netdev - [PATCH v1 net-next 1/3] net: update commnets for SKB_GSO_TCP_ECN and SKB_GSO_TCP

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20260128144426.15870-2-chia-yu.chang@nokia-bell-labs.com>
Date: Wed, 28 Jan 2026 15:44:24 +0100
From: chia-yu.chang@...ia-bell-labs.com
To: pabeni@...hat.com,
	edumazet@...gle.com,
	parav@...dia.com,
	linux-doc@...r.kernel.org,
	corbet@....net,
	horms@...nel.org,
	dsahern@...nel.org,
	kuniyu@...gle.com,
	bpf@...r.kernel.org,
	netdev@...r.kernel.org,
	dave.taht@...il.com,
	jhs@...atatu.com,
	kuba@...nel.org,
	stephen@...workplumber.org,
	xiyou.wangcong@...il.com,
	jiri@...nulli.us,
	davem@...emloft.net,
	andrew+netdev@...n.ch,
	donald.hunter@...il.com,
	ast@...erby.net,
	liuhangbin@...il.com,
	shuah@...nel.org,
	linux-kselftest@...r.kernel.org,
	ij@...nel.org,
	ncardwell@...gle.com,
	koen.de_schepper@...ia-bell-labs.com,
	g.white@...lelabs.com,
	ingemar.s.johansson@...csson.com,
	mirja.kuehlewind@...csson.com,
	cheshire@...le.com,
	rs.ietf@....at,
	Jason_Livingood@...cast.com,
	vidhi_goel@...le.com
Cc: Chia-Yu Chang <chia-yu.chang@...ia-bell-labs.com>
Subject: [PATCH v1 net-next 1/3] net: update commnets for SKB_GSO_TCP_ECN and SKB_GSO_TCP_ACCECN

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

No functional changes.

Co-developed-by: Ilpo Järvinen <ij@...nel.org>
Signed-off-by: Ilpo Järvinen <ij@...nel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@...ia-bell-labs.com>
---
 include/linux/skbuff.h | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index e6bfe5d0c525..30a8dc4233ba 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -671,7 +671,13 @@ enum {
 	/* This indicates the skb is from an untrusted source. */
 	SKB_GSO_DODGY = 1 << 1,
 
-	/* This indicates the tcp segment has CWR set. */
+	/* For Tx, this indicates the first TCP segment has CWR set, and any
+	 * subsequent segment in the same skb has CWR cleared. However, because
+	 * the connection to which the segment belongs is not tracked to use
+	 * RFC3168 or AccECN (RFC9768), and using RFC3168 ECN offload may clear
+	 * ACE signal (CWR is one of it). Therefore, this cannot be used on Rx.
+	 * Instead, SKB_GSO_TCP_ACCECN shall be used to avoid CWR corruption.
+	 */
 	SKB_GSO_TCP_ECN = 1 << 2,
 
 	__SKB_GSO_TCP_FIXEDID = 1 << 3,
@@ -706,6 +712,14 @@ enum {
 
 	SKB_GSO_FRAGLIST = 1 << 18,
 
+	/* For TX, this indicates the TCP segment uses the CWR flag as part of
+	 * ACE signal, and the CWR flag is not modified in the skb. For RX, any
+	 * CWR flagged segment must use SKB_GSO_TCP_ACCECN to ensure CWR flag
+	 * is not cleared by any RFC3168 ECN offload, and thus keeping ACE
+	 * signal of AccECN segments. This is particularly used for Rx of
+	 * virtio_net driver in order to tell latter GSO Tx in a forwarding
+	 * scenario that it is NOT ok to clean CWR flag from the 2nd segment.
+	 */
 	SKB_GSO_TCP_ACCECN = 1 << 19,
 
 	/* These indirectly map onto the same netdev feature.
-- 
2.34.1