mptcp: zero window probe mib

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 <[email protected]>
Signed-off-by: Paolo Abeni <[email protected]>
Tested-by: Geliang Tang <[email protected]>
Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Paolo Abeni

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

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
 };
 

net/mptcp/protocol.c

@@ -1355,6 +1355,7 @@ 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))