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

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 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 6003e47c770a7c..eb4645a9c5ac07 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("MPTcpWinProbe", MPTCP_MIB_MPTCPWINPROBE),
 };
 
 /* mptcp_mib_alloc - allocate percpu mib counters
diff --git a/net/mptcp/mib.h b/net/mptcp/mib.h
index 309bac6fea3252..f83a113700522e 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_MPTCPWINPROBE,	/* MPTCP-level zero window probe */
 	__MPTCP_MIB_MAX
 };
 
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index fe029359b7d7a2..67919ae774cc40 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1396,6 +1396,7 @@ 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_MPTCPWINPROBE);
 		mptcp_subflow_ctx(ssk)->rel_write_seq += copy;
 		mpext->frozen = 1;
 		if (READ_ONCE(msk->csum_enabled))
-- 
2.51.0

On Mon, 20 Oct 2025, Paolo Abeni wrote:

> Explicitly account for MPTCP-level zero windows probe, to catch
> hopefully earlier issues alike the one addressed by the previous
> patch.
>
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Helpful metric to track, looks good.

Reviewed-by: Mat Martineau <martineau@kernel.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 6003e47c770a7c..eb4645a9c5ac07 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("MPTcpWinProbe", MPTCP_MIB_MPTCPWINPROBE),
> };
>
> /* mptcp_mib_alloc - allocate percpu mib counters
> diff --git a/net/mptcp/mib.h b/net/mptcp/mib.h
> index 309bac6fea3252..f83a113700522e 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_MPTCPWINPROBE,	/* MPTCP-level zero window probe */
> 	__MPTCP_MIB_MAX
> };
>
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index fe029359b7d7a2..67919ae774cc40 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -1396,6 +1396,7 @@ 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_MPTCPWINPROBE);
> 		mptcp_subflow_ctx(ssk)->rel_write_seq += copy;
> 		mpext->frozen = 1;
> 		if (READ_ONCE(msk->csum_enabled))
> -- 
> 2.51.0
>
>
>