Fix: load plugins before initializing device data

Plugins were loaded after the device data inheritance has already
been processed, forcing us to declare device features for every
child device in device families like junos/ios.

This "simple" change in initialization sequence loads plugins
(and their default settings) before the device features are inherited,
making it easy to specify a single feature entry covering the whole
family of devices.

Please note that this change also requires daemon features to be
defined under 'daemons' not 'devices' (the 'daemons' parameters
are copied into 'devices' parameters during device initialization)

Author: ipspace

netsim/augment/main.py

@@ -15,24 +15,37 @@
 from . import addressing
 from .. import roles
 
+"""
+Initializing the topology transformation:
+
+* The global variables (stored in topology defaults) are initialized
+* The attribute lists are adjusted
+* The search paths are expanded into absolute paths and pruned
+* Plugins are loaded
+* Device settings are initialized, including daemon- and child device
+  inheritance
+
+Note that the plugins have to be loaded before the device settings are
+inherited, or we cannot specify the new features for generic devices.
+"""
 def topology_init(topology: Box) -> None:
   global_vars.init(topology)
   augment.config.attributes(topology)
   augment.config.paths(topology)
+  augment.plugin.init(topology)
   augment.devices.augment_device_settings(topology)
 
 def transform_setup(topology: Box) -> None:
-  topology_init(topology)
-  augment.topology.topology_sanity_check(topology)
-  versioning.check_topology_version(topology)
+  topology_init(topology)                                   # Initialize variables, load plugins
+  augment.topology.topology_sanity_check(topology)          # Do the basic sanity check
+  versioning.check_topology_version(topology)               # Check topology/netlab version mismatch
   topology.nodes = augment.nodes.create_node_dict(topology.nodes)
-  augment.groups.precheck_groups(topology)
-  augment.plugin.init(topology)                                         # Initialize plugins very early on in case they modify extra attributes
-  roles.init(topology)                                                  # Initialize node roles
-  augment.plugin.execute('topology_expand',topology)                    # topology-expanding plugins must be called before link checks
+  augment.groups.precheck_groups(topology)                  # Do basic sanity checks on groups
+  roles.init(topology)                                      # Initialize node roles
+  augment.plugin.execute('topology_expand',topology)        # Topology-expanding plugins must be called before link checks
 
   if 'links' in topology:
-    augment.links.links_init(topology)
+    augment.links.links_init(topology)                      # Rewrite links into canonical form
 
   log.exit_on_error()
 

netsim/extra/bgp.session/defaults.yml

@@ -1,7 +1,7 @@
 # bgp.session default settings -- mostly attributes
 #
 ---
-devices:
+daemons:
   bird:
     daemon_config:
       bgp@session: /etc/bird/bgp.session.conf
@@ -15,6 +15,7 @@ devices:
       rs: True
       rs_client: True
       timers: True
+devices:
   dellos10.features.bgp:
     allowas_in: True
     bfd: True