Add new network activators to bring up interfaces (#919)

Currently _bring_up_interfaces() is a no-op for any distro using
renderers. We need to be able to support bringing up a single
interfaces, a list of interfaces, and all interfaces. This should be
independent of the renderers, as the network config is often
generated independent of the mechanism used to apply it.

Additionally, I included a refactor to remove
"_supported_write_network_config". We had a confusing call chain of
apply_network_config->_write_network_config->_supported_write_network_config.
The last two have been combined.

1 files changed, 9 insertions, 4 deletions

diff --git a/cloudinit/net/renderers.py b/cloudinit/net/renderers.py
index c3931a98..822b45de 100644
--- a/cloudinit/net/renderers.py
+++ b/cloudinit/net/renderers.py
@@ -1,10 +1,13 @@
 # This file is part of cloud-init. See LICENSE file for license information.
 
+from typing import List, Tuple, Type
+
 from . import eni
 from . import freebsd
 from . import netbsd
 from . import netplan
 from . import networkd
+from . import renderer
 from . import RendererNotFoundError
 from . import openbsd
 from . import sysconfig
@@ -23,7 +26,9 @@ DEFAULT_PRIORITY = ["eni", "sysconfig", "netplan", "freebsd",
                     "netbsd", "openbsd", "networkd"]
 
 
-def search(priority=None, target=None, first=False):
+def search(
+    priority=None, target=None, first=False
+) -> List[Tuple[str, Type[renderer.Renderer]]]:
     if priority is None:
         priority = DEFAULT_PRIORITY
 
@@ -40,13 +45,13 @@ def search(priority=None, target=None, first=False):
         if render_mod.available(target):
             cur = (name, render_mod.Renderer)
             if first:
-                return cur
+                return [cur]
             found.append(cur)
 
     return found
 
 
-def select(priority=None, target=None):
+def select(priority=None, target=None) -> Tuple[str, Type[renderer.Renderer]]:
     found = search(priority, target=target, first=True)
     if not found:
         if priority is None:
@@ -57,6 +62,6 @@ def select(priority=None, target=None):
         raise RendererNotFoundError(
             "No available network renderers found%s. Searched "
             "through list: %s" % (tmsg, priority))
-    return found
+    return found[0]
 
 # vi: ts=4 expandtab