ifupdown: T6038: Cleanup network config properly

Cloud-init in environments where Meta-data is available via network configures
the main interface and keeps the config in `/etc/network/interfaces.d/`.

This config later interferes with the VyOS configuration.

To avoid the problem previously the code in the `cc_vyos.py` module was used,
but this is not enough. The module is running only once during instance
deployment. But Cloud-init will re-add the config file with each boot.

There are two ways to solve this incompatibility (within Cloud-init) - disable
network config or perform cleanup during each boot.

Disabling network config is not correct in this context, because it blocks the
ability to fetch Meta-data after the first boot, which in turn blocks the
ability to run per-boot modules with an updated config.

Therefore, the cleanup code was extracted to an independent
`cc_vyos_ifupdown.py` module that performs proper cleanup with each boot.

3 files changed, 64 insertions, 31 deletions

diff --git a/cloudinit/config/cc_vyos.py b/cloudinit/config/cc_vyos.py
index 3195dcaa..9c9ac697 100644
--- a/cloudinit/config/cc_vyos.py
+++ b/cloudinit/config/cc_vyos.py
@@ -23,7 +23,7 @@
 import re
 import ipaddress
 from pathlib import Path
-from subprocess import run, DEVNULL
+from subprocess import run
 from uuid import uuid4
 from cloudinit import log as logging
 from cloudinit.ssh_util import AuthKeyLineParser
@@ -992,33 +992,6 @@ def set_config_hostname(config, hostname, fqdn):
             logger.error("Failed to configure domain-name: {}".format(err))
 
 
-# cleanup network interface config file added by cloud-init
-def network_cleanup():
-    logger.debug("Cleaning up network configuration applied by Cloud-Init")
-    net_config_file = Path('/etc/network/interfaces.d/50-cloud-init')
-    if net_config_file.exists():
-        logger.debug(f"Configuration file {net_config_file} was found")
-        try:
-            # get a list of interfaces that need to be deconfigured
-            configured_ifaces = run(
-                ['ifquery', '-l', '-X', 'lo', '-i', net_config_file],
-                capture_output=True).stdout.decode().splitlines()
-            if configured_ifaces:
-                for iface in configured_ifaces:
-                    logger.debug(f"Deconfiguring interface: {iface}")
-                    run(['ifdown', iface], stdout=DEVNULL)
-            # delete the file
-            net_config_file.unlink()
-            logger.debug(f"Configuration file {net_config_file} was removed")
-        except Exception as err:
-            logger.error(f"Failed to cleanup network configuration: {err}")
-
-    udev_rules_file = Path('/etc/udev/rules.d/70-persistent-net.rules')
-    if udev_rules_file.exists():
-        logger.debug(f"Configuration file {udev_rules_file} was removed")
-        udev_rules_file.unlink()
-
-
 # main config handler
 def handle(name, cfg, cloud, log, _args):
     logger.debug("Cloud-init config: {}".format(cfg))
@@ -1182,6 +1155,3 @@ def handle(name, cfg, cloud, log, _args):
             logger.debug("Configuration file saved: {}".format(cfg_file_name))
     except Exception as e:
         logger.error("Failed to write configs into file {}: {}".format(cfg_file_name, e))
-
-    # since we already have a config file, it is a time to clean up what Cloud-init may left
-    network_cleanup()
diff --git a/cloudinit/config/cc_vyos_ifupdown.py b/cloudinit/config/cc_vyos_ifupdown.py
new file mode 100644
index 00000000..41457a1e
--- /dev/null
+++ b/cloudinit/config/cc_vyos_ifupdown.py
@@ -0,0 +1,62 @@
+# Copyright (C) 2024 VyOS Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or later as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# This module is used to cleanup ifupdown config that may be left by Cloud-init after its initialization.
+# This must be done during each boot to avoid interferring with VyOS CLI config.
+
+import logging
+from pathlib import Path
+from subprocess import run, DEVNULL
+from cloudinit.settings import PER_ALWAYS
+
+LOG = logging.getLogger(__name__)
+
+frequency = PER_ALWAYS
+
+
+# cleanup network interface config file added by cloud-init
+def network_cleanup() -> None:
+    LOG.debug("Cleaning up network configuration applied by Cloud-Init")
+    net_config_file = Path("/etc/network/interfaces.d/50-cloud-init")
+    if net_config_file.exists():
+        LOG.debug(f"Configuration file {net_config_file} was found")
+        try:
+            # get a list of interfaces that need to be deconfigured
+            configured_ifaces: list[str] = (
+                run(
+                    ["ifquery", "-l", "-X", "lo", "-i", net_config_file],
+                    capture_output=True,
+                )
+                .stdout.decode()
+                .splitlines()
+            )
+            if configured_ifaces:
+                for iface in configured_ifaces:
+                    LOG.debug(f"Deconfiguring interface: {iface}")
+                    run(["ifdown", iface], stdout=DEVNULL)
+            # delete the file
+            net_config_file.unlink()
+            LOG.debug(f"Configuration file {net_config_file} was removed")
+        except Exception as err:
+            LOG.error(f"Failed to cleanup network configuration: {err}")
+
+    udev_rules_file = Path("/etc/udev/rules.d/70-persistent-net.rules")
+    if udev_rules_file.exists():
+        LOG.debug(f"Configuration file {udev_rules_file} was removed")
+        udev_rules_file.unlink()
+
+
+def handle(*args) -> None:
+    LOG.debug('Running "cc_vyos_ifupdown" module')
+    network_cleanup()
diff --git a/config/cloud.cfg.d/10_vyos.cfg b/config/cloud.cfg.d/10_vyos.cfg
index d4415126..f34e262a 100644
--- a/config/cloud.cfg.d/10_vyos.cfg
+++ b/config/cloud.cfg.d/10_vyos.cfg
@@ -19,6 +19,7 @@ cloud_init_modules:
 
 # The modules that run in the 'config' stage
 cloud_config_modules:
+  - vyos_ifupdown
   - vyos
   - write_files
   - vyos_userdata