network: add automatic configuration for the networks created by nspawn --network-zone=

This way, they "just work", similar to --network-veth behaves, as long as
networkd is enabled and running on all involved nodes.

Makefile.am

@@ -3598,7 +3598,8 @@ INSTALL_DIRS += \
 dist_network_DATA = \
 	network/99-default.link \
 	network/80-container-host0.network \
-	network/80-container-ve.network
+	network/80-container-ve.network \
+	network/80-container-vz.network
 
 dist_udevrules_DATA += \
 	rules/50-udev-default.rules \

network/80-container-host0.network

@@ -5,6 +5,10 @@
 #  the Free Software Foundation; either version 2.1 of the License, or
 #  (at your option) any later version.
 
+# This network file matches the container-side of the virtual Ethernet link
+# created by systemd-nspawn's --network-veth switch. See systemd-nspawn(1) for
+# details.
+
 [Match]
 Virtualization=container
 Name=host0

network/80-container-ve.network

@@ -5,6 +5,10 @@
 #  the Free Software Foundation; either version 2.1 of the License, or
 #  (at your option) any later version.
 
+# This network file matches the host-side of the virtual Ethernet link
+# created by systemd-nspawn's --network-veth switch. See systemd-nspawn(1) for
+# details.
+
 [Match]
 Name=ve-*
 Driver=veth

network/80-container-vz.network

@@ -0,0 +1,22 @@
+#  This file is part of systemd.
+#
+#  systemd is free software; you can redistribute it and/or modify it
+#  under the terms of the GNU Lesser General Public License as published by
+#  the Free Software Foundation; either version 2.1 of the License, or
+#  (at your option) any later version.
+
+# This network file matches the bridge interface created by systemd-nspawn's
+# --network-zone= switch. See systemd-nspawn(1) for details.
+
+[Match]
+Name=vz-*
+Driver=bridge
+
+[Network]
+# Default to using a /24 prefix, giving up to 253 addresses per virtual network.
+Address=0.0.0.0/24
+LinkLocalAddressing=yes
+DHCPServer=yes
+IPMasquerade=yes
+LLDP=yes
+EmitLLDP=yes