.org/doc/html/draft-ietf-tcpm-accurate-ecn-28
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

10 files changed, 124 insertions, 77 deletions

diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
index 554804774628..e01492234b0b 100644
--- a/net/ipv4/bpf_tcp_ca.c
+++ b/net/ipv4/bpf_tcp_ca.c
@@ -121,7 +121,7 @@ static int bpf_tcp_ca_btf_struct_access(struct bpf_verifier_log *log,
 BPF_CALL_2(bpf_tcp_send_ack, struct tcp_sock *, tp, u32, rcv_nxt)
 {
 	/* bpf_tcp_ca prog cannot have NULL tp */
-	__tcp_send_ack((struct sock *)tp, rcv_nxt);
+	__tcp_send_ack((struct sock *)tp, rcv_nxt, 0);
 	return 0;
 }
 
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index ea7a260bec8a..6e18d7ec5062 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -75,7 +75,6 @@
 #include <net/checksum.h>
 #include <net/gso.h>
 #include <net/inetpeer.h>
-#include <net/inet_ecn.h>
 #include <net/lwtunnel.h>
 #include <net/inet_dscp.h>
 #include <linux/bpf-cgroup.h>
@@ -1640,7 +1639,7 @@ void ip_send_unicast_reply(struct sock *sk, const struct sock *orig_sk,
 	if (IS_ERR(rt))
 		return;
 
-	inet_sk(sk)->tos = arg->tos & ~INET_ECN_MASK;
+	inet_sk(sk)->tos = arg->tos;
 
 	sk->sk_protocol = ip_hdr(skb)->protocol;
 	sk->sk_bound_dev_if = arg->bound_dev_if;
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 46951e749308..989c3c3d8e75 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4138,7 +4138,7 @@ void tcp_get_info(struct sock *sk, struct tcp_info *info)
 		info->tcpi_rcv_wscale = tp->rx_opt.rcv_wscale;
 	}
 
-	if (tp->ecn_flags & TCP_ECN_OK)
+	if (tcp_ecn_mode_any(tp))
 		info->tcpi_options |= TCPI_OPT_ECN;
 	if (tp->ecn_flags & TCP_ECN_SEEN)
 		info->tcpi_options |= TCPI_OPT_ECN_SEEN;
diff --git a/net/ipv4/tcp_dctcp.c b/net/ipv4/tcp_dctcp.c
index 8a45a4aea933..03abe0848420 100644
--- a/net/ipv4/tcp_dctcp.c
+++ b/net/ipv4/tcp_dctcp.c
@@ -90,7 +90,7 @@ __bpf_kfunc static void dctcp_init(struct sock *sk)
 {
 	const struct tcp_sock *tp = tcp_sk(sk);
 
-	if ((tp->ecn_flags & TCP_ECN_OK) ||
+	if (tcp_ecn_mode_any(tp) ||
 	    (sk->sk_state == TCP_LISTEN ||
 	     sk->sk_state == TCP_CLOSE)) {
 		struct dctcp *ca = inet_csk_ca(sk);
diff --git a/net/ipv4/tcp_dctcp.h b/net/ipv4/tcp_dctcp.h
index d69a77cbd0c7..4b0259111d81 100644
--- a/net/ipv4/tcp_dctcp.h
+++ b/net/ipv4/tcp_dctcp.h
@@ -28,7 +28,7 @@ static inline void dctcp_ece_ack_update(struct sock *sk, enum tcp_ca_event evt,
 		 */
 		if (inet_csk(sk)->icsk_ack.pending & ICSK_ACK_TIMER) {
 			dctcp_ece_ack_cwr(sk, *ce_state);
-			__tcp_send_ack(sk, *prior_rcv_nxt);
+			__tcp_send_ack(sk, *prior_rcv_nxt, 0);
 		}
 		inet_csk(sk)->icsk_ack.pending |= ICSK_ACK_NOW;
 	}
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 4e2212348088..5c270cf96678 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -102,6 +102,7 @@ int sysctl_tcp_max_orphans __read_mostly = NR_FILE;
 #define FLAG_NO_CHALLENGE_ACK	0x8000 /* do not call tcp_send_challenge_ack()	*/
 #define FLAG_ACK_MAYBE_DELAYED	0x10000 /* Likely a delayed ACK */
 #define FLAG_DSACK_TLP		0x20000 /* DSACK for tail loss probe */
+#define FLAG_TS_PROGRESS	0x40000 /* Positive timestamp delta */
 
 #define FLAG_ACKED		(FLAG_DATA_ACKED|FLAG_SYN_ACKED)
 #define FLAG_NOT_DUP		(FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
@@ -341,7 +342,7 @@ static bool tcp_in_quickack_mode(struct sock *sk)
 
 static void tcp_ecn_queue_cwr(struct tcp_sock *tp)
 {
-	if (tp->ecn_flags & TCP_ECN_OK)
+	if (tcp_ecn_mode_rfc3168(tp))
 		tp->ecn_flags |= TCP_ECN_QUEUE_CWR;
 }
 
@@ -364,10 +365,13 @@ static void tcp_ecn_withdraw_cwr(struct tcp_sock *tp)
 	tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
 }
 
-static void __tcp_ecn_check_ce(struct sock *sk, const struct sk_buff *skb)
+static void tcp_data_ecn_check(struct sock *sk, const struct sk_buff *skb)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 
+	if (tcp_ecn_disabled(tp))
+		return;
+
 	switch (TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK) {
 	case INET_ECN_NOT_ECT:
 		/* Funny extension: if ECT is not set on a segment,
@@ -396,31 +400,39 @@ static void __tcp_ecn_check_ce(struct sock *sk, const struct sk_buff *skb)
 	}
 }
 
-static void tcp_ecn_check_ce(struct sock *sk, const struct sk_buff *skb)
-{
-	if (tcp_sk(sk)->ecn_flags & TCP_ECN_OK)
-		__tcp_ecn_check_ce(sk, skb);
-}
-
 static void tcp_ecn_rcv_synack(struct tcp_sock *tp, const struct tcphdr *th)
 {
-	if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr))
-		tp->ecn_flags &= ~TCP_ECN_OK;
+	if (tcp_ecn_mode_rfc3168(tp) && (!th->ece || th->cwr))
+		tcp_ecn_mode_set(tp, TCP_ECN_DISABLED);
 }
 
 static void tcp_ecn_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th)
 {
-	if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr))
-		tp->ecn_flags &= ~TCP_ECN_OK;
+	if (tcp_ecn_mode_rfc3168(tp) && (!th->ece || !th->cwr))
+		tcp_ecn_mode_set(tp, TCP_ECN_DISABLED);
 }
 
 static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock *tp, const struct tcphdr *th)
 {
-	if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK))
+	if (th->ece && !th->syn && tcp_ecn_mode_rfc3168(tp))
 		return true;
 	return false;
 }
 
+static void tcp_count_delivered_ce(struct tcp_sock *tp, u32 ecn_count)
+{
+	tp->delivered_ce += ecn_count;
+}
+
+/* Updates the delivered and delivered_ce counts */
+static void tcp_count_delivered(struct tcp_sock *tp, u32 delivered,
+				bool ece_ack)
+{
+	tp->delivered += delivered;
+	if (ece_ack)
+		tcp_count_delivered_ce(tp, delivered);
+}
+
 /* Buffer size and advertised window tuning.
  *
  * 1. Tuning sk->sk_sndbuf, when connection enters established state.
@@ -859,7 +871,7 @@ static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb)
 	icsk->icsk_ack.lrcvtime = now;
 	tcp_save_lrcv_flowlabel(sk, skb);
 
-	tcp_ecn_check_ce(sk, skb);
+	tcp_data_ecn_check(sk, skb);
 
 	if (skb->len >= 128)
 		tcp_grow_window(sk, skb, true);
@@ -1156,15 +1168,6 @@ void tcp_mark_skb_lost(struct sock *sk, struct sk_buff *skb)
 	}
 }
 
-/* Updates the delivered and delivered_ce counts */
-static void tcp_count_delivered(struct tcp_sock *tp, u32 delivered,
-				bool ece_ack)
-{
-	tp->delivered += delivered;
-	if (ece_ack)
-		tp->delivered_ce += delivered;
-}
-
 /* This procedure tags the retransmission queue when SACKs arrive.
  *
  * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
@@ -3816,8 +3819,16 @@ static void tcp_store_ts_recent(struct tcp_sock *tp)
 	tp->rx_opt.ts_recent_stamp = ktime_get_seconds();
 }
 
-static void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
+static int __tcp_replace_ts_recent(struct tcp_sock *tp, s32 tstamp_delta)
+{
+	tcp_store_ts_recent(tp);
+	return tstamp_delta > 0 ? FLAG_TS_PROGRESS : 0;
+}
+
+static int tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
 {
+	s32 delta;
+
 	if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
 		/* PAWS bug workaround wrt. ACK frames, the PAWS discard
 		 * extra check below makes sure this can only happen
@@ -3826,9 +3837,13 @@ static void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
 		 * Not only, also it occurs for expired timestamps.
 		 */
 
-		if (tcp_paws_check(&tp->rx_opt, 0))
-			tcp_store_ts_recent(tp);
+		if (tcp_paws_check(&tp->rx_opt, 0)) {
+			delta = tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent;
+			return __tcp_replace_ts_recent(tp, delta);
+		}
 	}
+
+	return 0;
 }
 
 /* This routine deals with acks during a TLP episode and ends an episode by
@@ -3864,12 +3879,23 @@ static void tcp_process_tlp_ack(struct sock *sk, u32 ack, int flag)
 	}
 }
 
-static inline void tcp_in_ack_event(struct sock *sk, u32 flags)
+static void tcp_in_ack_event(struct sock *sk, int flag)
 {
 	const struct inet_connection_sock *icsk = inet_csk(sk);
 
-	if (icsk->icsk_ca_ops->in_ack_event)
-		icsk->icsk_ca_ops->in_ack_event(sk, flags);
+	if (icsk->icsk_ca_ops->in_ack_event) {
+		u32 ack_ev_flags = 0;
+
+		if (flag & FLAG_WIN_UPDATE)
+			ack_ev_flags |= CA_ACK_WIN_UPDATE;
+		if (flag & FLAG_SLOWPATH) {
+			ack_ev_flags |= CA_ACK_SLOWPATH;
+			if (flag & FLAG_ECE)
+				ack_ev_flags |= CA_ACK_ECE;
+		}
+
+		icsk->icsk_ca_ops->in_ack_event(sk, ack_ev_flags);
+	}
 }
 
 /* Congestion control has updated the cwnd already. So if we're in
@@ -3974,7 +4000,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 	 * is in window.
 	 */
 	if (flag & FLAG_UPDATE_TS_RECENT)
-		tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
+		flag |= tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
 
 	if ((flag & (FLAG_SLOWPATH | FLAG_SND_UNA_ADVANCED)) ==
 	    FLAG_SND_UNA_ADVANCED) {
@@ -3986,12 +4012,8 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 		tcp_snd_una_update(tp, ack);
 		flag |= FLAG_WIN_UPDATE;
 
-		tcp_in_ack_event(sk, CA_ACK_WIN_UPDATE);
-
 		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPHPACKS);
 	} else {
-		u32 ack_ev_flags = CA_ACK_SLOWPATH;
-
 		if (ack_seq != TCP_SKB_CB(skb)->end_seq)
 			flag |= FLAG_DATA;
 		else
@@ -4003,19 +4025,12 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 			flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una,
 							&sack_state);
 
-		if (tcp_ecn_rcv_ecn_echo(tp, tcp_hdr(skb))) {
+		if (tcp_ecn_rcv_ecn_echo(tp, tcp_hdr(skb)))
 			flag |= FLAG_ECE;
-			ack_ev_flags |= CA_ACK_ECE;
-		}
 
 		if (sack_state.sack_delivered)
 			tcp_count_delivered(tp, sack_state.sack_delivered,
 					    flag & FLAG_ECE);
-
-		if (flag & FLAG_WIN_UPDATE)
-			ack_ev_flags |= CA_ACK_WIN_UPDATE;
-
-		tcp_in_ack_event(sk, ack_ev_flags);
 	}
 
 	/* This is a deviation from RFC3168 since it states that:
@@ -4042,6 +4057,8 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 
 	tcp_rack_update_reo_wnd(sk, &rs);
 
+	tcp_in_ack_event(sk, flag);
+
 	if (tp->tlp_high_seq)
 		tcp_process_tlp_ack(sk, ack, flag);
 
@@ -4073,6 +4090,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 	return 1;
 
 no_queue:
+	tcp_in_ack_event(sk, flag);
 	/* If data was DSACKed, see if we can undo a cwnd reduction. */
 	if (flag & FLAG_DSACKING_ACK) {
 		tcp_fastretrans_alert(sk, prior_snd_una, num_dupack, &flag,
@@ -5020,7 +5038,7 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
 	bool fragstolen;
 
 	tcp_save_lrcv_flowlabel(sk, skb);
-	tcp_ecn_check_ce(sk, skb);
+	tcp_data_ecn_check(sk, skb);
 
 	if (unlikely(tcp_try_rmem_schedule(sk, skb, skb->truesize))) {
 		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFODROP);
@@ -6157,6 +6175,8 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb)
 	    TCP_SKB_CB(skb)->seq == tp->rcv_nxt &&
 	    !after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) {
 		int tcp_header_len = tp->tcp_header_len;
+		s32 delta = 0;
+		int flag = 0;
 
 		/* Timestamp header prediction: tcp_header_len
 		 * is automatically equal to th->doff*4 due to pred_flags
@@ -6169,8 +6189,10 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb)
 			if (!tcp_parse_aligned_timestamp(tp, th))
 				goto slow_path;
 
+			delta = tp->rx_opt.rcv_tsval -
+				tp->rx_opt.ts_recent;
 			/* If PAWS failed, check it more carefully in slow path */
-			if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
+			if (delta < 0)
 				goto slow_path;
 
 			/* DO NOT update ts_recent here, if checksum fails
@@ -6190,12 +6212,13 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb)
 				if (tcp_header_len ==
 				    (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
 				    tp->rcv_nxt == tp->rcv_wup)
-					tcp_store_ts_recent(tp);
+					flag |= __tcp_replace_ts_recent(tp,
+									delta);
 
 				/* We know that such packets are checksummed
 				 * on entry.
 				 */
-				tcp_ack(sk, skb, 0);
+				tcp_ack(sk, skb, flag);
 				__kfree_skb(skb);
 				tcp_data_snd_check(sk);
 				/* When receiving pure ack in fast path, update
@@ -6226,7 +6249,8 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb)
 			if (tcp_header_len ==
 			    (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
 			    tp->rcv_nxt == tp->rcv_wup)
-				tcp_store_ts_recent(tp);
+				flag |= __tcp_replace_ts_recent(tp,
+								delta);
 
 			tcp_rcv_rtt_measure_ts(sk, skb);
 
@@ -6241,7 +6265,7 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb)
 
 			if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
 				/* Well, only one small jumplet in fast path... */
-				tcp_ack(sk, skb, FLAG_DATA);
+				tcp_ack(sk, skb, flag | FLAG_DATA);
 				tcp_data_snd_check(sk);
 				if (!inet_csk_ack_scheduled(sk))
 					goto no_ack;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index d9405b012dff..4fa4fbb0ad12 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -66,6 +66,7 @@
 #include <net/transp_v6.h>
 #include <net/ipv6.h>
 #include <net/inet_common.h>
+#include <net/inet_ecn.h>
 #include <net/timewait_sock.h>
 #include <net/xfrm.h>
 #include <net/secure_seq.h>
@@ -887,7 +888,8 @@ static void tcp_v4_send_reset(const struct sock *sk, struct sk_buff *skb,
 	BUILD_BUG_ON(offsetof(struct sock, sk_bound_dev_if) !=
 		     offsetof(struct inet_timewait_sock, tw_bound_dev_if));
 
-	arg.tos = ip_hdr(skb)->tos;
+	/* ECN bits of TW reset are cleared */
+	arg.tos = ip_hdr(skb)->tos & ~INET_ECN_MASK;
 	arg.uid = sock_net_uid(net, sk && sk_fullsock(sk) ? sk : NULL);
 	local_bh_disable();
 	local_lock_nested_bh(&ipv4_tcp_sk.bh_lock);
@@ -1033,11 +1035,21 @@ static void tcp_v4_send_ack(const struct sock *sk,
 	local_bh_enable();
 }
 
-static void tcp_v4_timewait_ack(struct sock *sk, struct sk_buff *skb)
+static void tcp_v4_timewait_ack(struct sock *sk, struct sk_buff *skb,
+				enum tcp_tw_status tw_status)
 {
 	struct inet_timewait_sock *tw = inet_twsk(sk);
 	struct tcp_timewait_sock *tcptw = tcp_twsk(sk);
 	struct tcp_key key = {};
+	u8 tos = tw->tw_tos;
+
+	/* Cleaning only ECN bits of TW ACKs of oow data or is paws_reject,
+	 * while not cleaning ECN bits of other TW ACKs to avoid these ACKs
+	 * being placed in a different service queues (Classic rather than L4S)
+	 */
+	if (tw_status == TCP_TW_ACK_OOW)
+		tos &= ~INET_ECN_MASK;
+
 #ifdef CONFIG_TCP_AO
 	struct tcp_ao_info *ao_info;
 
@@ -1081,7 +1093,7 @@ static void tcp_v4_timewait_ack(struct sock *sk, struct sk_buff *skb)
 			READ_ONCE(tcptw->tw_ts_recent),
 			tw->tw_bound_dev_if, &key,
 			tw->tw_transparent ? IP_REPLY_ARG_NOSRCCHECK : 0,
-			tw->tw_tos,
+			tos,
 			tw->tw_txhash);
 
 	inet_twsk_put(tw);
@@ -1151,6 +1163,7 @@ static void tcp_v4_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
 			key.type = TCP_KEY_MD5;
 	}
 
+	/* Cleaning ECN bits of TW ACKs of oow data or is paws_reject */
 	tcp_v4_send_ack(sk, skb, seq,
 			tcp_rsk(req)->rcv_nxt,
 			tcp_synack_window(req) >> inet_rsk(req)->rcv_wscale,
@@ -1158,7 +1171,7 @@ static void tcp_v4_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
 			req->ts_recent,
 			0, &key,
 			inet_rsk(req)->no_srccheck ? IP_REPLY_ARG_NOSRCCHECK : 0,
-			ip_hdr(skb)->tos,
+			ip_hdr(skb)->tos & ~INET_ECN_MASK,
 			READ_ONCE(tcp_rsk(req)->txhash));
 	if (tcp_key_is_ao(&key))
 		kfree(key.traffic_key);
@@ -2051,7 +2064,8 @@ bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb,
 	    !((TCP_SKB_CB(tail)->tcp_flags &
 	      TCP_SKB_CB(skb)->tcp_flags) & TCPHDR_ACK) ||
 	    ((TCP_SKB_CB(tail)->tcp_flags ^
-	      TCP_SKB_CB(skb)->tcp_flags) & (TCPHDR_ECE | TCPHDR_CWR)) ||
+	      TCP_SKB_CB(skb)->tcp_flags) &
+	     (TCPHDR_ECE | TCPHDR_CWR | TCPHDR_AE)) ||
 	    !tcp_skb_can_collapse_rx(tail, skb) ||
 	    thtail->doff != th->doff ||
 	    memcmp(thtail + 1, th + 1, hdrlen - sizeof(*th)))
@@ -2159,7 +2173,7 @@ static void tcp_v4_fill_cb(struct sk_buff *skb, const struct iphdr *iph,
 	TCP_SKB_CB(skb)->end_seq = (TCP_SKB_CB(skb)->seq + th->syn + th->fin +
 				    skb->len - th->doff * 4);
 	TCP_SKB_CB(skb)->ack_seq = ntohl(th->ack_seq);
-	TCP_SKB_CB(skb)->tcp_flags = tcp_flag_byte(th);
+	TCP_SKB_CB(skb)->tcp_flags = tcp_flags_ntohs(th);
 	TCP_SKB_CB(skb)->ip_dsfield = ipv4_get_dsfield(iph);
 	TCP_SKB_CB(skb)->sacked	 = 0;
 	TCP_SKB_CB(skb)->has_rxtstamp =
@@ -2174,6 +2188,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
 {
 	struct net *net = dev_net_rcu(skb->dev);
 	enum skb_drop_reason drop_reason;
+	enum tcp_tw_status tw_status;
 	int sdif = inet_sdif(skb);
 	int dif = inet_iif(skb);
 	const struct iphdr *iph;
@@ -2401,7 +2416,9 @@ do_time_wait:
 		inet_twsk_put(inet_twsk(sk));
 		goto csum_error;
 	}
-	switch (tcp_timewait_state_process(inet_twsk(sk), skb, th, &isn)) {
+
+	tw_status = tcp_timewait_state_process(inet_twsk(sk), skb, th, &isn);
+	switch (tw_status) {
 	case TCP_TW_SYN: {
 		struct sock *sk2 = inet_lookup_listener(net,
 							net->ipv4.tcp_death_row.hashinfo,
@@ -2422,7 +2439,8 @@ do_time_wait:
 		/* to ACK */
 		fallthrough;
 	case TCP_TW_ACK:
-		tcp_v4_timewait_ack(sk, skb);
+	case TCP_TW_ACK_OOW:
+		tcp_v4_timewait_ack(sk, skb, tw_status);
 		break;
 	case TCP_TW_RST:
 		tcp_v4_send_reset(sk, skb, SK_RST_REASON_TCP_TIMEWAIT_SOCKET);
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 3cb8f281186b..fb9349be36b8 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -44,7 +44,7 @@ tcp_timewait_check_oow_rate_limit(struct inet_timewait_sock *tw,
 		/* Send ACK. Note, we do not put the bucket,
 		 * it will be released by caller.
 		 */
-		return TCP_TW_ACK;
+		return TCP_TW_ACK_OOW;
 	}
 
 	/* We are rate-limiting, so just release the tw sock and drop skb. */
@@ -461,7 +461,9 @@ void tcp_openreq_init_rwin(struct request_sock *req,
 static void tcp_ecn_openreq_child(struct tcp_sock *tp,
 				  const struct request_sock *req)
 {
-	tp->ecn_flags = inet_rsk(req)->ecn_ok ? TCP_ECN_OK : 0;
+	tcp_ecn_mode_set(tp, inet_rsk(req)->ecn_ok ?
+			     TCP_ECN_MODE_RFC3168 :
+			     TCP_ECN_DISABLED);
 }
 
 void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst)
diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index e27f4ee2a0de..934f777f29d3 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -142,6 +142,7 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
 	struct sk_buff *gso_skb = skb;
 	__sum16 newcheck;
 	bool ooo_okay, copy_destructor;
+	bool ecn_cwr_mask;
 	__wsum delta;
 
 	th = tcp_hdr(skb);
@@ -201,6 +202,8 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
 
 	newcheck = ~csum_fold(csum_add(csum_unfold(th->check), delta));
 
+	ecn_cwr_mask = !!(skb_shinfo(gso_skb)->gso_type & SKB_GSO_TCP_ACCECN);
+
 	while (skb->next) {
 		th->fin = th->psh = 0;
 		th->check = newcheck;
@@ -220,7 +223,8 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
 		th = tcp_hdr(skb);
 
 		th->seq = htonl(seq);
-		th->cwr = 0;
+
+		th->cwr &= ecn_cwr_mask;
 	}
 
 	/* Following permits TCP Small Queues to work well with GSO :
@@ -328,7 +332,7 @@ struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb,
 	th2 = tcp_hdr(p);
 	flush = (__force int)(flags & TCP_FLAG_CWR);
 	flush |= (__force int)((flags ^ tcp_flag_word(th2)) &
-		  ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH));
+		  ~(TCP_FLAG_FIN | TCP_FLAG_PSH));
 	flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
 	for (i = sizeof(*th); i < thlen; i += 4)
 		flush |= *(u32 *)((u8 *)th + i) ^
@@ -404,7 +408,7 @@ void tcp_gro_complete(struct sk_buff *skb)
 	shinfo->gso_segs = NAPI_GRO_CB(skb)->count;
 
 	if (th->cwr)
-		shinfo->gso_type |= SKB_GSO_TCP_ECN;
+		shinfo->gso_type |= SKB_GSO_TCP_ACCECN;
 }
 EXPORT_SYMBOL(tcp_gro_complete);
 
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 24e56bf96747..e0a4e5432399 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -325,7 +325,7 @@ static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb)
 	const struct tcp_sock *tp = tcp_sk(sk);
 
 	TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR;
-	if (!(tp->ecn_flags & TCP_ECN_OK))
+	if (tcp_ecn_disabled(tp))
 		TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE;
 	else if (tcp_ca_needs_ecn(sk) ||
 		 tcp_bpf_ca_needs_ecn(sk))
@@ -351,7 +351,7 @@ static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
 
 	if (use_ecn) {
 		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
-		tp->ecn_flags = TCP_ECN_OK;
+		tcp_ecn_mode_set(tp, TCP_ECN_MODE_RFC3168);
 		if (tcp_ca_needs_ecn(sk) || bpf_needs_ecn)
 			INET_ECN_xmit(sk);
 	}
@@ -381,7 +381,7 @@ static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb,
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 
-	if (tp->ecn_flags & TCP_ECN_OK) {
+	if (tcp_ecn_mode_rfc3168(tp)) {
 		/* Not-retransmitted data segment: set ECT and inject CWR. */
 		if (skb->len != tcp_header_len &&
 		    !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) {
@@ -403,7 +403,7 @@ static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb,
 /* Constructs common control bits of non-data skb. If SYN/FIN is present,
  * auto increment end seqno.
  */
-static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
+static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u16 flags)
 {
 	skb->ip_summed = CHECKSUM_PARTIAL;
 
@@ -1395,7 +1395,7 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
 	th->seq			= htonl(tcb->seq);
 	th->ack_seq		= htonl(rcv_nxt);
 	*(((__be16 *)th) + 6)	= htons(((tcp_header_size >> 2) << 12) |
-					tcb->tcp_flags);
+					(tcb->tcp_flags & TCPHDR_FLAGS_MASK));
 
 	th->check		= 0;
 	th->urg_ptr		= 0;
@@ -1616,8 +1616,8 @@ int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue,
 	struct sk_buff *buff;
 	int old_factor;
 	long limit;
+	u16 flags;
 	int nlen;
-	u8 flags;
 
 	if (WARN_ON(len > skb->len))
 		return -EINVAL;
@@ -2171,7 +2171,7 @@ static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
 {
 	int nlen = skb->len - len;
 	struct sk_buff *buff;
-	u8 flags;
+	u16 flags;
 
 	/* All of a TSO frame must be composed of paged data.  */
 	DEBUG_NET_WARN_ON_ONCE(skb->len != skb->data_len);
@@ -4240,7 +4240,7 @@ void tcp_send_delayed_ack(struct sock *sk)
 }
 
 /* This routine sends an ack and also updates the window. */
-void __tcp_send_ack(struct sock *sk, u32 rcv_nxt)
+void __tcp_send_ack(struct sock *sk, u32 rcv_nxt, u16 flags)
 {
 	struct sk_buff *buff;
 
@@ -4269,7 +4269,7 @@ void __tcp_send_ack(struct sock *sk, u32 rcv_nxt)
 
 	/* Reserve space for headers and prepare control bits. */
 	skb_reserve(buff, MAX_TCP_HEADER);
-	tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK);
+	tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK | flags);
 
 	/* We do not want pure acks influencing TCP Small Queues or fq/pacing
 	 * too much.
@@ -4284,7 +4284,7 @@ EXPORT_SYMBOL_GPL(__tcp_send_ack);
 
 void tcp_send_ack(struct sock *sk)
 {
-	__tcp_send_ack(sk, tcp_sk(sk)->rcv_nxt);
+	__tcp_send_ack(sk, tcp_sk(sk)->rcv_nxt, 0);
 }
 
 /* This routine sends a packet with an out of date sequence