This patch adds a selftest for userpsace PM to remove id 0 subflow. Use
userspace_pm_add_sf() to add a subflow, and pass initial ip address to
userspace_pm_rm_sf() to remove id 0 subflow.

Add a new helper chk_all_subflows(), in it use 'ss' command

        ss -ti | grep -c tcp-ulp-mptcp

to get the "correct" amount of subflows, including the initial one.

When closing the initial subflow in __mptcp_close_ssk(), dispose_it is
false, then tcp_disconnect is invoked. This will send a MP_RST to close
a subflow on the peer too. So chk_rst_nr() is added in this test, and
chk_all_subflows after closing the initial subflow is '1 1', not '2 1'.

Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
 .../testing/selftests/net/mptcp/mptcp_join.sh | 47 +++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index 2ebe1692edeb..966977980d5c 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -1881,6 +1881,31 @@ chk_mptcp_info()
 	fi
 }
 
+# $1: subflows in ns1 ; $2: subflows in ns2
+# number of all subflows, including the initial subflow.
+chk_all_subflows()
+{
+	local cnt1
+	local cnt2
+
+	print_check "all subflows $1:$2"
+
+	cnt1=$(ss -N $ns1 -ti | grep -c tcp-ulp-mptcp)
+	cnt2=$(ss -N $ns2 -ti | 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
@@ -3430,6 +3455,28 @@ userspace_tests()
 		kill_events_pids
 		wait $tests_pid
 	fi
+
+	# userspace pm remove id 0 subflow
+	if reset_with_events "userspace pm remove id 0 subflow" &&
+	   continue_if mptcp_lib_has_file '/proc/sys/net/mptcp/pm_type'; then
+		set_userspace_pm $ns2
+		pm_nl_set_limits $ns1 0 1
+		speed=10 \
+			run_tests $ns1 $ns2 10.0.1.1 &
+		local tests_pid=$!
+		wait_mpj $ns2
+		userspace_pm_add_sf $ns2 10.0.3.2 20
+		chk_join_nr 1 1 1
+		chk_mptcp_info subflows 1 subflows 1
+		chk_all_subflows 2 2
+		userspace_pm_rm_sf $ns2 10.0.1.2
+		chk_rm_nr 0 1
+		chk_rst_nr 1 1 invert
+		chk_mptcp_info subflows 1 subflows 1
+		chk_all_subflows 1 1
+		kill_events_pids
+		wait $tests_pid
+	fi
 }
 
 endpoint_tests()
-- 
2.35.3