Fix requiring device-number on EC2 derivatives (#836)

#342 (70dbccbb) introduced the ability to determine route-metrics based on
the `device-number` provided by the EC2 IMDS. Not all datasources that
subclass EC2 will have this attribute, so allow the old behavior if
`device-number` is not present.

LP: #1917875

2 files changed, 32 insertions, 1 deletions

diff --git a/cloudinit/sources/DataSourceEc2.py b/cloudinit/sources/DataSourceEc2.py
index 1930a509..a2105dc7 100644
--- a/cloudinit/sources/DataSourceEc2.py
+++ b/cloudinit/sources/DataSourceEc2.py
@@ -765,13 +765,14 @@ def convert_ec2_metadata_network_config(
         netcfg['ethernets'][nic_name] = dev_config
         return netcfg
     # Apply network config for all nics and any secondary IPv4/v6 addresses
+    nic_idx = 0
     for mac, nic_name in sorted(macs_to_nics.items()):
         nic_metadata = macs_metadata.get(mac)
         if not nic_metadata:
             continue  # Not a physical nic represented in metadata
         # device-number is zero-indexed, we want it 1-indexed for the
         # multiplication on the following line
-        nic_idx = int(nic_metadata['device-number']) + 1
+        nic_idx = int(nic_metadata.get('device-number', nic_idx)) + 1
         dhcp_override = {'route-metric': nic_idx * 100}
         dev_config = {'dhcp4': True, 'dhcp4-overrides': dhcp_override,
                       'dhcp6': False,
diff --git a/tests/unittests/test_datasource/test_aliyun.py b/tests/unittests/test_datasource/test_aliyun.py
index eb2828d5..cab1ac2b 100644
--- a/tests/unittests/test_datasource/test_aliyun.py
+++ b/tests/unittests/test_datasource/test_aliyun.py
@@ -7,6 +7,7 @@ from unittest import mock
 
 from cloudinit import helpers
 from cloudinit.sources import DataSourceAliYun as ay
+from cloudinit.sources.DataSourceEc2 import convert_ec2_metadata_network_config
 from cloudinit.tests import helpers as test_helpers
 
 DEFAULT_METADATA = {
@@ -183,6 +184,35 @@ class TestAliYunDatasource(test_helpers.HttprettyTestCase):
         self.assertEqual(ay.parse_public_keys(public_keys),
                          public_keys['key-pair-0']['openssh-key'])
 
+    def test_route_metric_calculated_without_device_number(self):
+        """Test that route-metric code works without `device-number`
+
+        `device-number` is part of EC2 metadata, but not supported on aliyun.
+        Attempting to access it will raise a KeyError.
+
+        LP: #1917875
+        """
+        netcfg = convert_ec2_metadata_network_config(
+            {"interfaces": {"macs": {
+                "06:17:04:d7:26:09": {
+                    "interface-id": "eni-e44ef49e",
+                },
+                "06:17:04:d7:26:08": {
+                    "interface-id": "eni-e44ef49f",
+                }
+            }}},
+            macs_to_nics={
+                '06:17:04:d7:26:09': 'eth0',
+                '06:17:04:d7:26:08': 'eth1',
+            }
+        )
+
+        met0 = netcfg['ethernets']['eth0']['dhcp4-overrides']['route-metric']
+        met1 = netcfg['ethernets']['eth1']['dhcp4-overrides']['route-metric']
+
+        # route-metric numbers should be 100 apart
+        assert 100 == abs(met0 - met1)
+
 
 class TestIsAliYun(test_helpers.CiTestCase):
     ALIYUN_PRODUCT = 'Alibaba Cloud ECS'