sources/hetzner: Use EphemeralDHCPv4 instead of static configuration (#1251)

When the datasource was originally submitted, EphemeralDHCPv4 was not
yet available. Also avoid race conditions by skipping network
configuration if metadata service can be reached.

Signed-off-by: Markus Schade <markus.schade@hetzner.com>

2 files changed, 62 insertions, 36 deletions

diff --git a/cloudinit/sources/DataSourceHetzner.py b/cloudinit/sources/DataSourceHetzner.py
index 50324cc4..91a6f9c9 100644
--- a/cloudinit/sources/DataSourceHetzner.py
+++ b/cloudinit/sources/DataSourceHetzner.py
@@ -9,8 +9,8 @@
 import cloudinit.sources.helpers.hetzner as hc_helper
 from cloudinit import dmi
 from cloudinit import log as logging
-from cloudinit import net as cloudnet
-from cloudinit import sources, util
+from cloudinit import net, sources, util
+from cloudinit.net.dhcp import EphemeralDHCPv4, NoDHCPLeaseError
 
 LOG = logging.getLogger(__name__)
 
@@ -45,7 +45,7 @@ class DataSourceHetzner(sources.DataSource):
         self.retries = self.ds_cfg.get("retries", MD_RETRIES)
         self.timeout = self.ds_cfg.get("timeout", MD_TIMEOUT)
         self.wait_retry = self.ds_cfg.get("wait_retry", MD_WAIT_RETRY)
-        self._network_config = None
+        self._network_config = sources.UNSET
         self.dsmode = sources.DSMODE_NETWORK
 
     def _get_data(self):
@@ -54,22 +54,28 @@ class DataSourceHetzner(sources.DataSource):
         if not on_hetzner:
             return False
 
-        nic = cloudnet.find_fallback_nic()
-        with cloudnet.EphemeralIPv4Network(
-            nic, "169.254.0.1", 16, "169.254.255.255"
-        ):
-            md = hc_helper.read_metadata(
-                self.metadata_address,
-                timeout=self.timeout,
-                sec_between=self.wait_retry,
-                retries=self.retries,
-            )
-            ud = hc_helper.read_userdata(
-                self.userdata_address,
-                timeout=self.timeout,
-                sec_between=self.wait_retry,
-                retries=self.retries,
-            )
+        try:
+            with EphemeralDHCPv4(
+                iface=net.find_fallback_nic(),
+                connectivity_url_data={
+                    "url": BASE_URL_V1 + "/metadata/instance-id",
+                },
+            ):
+                md = hc_helper.read_metadata(
+                    self.metadata_address,
+                    timeout=self.timeout,
+                    sec_between=self.wait_retry,
+                    retries=self.retries,
+                )
+                ud = hc_helper.read_userdata(
+                    self.userdata_address,
+                    timeout=self.timeout,
+                    sec_between=self.wait_retry,
+                    retries=self.retries,
+                )
+        except (NoDHCPLeaseError) as e:
+            LOG.error("Bailing, DHCP Exception: %s", e)
+            raise
 
         # Hetzner cloud does not support binary user-data. So here, do a
         # base64 decode of the data if we can. The end result being that a
@@ -110,7 +116,14 @@ class DataSourceHetzner(sources.DataSource):
         migration.
         """
 
-        if self._network_config:
+        if self._network_config is None:
+            LOG.warning(
+                "Found None as cached _network_config. Resetting to %s",
+                sources.UNSET,
+            )
+            self._network_config = sources.UNSET
+
+        if self._network_config != sources.UNSET:
             return self._network_config
 
         _net_config = self.metadata["network-config"]
diff --git a/tests/unittests/sources/test_hetzner.py b/tests/unittests/sources/test_hetzner.py
index 9e70de34..f80ed45f 100644
--- a/tests/unittests/sources/test_hetzner.py
+++ b/tests/unittests/sources/test_hetzner.py
@@ -24,30 +24,24 @@ network-config:
     name: eth0
     subnets:
     - dns_nameservers:
-      - 213.133.99.99
-      - 213.133.100.100
-      - 213.133.98.98
+      - 185.12.64.1
+      - 185.12.64.2
       ipv4: true
       type: dhcp
-    type: physical
-  - name: eth0:0
-    subnets:
     - address: 2a01:4f8:beef:beef::1/64
+      dns_nameservers:
+      - 2a01:4ff:ff00::add:2
+      - 2a01:4ff:ff00::add:1
       gateway: fe80::1
       ipv6: true
-      routes:
-      - gateway: fe80::1%eth0
-        netmask: 0
-        network: '::'
-      type: static
     type: physical
   version: 1
 network-sysconfig: "DEVICE='eth0'\nTYPE=Ethernet\nBOOTPROTO=dhcp\n\
   ONBOOT='yes'\nHWADDR=96:00:00:08:19:da\n\
   IPV6INIT=yes\nIPV6ADDR=2a01:4f8:beef:beef::1/64\n\
   IPV6_DEFAULTGW=fe80::1%eth0\nIPV6_AUTOCONF=no\n\
-  DNS1=213.133.99.99\nDNS2=213.133.100.100\n"
-public-ipv4: 192.168.0.1
+  DNS1=185.12.64.1\nDNS2=185.12.64.2\n"
+public-ipv4: 192.168.0.2
 public-keys:
 - ssh-ed25519 \
   AAAAC3Nzac1lZdI1NTE5AaaAIaFrcac0yVITsmRrmueq6MD0qYNKlEvW8O1Ib4nkhmWh \
@@ -77,13 +71,20 @@ class TestDataSourceHetzner(CiTestCase):
         )
         return ds
 
-    @mock.patch("cloudinit.net.EphemeralIPv4Network")
+    @mock.patch("cloudinit.net.dhcp.maybe_perform_dhcp_discovery")
+    @mock.patch("cloudinit.sources.DataSourceHetzner.EphemeralDHCPv4")
     @mock.patch("cloudinit.net.find_fallback_nic")
     @mock.patch("cloudinit.sources.helpers.hetzner.read_metadata")
     @mock.patch("cloudinit.sources.helpers.hetzner.read_userdata")
     @mock.patch("cloudinit.sources.DataSourceHetzner.get_hcloud_data")
     def test_read_data(
-        self, m_get_hcloud_data, m_usermd, m_readmd, m_fallback_nic, m_net
+        self,
+        m_get_hcloud_data,
+        m_usermd,
+        m_readmd,
+        m_fallback_nic,
+        m_net,
+        m_dhcp,
     ):
         m_get_hcloud_data.return_value = (
             True,
@@ -92,13 +93,25 @@ class TestDataSourceHetzner(CiTestCase):
         m_readmd.return_value = METADATA.copy()
         m_usermd.return_value = USERDATA
         m_fallback_nic.return_value = "eth0"
+        m_dhcp.return_value = [
+            {
+                "interface": "eth0",
+                "fixed-address": "192.168.0.2",
+                "routers": "192.168.0.1",
+                "subnet-mask": "255.255.255.0",
+                "broadcast-address": "192.168.0.255",
+            }
+        ]
 
         ds = self.get_ds()
         ret = ds.get_data()
         self.assertTrue(ret)
 
         m_net.assert_called_once_with(
-            "eth0", "169.254.0.1", 16, "169.254.255.255"
+            iface="eth0",
+            connectivity_url_data={
+                "url": "http://169.254.169.254/hetzner/v1/metadata/instance-id"
+            },
         )
 
         self.assertTrue(m_readmd.called)