[PATCH v7 net-next 09/12] gro: prevent ACE field corruption & better AccECN handling

[PATCH v7 net-next 09/12] gro: prevent ACE field corruption & better AccECN handling

[chia-yu.chang]

From: Ilpo Järvinen <ij@kernel.org>

There are important differences in how the CWR field behaves
in RFC3168 and AccECN. With AccECN, CWR flag is part of the
ACE counter and its changes are important so adjust the flags
changed mask accordingly.

Also, if CWR is there, set the Accurate ECN GSO flag to avoid
corrupting CWR flag somewhere.

Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
---
 net/ipv4/tcp_offload.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index a4cea85288ff..ef12aee5deb4 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -329,7 +329,7 @@ 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) ^
@@ -405,7 +405,7 @@ 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);
 
-- 
2.34.1

[PATCH v7 net-next 00/12] AccECN protocol preparation patch series

[chia-yu.chang]

From: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>

Hello,

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

Best regards,
Chia-Yu

Chia-Yu Chang (1):
  tcp: use BIT() macro in include/net/tcp.h

Ilpo Järvinen (11):
  tcp: reorganize tcp_in_ack_event() and tcp_count_delivered()
  tcp: create FLAG_TS_PROGRESS
  tcp: extend TCP flags to allow AE bit/ACE field
  tcp: reorganize SYN ECN code
  tcp: rework {__,}tcp_ecn_check_ce() -> tcp_data_ecn_check()
  tcp: helpers for ECN mode handling
  gso: AccECN support
  gro: prevent ACE field corruption & better AccECN handling
  tcp: AccECN support to tcp_add_backlog
  tcp: add new TCP_TW_ACK_OOW state and allow ECN bits in TOS
  tcp: Pass flags to __tcp_send_ack

 include/linux/netdev_features.h |   8 ++-
 include/linux/netdevice.h       |   2 +
 include/linux/skbuff.h          |   2 +
 include/net/tcp.h               |  81 ++++++++++++++++-----
 include/uapi/linux/tcp.h        |   9 ++-
 net/ethtool/common.c            |   1 +
 net/ipv4/bpf_tcp_ca.c           |   2 +-
 net/ipv4/ip_output.c            |   3 +-
 net/ipv4/tcp.c                  |   2 +-
 net/ipv4/tcp_dctcp.c            |   2 +-
 net/ipv4/tcp_dctcp.h            |   2 +-
 net/ipv4/tcp_input.c            | 120 +++++++++++++++++++-------------
 net/ipv4/tcp_ipv4.c             |  34 ++++++---
 net/ipv4/tcp_minisocks.c        |   6 +-
 net/ipv4/tcp_offload.c          |  10 ++-
 net/ipv4/tcp_output.c           |  23 +++---
 net/ipv6/tcp_ipv6.c             |  26 ++++---
 net/netfilter/nf_log_syslog.c   |   8 ++-
 18 files changed, 228 insertions(+), 113 deletions(-)

-- 
2.34.1

[PATCH v7 net-next 01/12] tcp: reorganize tcp_in_ack_event() and tcp_count_delivered()

[chia-yu.chang]

From: Ilpo Järvinen <ij@kernel.org>

- Move tcp_count_delivered() earlier and split tcp_count_delivered_ce()
  out of it
- Move tcp_in_ack_event() later
- While at it, remove the inline from tcp_in_ack_event() and let
  the compiler to decide

Accurate ECN's heuristics does not know if there is going
to be ACE field based CE counter increase or not until after
rtx queue has been processed. Only then the number of ACKed
bytes/pkts is available. As CE or not affects presence of
FLAG_ECE, that information for tcp_in_ack_event is not yet
available in the old location of the call to tcp_in_ack_event().

Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
---
 net/ipv4/tcp_input.c | 56 +++++++++++++++++++++++++-------------------
 1 file changed, 32 insertions(+), 24 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 4e2212348088..6a8eca916580 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -421,6 +421,20 @@ static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock *tp, const struct tcphdr
 	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.
@@ -1156,15 +1170,6 @@ 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).
@@ -3864,12 +3869,23 @@ 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
@@ -3986,12 +4002,8 @@ 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 +4015,12 @@ 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 +4047,8 @@ 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 +4080,7 @@ 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,
-- 
2.34.1

[PATCH v7 net-next 02/12] tcp: create FLAG_TS_PROGRESS

[chia-yu.chang]

From: Ilpo Järvinen <ij@kernel.org>

Whenever timestamp advances, it declares progress which
can be used by the other parts of the stack to decide that
the ACK is the most recent one seen so far.

AccECN will use this flag when deciding whether to use the
ACK to update AccECN state or not.

Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/tcp_input.c | 37 ++++++++++++++++++++++++++++---------
 1 file changed, 28 insertions(+), 9 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 6a8eca916580..771e075d457d 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)
@@ -3821,8 +3822,16 @@ 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
@@ -3831,9 +3840,13 @@ 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
@@ -3990,7 +4003,7 @@ 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) {
@@ -6165,6 +6178,8 @@ 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
@@ -6177,8 +6192,10 @@ 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
@@ -6198,12 +6215,13 @@ 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
@@ -6234,7 +6252,8 @@ 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);
 
@@ -6249,7 +6268,7 @@ 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;
-- 
2.34.1

[PATCH v7 net-next 03/12] tcp: use BIT() macro in include/net/tcp.h

[chia-yu.chang]

From: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>

Use BIT() macro for TCP flags field and TCP congestion control
flags that will be used by the congestion control algorithm.

No functional changes.

Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
Reviewed-by: Ilpo Järvinen <ij@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
---
 include/net/tcp.h | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index a9bc959fb102..71754d5916f3 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -26,6 +26,7 @@
 #include <linux/kref.h>
 #include <linux/ktime.h>
 #include <linux/indirect_call_wrapper.h>
+#include <linux/bits.h>
 
 #include <net/inet_connection_sock.h>
 #include <net/inet_timewait_sock.h>
@@ -934,14 +935,14 @@ static inline u32 tcp_rsk_tsval(const struct tcp_request_sock *treq)
 
 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
 
-#define TCPHDR_FIN 0x01
-#define TCPHDR_SYN 0x02
-#define TCPHDR_RST 0x04
-#define TCPHDR_PSH 0x08
-#define TCPHDR_ACK 0x10
-#define TCPHDR_URG 0x20
-#define TCPHDR_ECE 0x40
-#define TCPHDR_CWR 0x80
+#define TCPHDR_FIN	BIT(0)
+#define TCPHDR_SYN	BIT(1)
+#define TCPHDR_RST	BIT(2)
+#define TCPHDR_PSH	BIT(3)
+#define TCPHDR_ACK	BIT(4)
+#define TCPHDR_URG	BIT(5)
+#define TCPHDR_ECE	BIT(6)
+#define TCPHDR_CWR	BIT(7)
 
 #define TCPHDR_SYN_ECN	(TCPHDR_SYN | TCPHDR_ECE | TCPHDR_CWR)
 
@@ -1132,9 +1133,9 @@ enum tcp_ca_ack_event_flags {
 #define TCP_CA_UNSPEC	0
 
 /* Algorithm can be set on socket without CAP_NET_ADMIN privileges */
-#define TCP_CONG_NON_RESTRICTED 0x1
+#define TCP_CONG_NON_RESTRICTED		BIT(0)
 /* Requires ECN/ECT set on all packets */
-#define TCP_CONG_NEEDS_ECN	0x2
+#define TCP_CONG_NEEDS_ECN		BIT(1)
 #define TCP_CONG_MASK	(TCP_CONG_NON_RESTRICTED | TCP_CONG_NEEDS_ECN)
 
 union tcp_cc_info;
-- 
2.34.1

[PATCH v7 net-next 04/12] tcp: extend TCP flags to allow AE bit/ACE field

[chia-yu.chang]

From: Ilpo Järvinen <ij@kernel.org>

With AccECN, there's one additional TCP flag to be used (AE)
and ACE field that overloads the definition of AE, CWR, and
ECE flags. As tcp_flags was previously only 1 byte, the
byte-order stuff needs to be added to it's handling.

Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
---
 include/net/tcp.h             | 11 +++++++++--
 include/uapi/linux/tcp.h      |  9 ++++++---
 net/ipv4/tcp_ipv4.c           |  2 +-
 net/ipv4/tcp_output.c         |  8 ++++----
 net/ipv6/tcp_ipv6.c           |  2 +-
 net/netfilter/nf_log_syslog.c |  8 +++++---
 6 files changed, 26 insertions(+), 14 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 71754d5916f3..49b66b499429 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -943,7 +943,14 @@ static inline u32 tcp_rsk_tsval(const struct tcp_request_sock *treq)
 #define TCPHDR_URG	BIT(5)
 #define TCPHDR_ECE	BIT(6)
 #define TCPHDR_CWR	BIT(7)
-
+#define TCPHDR_AE	BIT(8)
+#define TCPHDR_FLAGS_MASK (TCPHDR_FIN | TCPHDR_SYN | TCPHDR_RST | \
+			   TCPHDR_PSH | TCPHDR_ACK | TCPHDR_URG | \
+			   TCPHDR_ECE | TCPHDR_CWR | TCPHDR_AE)
+#define tcp_flags_ntohs(th) (ntohs(*(__be16 *)&tcp_flag_word(th)) & \
+			    TCPHDR_FLAGS_MASK)
+
+#define TCPHDR_ACE (TCPHDR_ECE | TCPHDR_CWR | TCPHDR_AE)
 #define TCPHDR_SYN_ECN	(TCPHDR_SYN | TCPHDR_ECE | TCPHDR_CWR)
 
 /* State flags for sacked in struct tcp_skb_cb */
@@ -978,7 +985,7 @@ struct tcp_skb_cb {
 			u16	tcp_gso_size;
 		};
 	};
-	__u8		tcp_flags;	/* TCP header flags. (tcp[13])	*/
+	__u16		tcp_flags;	/* TCP header flags (tcp[12-13])*/
 
 	__u8		sacked;		/* State flags for SACK.	*/
 	__u8		ip_dsfield;	/* IPv4 tos or IPv6 dsfield	*/
diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h
index 32a27b4a5020..92a2e79222ea 100644
--- a/include/uapi/linux/tcp.h
+++ b/include/uapi/linux/tcp.h
@@ -28,7 +28,8 @@ struct tcphdr {
 	__be32	seq;
 	__be32	ack_seq;
 #if defined(__LITTLE_ENDIAN_BITFIELD)
-	__u16	res1:4,
+	__u16	ae:1,
+		res1:3,
 		doff:4,
 		fin:1,
 		syn:1,
@@ -40,7 +41,8 @@ struct tcphdr {
 		cwr:1;
 #elif defined(__BIG_ENDIAN_BITFIELD)
 	__u16	doff:4,
-		res1:4,
+		res1:3,
+		ae:1,
 		cwr:1,
 		ece:1,
 		urg:1,
@@ -70,6 +72,7 @@ union tcp_word_hdr {
 #define tcp_flag_word(tp) (((union tcp_word_hdr *)(tp))->words[3])
 
 enum {
+	TCP_FLAG_AE  = __constant_cpu_to_be32(0x01000000),
 	TCP_FLAG_CWR = __constant_cpu_to_be32(0x00800000),
 	TCP_FLAG_ECE = __constant_cpu_to_be32(0x00400000),
 	TCP_FLAG_URG = __constant_cpu_to_be32(0x00200000),
@@ -78,7 +81,7 @@ enum {
 	TCP_FLAG_RST = __constant_cpu_to_be32(0x00040000),
 	TCP_FLAG_SYN = __constant_cpu_to_be32(0x00020000),
 	TCP_FLAG_FIN = __constant_cpu_to_be32(0x00010000),
-	TCP_RESERVED_BITS = __constant_cpu_to_be32(0x0F000000),
+	TCP_RESERVED_BITS = __constant_cpu_to_be32(0x0E000000),
 	TCP_DATA_OFFSET = __constant_cpu_to_be32(0xF0000000)
 };
 
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index d9405b012dff..fab684221bf7 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2159,7 +2159,7 @@ 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 =
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 24e56bf96747..efd3cb5e1ded 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -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);
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 85c4820bfe15..a2fcc317a88e 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1731,7 +1731,7 @@ static void tcp_v6_fill_cb(struct sk_buff *skb, const struct ipv6hdr *hdr,
 	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 = ipv6_get_dsfield(hdr);
 	TCP_SKB_CB(skb)->sacked = 0;
 	TCP_SKB_CB(skb)->has_rxtstamp =
diff --git a/net/netfilter/nf_log_syslog.c b/net/netfilter/nf_log_syslog.c
index 58402226045e..86d5fc5d28e3 100644
--- a/net/netfilter/nf_log_syslog.c
+++ b/net/netfilter/nf_log_syslog.c
@@ -216,7 +216,9 @@ nf_log_dump_tcp_header(struct nf_log_buf *m,
 	/* Max length: 9 "RES=0x3C " */
 	nf_log_buf_add(m, "RES=0x%02x ", (u_int8_t)(ntohl(tcp_flag_word(th) &
 					    TCP_RESERVED_BITS) >> 22));
-	/* Max length: 32 "CWR ECE URG ACK PSH RST SYN FIN " */
+	/* Max length: 35 "AE CWR ECE URG ACK PSH RST SYN FIN " */
+	if (th->ae)
+		nf_log_buf_add(m, "AE ");
 	if (th->cwr)
 		nf_log_buf_add(m, "CWR ");
 	if (th->ece)
@@ -516,7 +518,7 @@ dump_ipv4_packet(struct net *net, struct nf_log_buf *m,
 
 	/* Proto    Max log string length */
 	/* IP:	    40+46+6+11+127 = 230 */
-	/* TCP:     10+max(25,20+30+13+9+32+11+127) = 252 */
+	/* TCP:     10+max(25,20+30+13+9+35+11+127) = 255 */
 	/* UDP:     10+max(25,20) = 35 */
 	/* UDPLITE: 14+max(25,20) = 39 */
 	/* ICMP:    11+max(25, 18+25+max(19,14,24+3+n+10,3+n+10)) = 91+n */
@@ -526,7 +528,7 @@ dump_ipv4_packet(struct net *net, struct nf_log_buf *m,
 
 	/* (ICMP allows recursion one level deep) */
 	/* maxlen =  IP + ICMP +  IP + max(TCP,UDP,ICMP,unknown) */
-	/* maxlen = 230+   91  + 230 + 252 = 803 */
+	/* maxlen = 230+   91  + 230 + 255 = 806 */
 }
 
 static noinline_for_stack void
-- 
2.34.1

[PATCH v7 net-next 05/12] tcp: reorganize SYN ECN code

[chia-yu.chang]

From: Ilpo Järvinen <ij@kernel.org>

Prepare for AccECN that needs to have access here on IP ECN
field value which is only available after INET_ECN_xmit().

No functional changes.

Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/tcp_output.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index efd3cb5e1ded..98f2684e0006 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -350,10 +350,11 @@ static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
 	tp->ecn_flags = 0;
 
 	if (use_ecn) {
-		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
-		tp->ecn_flags = TCP_ECN_OK;
 		if (tcp_ca_needs_ecn(sk) || bpf_needs_ecn)
 			INET_ECN_xmit(sk);
+
+		TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR;
+		tp->ecn_flags = TCP_ECN_OK;
 	}
 }
 
-- 
2.34.1

[PATCH v7 net-next 06/12] tcp: rework {__,}tcp_ecn_check_ce() -> tcp_data_ecn_check()

[chia-yu.chang]

From: Ilpo Järvinen <ij@kernel.org>

Rename tcp_ecn_check_ce to tcp_data_ecn_check as it is
called only for data segments, not for ACKs (with AccECN,
also ACKs may get ECN bits).

The extra "layer" in tcp_ecn_check_ce() function just
checks for ECN being enabled, that can be moved into
tcp_ecn_field_check rather than having the __ variant.

No functional changes.

Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/tcp_input.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 771e075d457d..769048b559e5 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -365,10 +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_sk(sk)->ecn_flags & TCP_ECN_OK))
+		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,
@@ -397,12 +400,6 @@ 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))
@@ -874,7 +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);
@@ -5041,7 +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);
-- 
2.34.1

[PATCH v7 net-next 07/12] tcp: helpers for ECN mode handling

[chia-yu.chang]

From: Ilpo Järvinen <ij@kernel.org>

Create helpers for TCP ECN modes. No functional changes.

Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
---
 include/net/tcp.h        | 44 ++++++++++++++++++++++++++++++++++++----
 net/ipv4/tcp.c           |  2 +-
 net/ipv4/tcp_dctcp.c     |  2 +-
 net/ipv4/tcp_input.c     | 14 ++++++-------
 net/ipv4/tcp_minisocks.c |  4 +++-
 net/ipv4/tcp_output.c    |  6 +++---
 6 files changed, 55 insertions(+), 17 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 49b66b499429..7e553f27c0e9 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -374,10 +374,46 @@ static inline void tcp_dec_quickack_mode(struct sock *sk)
 	}
 }
 
-#define	TCP_ECN_OK		1
-#define	TCP_ECN_QUEUE_CWR	2
-#define	TCP_ECN_DEMAND_CWR	4
-#define	TCP_ECN_SEEN		8
+#define	TCP_ECN_MODE_RFC3168	BIT(0)
+#define	TCP_ECN_QUEUE_CWR	BIT(1)
+#define	TCP_ECN_DEMAND_CWR	BIT(2)
+#define	TCP_ECN_SEEN		BIT(3)
+#define	TCP_ECN_MODE_ACCECN	BIT(4)
+
+#define	TCP_ECN_DISABLED	0
+#define	TCP_ECN_MODE_PENDING	(TCP_ECN_MODE_RFC3168 | TCP_ECN_MODE_ACCECN)
+#define	TCP_ECN_MODE_ANY	(TCP_ECN_MODE_RFC3168 | TCP_ECN_MODE_ACCECN)
+
+static inline bool tcp_ecn_mode_any(const struct tcp_sock *tp)
+{
+	return tp->ecn_flags & TCP_ECN_MODE_ANY;
+}
+
+static inline bool tcp_ecn_mode_rfc3168(const struct tcp_sock *tp)
+{
+	return (tp->ecn_flags & TCP_ECN_MODE_ANY) == TCP_ECN_MODE_RFC3168;
+}
+
+static inline bool tcp_ecn_mode_accecn(const struct tcp_sock *tp)
+{
+	return (tp->ecn_flags & TCP_ECN_MODE_ANY) == TCP_ECN_MODE_ACCECN;
+}
+
+static inline bool tcp_ecn_disabled(const struct tcp_sock *tp)
+{
+	return !tcp_ecn_mode_any(tp);
+}
+
+static inline bool tcp_ecn_mode_pending(const struct tcp_sock *tp)
+{
+	return (tp->ecn_flags & TCP_ECN_MODE_PENDING) == TCP_ECN_MODE_PENDING;
+}
+
+static inline void tcp_ecn_mode_set(struct tcp_sock *tp, u8 mode)
+{
+	tp->ecn_flags &= ~TCP_ECN_MODE_ANY;
+	tp->ecn_flags |= mode;
+}
 
 enum tcp_tw_status {
 	TCP_TW_SUCCESS = 0,
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index eb5a60c7a9cc..aa2141aef15d 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_input.c b/net/ipv4/tcp_input.c
index 769048b559e5..5c270cf96678 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -342,7 +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;
 }
 
@@ -369,7 +369,7 @@ static void tcp_data_ecn_check(struct sock *sk, const struct sk_buff *skb)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 
-	if (!(tcp_sk(sk)->ecn_flags & TCP_ECN_OK))
+	if (tcp_ecn_disabled(tp))
 		return;
 
 	switch (TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK) {
@@ -402,19 +402,19 @@ static void tcp_data_ecn_check(struct sock *sk, const struct sk_buff *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;
 }
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 3cb8f281186b..0ae24add155b 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -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_output.c b/net/ipv4/tcp_output.c
index 98f2684e0006..0d275ee68a1a 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))
@@ -354,7 +354,7 @@ static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb)
 			INET_ECN_xmit(sk);
 
 		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);
 	}
 }
 
@@ -382,7 +382,7 @@ 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)) {
-- 
2.34.1

[PATCH v7 net-next 08/12] gso: AccECN support

[chia-yu.chang]

From: Ilpo Järvinen <ij@kernel.org>

Handling the CWR flag differs between RFC 3168 ECN and AccECN.
With RFC 3168 ECN aware TSO (NETIF_F_TSO_ECN) CWR flag is cleared
starting from 2nd segment which is incompatible how AccECN handles
the CWR flag. Such super-segments are indicated by SKB_GSO_TCP_ECN.
With AccECN, CWR flag (or more accurately, the ACE field that also
includes ECE & AE flags) changes only when new packet(s) with CE
mark arrives so the flag should not be changed within a super-skb.
The new skb/feature flags are necessary to prevent such TSO engines
corrupting AccECN ACE counters by clearing the CWR flag (if the
CWR handling feature cannot be turned off).

If NIC is completely unaware of RFC3168 ECN (doesn't support
NETIF_F_TSO_ECN) or its TSO engine can be set to not touch CWR flag
despite supporting also NETIF_F_TSO_ECN, TSO could be safely used
with AccECN on such NIC. This should be evaluated per NIC basis
(not done in this patch series for any NICs).

For the cases, where TSO cannot keep its hands off the CWR flag,
a GSO fallback is provided by this patch.

Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
---
 include/linux/netdev_features.h | 8 +++++---
 include/linux/netdevice.h       | 2 ++
 include/linux/skbuff.h          | 2 ++
 net/ethtool/common.c            | 1 +
 net/ipv4/tcp_offload.c          | 6 +++++-
 5 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/include/linux/netdev_features.h b/include/linux/netdev_features.h
index 11be70a7929f..7a01c518e573 100644
--- a/include/linux/netdev_features.h
+++ b/include/linux/netdev_features.h
@@ -53,12 +53,12 @@ enum {
 	NETIF_F_GSO_UDP_BIT,		/* ... UFO, deprecated except tuntap */
 	NETIF_F_GSO_UDP_L4_BIT,		/* ... UDP payload GSO (not UFO) */
 	NETIF_F_GSO_FRAGLIST_BIT,		/* ... Fraglist GSO */
+	NETIF_F_GSO_ACCECN_BIT,		/* TCP AccECN w/ TSO (no clear CWR) */
 	/**/NETIF_F_GSO_LAST =		/* last bit, see GSO_MASK */
-		NETIF_F_GSO_FRAGLIST_BIT,
+		NETIF_F_GSO_ACCECN_BIT,
 
 	NETIF_F_FCOE_CRC_BIT,		/* FCoE CRC32 */
 	NETIF_F_SCTP_CRC_BIT,		/* SCTP checksum offload */
-	__UNUSED_NETIF_F_37,
 	NETIF_F_NTUPLE_BIT,		/* N-tuple filters supported */
 	NETIF_F_RXHASH_BIT,		/* Receive hashing offload */
 	NETIF_F_RXCSUM_BIT,		/* Receive checksumming offload */
@@ -128,6 +128,7 @@ enum {
 #define NETIF_F_SG		__NETIF_F(SG)
 #define NETIF_F_TSO6		__NETIF_F(TSO6)
 #define NETIF_F_TSO_ECN		__NETIF_F(TSO_ECN)
+#define NETIF_F_GSO_ACCECN	__NETIF_F(GSO_ACCECN)
 #define NETIF_F_TSO		__NETIF_F(TSO)
 #define NETIF_F_VLAN_CHALLENGED	__NETIF_F(VLAN_CHALLENGED)
 #define NETIF_F_RXFCS		__NETIF_F(RXFCS)
@@ -210,7 +211,8 @@ static inline int find_next_netdev_feature(u64 feature, unsigned long start)
 				 NETIF_F_TSO_ECN | NETIF_F_TSO_MANGLEID)
 
 /* List of features with software fallbacks. */
-#define NETIF_F_GSO_SOFTWARE	(NETIF_F_ALL_TSO | NETIF_F_GSO_SCTP |	     \
+#define NETIF_F_GSO_SOFTWARE	(NETIF_F_ALL_TSO | \
+				 NETIF_F_GSO_ACCECN | NETIF_F_GSO_SCTP | \
 				 NETIF_F_GSO_UDP_L4 | NETIF_F_GSO_FRAGLIST)
 
 /*
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 15d83d89ae70..6ce7ff453774 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -5279,6 +5279,8 @@ static inline bool net_gso_ok(netdev_features_t features, int gso_type)
 	BUILD_BUG_ON(SKB_GSO_UDP != (NETIF_F_GSO_UDP >> NETIF_F_GSO_SHIFT));
 	BUILD_BUG_ON(SKB_GSO_UDP_L4 != (NETIF_F_GSO_UDP_L4 >> NETIF_F_GSO_SHIFT));
 	BUILD_BUG_ON(SKB_GSO_FRAGLIST != (NETIF_F_GSO_FRAGLIST >> NETIF_F_GSO_SHIFT));
+	BUILD_BUG_ON(SKB_GSO_TCP_ACCECN !=
+		     (NETIF_F_GSO_ACCECN >> NETIF_F_GSO_SHIFT));
 
 	return (features & feature) == feature;
 }
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 14517e95a46c..b8a1343d6785 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -708,6 +708,8 @@ enum {
 	SKB_GSO_UDP_L4 = 1 << 17,
 
 	SKB_GSO_FRAGLIST = 1 << 18,
+
+	SKB_GSO_TCP_ACCECN = 1 << 19,
 };
 
 #if BITS_PER_LONG > 32
diff --git a/net/ethtool/common.c b/net/ethtool/common.c
index ac8b6107863e..1c6f2a2f1871 100644
--- a/net/ethtool/common.c
+++ b/net/ethtool/common.c
@@ -36,6 +36,7 @@ const char netdev_features_strings[NETDEV_FEATURE_COUNT][ETH_GSTRING_LEN] = {
 	[NETIF_F_TSO_BIT] =              "tx-tcp-segmentation",
 	[NETIF_F_GSO_ROBUST_BIT] =       "tx-gso-robust",
 	[NETIF_F_TSO_ECN_BIT] =          "tx-tcp-ecn-segmentation",
+	[NETIF_F_GSO_ACCECN_BIT] =	 "tx-tcp-accecn-segmentation",
 	[NETIF_F_TSO_MANGLEID_BIT] =	 "tx-tcp-mangleid-segmentation",
 	[NETIF_F_TSO6_BIT] =             "tx-tcp6-segmentation",
 	[NETIF_F_FSO_BIT] =              "tx-fcoe-segmentation",
diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index ecef16c58c07..a4cea85288ff 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -139,6 +139,7 @@ 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);
@@ -198,6 +199,8 @@ 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;
@@ -217,7 +220,8 @@ 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 :
-- 
2.34.1

[PATCH v7 net-next 09/12] gro: prevent ACE field corruption & better AccECN handling

[chia-yu.chang]

From: Ilpo Järvinen <ij@kernel.org>

There are important differences in how the CWR field behaves
in RFC3168 and AccECN. With AccECN, CWR flag is part of the
ACE counter and its changes are important so adjust the flags
changed mask accordingly.

Also, if CWR is there, set the Accurate ECN GSO flag to avoid
corrupting CWR flag somewhere.

Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
---
 net/ipv4/tcp_offload.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index a4cea85288ff..ef12aee5deb4 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -329,7 +329,7 @@ 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) ^
@@ -405,7 +405,7 @@ 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);
 
-- 
2.34.1

[PATCH v7 net-next 10/12] tcp: AccECN support to tcp_add_backlog

[chia-yu.chang]

From: Ilpo Järvinen <ij@kernel.org>

AE flag needs to be preserved for AccECN.

Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/tcp_ipv4.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index fab684221bf7..87f270ebc635 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2051,7 +2051,8 @@ 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)))
-- 
2.34.1

[PATCH v7 net-next 11/12] tcp: add new TCP_TW_ACK_OOW state and allow ECN bits in TOS

[chia-yu.chang]

From: Ilpo Järvinen <ij@kernel.org>

ECN bits in TOS are always cleared when sending in ACKs in TW. Clearing
them is problematic for TCP flows that used Accurate ECN because ECN bits
decide which service queue the packet is placed into (L4S vs Classic).
Effectively, TW ACKs are always downgraded from L4S to Classic queue
which might impact, e.g., delay the ACK will experience on the path
compared with the other packets of the flow.

Change the TW ACK sending code to differentiate:
- In tcp_v4_send_reset(), commit ba9e04a7ddf4f ("ip: fix tos reflection
  in ack and reset packets") cleans ECN bits for TW reset and this is
  not affected.
- In tcp_v4_timewait_ack(), ECN bits for all TW ACKs are cleaned. But now
  only ECN bits of ACKs for oow data or paws_reject are cleaned, and ECN
  bits of other ACKs will not be cleaned.
- In tcp_v4_reqsk_send_ack(), commit 66b13d99d96a1 ("ipv4: tcp: fix TOS
  value in ACK messages sent from TIME_WAIT") did not clean ECN bits of
  ACKs for oow data or paws_reject. But now the ECN bits rae cleaned for
  these ACKs.

Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
---
 include/net/tcp.h        |  3 ++-
 net/ipv4/ip_output.c     |  3 +--
 net/ipv4/tcp_ipv4.c      | 29 +++++++++++++++++++++++------
 net/ipv4/tcp_minisocks.c |  2 +-
 net/ipv6/tcp_ipv6.c      | 24 +++++++++++++++++-------
 5 files changed, 44 insertions(+), 17 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 7e553f27c0e9..3b9b3cdbc0cc 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -419,7 +419,8 @@ enum tcp_tw_status {
 	TCP_TW_SUCCESS = 0,
 	TCP_TW_RST = 1,
 	TCP_TW_ACK = 2,
-	TCP_TW_SYN = 3
+	TCP_TW_SYN = 3,
+	TCP_TW_ACK_OOW = 4
 };
 
 
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_ipv4.c b/net/ipv4/tcp_ipv4.c
index 87f270ebc635..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);
@@ -2175,6 +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;
@@ -2402,7 +2416,9 @@ int tcp_v4_rcv(struct sk_buff *skb)
 		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,
@@ -2423,7 +2439,8 @@ int tcp_v4_rcv(struct sk_buff *skb)
 		/* 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 0ae24add155b..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. */
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index a2fcc317a88e..e182ee0a2330 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -999,7 +999,7 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
 	if (!IS_ERR(dst)) {
 		skb_dst_set(buff, dst);
 		ip6_xmit(ctl_sk, buff, &fl6, fl6.flowi6_mark, NULL,
-			 tclass & ~INET_ECN_MASK, priority);
+			 tclass, priority);
 		TCP_INC_STATS(net, TCP_MIB_OUTSEGS);
 		if (rst)
 			TCP_INC_STATS(net, TCP_MIB_OUTRSTS);
@@ -1135,7 +1135,8 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb,
 	trace_tcp_send_reset(sk, skb, reason);
 
 	tcp_v6_send_response(sk, skb, seq, ack_seq, 0, 0, 0, oif, 1,
-			     ipv6_get_dsfield(ipv6h), label, priority, txhash,
+			     ipv6_get_dsfield(ipv6h) & ~INET_ECN_MASK,
+			     label, priority, txhash,
 			     &key);
 
 #if defined(CONFIG_TCP_MD5SIG) || defined(CONFIG_TCP_AO)
@@ -1155,11 +1156,16 @@ static void tcp_v6_send_ack(const struct sock *sk, struct sk_buff *skb, u32 seq,
 			     tclass, label, priority, txhash, key);
 }
 
-static void tcp_v6_timewait_ack(struct sock *sk, struct sk_buff *skb)
+static void tcp_v6_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);
+	u8 tclass = tw->tw_tclass;
 	struct tcp_key key = {};
+
+	if (tw_status == TCP_TW_ACK_OOW)
+		tclass &= ~INET_ECN_MASK;
 #ifdef CONFIG_TCP_AO
 	struct tcp_ao_info *ao_info;
 
@@ -1203,7 +1209,7 @@ static void tcp_v6_timewait_ack(struct sock *sk, struct sk_buff *skb)
 			tcptw->tw_rcv_wnd >> tw->tw_rcv_wscale,
 			tcp_tw_tsval(tcptw),
 			READ_ONCE(tcptw->tw_ts_recent), tw->tw_bound_dev_if,
-			&key, tw->tw_tclass, cpu_to_be32(tw->tw_flowlabel),
+			&key, tclass, cpu_to_be32(tw->tw_flowlabel),
 			tw->tw_priority, tw->tw_txhash);
 
 #ifdef CONFIG_TCP_AO
@@ -1280,7 +1286,8 @@ static void tcp_v6_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
 			tcp_synack_window(req) >> inet_rsk(req)->rcv_wscale,
 			tcp_rsk_tsval(tcp_rsk(req)),
 			req->ts_recent, sk->sk_bound_dev_if,
-			&key, ipv6_get_dsfield(ipv6_hdr(skb)), 0,
+			&key, ipv6_get_dsfield(ipv6_hdr(skb)) & ~INET_ECN_MASK,
+			0,
 			READ_ONCE(sk->sk_priority),
 			READ_ONCE(tcp_rsk(req)->txhash));
 	if (tcp_key_is_ao(&key))
@@ -1742,6 +1749,7 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_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 = inet6_sdif(skb);
 	int dif = inet6_iif(skb);
 	const struct tcphdr *th;
@@ -1962,7 +1970,8 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
 		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;
@@ -1987,7 +1996,8 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
 		/* to ACK */
 		fallthrough;
 	case TCP_TW_ACK:
-		tcp_v6_timewait_ack(sk, skb);
+	case TCP_TW_ACK_OOW:
+		tcp_v6_timewait_ack(sk, skb, tw_status);
 		break;
 	case TCP_TW_RST:
 		tcp_v6_send_reset(sk, skb, SK_RST_REASON_TCP_TIMEWAIT_SOCKET);
-- 
2.34.1

[PATCH v7 net-next 12/12] tcp: Pass flags to __tcp_send_ack

[chia-yu.chang]

From: Ilpo Järvinen <ij@kernel.org>

Accurate ECN needs to send custom flags to handle IP-ECN
field reflection during handshake.

Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
---
 include/net/tcp.h     | 2 +-
 net/ipv4/bpf_tcp_ca.c | 2 +-
 net/ipv4/tcp_dctcp.h  | 2 +-
 net/ipv4/tcp_output.c | 6 +++---
 4 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 3b9b3cdbc0cc..297aeca9109e 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -707,7 +707,7 @@ void tcp_send_active_reset(struct sock *sk, gfp_t priority,
 			   enum sk_rst_reason reason);
 int tcp_send_synack(struct sock *);
 void tcp_push_one(struct sock *, unsigned int mss_now);
-void __tcp_send_ack(struct sock *sk, u32 rcv_nxt);
+void __tcp_send_ack(struct sock *sk, u32 rcv_nxt, u16 flags);
 void tcp_send_ack(struct sock *sk);
 void tcp_send_delayed_ack(struct sock *sk);
 void tcp_send_loss_probe(struct sock *sk);
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/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_output.c b/net/ipv4/tcp_output.c
index 0d275ee68a1a..124b2e95bb0a 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -4241,7 +4241,7 @@ 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;
 
@@ -4270,7 +4270,7 @@ 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.
@@ -4285,7 +4285,7 @@ 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
-- 
2.34.1

Re: [PATCH v7 net-next 09/12] gro: prevent ACE field corruption & better AccECN handling

[Paolo Abeni]

On 3/5/25 11:38 PM, chia-yu.chang@nokia-bell-labs.com wrote:
> From: Ilpo Järvinen <ij@kernel.org>
> 
> There are important differences in how the CWR field behaves
> in RFC3168 and AccECN. With AccECN, CWR flag is part of the
> ACE counter and its changes are important so adjust the flags
> changed mask accordingly.
> 
> Also, if CWR is there, set the Accurate ECN GSO flag to avoid
> corrupting CWR flag somewhere.
> 
> Signed-off-by: Ilpo Järvinen <ij@kernel.org>
> Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
> ---
>  net/ipv4/tcp_offload.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
> index a4cea85288ff..ef12aee5deb4 100644
> --- a/net/ipv4/tcp_offload.c
> +++ b/net/ipv4/tcp_offload.c
> @@ -329,7 +329,7 @@ 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) ^
> @@ -405,7 +405,7 @@ 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);

To recap: when an host implementing the above will receive a GSO_TCP_ECN
train transmitted by a RFC3168 endpoint, it will re-assemble it in 2
packets: a GSO one with !th->cwr and a non GSO one with th->cwr set.

When receiving a GSO train with constant CWR set on all the wire
packets, it will assemble it in a single SKB_GSO_TCP_ACCECN packet.

I think should work correctly.

Side note: the SKB_GSO_TCP_ACCECN flag is required: NETIF_F_TSO_ECN
enabled driver will likely unconditionally apply RFC3168-like TSO to any
GSO packet carrying the CWR flag, regardless of the skb gso_type.

@Eric: are you ok with this change?

Thanks,

Paolo

Re: [PATCH v7 net-next 00/12] AccECN protocol preparation patch series

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net-next.git (main)
by David S. Miller <davem@davemloft.net>:

On Wed,  5 Mar 2025 23:38:40 +0100 you wrote:
> From: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
> 
> Hello,
> 
> Please find the v7
> 
> v7 (03-Mar-2025)
> - Move 2 new patches added in v6 to the next AccECN patch series
> 
> [...]

Here is the summary with links:
  - [v7,net-next,01/12] tcp: reorganize tcp_in_ack_event() and tcp_count_delivered()
    https://git.kernel.org/netdev/net-next/c/149dfb31615e
  - [v7,net-next,02/12] tcp: create FLAG_TS_PROGRESS
    https://git.kernel.org/netdev/net-next/c/da610e18313b
  - [v7,net-next,03/12] tcp: use BIT() macro in include/net/tcp.h
    https://git.kernel.org/netdev/net-next/c/0114a91da672
  - [v7,net-next,04/12] tcp: extend TCP flags to allow AE bit/ACE field
    https://git.kernel.org/netdev/net-next/c/2c2f08d31d2f
  - [v7,net-next,05/12] tcp: reorganize SYN ECN code
    (no matching commit)
  - [v7,net-next,06/12] tcp: rework {__,}tcp_ecn_check_ce() -> tcp_data_ecn_check()
    https://git.kernel.org/netdev/net-next/c/f0db2bca0cf9
  - [v7,net-next,07/12] tcp: helpers for ECN mode handling
    (no matching commit)
  - [v7,net-next,08/12] gso: AccECN support
    https://git.kernel.org/netdev/net-next/c/023af5a72ab1
  - [v7,net-next,09/12] gro: prevent ACE field corruption & better AccECN handling
    https://git.kernel.org/netdev/net-next/c/4e4f7cefb130
  - [v7,net-next,10/12] tcp: AccECN support to tcp_add_backlog
    https://git.kernel.org/netdev/net-next/c/d722762c4eaa
  - [v7,net-next,11/12] tcp: add new TCP_TW_ACK_OOW state and allow ECN bits in TOS
    https://git.kernel.org/netdev/net-next/c/4618e195f925
  - [v7,net-next,12/12] tcp: Pass flags to __tcp_send_ack
    https://git.kernel.org/netdev/net-next/c/9866884ce8ef

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html

RE: [PATCH v7 net-next 00/12] AccECN protocol preparation patch series

[Chia-Yu Chang (Nokia)]

> Hello:
>
> This series was applied to netdev/net-next.git (main) by David S. Miller <davem@davemloft.net>:
>
> On Wed,  5 Mar 2025 23:38:40 +0100 you wrote:
> > From: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
> >
> > Hello,
> >
> > Please find the v7
> >
> > v7 (03-Mar-2025)
> > - Move 2 new patches added in v6 to the next AccECN patch series
> >
> > [...]
>
> Here is the summary with links:
>   - [v7,net-next,01/12] tcp: reorganize tcp_in_ack_event() and tcp_count_delivered()
>     https://git.kernel.org/netdev/net-next/c/149dfb31615e
>   - [v7,net-next,02/12] tcp: create FLAG_TS_PROGRESS
>     https://git.kernel.org/netdev/net-next/c/da610e18313b
>   - [v7,net-next,03/12] tcp: use BIT() macro in include/net/tcp.h
>     https://git.kernel.org/netdev/net-next/c/0114a91da672
>   - [v7,net-next,04/12] tcp: extend TCP flags to allow AE bit/ACE field
>     https://git.kernel.org/netdev/net-next/c/2c2f08d31d2f
>   - [v7,net-next,05/12] tcp: reorganize SYN ECN code
>     (no matching commit)
>   - [v7,net-next,06/12] tcp: rework {__,}tcp_ecn_check_ce() -> tcp_data_ecn_check()
>     https://git.kernel.org/netdev/net-next/c/f0db2bca0cf9
>   - [v7,net-next,07/12] tcp: helpers for ECN mode handling
>     (no matching commit)
>   - [v7,net-next,08/12] gso: AccECN support
>     https://git.kernel.org/netdev/net-next/c/023af5a72ab1
>   - [v7,net-next,09/12] gro: prevent ACE field corruption & better AccECN handling
>     https://git.kernel.org/netdev/net-next/c/4e4f7cefb130
>   - [v7,net-next,10/12] tcp: AccECN support to tcp_add_backlog
>     https://git.kernel.org/netdev/net-next/c/d722762c4eaa
>   - [v7,net-next,11/12] tcp: add new TCP_TW_ACK_OOW state and allow ECN bits in TOS
>     https://git.kernel.org/netdev/net-next/c/4618e195f925
>   - [v7,net-next,12/12] tcp: Pass flags to __tcp_send_ack
>     https://git.kernel.org/netdev/net-next/c/9866884ce8ef
>
> You are awesome, thank you!
> --
> Deet-doot-dot, I am a bot.
> https://korg.docs.kernel.org/patchwork/pwbot.html

Hello,

I see two patches are NOT applied in the net-next (05/12 and 07/12) repo.
So, I would like to ask would it be merged latter on, or shall I include in the next AccECN patch series? Thanks.

Best regards,
Chia-Yu

Re: [PATCH v7 net-next 00/12] AccECN protocol preparation patch series

[Paolo Abeni]

On 3/17/25 5:44 PM, Chia-Yu Chang (Nokia) wrote:
> Hello:
>> This series was applied to netdev/net-next.git (main) by David S. Miller <davem@davemloft.net>:
[...]
>> Here is the summary with links:
>>   - [v7,net-next,01/12] tcp: reorganize tcp_in_ack_event() and tcp_count_delivered()
>>     https://git.kernel.org/netdev/net-next/c/149dfb31615e
>>   - [v7,net-next,02/12] tcp: create FLAG_TS_PROGRESS
>>     https://git.kernel.org/netdev/net-next/c/da610e18313b
>>   - [v7,net-next,03/12] tcp: use BIT() macro in include/net/tcp.h
>>     https://git.kernel.org/netdev/net-next/c/0114a91da672
>>   - [v7,net-next,04/12] tcp: extend TCP flags to allow AE bit/ACE field
>>     https://git.kernel.org/netdev/net-next/c/2c2f08d31d2f
>>   - [v7,net-next,05/12] tcp: reorganize SYN ECN code
>>     (no matching commit)
>>   - [v7,net-next,06/12] tcp: rework {__,}tcp_ecn_check_ce() -> tcp_data_ecn_check()
>>     https://git.kernel.org/netdev/net-next/c/f0db2bca0cf9
>>   - [v7,net-next,07/12] tcp: helpers for ECN mode handling
>>     (no matching commit)
>>   - [v7,net-next,08/12] gso: AccECN support
>>     https://git.kernel.org/netdev/net-next/c/023af5a72ab1
>>   - [v7,net-next,09/12] gro: prevent ACE field corruption & better AccECN handling
>>     https://git.kernel.org/netdev/net-next/c/4e4f7cefb130
>>   - [v7,net-next,10/12] tcp: AccECN support to tcp_add_backlog
>>     https://git.kernel.org/netdev/net-next/c/d722762c4eaa
>>   - [v7,net-next,11/12] tcp: add new TCP_TW_ACK_OOW state and allow ECN bits in TOS
>>     https://git.kernel.org/netdev/net-next/c/4618e195f925
>>   - [v7,net-next,12/12] tcp: Pass flags to __tcp_send_ack
>>     https://git.kernel.org/netdev/net-next/c/9866884ce8ef
>>
>> You are awesome, thank you!
>> --
>> Deet-doot-dot, I am a bot.
>> https://korg.docs.kernel.org/patchwork/pwbot.html
> 
> Hello,
> 
> I see two patches are NOT applied in the net-next (05/12 and 07/12) repo.
> So, I would like to ask would it be merged latter on, or shall I include in the next AccECN patch series? Thanks.

Something went wrong at apply time.

AFAICS patch 7 is there with commit 041fb11d518f ("tcp: helpers for ECN
mode handling") while patch got lost somehow. I think it's better if you
repost them, rebased on top of current net-next.

Thanks!

Paolo

RE: [PATCH v7 net-next 00/12] AccECN protocol preparation patch series

[Chia-Yu Chang (Nokia)]

Please see below.

-----Original Message-----
> From: Paolo Abeni <pabeni@redhat.com>
> Sent: Monday, March 17, 2025 10:04 PM
> To: Chia-Yu Chang (Nokia) <chia-yu.chang@nokia-bell-labs.com>; patchwork-bot+netdevbpf@kernel.org
> Cc: netdev@vger.kernel.org; dsahern@gmail.com; davem@davemloft.net; edumazet@google.com; dsahern@kernel.org; joel.granados@kernel.org; kuba@kernel.org; andrew+netdev@lunn.ch; horms@kernel.org; pablo@netfilter.org; kadlec@netfilter.org; netfilter-devel@vger.kernel.org; coreteam@netfilter.org; kory.maincent@bootlin.com; bpf@vger.kernel.org; kuniyu@amazon.com; andrew@lunn.ch; ij@kernel.org; ncardwell@google.com; Koen De Schepper (Nokia) <koen.de_schepper@nokia-bell-labs.com>; g.white <g.white@cablelabs.com>; ingemar.s.johansson@ericsson.com; mirja.kuehlewind@ericsson.com; cheshire@apple.com; rs.ietf@gmx.at; Jason_Livingood@comcast.com; vidhi_goel <vidhi_goel@apple.com>
> Subject: Re: [PATCH v7 net-next 00/12] AccECN protocol preparation patch series
>
>
> CAUTION: This is an external email. Please be very careful when clicking links or opening attachments. See the URL nok.it/ext for additional information.
>
>
>
> On 3/17/25 5:44 PM, Chia-Yu Chang (Nokia) wrote:
> > Hello:
> >> This series was applied to netdev/net-next.git (main) by David S. Miller <davem@davemloft.net>:
> [...]
> >> Here is the summary with links:
> >>   - [v7,net-next,01/12] tcp: reorganize tcp_in_ack_event() and tcp_count_delivered()
> >>     https://git.kernel.org/netdev/net-next/c/149dfb31615e
> >>   - [v7,net-next,02/12] tcp: create FLAG_TS_PROGRESS
> >>     https://git.kernel.org/netdev/net-next/c/da610e18313b
> >>   - [v7,net-next,03/12] tcp: use BIT() macro in include/net/tcp.h
> >>     https://git.kernel.org/netdev/net-next/c/0114a91da672
> >>   - [v7,net-next,04/12] tcp: extend TCP flags to allow AE bit/ACE field
> >>     https://git.kernel.org/netdev/net-next/c/2c2f08d31d2f
> >>   - [v7,net-next,05/12] tcp: reorganize SYN ECN code
> >>     (no matching commit)
> >>   - [v7,net-next,06/12] tcp: rework {__,}tcp_ecn_check_ce() -> tcp_data_ecn_check()
> >>     https://git.kernel.org/netdev/net-next/c/f0db2bca0cf9
> >>   - [v7,net-next,07/12] tcp: helpers for ECN mode handling
> >>     (no matching commit)
> >>   - [v7,net-next,08/12] gso: AccECN support
> >>     https://git.kernel.org/netdev/net-next/c/023af5a72ab1
> >>   - [v7,net-next,09/12] gro: prevent ACE field corruption & better AccECN handling
> >>     https://git.kernel.org/netdev/net-next/c/4e4f7cefb130
> >>   - [v7,net-next,10/12] tcp: AccECN support to tcp_add_backlog
> >>     https://git.kernel.org/netdev/net-next/c/d722762c4eaa
> >>   - [v7,net-next,11/12] tcp: add new TCP_TW_ACK_OOW state and allow ECN bits in TOS
> >>     https://git.kernel.org/netdev/net-next/c/4618e195f925
> >>   - [v7,net-next,12/12] tcp: Pass flags to __tcp_send_ack
> >>
> >> https://git/
> >> .kernel.org%2Fnetdev%2Fnet-next%2Fc%2F9866884ce8ef&data=05%7C02%7Cchi
> >> a-yu.chang%40nokia-bell-labs.com%7C72e33ae0d7f0420790c208dd659742f9%7
> >> C5d4717519675428d917b70f44f9630b0%7C0%7C0%7C638778422522699339%7CUnkn
> >> own%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJ
> >> XaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=kcRwgx%2
> >> FWDHKWt9hvGogvLksNHjjjQcd%2BAbCuSsJrtoo%3D&reserved=0
> >>
> >> You are awesome, thank you!
> >> --
> >> Deet-doot-dot, I am a bot.
> >> https://kor/
> >> g.docs.kernel.org%2Fpatchwork%2Fpwbot.html&data=05%7C02%7Cchia-yu.cha
> >> ng%40nokia-bell-labs.com%7C72e33ae0d7f0420790c208dd659742f9%7C5d47175
> >> 19675428d917b70f44f9630b0%7C0%7C0%7C638778422522710517%7CUnknown%7CTW
> >> FpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiI
> >> sIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=3MvKCWlvavf14mcp
> >> i3Xt1L9UNX8VyJ51n0rK3vpcT6U%3D&reserved=0
> >
> > Hello,
> >
> > I see two patches are NOT applied in the net-next (05/12 and 07/12) repo.
> > So, I would like to ask would it be merged latter on, or shall I include in the next AccECN patch series? Thanks.
>
> Something went wrong at apply time.
>
> AFAICS patch 7 is there with commit 041fb11d518f ("tcp: helpers for ECN mode handling") while patch got lost somehow. I think it's better if you repost them, rebased on top of current net-next.
>
> Thanks!
>
> Paolo

Yes, you are right. Thanks for pointing out.
I will merge this missing one into the next Accurate ECN series.

Chia-Yu