net: Ephemeral*Network: add connectivity check via URL

We add a new Optional parameter: connectivity_url
This is used in __enter__ to verify if a connection already exists.
If it does exist, no operations are performed.

2 files changed, 86 insertions, 2 deletions

diff --git a/cloudinit/net/tests/test_dhcp.py b/cloudinit/net/tests/test_dhcp.py
index db25b6f2..cd3e7328 100644
--- a/cloudinit/net/tests/test_dhcp.py
+++ b/cloudinit/net/tests/test_dhcp.py
@@ -1,15 +1,17 @@
 # This file is part of cloud-init. See LICENSE file for license information.
 
+import httpretty
 import os
 import signal
 from textwrap import dedent
 
+import cloudinit.net as net
 from cloudinit.net.dhcp import (
     InvalidDHCPLeaseFileError, maybe_perform_dhcp_discovery,
     parse_dhcp_lease_file, dhcp_discovery, networkd_load_leases)
 from cloudinit.util import ensure_file, write_file
 from cloudinit.tests.helpers import (
-    CiTestCase, mock, populate_dir, wrap_and_call)
+    CiTestCase, HttprettyTestCase, mock, populate_dir, wrap_and_call)
 
 
 class TestParseDHCPLeasesFile(CiTestCase):
@@ -321,3 +323,35 @@ class TestSystemdParseLeases(CiTestCase):
                                     '9': self.lxd_lease})
         self.assertEqual({'1': self.azure_parsed, '9': self.lxd_parsed},
                          networkd_load_leases(self.lease_d))
+
+
+class TestEphemeralDhcpNoNetworkSetup(HttprettyTestCase):
+
+    @mock.patch('cloudinit.net.dhcp.maybe_perform_dhcp_discovery')
+    def test_ephemeral_dhcp_no_network_if_url_connectivity(self, m_dhcp):
+        """No EphemeralDhcp4 network setup when connectivity_url succeeds."""
+        url = 'http://example.org/index.html'
+
+        httpretty.register_uri(httpretty.GET, url)
+        with net.dhcp.EphemeralDHCPv4(connectivity_url=url) as lease:
+            self.assertIsNone(lease)
+        # Ensure that no teardown happens:
+        m_dhcp.assert_not_called()
+
+    @mock.patch('cloudinit.net.dhcp.util.subp')
+    @mock.patch('cloudinit.net.dhcp.maybe_perform_dhcp_discovery')
+    def test_ephemeral_dhcp_setup_network_if_url_connectivity(
+            self, m_dhcp, m_subp):
+        """No EphemeralDhcp4 network setup when connectivity_url succeeds."""
+        url = 'http://example.org/index.html'
+        fake_lease = {
+            'interface': 'eth9', 'fixed-address': '192.168.2.2',
+            'subnet-mask': '255.255.0.0'}
+        m_dhcp.return_value = [fake_lease]
+        m_subp.return_value = ('', '')
+
+        httpretty.register_uri(httpretty.GET, url, body={}, status=404)
+        with net.dhcp.EphemeralDHCPv4(connectivity_url=url) as lease:
+            self.assertEqual(fake_lease, lease)
+        # Ensure that dhcp discovery occurs
+        m_dhcp.called_once_with()
diff --git a/cloudinit/net/tests/test_init.py b/cloudinit/net/tests/test_init.py
index 58e0a591..f55c31e8 100644
--- a/cloudinit/net/tests/test_init.py
+++ b/cloudinit/net/tests/test_init.py
@@ -2,14 +2,16 @@
 
 import copy
 import errno
+import httpretty
 import mock
 import os
+import requests
 import textwrap
 import yaml
 
 import cloudinit.net as net
 from cloudinit.util import ensure_file, write_file, ProcessExecutionError
-from cloudinit.tests.helpers import CiTestCase
+from cloudinit.tests.helpers import CiTestCase, HttprettyTestCase
 
 
 class TestSysDevPath(CiTestCase):
@@ -458,6 +460,22 @@ class TestEphemeralIPV4Network(CiTestCase):
             self.assertEqual(expected_setup_calls, m_subp.call_args_list)
         m_subp.assert_has_calls(expected_teardown_calls)
 
+    @mock.patch('cloudinit.net.readurl')
+    def test_ephemeral_ipv4_no_network_if_url_connectivity(
+            self, m_readurl, m_subp):
+        """No network setup is performed if we can successfully connect to
+        connectivity_url."""
+        params = {
+            'interface': 'eth0', 'ip': '192.168.2.2',
+            'prefix_or_mask': '255.255.255.0', 'broadcast': '192.168.2.255',
+            'connectivity_url': 'http://example.org/index.html'}
+
+        with net.EphemeralIPv4Network(**params):
+            self.assertEqual([mock.call('http://example.org/index.html',
+                                        timeout=5)], m_readurl.call_args_list)
+        # Ensure that no teardown happens:
+        m_subp.assert_has_calls([])
+
     def test_ephemeral_ipv4_network_noop_when_configured(self, m_subp):
         """EphemeralIPv4Network handles exception when address is setup.
 
@@ -619,3 +637,35 @@ class TestApplyNetworkCfgNames(CiTestCase):
     def test_apply_v2_renames_raises_runtime_error_on_unknown_version(self):
         with self.assertRaises(RuntimeError):
             net.apply_network_config_names(yaml.load("version: 3"))
+
+
+class TestHasURLConnectivity(HttprettyTestCase):
+
+    def setUp(self):
+        super(TestHasURLConnectivity, self).setUp()
+        self.url = 'http://fake/'
+        self.kwargs = {'allow_redirects': True, 'timeout': 5.0}
+
+    @mock.patch('cloudinit.net.readurl')
+    def test_url_timeout_on_connectivity_check(self, m_readurl):
+        """A timeout of 5 seconds is provided when reading a url."""
+        self.assertTrue(
+            net.has_url_connectivity(self.url), 'Expected True on url connect')
+
+    def test_true_on_url_connectivity_success(self):
+        httpretty.register_uri(httpretty.GET, self.url)
+        self.assertTrue(
+            net.has_url_connectivity(self.url), 'Expected True on url connect')
+
+    @mock.patch('requests.Session.request')
+    def test_true_on_url_connectivity_timeout(self, m_request):
+        """A timeout raised accessing the url will return False."""
+        m_request.side_effect = requests.Timeout('Fake Connection Timeout')
+        self.assertFalse(
+            net.has_url_connectivity(self.url),
+            'Expected False on url timeout')
+
+    def test_true_on_url_connectivity_failure(self):
+        httpretty.register_uri(httpretty.GET, self.url, body={}, status=404)
+        self.assertFalse(
+            net.has_url_connectivity(self.url), 'Expected False on url fail')