network: add .link file to match 80-namespace.network

This file makes clear the interface shall be owned by networkd.

This does what 658169e6d307b5b1aea0d82b4a6430fa9d529c68 did for nspawn's
regular devices for the devices defined through
8aee931e7ae1adb01eeac0e1e4c0aef6ed3969ec too.

network/80-namespace-ns.link

@@ -0,0 +1,24 @@
+# SPDX-License-Identifier: MIT-0
+#
+# This config file is installed as part of systemd.
+# It may be freely copied and edited (following the MIT No Attribution license).
+#
+# To make local modifications, one of the following methods may be used:
+# 1. add a drop-in file that extends this file by creating the
+#    /etc/systemd/network/80-container-ve.link.d/ directory and creating a
+#    new .conf file there.
+# 2. copy this file into /etc/systemd/network/ or one of the other paths checked
+#    by systemd-udevd and edit it there.
+# This file should not be edited in place, because it'll be overwritten on upgrades.
+
+# This network file matches the host-side of the virtual Ethernet link
+# created by systemd-nsresourced's network support. See systemd-nsresourced(1) for
+# details.
+
+[Match]
+Kind=veth
+OriginalName=ns-*
+
+[Link]
+NamePolicy=keep
+Property=ID_NET_MANAGED_BY=io.systemd.Network

network/meson.build

@@ -12,6 +12,7 @@ if conf.get('ENABLE_NETWORKD') == 1
                 '80-container-vz.network',
                 '80-container-vz.link',
                 '80-namespace-ns.network',
+                '80-namespace-ns.link',
                 '80-vm-vt.network',
                 '80-vm-vt.link',
                 '80-wifi-adhoc.network',