From 38bb84dd674805124021b5b7c3cf1c01f3f60915 Mon Sep 17 00:00:00 2001
From: Philipp Bender <philipp.bender@hetzner.com>
Date: Tue, 1 Apr 2025 11:38:03 +0200
Subject: [PATCH 01/12] fix: hetzner networking setup (WIP)

---
 cloudinit/sources/DataSourceHetzner.py | 103 ++++++++++++++++++++++++-
 cloudinit/sources/helpers/hetzner.py   |   2 +-
 2 files changed, 102 insertions(+), 3 deletions(-)

diff --git a/cloudinit/sources/DataSourceHetzner.py b/cloudinit/sources/DataSourceHetzner.py
index 7b919f66fa4..13da635e516 100644
--- a/cloudinit/sources/DataSourceHetzner.py
+++ b/cloudinit/sources/DataSourceHetzner.py
@@ -19,6 +19,8 @@
 
 BUILTIN_DS_CONFIG = {
     "metadata_url": BASE_URL_V1 + "/metadata",
+    "metadata_private_networks_url": BASE_URL_V1
+    + "/metadata/private-networks",
     "userdata_url": BASE_URL_V1 + "/userdata",
 }
 
@@ -26,6 +28,13 @@
 MD_TIMEOUT = 2
 MD_WAIT_RETRY = 2
 
+# Do not re-configure the network on non-Hetzner network interface
+# changes. Currently, Hetzner private network addresses start with 0x86.
+EXTRA_HOTPLUG_UDEV_RULES = """
+SUBSYSTEM=="net", ATTR{address}=="86:*", GOTO="cloudinit_hook"
+GOTO="cloudinit_end"
+"""
+
 
 class DataSourceHetzner(sources.DataSource):
 
@@ -42,6 +51,9 @@ def __init__(self, sys_cfg, distro, paths):
             ]
         )
         self.metadata_address = self.ds_cfg["metadata_url"]
+        self.metadata_private_networks_address = self.ds_cfg[
+            "metadata_private_networks_url"
+        ]
         self.userdata_address = self.ds_cfg["userdata_url"]
         self.retries = self.ds_cfg.get("retries", MD_RETRIES)
         self.timeout = self.ds_cfg.get("timeout", MD_TIMEOUT)
@@ -50,6 +62,8 @@ def __init__(self, sys_cfg, distro, paths):
         self.dsmode = sources.DSMODE_NETWORK
         self.metadata_full = None
 
+        self.extra_hotplug_udev_rules = EXTRA_HOTPLUG_UDEV_RULES
+
     def _get_data(self):
         (on_hetzner, serial) = get_hcloud_data()
 
@@ -72,6 +86,12 @@ def _get_data(self):
                     sec_between=self.wait_retry,
                     retries=self.retries,
                 )
+                md["private-networks"] = hc_helper.read_metadata(
+                    self.metadata_private_networks_address,
+                    timeout=self.timeout,
+                    sec_between=self.wait_retry,
+                    retries=self.retries,
+                )
                 ud = hc_helper.read_userdata(
                     self.userdata_address,
                     timeout=self.timeout,
@@ -99,6 +119,7 @@ def _get_data(self):
         self.metadata["local-hostname"] = md["hostname"]
         self.metadata["network-config"] = md.get("network-config", None)
         self.metadata["public-keys"] = md.get("public-keys", None)
+        self.metadata["private-networks"] = md.get("private-networks", [])
         self.vendordata_raw = md.get("vendor_data", None)
 
         # instance-id and serial from SMBIOS should be identical
@@ -135,9 +156,87 @@ def network_config(self):
         if not _net_config:
             raise RuntimeError("Unable to get meta-data from server....")
 
-        self._network_config = _net_config
+        self._network_config_v2 = {
+            "version": 2,
+            "ethernets": {},
+        }
+        self._network_config_v2["ethernets"] = self._network_config_v1_to_v2(
+            _net_config
+        )
 
-        return self._network_config
+        for private_network in self.metadata.get("private-networks", []):
+            network_config_v2 = {
+                "match": {
+                    "macaddress": private_network["mac_address"],
+                },
+                "dhcp4": True,
+            }
+            idx = private_network["interface_num"]
+            # The key name (priv...) is just a virtual interface name.
+            # To rename the interface, "set-name" must be used, but we
+            # want to keep the OS-chosen name.
+            self._network_config_v2["ethernets"][
+                f"priv{idx}"
+            ] = network_config_v2
+
+        return self._network_config_v2
+
+    def _network_config_v1_to_v2(self, network_config_v1):
+        ethernets = {}
+
+        for network in network_config_v1["config"]:
+            networkv2 = {
+                "match": {
+                    "macaddress": network["mac_address"],
+                },
+                "set-name": network["name"],
+                "addresses": [],
+                "nameservers": {
+                    "addresses": [],
+                },
+                "routes": [],
+            }
+
+            for subnet in network["subnets"]:
+                if (
+                    "ipv4" in subnet
+                    and subnet["ipv4"]
+                    and subnet["type"] == "dhcp"
+                ):
+                    networkv2["dhcp4"] = True
+                if (
+                    "ipv6" in subnet
+                    and subnet["ipv6"]
+                    and subnet["type"] == "dhcp"
+                ):
+                    networkv2["dhcp6"] = True
+
+                if subnet["type"] == "static":
+                    if "address" in subnet:
+                        networkv2["addresses"].append(subnet["address"])
+
+                    if "dns_nameservers" in subnet:
+                        for ns in subnet["dns_nameservers"]:
+                            networkv2["nameservers"]["addresses"].append(ns)
+
+                    target = None
+                    if "ipv4" in subnet and subnet["ipv4"]:
+                        target = "0.0.0.0/0"
+                    elif "ipv6" in subnet and subnet["ipv6"]:
+                        target = "::/0"
+
+                    if "gateway" in subnet and target:
+                        networkv2["routes"].append(
+                            {
+                                "on-link": True,
+                                "to": target,
+                                "via": subnet["gateway"],
+                            }
+                        )
+
+            ethernets[network["name"]] = networkv2
+
+        return ethernets
 
 
 def get_hcloud_data():
diff --git a/cloudinit/sources/helpers/hetzner.py b/cloudinit/sources/helpers/hetzner.py
index a1fd92ff37d..50fbcb0468a 100644
--- a/cloudinit/sources/helpers/hetzner.py
+++ b/cloudinit/sources/helpers/hetzner.py
@@ -12,7 +12,7 @@ def read_metadata(url, timeout=2, sec_between=2, retries=30):
     )
     if not response.ok():
         raise RuntimeError("unable to read metadata at %s" % url)
-    return util.load_yaml(response.contents.decode())
+    return util.load_yaml(response.contents.decode(), allowed=(dict, list))
 
 
 def read_userdata(url, timeout=2, sec_between=2, retries=30):

From 0149efbee5d4022e3911cf76228d6a7709af1dcf Mon Sep 17 00:00:00 2001
From: Philipp Bender <philipp.bender@hetzner.com>
Date: Mon, 18 Aug 2025 13:24:38 +0000
Subject: [PATCH 02/12] Enable HOTPLUG support by default

---
 cloudinit/sources/DataSourceHetzner.py | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/cloudinit/sources/DataSourceHetzner.py b/cloudinit/sources/DataSourceHetzner.py
index 13da635e516..8db8b020e6a 100644
--- a/cloudinit/sources/DataSourceHetzner.py
+++ b/cloudinit/sources/DataSourceHetzner.py
@@ -10,6 +10,7 @@
 
 import cloudinit.sources.helpers.hetzner as hc_helper
 from cloudinit import dmi, net, sources, util
+from cloudinit.event import EventScope, EventType
 from cloudinit.net.dhcp import NoDHCPLeaseError
 from cloudinit.net.ephemeral import EphemeralDHCPv4
 
@@ -40,6 +41,13 @@ class DataSourceHetzner(sources.DataSource):
 
     dsname = "Hetzner"
 
+    default_update_events = {
+        EventScope.NETWORK: {
+            EventType.BOOT_NEW_INSTANCE,
+            EventType.HOTPLUG,
+        }
+    }
+
     def __init__(self, sys_cfg, distro, paths):
         sources.DataSource.__init__(self, sys_cfg, distro, paths)
         self.distro = distro

From d97988af906a8342279d0b840c84d5aa328d4724 Mon Sep 17 00:00:00 2001
From: Philipp Bender <philipp.bender@hetzner.com>
Date: Mon, 18 Aug 2025 13:55:11 +0000
Subject: [PATCH 03/12] Refactor Hetzner datasource to simplify network
 configuration handling

---
 cloudinit/sources/DataSourceHetzner.py | 101 +++++--------------------
 cloudinit/sources/helpers/hetzner.py   |   8 +-
 2 files changed, 28 insertions(+), 81 deletions(-)

diff --git a/cloudinit/sources/DataSourceHetzner.py b/cloudinit/sources/DataSourceHetzner.py
index 8db8b020e6a..48df402cdab 100644
--- a/cloudinit/sources/DataSourceHetzner.py
+++ b/cloudinit/sources/DataSourceHetzner.py
@@ -38,7 +38,6 @@
 
 
 class DataSourceHetzner(sources.DataSource):
-
     dsname = "Hetzner"
 
     default_update_events = {
@@ -164,87 +163,29 @@ def network_config(self):
         if not _net_config:
             raise RuntimeError("Unable to get meta-data from server....")
 
-        self._network_config_v2 = {
-            "version": 2,
-            "ethernets": {},
-        }
-        self._network_config_v2["ethernets"] = self._network_config_v1_to_v2(
-            _net_config
-        )
-
-        for private_network in self.metadata.get("private-networks", []):
-            network_config_v2 = {
-                "match": {
-                    "macaddress": private_network["mac_address"],
-                },
-                "dhcp4": True,
-            }
-            idx = private_network["interface_num"]
-            # The key name (priv...) is just a virtual interface name.
-            # To rename the interface, "set-name" must be used, but we
-            # want to keep the OS-chosen name.
-            self._network_config_v2["ethernets"][
-                f"priv{idx}"
-            ] = network_config_v2
-
-        return self._network_config_v2
-
-    def _network_config_v1_to_v2(self, network_config_v1):
-        ethernets = {}
-
-        for network in network_config_v1["config"]:
-            networkv2 = {
-                "match": {
-                    "macaddress": network["mac_address"],
-                },
-                "set-name": network["name"],
-                "addresses": [],
-                "nameservers": {
-                    "addresses": [],
-                },
-                "routes": [],
-            }
-
-            for subnet in network["subnets"]:
-                if (
-                    "ipv4" in subnet
-                    and subnet["ipv4"]
-                    and subnet["type"] == "dhcp"
-                ):
-                    networkv2["dhcp4"] = True
-                if (
-                    "ipv6" in subnet
-                    and subnet["ipv6"]
-                    and subnet["type"] == "dhcp"
-                ):
-                    networkv2["dhcp6"] = True
-
-                if subnet["type"] == "static":
-                    if "address" in subnet:
-                        networkv2["addresses"].append(subnet["address"])
-
-                    if "dns_nameservers" in subnet:
-                        for ns in subnet["dns_nameservers"]:
-                            networkv2["nameservers"]["addresses"].append(ns)
-
-                    target = None
-                    if "ipv4" in subnet and subnet["ipv4"]:
-                        target = "0.0.0.0/0"
-                    elif "ipv6" in subnet and subnet["ipv6"]:
-                        target = "::/0"
-
-                    if "gateway" in subnet and target:
-                        networkv2["routes"].append(
+        _private_networks = self.metadata.get("private-networks", [])
+        _private_networks_config = []
+        for _private_network in _private_networks:
+            _private_networks_config.extend(
+                [
+                    {
+                        "type": "physical",
+                        "mac_address": _private_network["mac_address"],
+                        "name": hc_helper.get_interface_name_from_mac(
+                            _private_network["mac_address"]
+                        ),
+                        "subnets": [
                             {
-                                "on-link": True,
-                                "to": target,
-                                "via": subnet["gateway"],
+                                "ipv4": True,
+                                "type": "dhcp",
                             }
-                        )
-
-            ethernets[network["name"]] = networkv2
-
-        return ethernets
+                        ],
+                    }
+                ]
+            )
+        _net_config["config"].extend(_private_networks_config)
+        self._network_config = _net_config
+        return self._network_config
 
 
 def get_hcloud_data():
diff --git a/cloudinit/sources/helpers/hetzner.py b/cloudinit/sources/helpers/hetzner.py
index 50fbcb0468a..da073fe0cff 100644
--- a/cloudinit/sources/helpers/hetzner.py
+++ b/cloudinit/sources/helpers/hetzner.py
@@ -3,7 +3,7 @@
 #
 # This file is part of cloud-init. See LICENSE file for license information.
 
-from cloudinit import url_helper, util
+from cloudinit import url_helper, util, net
 
 
 def read_metadata(url, timeout=2, sec_between=2, retries=30):
@@ -22,3 +22,9 @@ def read_userdata(url, timeout=2, sec_between=2, retries=30):
     if not response.ok():
         raise RuntimeError("unable to read userdata at %s" % url)
     return response.contents
+
+
+def get_interface_name_from_mac(mac: str) -> str | None:
+    mac_to_iface = net.get_interfaces_by_mac()
+    return mac_to_iface.get(mac.lower())
+

From a4ef1b5c522bb16c59058f7d49839558e0fc56eb Mon Sep 17 00:00:00 2001
From: Philipp Bender <philipp.bender@hetzner.com>
Date: Tue, 19 Aug 2025 10:35:29 +0000
Subject: [PATCH 04/12] Add BOOT event support and refactor optional typing in
 Hetzner datasource

---
 cloudinit/sources/DataSourceHetzner.py | 1 +
 cloudinit/sources/helpers/hetzner.py   | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/cloudinit/sources/DataSourceHetzner.py b/cloudinit/sources/DataSourceHetzner.py
index 48df402cdab..040392ba409 100644
--- a/cloudinit/sources/DataSourceHetzner.py
+++ b/cloudinit/sources/DataSourceHetzner.py
@@ -43,6 +43,7 @@ class DataSourceHetzner(sources.DataSource):
     default_update_events = {
         EventScope.NETWORK: {
             EventType.BOOT_NEW_INSTANCE,
+            EventType.BOOT,
             EventType.HOTPLUG,
         }
     }
diff --git a/cloudinit/sources/helpers/hetzner.py b/cloudinit/sources/helpers/hetzner.py
index da073fe0cff..ff9735825c8 100644
--- a/cloudinit/sources/helpers/hetzner.py
+++ b/cloudinit/sources/helpers/hetzner.py
@@ -4,6 +4,7 @@
 # This file is part of cloud-init. See LICENSE file for license information.
 
 from cloudinit import url_helper, util, net
+from typing import Optional
 
 
 def read_metadata(url, timeout=2, sec_between=2, retries=30):
@@ -24,7 +25,7 @@ def read_userdata(url, timeout=2, sec_between=2, retries=30):
     return response.contents
 
 
-def get_interface_name_from_mac(mac: str) -> str | None:
+def get_interface_name_from_mac(mac: str) -> Optional[str] :
     mac_to_iface = net.get_interfaces_by_mac()
     return mac_to_iface.get(mac.lower())
 

From f9dfe48fd41d404f9b10d9c174d96530036802e5 Mon Sep 17 00:00:00 2001
From: Philipp Bender <philipp.bender@hetzner.com>
Date: Sat, 23 Aug 2025 14:43:58 +0000
Subject: [PATCH 05/12] Refactor Hetzner datasource to support IPv6, streamline
 metadata retrieval, and improve timeout handling

---
 cloudinit/sources/DataSourceHetzner.py | 90 +++++++++++++++++---------
 cloudinit/sources/helpers/hetzner.py   | 52 +++++++++------
 2 files changed, 95 insertions(+), 47 deletions(-)

diff --git a/cloudinit/sources/DataSourceHetzner.py b/cloudinit/sources/DataSourceHetzner.py
index 040392ba409..c5257922967 100644
--- a/cloudinit/sources/DataSourceHetzner.py
+++ b/cloudinit/sources/DataSourceHetzner.py
@@ -9,25 +9,30 @@
 import logging
 
 import cloudinit.sources.helpers.hetzner as hc_helper
-from cloudinit import dmi, net, sources, util
+from cloudinit import dmi, net, sources, util, url_helper
 from cloudinit.event import EventScope, EventType
 from cloudinit.net.dhcp import NoDHCPLeaseError
-from cloudinit.net.ephemeral import EphemeralDHCPv4
+from cloudinit.net.ephemeral import EphemeralIPNetwork
 
 LOG = logging.getLogger(__name__)
 
-BASE_URL_V1 = "http://169.254.169.254/hetzner/v1"
+BASE_URLS_V1 = [
+    f"http://[fe80::a9fe:a9fe%25{net.find_fallback_nic()}]/hetzner/v1/",
+    "http://169.254.169.254/hetzner/v1/",
+]
+
 
 BUILTIN_DS_CONFIG = {
-    "metadata_url": BASE_URL_V1 + "/metadata",
-    "metadata_private_networks_url": BASE_URL_V1
-    + "/metadata/private-networks",
-    "userdata_url": BASE_URL_V1 + "/userdata",
+    "metadata_path": "metadata",
+    "metadata_private_networks_path": "metadata/private-networks",
+    "userdata_path": "userdata",
 }
 
 MD_RETRIES = 60
 MD_TIMEOUT = 2
 MD_WAIT_RETRY = 2
+MD_MAX_WAIT = 120
+MD_SLEEP_TIME = 2
 
 # Do not re-configure the network on non-Hetzner network interface
 # changes. Currently, Hetzner private network addresses start with 0x86.
@@ -51,21 +56,23 @@ class DataSourceHetzner(sources.DataSource):
     def __init__(self, sys_cfg, distro, paths):
         sources.DataSource.__init__(self, sys_cfg, distro, paths)
         self.distro = distro
-        self.metadata = dict()
+        self.metadata = {}
         self.ds_cfg = util.mergemanydict(
             [
                 util.get_cfg_by_path(sys_cfg, ["datasource", "Hetzner"], {}),
                 BUILTIN_DS_CONFIG,
             ]
         )
-        self.metadata_address = self.ds_cfg["metadata_url"]
-        self.metadata_private_networks_address = self.ds_cfg[
-            "metadata_private_networks_url"
+        self.metadata_path = self.ds_cfg["metadata_path"]
+        self.metadata_private_networks_path = self.ds_cfg[
+            "metadata_private_networks_path"
         ]
-        self.userdata_address = self.ds_cfg["userdata_url"]
+        self.userdata_path = self.ds_cfg["userdata_path"]
         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.max_wait = self.ds_cfg.get("max_wait", MD_MAX_WAIT)
+        self.sleep_time = self.ds_cfg.get("sleep_time", MD_SLEEP_TIME)
         self._network_config = sources.UNSET
         self.dsmode = sources.DSMODE_NETWORK
         self.metadata_full = None
@@ -79,33 +86,58 @@ def _get_data(self):
             return False
 
         try:
-            with EphemeralDHCPv4(
+            with EphemeralIPNetwork(
                 self.distro,
-                iface=net.find_fallback_nic(),
+                interface=net.find_fallback_nic(),
+                ipv4=True,
+                ipv6=True,
                 connectivity_urls_data=[
                     {
-                        "url": BASE_URL_V1 + "/metadata/instance-id",
+                        "url": url_helper.combine_url(
+                            url, "metadata/instance-id"
+                        )
                     }
+                    for url in BASE_URLS_V1
                 ],
             ):
-                md = hc_helper.read_metadata(
-                    self.metadata_address,
+                url, contents = hc_helper.get_metadata(
+                    [
+                        url_helper.combine_url(url, self.metadata_path)
+                        for url in BASE_URLS_V1
+                    ],
+                    max_wait=self.max_wait,
                     timeout=self.timeout,
-                    sec_between=self.wait_retry,
-                    retries=self.retries,
+                    sleep_time=self.sleep_time,
                 )
-                md["private-networks"] = hc_helper.read_metadata(
-                    self.metadata_private_networks_address,
+                LOG.debug("Using metadata source: '%s'", url)
+                md = util.load_yaml(contents.decode(), allowed=(dict, list))
+                url, contents = hc_helper.get_metadata(
+                    [
+                        url_helper.combine_url(
+                            url, self.metadata_private_networks_path
+                        )
+                        for url in BASE_URLS_V1
+                    ],
+                    max_wait=self.max_wait,
                     timeout=self.timeout,
-                    sec_between=self.wait_retry,
-                    retries=self.retries,
+                    sleep_time=self.sleep_time,
+                )
+                LOG.debug("Using private_networks source: '%s'", url)
+                md["private-networks"] = util.load_yaml(
+                    contents.decode(), allowed=(dict, list)
                 )
-                ud = hc_helper.read_userdata(
-                    self.userdata_address,
+                url, ud = hc_helper.get_metadata(
+                    [
+                        url_helper.combine_url(url, self.userdata_path)
+                        for url in BASE_URLS_V1
+                    ],
+                    max_wait=self.max_wait,
                     timeout=self.timeout,
-                    sec_between=self.wait_retry,
-                    retries=self.retries,
+                    sleep_time=self.sleep_time,
                 )
+                LOG.debug("Using userdata source: '%s'", url)
+                if not ud:
+                    LOG.debug("Got empty userdata")
         except NoDHCPLeaseError as e:
             LOG.error("Bailing, DHCP Exception: %s", e)
             raise
@@ -192,7 +224,7 @@ def network_config(self):
 def get_hcloud_data():
     vendor_name = dmi.read_dmi_data("system-manufacturer")
     if vendor_name != "Hetzner":
-        return (False, None)
+        return False, None
 
     serial = dmi.read_dmi_data("system-serial-number")
     if serial:
@@ -200,7 +232,7 @@ def get_hcloud_data():
     else:
         raise RuntimeError("Hetzner Cloud detected, but no serial found")
 
-    return (True, serial)
+    return True, serial
 
 
 # Used to match classes to dependencies
diff --git a/cloudinit/sources/helpers/hetzner.py b/cloudinit/sources/helpers/hetzner.py
index ff9735825c8..26f8a98f49f 100644
--- a/cloudinit/sources/helpers/hetzner.py
+++ b/cloudinit/sources/helpers/hetzner.py
@@ -3,29 +3,45 @@
 #
 # This file is part of cloud-init. See LICENSE file for license information.
 
-from cloudinit import url_helper, util, net
+from cloudinit import url_helper, net
 from typing import Optional
 
 
-def read_metadata(url, timeout=2, sec_between=2, retries=30):
-    response = url_helper.readurl(
-        url, timeout=timeout, sec_between=sec_between, retries=retries
+def skip_retry_on_empty_response(cause: url_helper.UrlError) -> bool:
+    """Returns False if cause.code is 200 and 'Content-Length' is '0'."""
+    return not (
+        cause.code == 200 and cause.headers.get("Content-Length") == "0"
     )
-    if not response.ok():
-        raise RuntimeError("unable to read metadata at %s" % url)
-    return util.load_yaml(response.contents.decode(), allowed=(dict, list))
 
 
-def read_userdata(url, timeout=2, sec_between=2, retries=30):
-    response = url_helper.readurl(
-        url, timeout=timeout, sec_between=sec_between, retries=retries
-    )
-    if not response.ok():
-        raise RuntimeError("unable to read userdata at %s" % url)
-    return response.contents
-
-
-def get_interface_name_from_mac(mac: str) -> Optional[str] :
+def get_metadata(
+    urls,
+    max_wait=120,
+    sec_between=2,
+    retries=30,
+    timeout=2,
+    sleep_time=2,
+    exception_cb=None,
+) -> tuple[str, bytes]:
+    try:
+        if not exception_cb:
+            # It is ok for userdata to not exist (thats why we are stopping if
+            # response is empty) and just in that case returning an empty
+            # string.
+            exception_cb = skip_retry_on_empty_response
+        url, contents = url_helper.wait_for_url(
+            urls=urls,
+            max_wait=max_wait,
+            timeout=timeout,
+            sleep_time=sleep_time,
+            exception_cb=exception_cb,
+        )
+        return url, contents
+    except url_helper.UrlError as e:
+        if e.code == 200 and e.headers.get("Content-Length") == "0":
+            return e.url, b""
+
+
+def get_interface_name_from_mac(mac: str) -> Optional[str]:
     mac_to_iface = net.get_interfaces_by_mac()
     return mac_to_iface.get(mac.lower())
-

From 54a0ccf223fb4e238176f3ba268b1296abe99ebb Mon Sep 17 00:00:00 2001
From: Philipp Bender <philipp.bender@hetzner.com>
Date: Mon, 25 Aug 2025 19:32:56 +0000
Subject: [PATCH 06/12] Refactor Hetzner unit tests to support expanded
 metadata, private networks, and improve mocking consistency

---
 tests/unittests/sources/test_hetzner.py | 63 ++++++++++++++++++-------
 1 file changed, 47 insertions(+), 16 deletions(-)

diff --git a/tests/unittests/sources/test_hetzner.py b/tests/unittests/sources/test_hetzner.py
index 5867a4fac91..84014d5069c 100644
--- a/tests/unittests/sources/test_hetzner.py
+++ b/tests/unittests/sources/test_hetzner.py
@@ -8,8 +8,7 @@
 from cloudinit.sources import DataSourceHetzner
 from tests.unittests.helpers import CiTestCase, mock
 
-METADATA = util.load_yaml(
-    """
+METADATA = b"""
 hostname: cloudinit-test
 instance-id: 123456
 local-ipv4: ''
@@ -43,13 +42,24 @@
   test-key@workstation
 vendor_data: "test"
 """
-)
 
 USERDATA = b"""#cloud-config
 runcmd:
 - [touch, /root/cloud-init-worked ]
 """
 
+PRIVATE_NETWORKS = b"""
+- ip: 10.1.0.2
+  alias_ips: []
+  interface_num: 2
+  mac_address: 86:00:00:aa:5d:f8
+  network_id: 11352901
+  network_name: network-2
+  network: 10.1.0.0/16
+  subnet: 10.1.0.0/24
+  gateway: 10.1.0.1
+"""
+
 
 class TestDataSourceHetzner(CiTestCase):
     """
@@ -69,15 +79,13 @@ def get_ds(self):
         return ds
 
     @mock.patch("cloudinit.net.dhcp.maybe_perform_dhcp_discovery")
-    @mock.patch("cloudinit.sources.DataSourceHetzner.EphemeralDHCPv4")
+    @mock.patch("cloudinit.sources.DataSourceHetzner.EphemeralIPNetwork")
     @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.helpers.hetzner.get_metadata")
     @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,
@@ -85,10 +93,15 @@ def test_read_data(
     ):
         m_get_hcloud_data.return_value = (
             True,
-            str(METADATA.get("instance-id")),
+            str(util.load_yaml(METADATA).get("instance-id")),
         )
-        m_readmd.return_value = METADATA.copy()
-        m_usermd.return_value = USERDATA
+        # Use side_effect to return values for the three sequential calls to
+        # helpers.hetzner.get_metadata: metadata, private-networks, userdata
+        m_readmd.side_effect = [
+            ("metadata_url", METADATA),
+            ("privnets_url", PRIVATE_NETWORKS),
+            ("userdata_url", USERDATA),
+        ]
         m_fallback_nic.return_value = "eth0"
         m_dhcp.return_value = [
             {
@@ -106,25 +119,43 @@ def test_read_data(
 
         m_net.assert_called_once_with(
             ds.distro,
-            iface="eth0",
+            interface="eth0",
+            ipv4=True,
+            ipv6=True,
             connectivity_urls_data=[
+                {
+                    "url": "http://[fe80::a9fe:a9fe%25eth0]/hetzner/v1/metadata/instance-id"
+                },
                 {
                     "url": "http://169.254.169.254/hetzner/v1/metadata/instance-id"
-                }
+                },
             ],
         )
 
         self.assertTrue(m_readmd.called)
 
-        self.assertEqual(METADATA.get("hostname"), ds.get_hostname().hostname)
+        self.assertEqual(
+            util.load_yaml(METADATA).get("hostname"),
+            ds.get_hostname().hostname,
+        )
 
-        self.assertEqual(METADATA.get("public-keys"), ds.get_public_ssh_keys())
+        self.assertEqual(
+            util.load_yaml(METADATA).get("public-keys"),
+            ds.get_public_ssh_keys(),
+        )
 
+        self.assertEqual(
+            ds.metadata["private-networks"],
+            util.load_yaml(PRIVATE_NETWORKS, allowed=(dict, list)),
+        )
         self.assertIsInstance(ds.get_public_ssh_keys(), list)
         self.assertEqual(ds.get_userdata_raw(), USERDATA)
-        self.assertEqual(ds.get_vendordata_raw(), METADATA.get("vendor_data"))
+        self.assertEqual(
+            ds.get_vendordata_raw(),
+            util.load_yaml(METADATA).get("vendor_data"),
+        )
 
-    @mock.patch("cloudinit.sources.helpers.hetzner.read_metadata")
+    @mock.patch("cloudinit.sources.helpers.hetzner.get_metadata")
     @mock.patch("cloudinit.net.find_fallback_nic")
     @mock.patch("cloudinit.sources.DataSourceHetzner.get_hcloud_data")
     def test_not_on_hetzner_returns_false(

From fad5e5ad9f8b224488b8a9549b257c8c1bebed00 Mon Sep 17 00:00:00 2001
From: Philipp Bender <philipp.bender@hetzner.com>
Date: Mon, 1 Sep 2025 16:17:53 +0000
Subject: [PATCH 07/12] Switch to new API return code 204 on empty string

---
 cloudinit/sources/helpers/hetzner.py | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/cloudinit/sources/helpers/hetzner.py b/cloudinit/sources/helpers/hetzner.py
index 26f8a98f49f..0e22d890342 100644
--- a/cloudinit/sources/helpers/hetzner.py
+++ b/cloudinit/sources/helpers/hetzner.py
@@ -8,10 +8,8 @@
 
 
 def skip_retry_on_empty_response(cause: url_helper.UrlError) -> bool:
-    """Returns False if cause.code is 200 and 'Content-Length' is '0'."""
-    return not (
-        cause.code == 200 and cause.headers.get("Content-Length") == "0"
-    )
+    """Returns False if cause.code is 204."""
+    return cause.code != 204
 
 
 def get_metadata(
@@ -26,7 +24,7 @@ def get_metadata(
     try:
         if not exception_cb:
             # It is ok for userdata to not exist (thats why we are stopping if
-            # response is empty) and just in that case returning an empty
+            # HTTP code is 204) and just in that case returning an empty
             # string.
             exception_cb = skip_retry_on_empty_response
         url, contents = url_helper.wait_for_url(
@@ -38,7 +36,7 @@ def get_metadata(
         )
         return url, contents
     except url_helper.UrlError as e:
-        if e.code == 200 and e.headers.get("Content-Length") == "0":
+        if e.code == 204:
             return e.url, b""
 
 

From d6762f8012517bf2053676647b71b0fd25065cdf Mon Sep 17 00:00:00 2001
From: Philipp Bender <philipp.bender@hetzner.com>
Date: Tue, 2 Sep 2025 15:52:39 +0000
Subject: [PATCH 08/12] Refactor imports and replace unittest assertions with
 `assert` in Hetzner datasource and tests for consistency and readability

# Conflicts:
#	tests/unittests/sources/test_hetzner.py
---
 cloudinit/sources/DataSourceHetzner.py  |  2 +-
 cloudinit/sources/helpers/hetzner.py    |  3 +-
 tests/unittests/sources/test_hetzner.py | 61 ++++++++++++-------------
 3 files changed, 31 insertions(+), 35 deletions(-)

diff --git a/cloudinit/sources/DataSourceHetzner.py b/cloudinit/sources/DataSourceHetzner.py
index c5257922967..09a0eb938d0 100644
--- a/cloudinit/sources/DataSourceHetzner.py
+++ b/cloudinit/sources/DataSourceHetzner.py
@@ -9,7 +9,7 @@
 import logging
 
 import cloudinit.sources.helpers.hetzner as hc_helper
-from cloudinit import dmi, net, sources, util, url_helper
+from cloudinit import dmi, net, sources, url_helper, util
 from cloudinit.event import EventScope, EventType
 from cloudinit.net.dhcp import NoDHCPLeaseError
 from cloudinit.net.ephemeral import EphemeralIPNetwork
diff --git a/cloudinit/sources/helpers/hetzner.py b/cloudinit/sources/helpers/hetzner.py
index 0e22d890342..9ccea9492d1 100644
--- a/cloudinit/sources/helpers/hetzner.py
+++ b/cloudinit/sources/helpers/hetzner.py
@@ -3,9 +3,10 @@
 #
 # This file is part of cloud-init. See LICENSE file for license information.
 
-from cloudinit import url_helper, net
 from typing import Optional
 
+from cloudinit import net, url_helper
+
 
 def skip_retry_on_empty_response(cause: url_helper.UrlError) -> bool:
     """Returns False if cause.code is 204."""
diff --git a/tests/unittests/sources/test_hetzner.py b/tests/unittests/sources/test_hetzner.py
index 84014d5069c..81646feb606 100644
--- a/tests/unittests/sources/test_hetzner.py
+++ b/tests/unittests/sources/test_hetzner.py
@@ -4,9 +4,11 @@
 #
 # This file is part of cloud-init. See LICENSE file for license information.
 
-from cloudinit import helpers, settings, util
+import pytest
+
+from cloudinit import settings, util
 from cloudinit.sources import DataSourceHetzner
-from tests.unittests.helpers import CiTestCase, mock
+from tests.unittests.helpers import mock
 
 METADATA = b"""
 hostname: cloudinit-test
@@ -61,20 +63,17 @@
 """
 
 
-class TestDataSourceHetzner(CiTestCase):
+class TestDataSourceHetzner:
     """
     Test reading the meta-data
     """
 
-    def setUp(self):
-        super(TestDataSourceHetzner, self).setUp()
-        self.tmp = self.tmp_dir()
-
-    def get_ds(self):
+    @pytest.fixture
+    def ds(self, paths, tmp_path):
         distro = mock.MagicMock()
-        distro.get_tmp_exec_path = self.tmp_dir
+        distro.get_tmp_exec_path = str(tmp_path)
         ds = DataSourceHetzner.DataSourceHetzner(
-            settings.CFG_BUILTIN, distro, helpers.Paths({"run_dir": self.tmp})
+            settings.CFG_BUILTIN, distro, paths
         )
         return ds
 
@@ -90,6 +89,7 @@ def test_read_data(
         m_fallback_nic,
         m_net,
         m_dhcp,
+        ds,
     ):
         m_get_hcloud_data.return_value = (
             True,
@@ -113,9 +113,7 @@ def test_read_data(
             }
         ]
 
-        ds = self.get_ds()
-        ret = ds.get_data()
-        self.assertTrue(ret)
+        assert True is ds.get_data()
 
         m_net.assert_called_once_with(
             ds.distro,
@@ -132,42 +130,39 @@ def test_read_data(
             ],
         )
 
-        self.assertTrue(m_readmd.called)
+        assert 0 != m_readmd.call_count
 
-        self.assertEqual(
-            util.load_yaml(METADATA).get("hostname"),
-            ds.get_hostname().hostname,
+        assert (
+            util.load_yaml(METADATA).get("hostname")
+            == ds.get_hostname().hostname
         )
 
-        self.assertEqual(
-            util.load_yaml(METADATA).get("public-keys"),
-            ds.get_public_ssh_keys(),
+        assert (
+            util.load_yaml(METADATA).get("public-keys")
+            == ds.get_public_ssh_keys()
         )
 
-        self.assertEqual(
-            ds.metadata["private-networks"],
-            util.load_yaml(PRIVATE_NETWORKS, allowed=(dict, list)),
+        assert ds.metadata["private-networks"] == util.load_yaml(
+            PRIVATE_NETWORKS, allowed=(dict, list)
         )
-        self.assertIsInstance(ds.get_public_ssh_keys(), list)
-        self.assertEqual(ds.get_userdata_raw(), USERDATA)
-        self.assertEqual(
-            ds.get_vendordata_raw(),
-            util.load_yaml(METADATA).get("vendor_data"),
+        assert isinstance(ds.get_public_ssh_keys(), list)
+        assert ds.get_userdata_raw() == USERDATA
+        assert ds.get_vendordata_raw() == util.load_yaml(METADATA).get(
+            "vendor_data"
         )
 
     @mock.patch("cloudinit.sources.helpers.hetzner.get_metadata")
     @mock.patch("cloudinit.net.find_fallback_nic")
     @mock.patch("cloudinit.sources.DataSourceHetzner.get_hcloud_data")
     def test_not_on_hetzner_returns_false(
-        self, m_get_hcloud_data, m_find_fallback, m_read_md
+        self, m_get_hcloud_data, m_find_fallback, m_read_md, ds
     ):
         """If helper 'get_hcloud_data' returns False,
         return False from get_data."""
         m_get_hcloud_data.return_value = (False, None)
-        ds = self.get_ds()
         ret = ds.get_data()
 
-        self.assertFalse(ret)
+        assert not ret
         # These are a white box attempt to ensure it did not search.
-        m_find_fallback.assert_not_called()
-        m_read_md.assert_not_called()
+        assert 0 == m_find_fallback.call_count
+        assert 0 == m_read_md.call_count

From 8c7fed5628fe2445d67f745847b48eb4f171fded Mon Sep 17 00:00:00 2001
From: Philipp Bender <philipp.bender@hetzner.com>
Date: Tue, 2 Sep 2025 15:35:37 +0000
Subject: [PATCH 09/12] fix(ci): apply suggestions

---
 cloudinit/sources/DataSourceHetzner.py | 34 ++++++++++++++++++--------
 cloudinit/sources/helpers/hetzner.py   |  9 ++++---
 2 files changed, 29 insertions(+), 14 deletions(-)

diff --git a/cloudinit/sources/DataSourceHetzner.py b/cloudinit/sources/DataSourceHetzner.py
index 09a0eb938d0..6d8d77d63ba 100644
--- a/cloudinit/sources/DataSourceHetzner.py
+++ b/cloudinit/sources/DataSourceHetzner.py
@@ -16,12 +16,6 @@
 
 LOG = logging.getLogger(__name__)
 
-BASE_URLS_V1 = [
-    f"http://[fe80::a9fe:a9fe%25{net.find_fallback_nic()}]/hetzner/v1/",
-    "http://169.254.169.254/hetzner/v1/",
-]
-
-
 BUILTIN_DS_CONFIG = {
     "metadata_path": "metadata",
     "metadata_private_networks_path": "metadata/private-networks",
@@ -42,6 +36,13 @@
 """
 
 
+def base_urls_v1():
+    return (
+        f"http://[fe80::a9fe:a9fe%25{net.find_fallback_nic()}]/hetzner/v1/",
+        "http://169.254.169.254/hetzner/v1/",
+    )
+
+
 class DataSourceHetzner(sources.DataSource):
     dsname = "Hetzner"
 
@@ -79,12 +80,25 @@ def __init__(self, sys_cfg, distro, paths):
 
         self.extra_hotplug_udev_rules = EXTRA_HOTPLUG_UDEV_RULES
 
+    def _unpickle(self, ci_pkl_version: int) -> None:
+        super()._unpickle(ci_pkl_version)
+        self.extra_hotplug_udev_rules = EXTRA_HOTPLUG_UDEV_RULES
+        self.wait_retry = self.ds_cfg.get("wait_retry", MD_WAIT_RETRY)
+        self.max_wait = self.ds_cfg.get("max_wait", MD_MAX_WAIT)
+        self.sleep_time = self.ds_cfg.get("sleep_time", MD_SLEEP_TIME)
+        self.metadata_path = self.ds_cfg["metadata_path"]
+        self.metadata_private_networks_path = self.ds_cfg[
+            "metadata_private_networks_path"
+        ]
+        self.userdata_path = self.ds_cfg["userdata_path"]
+
     def _get_data(self):
         (on_hetzner, serial) = get_hcloud_data()
 
         if not on_hetzner:
             return False
 
+        base_urls = base_urls_v1()
         try:
             with EphemeralIPNetwork(
                 self.distro,
@@ -97,13 +111,13 @@ def _get_data(self):
                             url, "metadata/instance-id"
                         )
                     }
-                    for url in BASE_URLS_V1
+                    for url in base_urls
                 ],
             ):
                 url, contents = hc_helper.get_metadata(
                     [
                         url_helper.combine_url(url, self.metadata_path)
-                        for url in BASE_URLS_V1
+                        for url in base_urls
                     ],
                     max_wait=self.max_wait,
                     timeout=self.timeout,
@@ -116,7 +130,7 @@ def _get_data(self):
                         url_helper.combine_url(
                             url, self.metadata_private_networks_path
                         )
-                        for url in BASE_URLS_V1
+                        for url in base_urls
                     ],
                     max_wait=self.max_wait,
                     timeout=self.timeout,
@@ -129,7 +143,7 @@ def _get_data(self):
                 url, ud = hc_helper.get_metadata(
                     [
                         url_helper.combine_url(url, self.userdata_path)
-                        for url in BASE_URLS_V1
+                        for url in base_urls
                     ],
                     max_wait=self.max_wait,
                     timeout=self.timeout,
diff --git a/cloudinit/sources/helpers/hetzner.py b/cloudinit/sources/helpers/hetzner.py
index 9ccea9492d1..ba5bd975246 100644
--- a/cloudinit/sources/helpers/hetzner.py
+++ b/cloudinit/sources/helpers/hetzner.py
@@ -3,7 +3,7 @@
 #
 # This file is part of cloud-init. See LICENSE file for license information.
 
-from typing import Optional
+from typing import Optional, Tuple
 
 from cloudinit import net, url_helper
 
@@ -16,12 +16,10 @@ def skip_retry_on_empty_response(cause: url_helper.UrlError) -> bool:
 def get_metadata(
     urls,
     max_wait=120,
-    sec_between=2,
-    retries=30,
     timeout=2,
     sleep_time=2,
     exception_cb=None,
-) -> tuple[str, bytes]:
+) -> Tuple[Optional[str], bytes]:
     try:
         if not exception_cb:
             # It is ok for userdata to not exist (thats why we are stopping if
@@ -35,10 +33,13 @@ def get_metadata(
             sleep_time=sleep_time,
             exception_cb=exception_cb,
         )
+        if not url:
+            raise RuntimeError("No data received from urls: '%s:", urls)
         return url, contents
     except url_helper.UrlError as e:
         if e.code == 204:
             return e.url, b""
+        raise
 
 
 def get_interface_name_from_mac(mac: str) -> Optional[str]:

From 135ae07137df985d7c30352e31d051713da4fc5f Mon Sep 17 00:00:00 2001
From: Philipp Bender <philipp.bender@hetzner.com>
Date: Tue, 2 Sep 2025 19:00:40 +0000
Subject: [PATCH 10/12] fix(ci): apply suggestions

---
 cloudinit/sources/helpers/hetzner.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/cloudinit/sources/helpers/hetzner.py b/cloudinit/sources/helpers/hetzner.py
index ba5bd975246..99a3712e318 100644
--- a/cloudinit/sources/helpers/hetzner.py
+++ b/cloudinit/sources/helpers/hetzner.py
@@ -34,7 +34,7 @@ def get_metadata(
             exception_cb=exception_cb,
         )
         if not url:
-            raise RuntimeError("No data received from urls: '%s:", urls)
+            raise RuntimeError("No data received from urls: '%s':" % urls)
         return url, contents
     except url_helper.UrlError as e:
         if e.code == 204:

From 3b20582108799321a7f8ece3689a6ec278276cab Mon Sep 17 00:00:00 2001
From: Philipp Bender <philipp.bender@hetzner.com>
Date: Tue, 2 Sep 2025 19:03:50 +0000
Subject: [PATCH 11/12] feat(doc): Add Hetzner to list of supported providers
 for hotplug

---
 doc/module-docs/cc_install_hotplug/data.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/module-docs/cc_install_hotplug/data.yaml b/doc/module-docs/cc_install_hotplug/data.yaml
index 2277c9f274a..abdac913a46 100644
--- a/doc/module-docs/cc_install_hotplug/data.yaml
+++ b/doc/module-docs/cc_install_hotplug/data.yaml
@@ -14,7 +14,7 @@ cc_install_hotplug:
     around this limitation, one can wait until cloud-init has completed
     before hotplugging devices.
 
-    Currently supported datasources: Openstack, EC2
+    Currently supported datasources: Openstack, EC2, Hetzner
   examples:
   - comment: |
       Example 1: Enable hotplug of network devices

From f57e6c26d98727fd53f6db627e6ceafe20cb5692 Mon Sep 17 00:00:00 2001
From: Philipp Bender <philipp.bender@hetzner.com>
Date: Thu, 4 Sep 2025 22:34:28 +0000
Subject: [PATCH 12/12] apply suggestions

---
 cloudinit/sources/DataSourceHetzner.py  | 46 ++++++++++++-------------
 cloudinit/sources/helpers/hetzner.py    | 14 +++-----
 tests/unittests/sources/test_hetzner.py | 10 +++---
 3 files changed, 32 insertions(+), 38 deletions(-)

diff --git a/cloudinit/sources/DataSourceHetzner.py b/cloudinit/sources/DataSourceHetzner.py
index 6d8d77d63ba..2aaba2a5435 100644
--- a/cloudinit/sources/DataSourceHetzner.py
+++ b/cloudinit/sources/DataSourceHetzner.py
@@ -108,7 +108,7 @@ def _get_data(self):
                 connectivity_urls_data=[
                     {
                         "url": url_helper.combine_url(
-                            url, "metadata/instance-id"
+                            url, f"{self.metadata_path}/instance-id"
                         )
                     }
                     for url in base_urls
@@ -206,32 +206,30 @@ def network_config(self):
         if self._network_config != sources.UNSET:
             return self._network_config
 
-        _net_config = self.metadata["network-config"]
-        if not _net_config:
+        net_config = self.metadata["network-config"]
+        if not net_config:
             raise RuntimeError("Unable to get meta-data from server....")
 
-        _private_networks = self.metadata.get("private-networks", [])
-        _private_networks_config = []
-        for _private_network in _private_networks:
-            _private_networks_config.extend(
-                [
-                    {
-                        "type": "physical",
-                        "mac_address": _private_network["mac_address"],
-                        "name": hc_helper.get_interface_name_from_mac(
-                            _private_network["mac_address"]
-                        ),
-                        "subnets": [
-                            {
-                                "ipv4": True,
-                                "type": "dhcp",
-                            }
-                        ],
-                    }
-                ]
+        private_networks = self.metadata.get("private-networks", [])
+        private_networks_config = []
+        for private_network in private_networks:
+            private_networks_config.append(
+                {
+                    "type": "physical",
+                    "mac_address": private_network["mac_address"],
+                    "name": hc_helper.get_interface_name_from_mac(
+                        private_network["mac_address"]
+                    ),
+                    "subnets": [
+                        {
+                            "ipv4": True,
+                            "type": "dhcp",
+                        }
+                    ],
+                }
             )
-        _net_config["config"].extend(_private_networks_config)
-        self._network_config = _net_config
+        net_config["config"].extend(private_networks_config)
+        self._network_config = net_config
         return self._network_config
 
 
diff --git a/cloudinit/sources/helpers/hetzner.py b/cloudinit/sources/helpers/hetzner.py
index 99a3712e318..68abd4dc48d 100644
--- a/cloudinit/sources/helpers/hetzner.py
+++ b/cloudinit/sources/helpers/hetzner.py
@@ -8,8 +8,7 @@
 from cloudinit import net, url_helper
 
 
-def skip_retry_on_empty_response(cause: url_helper.UrlError) -> bool:
-    """Returns False if cause.code is 204."""
+def _skip_retry_on_empty_response(cause: url_helper.UrlError) -> bool:
     return cause.code != 204
 
 
@@ -18,20 +17,17 @@ def get_metadata(
     max_wait=120,
     timeout=2,
     sleep_time=2,
-    exception_cb=None,
 ) -> Tuple[Optional[str], bytes]:
     try:
-        if not exception_cb:
-            # It is ok for userdata to not exist (thats why we are stopping if
-            # HTTP code is 204) and just in that case returning an empty
-            # string.
-            exception_cb = skip_retry_on_empty_response
         url, contents = url_helper.wait_for_url(
             urls=urls,
             max_wait=max_wait,
             timeout=timeout,
             sleep_time=sleep_time,
-            exception_cb=exception_cb,
+            # It is ok for userdata to not exist (that's why we are stopping if
+            # HTTP code is 204) and just in that case returning an empty
+            # string.
+            exception_cb=_skip_retry_on_empty_response,
         )
         if not url:
             raise RuntimeError("No data received from urls: '%s':" % urls)
diff --git a/tests/unittests/sources/test_hetzner.py b/tests/unittests/sources/test_hetzner.py
index 81646feb606..af0a893cd0f 100644
--- a/tests/unittests/sources/test_hetzner.py
+++ b/tests/unittests/sources/test_hetzner.py
@@ -85,7 +85,7 @@ def ds(self, paths, tmp_path):
     def test_read_data(
         self,
         m_get_hcloud_data,
-        m_readmd,
+        m_get_metadata,
         m_fallback_nic,
         m_net,
         m_dhcp,
@@ -97,7 +97,7 @@ def test_read_data(
         )
         # Use side_effect to return values for the three sequential calls to
         # helpers.hetzner.get_metadata: metadata, private-networks, userdata
-        m_readmd.side_effect = [
+        m_get_metadata.side_effect = [
             ("metadata_url", METADATA),
             ("privnets_url", PRIVATE_NETWORKS),
             ("userdata_url", USERDATA),
@@ -130,7 +130,7 @@ def test_read_data(
             ],
         )
 
-        assert 0 != m_readmd.call_count
+        assert 0 != m_get_metadata.call_count
 
         assert (
             util.load_yaml(METADATA).get("hostname")
@@ -155,7 +155,7 @@ def test_read_data(
     @mock.patch("cloudinit.net.find_fallback_nic")
     @mock.patch("cloudinit.sources.DataSourceHetzner.get_hcloud_data")
     def test_not_on_hetzner_returns_false(
-        self, m_get_hcloud_data, m_find_fallback, m_read_md, ds
+        self, m_get_hcloud_data, m_find_fallback, m_get_metadata, ds
     ):
         """If helper 'get_hcloud_data' returns False,
         return False from get_data."""
@@ -165,4 +165,4 @@ def test_not_on_hetzner_returns_false(
         assert not ret
         # These are a white box attempt to ensure it did not search.
         assert 0 == m_find_fallback.call_count
-        assert 0 == m_read_md.call_count
+        assert 0 == m_get_metadata.call_count