compat: Only create interface when configured to do so.

Add config option <compat_create_interfaces>:

  Denotes where or not to create interfaces when compat_* settings are
  active and it would be necessary to create an interface to be fully
  compliant.  This could happen when inheriting bridge VLAN settings to
  an interface within a bridges bridge-ports setting but no interface
  stanza is found.  Valid values are 0 and 1, the default is 1.

Signed-off-by: Maximilian Wilhelm <max@sdn.clinic>

dist/ifupdown-ng.conf.example

@@ -17,6 +17,14 @@ allow_addon_scripts = 1
 # templates.  Valid values are 0 and 1, the default is 1.
 allow_any_iface_as_template = 1
 
+# compat_create_interfaces:
+# Denotes where or not to create interfaces when compat_* settings are
+# active and it would be necessary to create an interface to be fully
+# compliant.  This could happen when inheriting bridge VLAN settings to
+# an interface within a bridges bridge-ports setting but no interface
+# stanza is found.  Valid values are 0 and 1, the default is 1.
+compat_create_interfaces = 1
+
 # compat_ifupdown2_bridge_ports_inherit_vlans:
 # In ifupdown2 <bridge-vids> as well as the <bridge-pvid> set on a bridge
 # interface will be inherited by all member ports if not set explicitly.

doc/ADMIN-GUIDE.md

@@ -60,6 +60,13 @@ Currently the following settings are supported in
   in order to require inheritance from specified templates.
   Valid values are `0` and `1`, the default is `1`.
 
+* `compat_create_interfaces`:
+  Denotes where or not to create interfaces when compat\_* settings are
+  active and it would be necessary to create an interface to be fully
+  compliant.  This could happen when inheriting bridge VLAN settings to
+  an interface within a bridges bridge-ports setting but no interface
+  stanza is found.  Valid values are `0` and `1`, the default is `1`.
+
 * `compat_ifupdown2_bridge_ports_inherit_vlans`: In ifupdown2 `bridge-vids`
   as well as the <bridge-pvid> set on a bridge interface will be inherited
   by all member ports if not set explicitly.  When set to `1` ifupdown-ng

libifupdown/compat.c

@@ -68,7 +68,7 @@ compat_ifupdown2_bridge_ports_inherit_vlans(struct lif_dict *collection)
 			if (entry)
 				bridge_port = entry->data;
 
-			else
+			else if (lif_config.compat_create_interfaces)
 			{
 				bridge_port = lif_interface_collection_find(collection, tokenp);
 				if (bridge_port == NULL)
@@ -78,6 +78,14 @@ compat_ifupdown2_bridge_ports_inherit_vlans(struct lif_dict *collection)
 				}
 			}
 
+			/* We would have to creaet an interface, but shouldn't */
+			else
+			{
+				fprintf(stderr, "compat: Missing interface stanza for bridge-port \"%s\" but should not create one.\n",
+				        tokenp);
+				continue;
+			}
+
 			/* Maybe pimp bridge-pvid */
 			struct lif_dict_entry *port_pvid = lif_dict_find(&bridge_port->vars, "bridge-pvid");
 			if (bridge_pvid && !port_pvid)

libifupdown/config-file.c

@@ -21,6 +21,7 @@
 struct lif_config_file lif_config = {
 	.allow_addon_scripts = true,
 	.allow_any_iface_as_template = true,
+	.compat_create_interfaces = true,
 	.compat_ifupdown2_bridge_ports_inherit_vlans = true,
 	.implicit_template_conversion = true,
 	.use_hostname_for_dhcp = true,
@@ -48,6 +49,7 @@ set_bool_value(const char *key, const char *value, void *opaque)
 static struct lif_config_handler handlers[] = {
 	{"allow_addon_scripts", set_bool_value, &lif_config.allow_addon_scripts},
 	{"allow_any_iface_as_template", set_bool_value, &lif_config.allow_any_iface_as_template},
+	{"compat_create_interfaces", set_bool_value, &lif_config.compat_create_interfaces},
 	{"compat_ifupdown2_bridge_ports_inherit_vlans", set_bool_value, &lif_config.compat_ifupdown2_bridge_ports_inherit_vlans},
 	{"implicit_template_conversion", set_bool_value, &lif_config.implicit_template_conversion},
 	{"use_hostname_for_dhcp", set_bool_value, &lif_config.use_hostname_for_dhcp},

libifupdown/config-file.h

@@ -21,6 +21,7 @@
 struct lif_config_file {
 	bool allow_addon_scripts;
 	bool allow_any_iface_as_template;
+	bool compat_create_interfaces;
 	bool compat_ifupdown2_bridge_ports_inherit_vlans;
 	bool implicit_template_conversion;
 	bool use_hostname_for_dhcp;