From eb1965a434360b3198768302f4196488d7c2511f Mon Sep 17 00:00:00 2001
From: Bryan Fraschetti <bryan.fraschetti@canonical.com>
Date: Mon, 3 Feb 2025 16:13:19 -0500
Subject: [PATCH] Fix: GCE _get_data crashes if DHCP lease fails (#5998)

This commit addresses issue #5997 which reported crashes in init-local
when cloud-init was examining GCELocal as a potential datasource. When
all NICs failed at DHCP discovery cloud-init attempts to log the events
by dereferencing a value that was never assigned.

This commit modifies the _get_data function of DataSourceGCE.py by
adding an empty dictionary definition for the ret variable at the
top level of the function and some debugging logs when a candidate NIC
fails to obtain a DHCP lease. At the same time, the commit replaces the
direct key access operator on ret with the safe lookup method get(). This
commit also adds a unit test that mocks the observed situation.

Reference:https://github.com/canonical/cloud-init/commit/eb1965a434360b3198768302f4196488d7c2511f
Conflict:not change test_gce.py (M_PATH and net.find_candidate_nics doesn't exist)

Fixes GH-5997
---
 cloudinit/sources/DataSourceGCE.py | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/cloudinit/sources/DataSourceGCE.py b/cloudinit/sources/DataSourceGCE.py
index c730ae8..87dc4e0 100644
--- a/cloudinit/sources/DataSourceGCE.py
+++ b/cloudinit/sources/DataSourceGCE.py
@@ -88,6 +88,7 @@ class DataSourceGCE(sources.DataSource):

     def _get_data(self):
         url_params = self.get_url_params()
+        ret = {}
         if self.perform_dhcp_setup:
             candidate_nics = net.find_candidate_nics()
             if DEFAULT_PRIMARY_INTERFACE in candidate_nics:
@@ -122,6 +123,9 @@ class DataSourceGCE(sources.DataSource):
                             )
                             continue
                 except NoDHCPLeaseError:
+                    LOG.debug(
+                        "Unable to obtain a DHCP lease for %s", candidate_nic
+                    )
                     continue
                 if ret["success"]:
                     self._fallback_interface = candidate_nic
@@ -142,14 +146,14 @@ class DataSourceGCE(sources.DataSource):
                 },
             )

-        if not ret["success"]:
-            if ret["platform_reports_gce"]:
-                LOG.warning(ret["reason"])
+        if not ret.get("success"):
+            if ret.get("platform_reports_gce"):
+                LOG.warning(ret.get("reason"))
             else:
-                LOG.debug(ret["reason"])
+                LOG.debug(ret.get("reason"))
             return False
-        self.metadata = ret["meta-data"]
-        self.userdata_raw = ret["user-data"]
+        self.metadata = ret.get("meta-data")
+        self.userdata_raw = ret.get("user-data")
         return True

     @property
--
2.33.0