mptcp: update selftest for fallback due to OoO

The previous commit noted that we can have fallback
scenario due to OoO (or packet drop). Update the self-tests
accordingly

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/mptcp/mptcp_connect.sh

@@ -501,6 +501,7 @@ do_transfer()
 	local stat_ackrx_now_l=$(get_mib_counter "${listener_ns}" "MPTcpExtMPCapableACKRX")
 	local stat_cookietx_now=$(get_mib_counter "${listener_ns}" "TcpExtSyncookiesSent")
 	local stat_cookierx_now=$(get_mib_counter "${listener_ns}" "TcpExtSyncookiesRecv")
+	local stat_ooo_now=$(get_mib_counter "${listener_ns}" "TcpExtTCPOFOQueue")
 
 	expect_synrx=$((stat_synrx_last_l))
 	expect_ackrx=$((stat_ackrx_last_l))
@@ -518,10 +519,14 @@ do_transfer()
 			"${stat_synrx_now_l}" "${expect_synrx}" 1>&2
 		retc=1
 	fi
-	if [ ${stat_ackrx_now_l} -lt ${expect_ackrx} ]; then
-		printf "[ FAIL ] lower MPC ACK rx (%d) than expected (%d)\n" \
-			"${stat_ackrx_now_l}" "${expect_ackrx}" 1>&2
-		rets=1
+	if [ ${stat_ackrx_now_l} -lt ${expect_ackrx} -a ${stat_ooo_now} -eq 0 ]; then
+		if [ ${stat_ooo_now} -eq 0 ]; then
+			printf "[ FAIL ] lower MPC ACK rx (%d) than expected (%d)\n" \
+				"${stat_ackrx_now_l}" "${expect_ackrx}" 1>&2
+			rets=1
+		else
+			printf "[ Note ] fallback due to TCP OoO"
+		fi
 	fi
 
 	if [ $retc -eq 0 ] && [ $rets -eq 0 ]; then