netdev - [PATCH net-next 2/8] tcp: add LINUX_MIB_BEYOND

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Message-ID: <20250711114006.480026-3-edumazet@google.com>
Date: Fri, 11 Jul 2025 11:40:00 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Neal Cardwell <ncardwell@...gle.com>
Cc: Simon Horman <horms@...nel.org>, Kuniyuki Iwashima <kuniyu@...gle.com>, 
	Willem de Bruijn <willemb@...gle.com>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 2/8] tcp: add LINUX_MIB_BEYOND_WINDOW

Add a new SNMP MIB : LINUX_MIB_BEYOND_WINDOW

Incremented when an incoming packet is received beyond the
receiver window.

nstat -az | grep TcpExtBeyondWindow

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 Documentation/networking/net_cachelines/snmp.rst | 1 +
 include/net/dropreason-core.h                    | 2 ++
 include/uapi/linux/snmp.h                        | 1 +
 net/ipv4/proc.c                                  | 1 +
 net/ipv4/tcp_input.c                             | 1 +
 5 files changed, 6 insertions(+)

diff --git a/Documentation/networking/net_cachelines/snmp.rst b/Documentation/networking/net_cachelines/snmp.rst
index bd44b3eebbef75352599883b9dde36e7889d4120..bce4eb35ec48112ec43d99c58351d3b646a708ec 100644
--- a/Documentation/networking/net_cachelines/snmp.rst
+++ b/Documentation/networking/net_cachelines/snmp.rst
@@ -36,6 +36,7 @@ unsigned_long  LINUX_MIB_TIMEWAITRECYCLED
 unsigned_long  LINUX_MIB_TIMEWAITKILLED
 unsigned_long  LINUX_MIB_PAWSACTIVEREJECTED
 unsigned_long  LINUX_MIB_PAWSESTABREJECTED
+unsigned_long  LINUX_MIB_BEYOND_WINDOW
 unsigned_long  LINUX_MIB_TSECR_REJECTED
 unsigned_long  LINUX_MIB_PAWS_OLD_ACK
 unsigned_long  LINUX_MIB_PAWS_TW_REJECTED
diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index d88ff9a75d15fe60a961332a7eb4be94c5c7c3ec..6176e060541f330792014dd6081d1d0857536640 100644
--- a/include/net/dropreason-core.h
+++ b/include/net/dropreason-core.h
@@ -305,9 +305,11 @@ enum skb_drop_reason {
 	/** @SKB_DROP_REASON_TCP_OLD_SEQUENCE: Old SEQ field (duplicate packet) */
 	SKB_DROP_REASON_TCP_OLD_SEQUENCE,
 	/** @SKB_DROP_REASON_TCP_INVALID_SEQUENCE: Not acceptable SEQ field.
+	 * Corresponds to LINUX_MIB_BEYOND_WINDOW.
 	 */
 	SKB_DROP_REASON_TCP_INVALID_SEQUENCE,
 	/** @SKB_DROP_REASON_TCP_INVALID_END_SEQUENCE: Not acceptable END_SEQ field.
+	 * Corresponds to LINUX_MIB_BEYOND_WINDOW.
 	 */
 	SKB_DROP_REASON_TCP_INVALID_END_SEQUENCE,
 	/**
diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index 1d234d7e1892778c5ff04c240f8360608f391401..49f5640092a0df7ca2bfb01e87a627d9b1bc4233 100644
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -186,6 +186,7 @@ enum
 	LINUX_MIB_TIMEWAITKILLED,		/* TimeWaitKilled */
 	LINUX_MIB_PAWSACTIVEREJECTED,		/* PAWSActiveRejected */
 	LINUX_MIB_PAWSESTABREJECTED,		/* PAWSEstabRejected */
+	LINUX_MIB_BEYOND_WINDOW,		/* BeyondWindow */
 	LINUX_MIB_TSECRREJECTED,		/* TSEcrRejected */
 	LINUX_MIB_PAWS_OLD_ACK,			/* PAWSOldAck */
 	LINUX_MIB_PAWS_TW_REJECTED,		/* PAWSTimewait */
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index ea2f01584379a59a0a01226ae0f45d3614733fef..65b0d0ab0084029db43135a91da6eeb1f1fba024 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -189,6 +189,7 @@ static const struct snmp_mib snmp4_net_list[] = {
 	SNMP_MIB_ITEM("TWKilled", LINUX_MIB_TIMEWAITKILLED),
 	SNMP_MIB_ITEM("PAWSActive", LINUX_MIB_PAWSACTIVEREJECTED),
 	SNMP_MIB_ITEM("PAWSEstab", LINUX_MIB_PAWSESTABREJECTED),
+	SNMP_MIB_ITEM("BeyondWindow", LINUX_MIB_BEYOND_WINDOW),
 	SNMP_MIB_ITEM("TSEcrRejected", LINUX_MIB_TSECRREJECTED),
 	SNMP_MIB_ITEM("PAWSOldAck", LINUX_MIB_PAWS_OLD_ACK),
 	SNMP_MIB_ITEM("PAWSTimewait", LINUX_MIB_PAWS_TW_REJECTED),
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index f0f9c78654b449cb2a122e8c53fdcc96e5317de7..5e2d82c273e2fc914706651a660464db4aba8504 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5900,6 +5900,7 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
 		if (!th->rst) {
 			if (th->syn)
 				goto syn_challenge;
+			NET_INC_STATS(sock_net(sk), LINUX_MIB_BEYOND_WINDOW);
 			if (!tcp_oow_rate_limited(sock_net(sk), skb,
 						  LINUX_MIB_TCPACKSKIPPEDSEQ,
 						  &tp->last_oow_ack_time))
-- 
2.50.0.727.gbf7dc18ff4-goog