From 2a2a5cdec0de0b96d503f9357c1641043574f90a Mon Sep 17 00:00:00 2001

From: Thomas Stringer <thstring@microsoft.com>

Date: Wed, 3 Mar 2021 11:07:43 -0500

Subject: [PATCH 1/7] Add flexibility to IMDS api-version (#793)

RH-Author: Eduardo Otubo <otubo@redhat.com>

RH-MergeRequest: 45: Add support for userdata on Azure from IMDS

RH-Commit: [1/7] 9aa42581c4ff175fb6f8f4a78d94cac9c9971062

RH-Bugzilla: 2023940

RH-Acked-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>

RH-Acked-by: Mohamed Gamal Morsy <mmorsy@redhat.com>

Add flexibility to IMDS api-version by having both a desired IMDS

api-version and a minimum api-version. The desired api-version will

be used first, and if that fails it will fall back to the minimum

api-version.

---

 cloudinit/sources/DataSourceAzure.py          | 113 ++++++++++++++----

 tests/unittests/test_datasource/test_azure.py |  42 ++++++-

 2 files changed, 129 insertions(+), 26 deletions(-)

diff --git a/cloudinit/sources/DataSourceAzure.py b/cloudinit/sources/DataSourceAzure.py

index 553b5a7e..de1452ce 100755

--- a/cloudinit/sources/DataSourceAzure.py

+++ b/cloudinit/sources/DataSourceAzure.py

@@ -78,17 +78,15 @@ AGENT_SEED_DIR = '/var/lib/waagent'

 # In the event where the IMDS primary server is not

 # available, it takes 1s to fallback to the secondary one

 IMDS_TIMEOUT_IN_SECONDS = 2

-IMDS_URL = "http://169.254.169.254/metadata/"

-IMDS_VER = "2019-06-01"

-IMDS_VER_PARAM = "api-version={}".format(IMDS_VER)

+IMDS_URL = "http://169.254.169.254/metadata"

+IMDS_VER_MIN = "2019-06-01"

+IMDS_VER_WANT = "2020-09-01"

 class metadata_type(Enum):

-    compute = "{}instance?{}".format(IMDS_URL, IMDS_VER_PARAM)

-    network = "{}instance/network?{}".format(IMDS_URL,

-                                             IMDS_VER_PARAM)

-    reprovisiondata = "{}reprovisiondata?{}".format(IMDS_URL,

-                                                    IMDS_VER_PARAM)

+    compute = "{}/instance".format(IMDS_URL)

+    network = "{}/instance/network".format(IMDS_URL)

+    reprovisiondata = "{}/reprovisiondata".format(IMDS_URL)

 PLATFORM_ENTROPY_SOURCE = "/sys/firmware/acpi/tables/OEM0"

@@ -349,6 +347,8 @@ class DataSourceAzure(sources.DataSource):

         self.update_events['network'].add(EventType.BOOT)

         self._ephemeral_dhcp_ctx = None

+        self.failed_desired_api_version = False

+

     def __str__(self):

         root = sources.DataSource.__str__(self)

         return "%s [seed=%s]" % (root, self.seed)

@@ -520,8 +520,10 @@ class DataSourceAzure(sources.DataSource):

                     self._wait_for_all_nics_ready()

                 ret = self._reprovision()

-            imds_md = get_metadata_from_imds(

-                self.fallback_interface, retries=10)

+            imds_md = self.get_imds_data_with_api_fallback(

+                self.fallback_interface,

+                retries=10

+            )

             (md, userdata_raw, cfg, files) = ret

             self.seed = cdev

             crawled_data.update({

@@ -652,6 +654,57 @@ class DataSourceAzure(sources.DataSource):

             self.ds_cfg['data_dir'], crawled_data['files'], dirmode=0o700)

         return True

+    @azure_ds_telemetry_reporter

+    def get_imds_data_with_api_fallback(

+            self,

+            fallback_nic,

+            retries,

+            md_type=metadata_type.compute):

+        """

+        Wrapper for get_metadata_from_imds so that we can have flexibility

+        in which IMDS api-version we use. If a particular instance of IMDS

+        does not have the api version that is desired, we want to make

+        this fault tolerant and fall back to a good known minimum api

+        version.

+        """

+

+        if not self.failed_desired_api_version:

+            for _ in range(retries):

+                try:

+                    LOG.info(

+                        "Attempting IMDS api-version: %s",

+                        IMDS_VER_WANT

+                    )

+                    return get_metadata_from_imds(

+                        fallback_nic=fallback_nic,

+                        retries=0,

+                        md_type=md_type,

+                        api_version=IMDS_VER_WANT

+                    )

+                except UrlError as err:

+                    LOG.info(

+                        "UrlError with IMDS api-version: %s",

+                        IMDS_VER_WANT

+                    )

+                    if err.code == 400:

+                        log_msg = "Fall back to IMDS api-version: {}".format(

+                            IMDS_VER_MIN

+                        )

+                        report_diagnostic_event(

+                            log_msg,

+                            logger_func=LOG.info

+                        )

+                        self.failed_desired_api_version = True

+                        break

+

+        LOG.info("Using IMDS api-version: %s", IMDS_VER_MIN)

+        return get_metadata_from_imds(

+            fallback_nic=fallback_nic,

+            retries=retries,

+            md_type=md_type,

+            api_version=IMDS_VER_MIN

+        )

+

     def device_name_to_device(self, name):

         return self.ds_cfg['disk_aliases'].get(name)

@@ -880,10 +933,11 @@ class DataSourceAzure(sources.DataSource):

         # primary nic is being attached first helps here. Otherwise each nic

         # could add several seconds of delay.

         try:

-            imds_md = get_metadata_from_imds(

+            imds_md = self.get_imds_data_with_api_fallback(

                 ifname,

                 5,

-                metadata_type.network)

+                metadata_type.network

+            )

         except Exception as e:

             LOG.warning(

                 "Failed to get network metadata using nic %s. Attempt to "

@@ -1017,7 +1071,10 @@ class DataSourceAzure(sources.DataSource):

     def _poll_imds(self):

         """Poll IMDS for the new provisioning data until we get a valid

         response. Then return the returned JSON object."""

-        url = metadata_type.reprovisiondata.value

+        url = "{}?api-version={}".format(

+            metadata_type.reprovisiondata.value,

+            IMDS_VER_MIN

+        )

         headers = {"Metadata": "true"}

         nl_sock = None

         report_ready = bool(not os.path.isfile(REPORTED_READY_MARKER_FILE))

@@ -2059,7 +2116,8 @@ def _generate_network_config_from_fallback_config() -> dict:

 @azure_ds_telemetry_reporter

 def get_metadata_from_imds(fallback_nic,

                            retries,

-                           md_type=metadata_type.compute):

+                           md_type=metadata_type.compute,

+                           api_version=IMDS_VER_MIN):

     """Query Azure's instance metadata service, returning a dictionary.

     If network is not up, setup ephemeral dhcp on fallback_nic to talk to the

@@ -2069,13 +2127,16 @@ def get_metadata_from_imds(fallback_nic,

     @param fallback_nic: String. The name of the nic which requires active

         network in order to query IMDS.

     @param retries: The number of retries of the IMDS_URL.

+    @param md_type: Metadata type for IMDS request.

+    @param api_version: IMDS api-version to use in the request.

     @return: A dict of instance metadata containing compute and network

         info.

     """

     kwargs = {'logfunc': LOG.debug,

               'msg': 'Crawl of Azure Instance Metadata Service (IMDS)',

-              'func': _get_metadata_from_imds, 'args': (retries, md_type,)}

+              'func': _get_metadata_from_imds,

+              'args': (retries, md_type, api_version,)}

     if net.is_up(fallback_nic):

         return util.log_time(**kwargs)

     else:

@@ -2091,20 +2152,26 @@ def get_metadata_from_imds(fallback_nic,

 @azure_ds_telemetry_reporter

-def _get_metadata_from_imds(retries, md_type=metadata_type.compute):

-

-    url = md_type.value

+def _get_metadata_from_imds(

+        retries,

+        md_type=metadata_type.compute,

+        api_version=IMDS_VER_MIN):

+    url = "{}?api-version={}".format(md_type.value, api_version)

     headers = {"Metadata": "true"}

     try:

         response = readurl(

             url, timeout=IMDS_TIMEOUT_IN_SECONDS, headers=headers,

             retries=retries, exception_cb=retry_on_url_exc)

     except Exception as e:

-        report_diagnostic_event(

-            'Ignoring IMDS instance metadata. '

-            'Get metadata from IMDS failed: %s' % e,

-            logger_func=LOG.warning)

-        return {}

+        # pylint:disable=no-member

+        if isinstance(e, UrlError) and e.code == 400:

+            raise

+        else:

+            report_diagnostic_event(

+                'Ignoring IMDS instance metadata. '

+                'Get metadata from IMDS failed: %s' % e,

+                logger_func=LOG.warning)

+            return {}

     try:

         from json.decoder import JSONDecodeError

         json_decode_error = JSONDecodeError

diff --git a/tests/unittests/test_datasource/test_azure.py b/tests/unittests/test_datasource/test_azure.py

index f597c723..dedebeb1 100644

--- a/tests/unittests/test_datasource/test_azure.py

+++ b/tests/unittests/test_datasource/test_azure.py

@@ -408,7 +408,9 @@ class TestGetMetadataFromIMDS(HttprettyTestCase):

     def setUp(self):

         super(TestGetMetadataFromIMDS, self).setUp()

-        self.network_md_url = dsaz.IMDS_URL + "instance?api-version=2019-06-01"

+        self.network_md_url = "{}/instance?api-version=2019-06-01".format(

+            dsaz.IMDS_URL

+        )

     @mock.patch(MOCKPATH + 'readurl')

     @mock.patch(MOCKPATH + 'EphemeralDHCPv4', autospec=True)

@@ -518,7 +520,7 @@ class TestGetMetadataFromIMDS(HttprettyTestCase):

         """Return empty dict when IMDS network metadata is absent."""

         httpretty.register_uri(

             httpretty.GET,

-            dsaz.IMDS_URL + 'instance?api-version=2017-12-01',

+            dsaz.IMDS_URL + '/instance?api-version=2017-12-01',

             body={}, status=404)

         m_net_is_up.return_value = True  # skips dhcp

@@ -1877,6 +1879,40 @@ scbus-1 on xpt0 bus 0

         ssh_keys = dsrc.get_public_ssh_keys()

         self.assertEqual(ssh_keys, ['key2'])

+    @mock.patch(MOCKPATH + 'get_metadata_from_imds')

+    def test_imds_api_version_wanted_nonexistent(

+            self,

+            m_get_metadata_from_imds):

+        def get_metadata_from_imds_side_eff(*args, **kwargs):

+            if kwargs['api_version'] == dsaz.IMDS_VER_WANT:

+                raise url_helper.UrlError("No IMDS version", code=400)

+            return NETWORK_METADATA

+        m_get_metadata_from_imds.side_effect = get_metadata_from_imds_side_eff

+        sys_cfg = {'datasource': {'Azure': {'apply_network_config': True}}}

+        odata = {'HostName': "myhost", 'UserName': "myuser"}

+        data = {

+            'ovfcontent': construct_valid_ovf_env(data=odata),

+            'sys_cfg': sys_cfg

+        }

+        dsrc = self._get_ds(data)

+        dsrc.get_data()

+        self.assertIsNotNone(dsrc.metadata)

+        self.assertTrue(dsrc.failed_desired_api_version)

+

+    @mock.patch(

+        MOCKPATH + 'get_metadata_from_imds', return_value=NETWORK_METADATA)

+    def test_imds_api_version_wanted_exists(self, m_get_metadata_from_imds):

+        sys_cfg = {'datasource': {'Azure': {'apply_network_config': True}}}

+        odata = {'HostName': "myhost", 'UserName': "myuser"}

+        data = {

+            'ovfcontent': construct_valid_ovf_env(data=odata),

+            'sys_cfg': sys_cfg

+        }

+        dsrc = self._get_ds(data)

+        dsrc.get_data()

+        self.assertIsNotNone(dsrc.metadata)

+        self.assertFalse(dsrc.failed_desired_api_version)

+

 class TestAzureBounce(CiTestCase):

@@ -2657,7 +2693,7 @@ class TestPreprovisioningHotAttachNics(CiTestCase):

     @mock.patch(MOCKPATH + 'DataSourceAzure.wait_for_link_up')

     @mock.patch('cloudinit.sources.helpers.netlink.wait_for_nic_attach_event')

     @mock.patch('cloudinit.sources.net.find_fallback_nic')

-    @mock.patch(MOCKPATH + 'get_metadata_from_imds')

+    @mock.patch(MOCKPATH + 'DataSourceAzure.get_imds_data_with_api_fallback')

     @mock.patch(MOCKPATH + 'EphemeralDHCPv4')

     @mock.patch(MOCKPATH + 'DataSourceAzure._wait_for_nic_detach')

     @mock.patch('os.path.isfile')

-- 

2.27.0