test-execute: add test for PrivateNetwork= with/without mount namespacing

test/test-execute/exec-privatenetwork-yes-privatemounts-no.service

@@ -1,9 +1,13 @@
 # SPDX-License-Identifier: LGPL-2.1-or-later
 [Unit]
-Description=Test for PrivateNetwork
+Description=Test for PrivateNetwork= without mount namespacing
 
 [Service]
 ExecStart=/bin/sh -x -c '! ip link | grep -E "^[0-9]+: " | grep -Ev ": (lo|(erspan|gre|gretap|ip_vti|ip6_vti|ip6gre|ip6tnl|sit|tunl)0@.*):"'
 ExecStart=/bin/sh -x -c '! ip link | grep -E "^[0-9]+: " | grep -F ": dummy-test-exec:"'
+ExecStart=/bin/sh -x -c 'test ! -e /proc/sys/net/ipv4/conf/dummy-test-exec'
+# Without mount namespacing, we can access the dummy-test-exec interface through sysfs
+ExecStart=/bin/sh -x -c 'test -d /sys/class/net/dummy-test-exec'
 Type=oneshot
 PrivateNetwork=yes
+PrivateMounts=no

test/test-execute/exec-privatenetwork-yes-privatemounts-yes.service

@@ -0,0 +1,13 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+[Unit]
+Description=Test for PrivateNetwork= with mount namespacing
+
+[Service]
+ExecStart=/bin/sh -x -c '! ip link | grep -E "^[0-9]+: " | grep -Ev ": (lo|(erspan|gre|gretap|ip_vti|ip6_vti|ip6gre|ip6tnl|sit|tunl)0@.*):"'
+ExecStart=/bin/sh -x -c '! ip link | grep -E "^[0-9]+: " | grep -F ": dummy-test-exec:"'
+ExecStart=/bin/sh -x -c 'test ! -e /proc/sys/net/ipv4/conf/dummy-test-exec'
+# With mount namespacing, we cannot access the dummy-test-exec interface through sysfs.
+ExecStart=/bin/sh -x -c 'test ! -e /sys/class/net/dummy-test-exec'
+Type=oneshot
+PrivateNetwork=yes
+# PrivateNetwork=yes implies PrivateMounts=yes