linux-kernel - [PATCH net 4/4] mptcp: zero window probe mib

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Message-Id: <20251028-net-mptcp-send-timeout-v1-4-38ffff5a9ec8@kernel.org>
Date: Tue, 28 Oct 2025 09:16:55 +0100
From: "Matthieu Baerts (NGI0)" <matttbe@...nel.org>
To: Mat Martineau <martineau@...nel.org>, Geliang Tang <geliang@...nel.org>, 
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
 Simon Horman <horms@...nel.org>, Florian Westphal <fw@...len.de>, 
 Yonglong Li <liyonglong@...natelecom.cn>
Cc: netdev@...r.kernel.org, mptcp@...ts.linux.dev, 
 linux-kernel@...r.kernel.org, "Matthieu Baerts (NGI0)" <matttbe@...nel.org>
Subject: [PATCH net 4/4] mptcp: zero window probe mib

From: Paolo Abeni <pabeni@...hat.com>

Explicitly account for MPTCP-level zero windows probe, to catch
hopefully earlier issues alike the one addressed by the previous
patch.

Reviewed-by: Mat Martineau <martineau@...nel.org>
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
Tested-by: Geliang Tang <geliang@...nel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>
---
 net/mptcp/mib.c      | 1 +
 net/mptcp/mib.h      | 1 +
 net/mptcp/protocol.c | 1 +
 3 files changed, 3 insertions(+)

diff --git a/net/mptcp/mib.c b/net/mptcp/mib.c
index 6003e47c770a..171643815076 100644
--- a/net/mptcp/mib.c
+++ b/net/mptcp/mib.c
@@ -85,6 +85,7 @@ static const struct snmp_mib mptcp_snmp_list[] = {
 	SNMP_MIB_ITEM("DssFallback", MPTCP_MIB_DSSFALLBACK),
 	SNMP_MIB_ITEM("SimultConnectFallback", MPTCP_MIB_SIMULTCONNFALLBACK),
 	SNMP_MIB_ITEM("FallbackFailed", MPTCP_MIB_FALLBACKFAILED),
+	SNMP_MIB_ITEM("WinProbe", MPTCP_MIB_WINPROBE),
 };

 /* mptcp_mib_alloc - allocate percpu mib counters
diff --git a/net/mptcp/mib.h b/net/mptcp/mib.h
index 309bac6fea32..a1d3e9369fbb 100644
--- a/net/mptcp/mib.h
+++ b/net/mptcp/mib.h
@@ -88,6 +88,7 @@ enum linux_mptcp_mib_field {
 	MPTCP_MIB_DSSFALLBACK,		/* Bad or missing DSS */
 	MPTCP_MIB_SIMULTCONNFALLBACK,	/* Simultaneous connect */
 	MPTCP_MIB_FALLBACKFAILED,	/* Can't fallback due to msk status */
+	MPTCP_MIB_WINPROBE,		/* MPTCP-level zero window probe */
 	__MPTCP_MIB_MAX
 };

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 2feaf7afba49..49fed273f4dd 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1346,6 +1346,7 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
 		 mpext->dsn64);

 	if (zero_window_probe) {
+		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_WINPROBE);
 		mptcp_subflow_ctx(ssk)->rel_write_seq += copy;
 		mpext->frozen = 1;
 		if (READ_ONCE(msk->csum_enabled))

-- 
2.51.0