selftests: mptcp: check subflow errors in close events

This validates the previous commit: subflow closed events should contain
an error field when a subflow got closed with an error, e.g. reset or
timeout.

For this test, the chk_evt_nr helper has been extended to check
attributes in the matched events.

In this test, the 2 subflow closed events should have an error.

The 'Fixes' tag here below is the same as the one from the previous
commit: this patch here is not fixing anything wrong in the selftests,
but it validates the previous fix for an issue introduced by this commit
ID.

Fixes: 15cc104 ("mptcp: deliver ssk errors to msk")
Cc: stable@vger.kernel.org
Reviewed-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260127-net-mptcp-dup-nl-events-v1-4-7f71e1bc4feb@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: matttbe

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

@@ -3847,21 +3847,28 @@ userspace_pm_chk_get_addr()
 	fi
 }
 
-# $1: ns ; $2: event type ; $3: count
+# $1: ns ; $2: event type ; $3: count ; [ $4: attr ; $5: attr count ]
 chk_evt_nr()
 {
 	local ns=${1}
 	local evt_name="${2}"
 	local exp="${3}"
+	local attr="${4}"
+	local attr_exp="${5}"
 
 	local evts="${evts_ns1}"
 	local evt="${!evt_name}"
+	local attr_name
 	local count
 
+	if [ -n "${attr}" ]; then
+		attr_name=", ${attr}: ${attr_exp}"
+	fi
+
 	evt_name="${evt_name:16}" # without MPTCP_LIB_EVENT_
 	[ "${ns}" == "ns2" ] && evts="${evts_ns2}"
 
-	print_check "event ${ns} ${evt_name} (${exp})"
+	print_check "event ${ns} ${evt_name} (${exp}${attr_name})"
 
 	if [[ "${evt_name}" = "LISTENER_"* ]] &&
 	   ! mptcp_lib_kallsyms_has "mptcp_event_pm_listener$"; then
@@ -3873,6 +3880,16 @@ chk_evt_nr()
 	if [ "${count}" != "${exp}" ]; then
 		fail_test "got ${count} events, expected ${exp}"
 		cat "${evts}"
+		return
+	elif [ -z "${attr}" ]; then
+		print_ok
+		return
+	fi
+
+	count=$(grep -w "type:${evt}" "${evts}" | grep -c ",${attr}:")
+	if [ "${count}" != "${attr_exp}" ]; then
+		fail_test "got ${count} event attributes, expected ${attr_exp}"
+		grep -w "type:${evt}" "${evts}"
 	else
 		print_ok
 	fi
@@ -4131,7 +4148,7 @@ userspace_tests()
 			chk_subflows_total 1 1
 			userspace_pm_add_sf $ns2 10.0.1.2 0
 			wait_event ns2 MPTCP_LIB_EVENT_SUB_CLOSED 2
-			chk_evt_nr ns2 MPTCP_LIB_EVENT_SUB_CLOSED 2
+			chk_evt_nr ns2 MPTCP_LIB_EVENT_SUB_CLOSED 2 error 2
 		fi
 		kill_events_pids
 		mptcp_lib_kill_group_wait $tests_pid