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, 156 insertions, 0 deletions

diff --git a/cloudinit/net/activators.py b/cloudinit/net/activators.py
new file mode 100644
index 00000000..34fee3bf
--- /dev/null
+++ b/cloudinit/net/activators.py
@@ -0,0 +1,156 @@
+# This file is part of cloud-init. See LICENSE file for license information.
+import logging
+import os
+from abc import ABC, abstractmethod
+from typing import Iterable, List, Type
+
+from cloudinit import subp
+from cloudinit import util
+from cloudinit.net.eni import available as eni_available
+from cloudinit.net.netplan import available as netplan_available
+from cloudinit.net.network_state import NetworkState
+from cloudinit.net.sysconfig import NM_CFG_FILE
+
+
+LOG = logging.getLogger(__name__)
+
+
+class NetworkActivator(ABC):
+    @staticmethod
+    @abstractmethod
+    def available() -> bool:
+        raise NotImplementedError()
+
+    @staticmethod
+    @abstractmethod
+    def bring_up_interface(device_name: str) -> bool:
+        raise NotImplementedError()
+
+    @classmethod
+    def bring_up_interfaces(cls, device_names: Iterable[str]) -> bool:
+        all_succeeded = True
+        for device in device_names:
+            if not cls.bring_up_interface(device):
+                all_succeeded = False
+        return all_succeeded
+
+    @classmethod
+    def bring_up_all_interfaces(cls, network_state: NetworkState) -> bool:
+        return cls.bring_up_interfaces(
+            [i['name'] for i in network_state.iter_interfaces()]
+        )
+
+
+class IfUpDownActivator(NetworkActivator):
+    # Note that we're not overriding bring_up_interfaces to pass something
+    # like ifup --all because it isn't supported everywhere.
+    # E.g., NetworkManager has a ifupdown plugin that requires the name
+    # of a specific connection.
+    @staticmethod
+    def available(target=None) -> bool:
+        """Return true if ifupdown can be used on this system."""
+        return eni_available(target=target)
+
+    @staticmethod
+    def bring_up_interface(device_name: str) -> bool:
+        """Bring up interface using ifup."""
+        cmd = ['ifup', device_name]
+        LOG.debug("Attempting to run bring up interface %s using command %s",
+                  device_name, cmd)
+        try:
+            (_out, err) = subp.subp(cmd)
+            if len(err):
+                LOG.warning("Running %s resulted in stderr output: %s",
+                            cmd, err)
+            return True
+        except subp.ProcessExecutionError:
+            util.logexc(LOG, "Running interface command %s failed", cmd)
+            return False
+
+
+class NetworkManagerActivator(NetworkActivator):
+    @staticmethod
+    def available(target=None) -> bool:
+        config_present = os.path.isfile(
+            subp.target_path(target, path=NM_CFG_FILE)
+        )
+        nmcli_present = subp.which('nmcli', target=target)
+        return config_present and bool(nmcli_present)
+
+    @staticmethod
+    def bring_up_interface(device_name: str) -> bool:
+        try:
+            subp.subp(['nmcli', 'connection', 'up', device_name])
+        except subp.ProcessExecutionError:
+            util.logexc(LOG, "nmcli failed to bring up {}".format(device_name))
+            return False
+        return True
+
+
+class NetplanActivator(NetworkActivator):
+    @staticmethod
+    def available(target=None) -> bool:
+        return netplan_available(target=target)
+
+    @staticmethod
+    def _apply_netplan():
+        LOG.debug('Applying current netplan config')
+        try:
+            subp.subp(['netplan', 'apply'], capture=True)
+        except subp.ProcessExecutionError:
+            util.logexc(LOG, "netplan apply failed")
+            return False
+        return True
+
+    @staticmethod
+    def bring_up_interface(device_name: str) -> bool:
+        LOG.debug("Calling 'netplan apply' rather than "
+                  "bringing up individual interfaces")
+        return NetplanActivator._apply_netplan()
+
+    @staticmethod
+    def bring_up_interfaces(device_names: Iterable[str]) -> bool:
+        LOG.debug("Calling 'netplan apply' rather than "
+                  "bringing up individual interfaces")
+        return NetplanActivator._apply_netplan()
+
+    @staticmethod
+    def bring_up_all_interfaces(network_state: NetworkState) -> bool:
+        return NetplanActivator._apply_netplan()
+
+
+# This section is mostly copied and pasted from renderers.py. An abstract
+# version to encompass both seems overkill at this point
+DEFAULT_PRIORITY = [
+    IfUpDownActivator,
+    NetworkManagerActivator,
+    NetplanActivator,
+]
+
+
+def search_activator(
+    priority=None, target=None
+) -> List[Type[NetworkActivator]]:
+    if priority is None:
+        priority = DEFAULT_PRIORITY
+
+    unknown = [i for i in priority if i not in DEFAULT_PRIORITY]
+    if unknown:
+        raise ValueError(
+            "Unknown activators provided in priority list: %s" % unknown)
+
+    return [activator for activator in priority if activator.available(target)]
+
+
+def select_activator(priority=None, target=None) -> Type[NetworkActivator]:
+    found = search_activator(priority, target)
+    if not found:
+        if priority is None:
+            priority = DEFAULT_PRIORITY
+        tmsg = ""
+        if target and target != "/":
+            tmsg = " in target=%s" % target
+        raise RuntimeError(
+            "No available network activators found%s. Searched "
+            "through list: %s" % (tmsg, priority))
+    return found[0]