support 'loopback' as a device type.

As reported in bug 1671927, sysconfig had an issue with rendering
a loopback device.  The problem was that some as yet unknown issue was
causing the openstack config drive to parse the provided ENI file rather
than reading the network_data.json.  Parsing an ENI file would add a
a 'lo' device of type 'physical', and sysconfig was failing to render
that.

The change here is:
 a.) add a 'loopback' type rather than 'physical' for network config.
     {'name': 'lo', 'type': 'loopback', 'subnets': ['type': 'loopback']}
 b.) support skipping that type in the eni and sysconfig renderers.
 c.) make network_state just piggy back on 'physical' renderer for
     loopback (this was what was happening before).

Tests are added for eni and sysconfig renderer.

3 files changed, 16 insertions, 6 deletions

diff --git a/cloudinit/net/eni.py b/cloudinit/net/eni.py
index 5b249f1f..69ecbb5d 100644
--- a/cloudinit/net/eni.py
+++ b/cloudinit/net/eni.py
@@ -273,8 +273,11 @@ def _ifaces_to_net_config_data(ifaces):
         # devname is 'eth0' for name='eth0:1'
         devname = name.partition(":")[0]
         if devname not in devs:
-            devs[devname] = {'type': 'physical', 'name': devname,
-                             'subnets': []}
+            if devname == "lo":
+                dtype = "loopback"
+            else:
+                dtype = "physical"
+            devs[devname] = {'type': dtype, 'name': devname, 'subnets': []}
             # this isnt strictly correct, but some might specify
             # hwaddress on a nic for matching / declaring name.
             if 'hwaddress' in data:
@@ -423,10 +426,11 @@ class Renderer(renderer.Renderer):
             bonding
         '''
         order = {
-            'physical': 0,
-            'bond': 1,
-            'bridge': 2,
-            'vlan': 3,
+            'loopback': 0,
+            'physical': 1,
+            'bond': 2,
+            'bridge': 3,
+            'vlan': 4,
         }
 
         sections = []
diff --git a/cloudinit/net/network_state.py b/cloudinit/net/network_state.py
index 11ef585b..90b2835a 100644
--- a/cloudinit/net/network_state.py
+++ b/cloudinit/net/network_state.py
@@ -212,6 +212,10 @@ class NetworkStateInterpreter(object):
                     LOG.debug(self.dump_network_state())
 
     @ensure_command_keys(['name'])
+    def handle_loopback(self, command):
+        return self.handle_physical(command)
+
+    @ensure_command_keys(['name'])
     def handle_physical(self, command):
         '''
         command = {
diff --git a/cloudinit/net/sysconfig.py b/cloudinit/net/sysconfig.py
index 06de660f..7f52db4a 100644
--- a/cloudinit/net/sysconfig.py
+++ b/cloudinit/net/sysconfig.py
@@ -368,6 +368,8 @@ class Renderer(renderer.Renderer):
         '''Given state, return /etc/sysconfig files + contents'''
         iface_contents = {}
         for iface in network_state.iter_interfaces():
+            if iface['type'] == "loopback":
+                continue
             iface_name = iface['name']
             iface_cfg = NetInterface(iface_name, base_sysconf_dir)
             cls._render_iface_shared(iface, iface_cfg)