Initial hotplug support (#936)

Adds a udev script which will invoke a hotplug hook script on all net
add events. The script will write some udev arguments to a systemd FIFO
socket (to ensure we have only instance of cloud-init running at a
time), which is then read by a new service that calls a new 'cloud-init
devel hotplug-hook' command to handle the new event.

This hotplug-hook command will:
- Fetch the pickled datsource
- Verify that the hotplug event is supported/enabled
- Update the metadata for the datasource
- Ensure the hotplugged device exists within the datasource
- Apply the config change on the datasource metadata
- Bring up the new interface (or apply global network configuration)
- Save the updated metadata back to the pickle cache

Also scattered in some unrelated typing where helpful

1 files changed, 94 insertions, 0 deletions

diff --git a/tests/integration_tests/modules/test_hotplug.py b/tests/integration_tests/modules/test_hotplug.py
new file mode 100644
index 00000000..b683566f
--- /dev/null
+++ b/tests/integration_tests/modules/test_hotplug.py
@@ -0,0 +1,94 @@
+import pytest
+import time
+import yaml
+from collections import namedtuple
+
+from tests.integration_tests.instances import IntegrationInstance
+
+USER_DATA = """\
+#cloud-config
+updates:
+  network:
+    when: ['hotplug']
+"""
+
+ip_addr = namedtuple('ip_addr', 'interface state ip4 ip6')
+
+
+def _wait_till_hotplug_complete(client, expected_runs=1):
+    for _ in range(60):
+        log = client.read_from_file('/var/log/cloud-init.log')
+        if log.count('Exiting hotplug handler') == expected_runs:
+            return log
+        time.sleep(1)
+    raise Exception('Waiting for hotplug handler failed')
+
+
+def _get_ip_addr(client):
+    ips = []
+    lines = client.execute('ip --brief addr').split('\n')
+    for line in lines:
+        attributes = line.split()
+        interface, state = attributes[0], attributes[1]
+        ip4_cidr = attributes[2] if len(attributes) > 2 else None
+        ip6_cidr = attributes[3] if len(attributes) > 3 else None
+        ip4 = ip4_cidr.split('/')[0] if ip4_cidr else None
+        ip6 = ip6_cidr.split('/')[0] if ip6_cidr else None
+        ip = ip_addr(interface, state, ip4, ip6)
+        ips.append(ip)
+    return ips
+
+
+@pytest.mark.openstack
+@pytest.mark.user_data(USER_DATA)
+def test_hotplug_add_remove(client: IntegrationInstance):
+    ips_before = _get_ip_addr(client)
+    log = client.read_from_file('/var/log/cloud-init.log')
+    assert 'Exiting hotplug handler' not in log
+
+    # Add new NIC
+    added_ip = client.instance.add_network_interface()
+    _wait_till_hotplug_complete(client)
+    ips_after_add = _get_ip_addr(client)
+    new_addition = [ip for ip in ips_after_add if ip.ip4 == added_ip][0]
+
+    assert len(ips_after_add) == len(ips_before) + 1
+    assert added_ip not in [ip.ip4 for ip in ips_before]
+    assert added_ip in [ip.ip4 for ip in ips_after_add]
+    assert new_addition.state == 'UP'
+
+    netplan_cfg = client.read_from_file('/etc/netplan/50-cloud-init.yaml')
+    config = yaml.safe_load(netplan_cfg)
+    assert new_addition.interface in config['network']['ethernets']
+
+    # Remove new NIC
+    client.instance.remove_network_interface(added_ip)
+    _wait_till_hotplug_complete(client, expected_runs=2)
+    ips_after_remove = _get_ip_addr(client)
+    assert len(ips_after_remove) == len(ips_before)
+    assert added_ip not in [ip.ip4 for ip in ips_after_remove]
+
+    netplan_cfg = client.read_from_file('/etc/netplan/50-cloud-init.yaml')
+    config = yaml.safe_load(netplan_cfg)
+    assert new_addition.interface not in config['network']['ethernets']
+
+
+@pytest.mark.openstack
+def test_no_hotplug_in_userdata(client: IntegrationInstance):
+    ips_before = _get_ip_addr(client)
+    log = client.read_from_file('/var/log/cloud-init.log')
+    assert 'Exiting hotplug handler' not in log
+
+    # Add new NIC
+    client.instance.add_network_interface()
+    _wait_till_hotplug_complete(client)
+    log = client.read_from_file('/var/log/cloud-init.log')
+    assert 'hotplug not enabled for event of type network' in log
+
+    ips_after_add = _get_ip_addr(client)
+    if len(ips_after_add) == len(ips_before) + 1:
+        # We can see the device, but it should not have been brought up
+        new_ip = [ip for ip in ips_after_add if ip not in ips_before][0]
+        assert new_ip.state == 'DOWN'
+    else:
+        assert len(ips_after_add) == len(ips_before)