chore: Add feature flag for manual network waiting (canonical#5977)

Controls the behavior added in e30549e for easier downstream patching

Author: TheRealFalcon

cloudinit/cmd/main.py

@@ -21,7 +21,7 @@
 import yaml
 from typing import Optional, Tuple, Callable, Union
 
-from cloudinit import netinfo
+from cloudinit import features, netinfo
 from cloudinit import signal_handler
 from cloudinit import sources
 from cloudinit import socket
@@ -486,7 +486,9 @@ def main_init(name, args):
     mode = sources.DSMODE_LOCAL if args.local else sources.DSMODE_NETWORK
 
     if mode == sources.DSMODE_NETWORK:
-        if not os.path.exists(init.paths.get_runpath(".skip-network")):
+        if features.MANUAL_NETWORK_WAIT and not os.path.exists(
+            init.paths.get_runpath(".skip-network")
+        ):
             LOG.debug("Will wait for network connectivity before continuing")
             init.distro.wait_for_network()
         existing = "trust"
@@ -560,20 +562,21 @@ def main_init(name, args):
     init.apply_network_config(bring_up=bring_up_interfaces)
 
     if mode == sources.DSMODE_LOCAL:
-        should_wait, reason = _should_wait_on_network(init.datasource)
-        if should_wait:
-            LOG.debug(
-                "Network connectivity determined necessary for "
-                "cloud-init's network stage. Reason: %s",
-                reason,
-            )
-        else:
-            LOG.debug(
-                "Network connectivity determined unnecessary for "
-                "cloud-init's network stage. Reason: %s",
-                reason,
-            )
-            util.write_file(init.paths.get_runpath(".skip-network"), "")
+        if features.MANUAL_NETWORK_WAIT:
+            should_wait, reason = _should_wait_on_network(init.datasource)
+            if should_wait:
+                LOG.debug(
+                    "Network connectivity determined necessary for "
+                    "cloud-init's network stage. Reason: %s",
+                    reason,
+                )
+            else:
+                LOG.debug(
+                    "Network connectivity determined unnecessary for "
+                    "cloud-init's network stage. Reason: %s",
+                    reason,
+                )
+                util.write_file(init.paths.get_runpath(".skip-network"), "")
 
         if init.datasource.dsmode != mode:
             LOG.debug(

cloudinit/features.py

@@ -87,6 +87,17 @@
 to write /etc/apt/sources.list directly.
 """
 
+MANUAL_NETWORK_WAIT = True
+"""
+On Ubuntu systems, cloud-init-network.service will start immediately after
+cloud-init-local.service and manually wait for network online when necessary.
+If False, rely on systemd ordering to ensure network is available before
+starting cloud-init-network.service.
+
+Note that in addition to this flag, downstream patches are also likely needed
+to modify the systemd unit files.
+"""
+
 DEPRECATION_INFO_BOUNDARY = "devel"
 """
 DEPRECATION_INFO_BOUNDARY is used by distros to configure at which upstream

tests/integration_tests/datasources/test_nocloud.py

@@ -5,7 +5,7 @@
 import pytest
 from pycloudlib.lxd.instance import LXDInstance
 
-from cloudinit import lifecycle
+from cloudinit import features, lifecycle
 from cloudinit.subp import subp
 from tests.integration_tests.instances import IntegrationInstance
 from tests.integration_tests.integration_settings import PLATFORM
@@ -100,7 +100,10 @@ def test_nocloud_seedfrom_vendordata(client: IntegrationInstance):
     client.restart()
     assert client.execute("cloud-init status").ok
     assert "seeded_vendordata_test_file" in client.execute("ls /var/tmp")
-    assert network_wait_logged(client.execute("cat /var/log/cloud-init.log"))
+    assert (
+        network_wait_logged(client.execute("cat /var/log/cloud-init.log"))
+        == features.MANUAL_NETWORK_WAIT
+    )
 
 
 SMBIOS_USERDATA = """\

tests/integration_tests/modules/test_boothook.py

@@ -3,6 +3,7 @@
 
 import pytest
 
+from cloudinit import features
 from tests.integration_tests.instances import IntegrationInstance
 from tests.integration_tests.util import (
     network_wait_logged,
@@ -55,6 +56,9 @@ def test_boothook_waits_for_network(
     ):
         """Test boothook handling waits for network before running."""
         client = class_client
-        assert network_wait_logged(
-            client.read_from_file("/var/log/cloud-init.log")
+        assert (
+            network_wait_logged(
+                client.read_from_file("/var/log/cloud-init.log")
+            )
+            == features.MANUAL_NETWORK_WAIT
         )

tests/unittests/cmd/test_main.py

@@ -9,7 +9,7 @@
 
 import pytest
 
-from cloudinit import safeyaml, util
+from cloudinit import features, safeyaml, util
 from cloudinit.cmd import main
 from cloudinit.util import ensure_dir, load_text_file, write_file
 
@@ -363,7 +363,7 @@ def test_distro_wait_for_network(
             skip_log_setup=False,
         )
         main.main_init("init", cmdargs)
-        if expected_add_wait:
+        if features.MANUAL_NETWORK_WAIT and expected_add_wait:
             m_nm.assert_called_once()
             m_subp.assert_called_with(
                 ["systemctl", "start", "systemd-networkd-wait-online.service"]

tests/unittests/test_data.py

@@ -516,6 +516,7 @@ def test_shellscript(self, init_tmp, tmpdir, caplog):
                 "DEPRECATION_INFO_BOUNDARY": "devel",
                 "NOCLOUD_SEED_URL_APPEND_FORWARD_SLASH": False,
                 "APT_DEB822_SOURCE_LIST_FILE": True,
+                "MANUAL_NETWORK_WAIT": True,
             },
             "system_info": {
                 "default_user": {"name": "ubuntu"},

tests/unittests/test_features.py

@@ -22,6 +22,7 @@ def test_feature_without_override(self):
             DEPRECATION_INFO_BOUNDARY="devel",
             NOCLOUD_SEED_URL_APPEND_FORWARD_SLASH=False,
             APT_DEB822_SOURCE_LIST_FILE=True,
+            MANUAL_NETWORK_WAIT=False,
         ):
             assert {
                 "ERROR_ON_USER_DATA_FAILURE": True,
@@ -31,4 +32,5 @@ def test_feature_without_override(self):
                 "NOCLOUD_SEED_URL_APPEND_FORWARD_SLASH": False,
                 "APT_DEB822_SOURCE_LIST_FILE": True,
                 "DEPRECATION_INFO_BOUNDARY": "devel",
+                "MANUAL_NETWORK_WAIT": False,
             } == features.get_features()