selftests: mptcp: add pm sysctl mapping tests

This patch checks if the newly added net.mptcp.path_manager is mapped
successfully from or to the old net.mptcp.pm_type in userspace_pm.sh.

Signed-off-by: Geliang Tang <[email protected]>
Reviewed-by: Matthieu Baerts (NGI0) <[email protected]>
Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Link: https://patch.msgid.link/20250313-net-next-mptcp-pm-ops-intro-v1-12-f4e4a88efc50@kernel.org
Signed-off-by: Paolo Abeni <[email protected]>

Author: Geliang Tang

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

@@ -117,7 +117,36 @@ cleanup()
 trap cleanup EXIT
 
 # Create and configure network namespaces for testing
+print_title "Init"
 mptcp_lib_ns_init ns1 ns2
+
+# check path_manager and pm_type sysctl mapping
+if [ -f /proc/sys/net/mptcp/path_manager ]; then
+	ip netns exec "$ns1" sysctl -q net.mptcp.path_manager=userspace
+	pm_type="$(ip netns exec "$ns1" sysctl -n net.mptcp.pm_type)"
+	if [ "${pm_type}" != "1" ]; then
+		test_fail "unexpected pm_type: ${pm_type}"
+		mptcp_lib_result_print_all_tap
+		exit ${KSFT_FAIL}
+	fi
+
+	ip netns exec "$ns1" sysctl -q net.mptcp.path_manager=error 2>/dev/null
+	pm_type="$(ip netns exec "$ns1" sysctl -n net.mptcp.pm_type)"
+	if [ "${pm_type}" != "1" ]; then
+		test_fail "unexpected pm_type after error: ${pm_type}"
+		mptcp_lib_result_print_all_tap
+		exit ${KSFT_FAIL}
+	fi
+
+	ip netns exec "$ns1" sysctl -q net.mptcp.pm_type=0
+	pm_name="$(ip netns exec "$ns1" sysctl -n net.mptcp.path_manager)"
+	if [ "${pm_name}" != "kernel" ]; then
+		test_fail "unexpected path-manager: ${pm_name}"
+		mptcp_lib_result_print_all_tap
+		exit ${KSFT_FAIL}
+	fi
+fi
+
 for i in "$ns1" "$ns2" ;do
 	ip netns exec "$i" sysctl -q net.mptcp.pm_type=1
 done
@@ -152,7 +181,6 @@ mptcp_lib_events "${ns1}" "${server_evts}" server_evts_pid
 sleep 0.5
 mptcp_lib_subtests_last_ts_reset
 
-print_title "Init"
 print_test "Created network namespaces ns1, ns2"
 test_pass