selftests: mptcp: add chk_subflows_total helper

This patch adds a new helper chk_subflows_total(), in it use the newly
added counter mptcpi_subflows_total to get the "correct" amount of
subflows, including the initial one.

To be compatible with old 'ss' or kernel versions not supporting this
counter, get the total subflows by listing TCP connections that are
MPTCP subflows:

    ss -ti state state established state syn-sent state syn-recv |
        grep -c tcp-ulp-mptcp.
Reviewed-by: Matthieu Baerts <matttbe@kernel.org>
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20231128-send-net-next-2023107-v4-3-8d6b94150f6b@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -1867,7 +1867,7 @@ chk_mptcp_info()
 	local cnt2
 	local dump_stats
 
-	print_check "mptcp_info ${info1:0:8}=$exp1:$exp2"
+	print_check "mptcp_info ${info1:0:15}=$exp1:$exp2"
 
 	cnt1=$(ss -N $ns1 -inmHM | mptcp_lib_get_info_value "$info1" "$info1")
 	cnt2=$(ss -N $ns2 -inmHM | mptcp_lib_get_info_value "$info2" "$info2")
@@ -1888,6 +1888,42 @@ chk_mptcp_info()
 	fi
 }
 
+# $1: subflows in ns1 ; $2: subflows in ns2
+# number of all subflows, including the initial subflow.
+chk_subflows_total()
+{
+	local cnt1
+	local cnt2
+	local info="subflows_total"
+	local dump_stats
+
+	# if subflows_total counter is supported, use it:
+	if [ -n "$(ss -N $ns1 -inmHM | mptcp_lib_get_info_value $info $info)" ]; then
+		chk_mptcp_info $info $1 $info $2
+		return
+	fi
+
+	print_check "$info $1:$2"
+
+	# if not, count the TCP connections that are in fact MPTCP subflows
+	cnt1=$(ss -N $ns1 -ti state established state syn-sent state syn-recv |
+	       grep -c tcp-ulp-mptcp)
+	cnt2=$(ss -N $ns2 -ti state established state syn-sent state syn-recv |
+	       grep -c tcp-ulp-mptcp)
+
+	if [ "$1" != "$cnt1" ] || [ "$2" != "$cnt2" ]; then
+		fail_test "got subflows $cnt1:$cnt2 expected $1:$2"
+		dump_stats=1
+	else
+		print_ok
+	fi
+
+	if [ "$dump_stats" = 1 ]; then
+		ss -N $ns1 -ti
+		ss -N $ns2 -ti
+	fi
+}
+
 chk_link_usage()
 {
 	local ns=$1
@@ -3431,10 +3467,12 @@ userspace_tests()
 		chk_join_nr 1 1 1
 		chk_add_nr 1 1
 		chk_mptcp_info subflows 1 subflows 1
+		chk_subflows_total 2 2
 		chk_mptcp_info add_addr_signal 1 add_addr_accepted 1
 		userspace_pm_rm_sf_addr_ns1 10.0.2.1 10
 		chk_rm_nr 1 1 invert
 		chk_mptcp_info subflows 0 subflows 0
+		chk_subflows_total 1 1
 		kill_events_pids
 		wait $tests_pid
 	fi
@@ -3451,9 +3489,11 @@ userspace_tests()
 		userspace_pm_add_sf 10.0.3.2 20
 		chk_join_nr 1 1 1
 		chk_mptcp_info subflows 1 subflows 1
+		chk_subflows_total 2 2
 		userspace_pm_rm_sf_addr_ns2 10.0.3.2 20
 		chk_rm_nr 1 1
 		chk_mptcp_info subflows 0 subflows 0
+		chk_subflows_total 1 1
 		kill_events_pids
 		wait $tests_pid
 	fi