generate: Don't run during netplan try

Generate may be called by NetworkManager (via Dbus) in Ubuntu >23.10.

While `netplan try` is waiting for revert, there is no situation where
the generator should be called.

Signed-off-by: Wesley Hershberger <wesley.hershberger@canonical.com>

Author: MggMuggins

src/generate.c

@@ -208,6 +208,7 @@ int main(int argc, char** argv)
     /* are we being called as systemd generator? */
     gboolean called_as_generator = (strstr(argv[0], "systemd/system-generators/") != NULL);
     g_autofree char* generator_run_stamp = NULL;
+    g_autofree char* netplan_try_stamp = NULL;
     glob_t gl;
     int error_code = 0;
     char* ignore_errors_env = NULL;
@@ -243,6 +244,22 @@ int main(int argc, char** argv)
         }
     }
 
+    // The file at netplan_try_stamp is created while `netplan try` is waiting
+    // for user confirmation. If generate is triggered while netplan try is
+    // running, we shouldn't regenerate the configuration.
+    // We can be called by either systemd (as a generator during daemon-reload)
+    // or by NetworkManager when it is reloading configuration (Ubuntu >23.10),
+    // see https://netplan.readthedocs.io/en/stable/netplan-everywhere/.
+    // LP #2083029
+    netplan_try_stamp = g_build_path(G_DIR_SEPARATOR_S,
+                                     rootdir != NULL ? rootdir : G_DIR_SEPARATOR_S,
+                                     "run/netplan/netplan-try.ready",
+                                     NULL);
+    if (g_access(netplan_try_stamp, F_OK) == 0) {
+        g_fprintf(stderr, "'netplan try' is restoring configuration, remove %s to force re-run.\n", netplan_try_stamp);
+        return 1;
+    }
+
     if ((ignore_errors_env = getenv("NETPLAN_PARSER_IGNORE_ERRORS"))) {
         // This is used mostly by autopkgtests
         // LCOV_EXCL_START

tests/generator/base.py

@@ -261,6 +261,7 @@ class TestBase(unittest.TestCase):
     def setUp(self):
         self.workdir = tempfile.TemporaryDirectory()
         self.confdir = os.path.join(self.workdir.name, 'etc', 'netplan')
+        self.rundir = os.path.join(self.workdir.name, 'run', 'netplan')
         self.nm_enable_all_conf = os.path.join(
             self.workdir.name, 'run', 'NetworkManager', 'conf.d', '10-globally-managed-devices.conf')
         self.maxDiff = None

tests/generator/test_args.py

@@ -54,6 +54,12 @@ def test_empty_config(self):
         self.assert_nm_udev(None)
         self.assert_ovs({'cleanup.service': OVS_CLEANUP % {'iface': 'cleanup'}})
 
+    def test_generate_fails_during_try(self):
+        os.makedirs(self.rundir, mode=0o700, exist_ok=True)
+        open(os.path.join(self.rundir, "netplan-try.ready"), "w").close()
+
+        self.generate('network:\n  version: 2', expect_fail=True)
+
     def test_file_args(self):
         conf = os.path.join(self.workdir.name, 'config')
         with open(conf, 'w') as f: