Ability to hot-attach NICs to preprovisioned VMs before reprovisioning (#613)

Adds the ability to run the Azure preprovisioned VMs as NIC-less and
then hot-attach them when assigned for reprovision.

The NIC on the preprovisioned VM is hot-detached as soon as it reports
ready and goes into wait for one or more interfaces to be hot-attached.
Once they are attached, cloud-init gets the expected number of NICs (in
case there are more than one) that will be attached from IMDS and waits
until all of them are attached. After all the NICs are attached,
reprovision proceeds as usual.

1 files changed, 72 insertions, 2 deletions

diff --git a/cloudinit/sources/helpers/tests/test_netlink.py b/cloudinit/sources/helpers/tests/test_netlink.py
index 10760bd6..cafe3961 100644
--- a/cloudinit/sources/helpers/tests/test_netlink.py
+++ b/cloudinit/sources/helpers/tests/test_netlink.py
@@ -9,9 +9,10 @@ import codecs
 from cloudinit.sources.helpers.netlink import (
     NetlinkCreateSocketError, create_bound_netlink_socket, read_netlink_socket,
     read_rta_oper_state, unpack_rta_attr, wait_for_media_disconnect_connect,
+    wait_for_nic_attach_event, wait_for_nic_detach_event,
     OPER_DOWN, OPER_UP, OPER_DORMANT, OPER_LOWERLAYERDOWN, OPER_NOTPRESENT,
-    OPER_TESTING, OPER_UNKNOWN, RTATTR_START_OFFSET, RTM_NEWLINK, RTM_SETLINK,
-    RTM_GETLINK, MAX_SIZE)
+    OPER_TESTING, OPER_UNKNOWN, RTATTR_START_OFFSET, RTM_NEWLINK, RTM_DELLINK,
+    RTM_SETLINK, RTM_GETLINK, MAX_SIZE)
 
 
 def int_to_bytes(i):
@@ -135,6 +136,75 @@ class TestParseNetlinkMessage(CiTestCase):
 
 @mock.patch('cloudinit.sources.helpers.netlink.socket.socket')
 @mock.patch('cloudinit.sources.helpers.netlink.read_netlink_socket')
+class TestNicAttachDetach(CiTestCase):
+    with_logs = True
+
+    def _media_switch_data(self, ifname, msg_type, operstate):
+        '''construct netlink data with specified fields'''
+        if ifname and operstate is not None:
+            data = bytearray(48)
+            bytes = ifname.encode("utf-8")
+            struct.pack_into("HH4sHHc", data, RTATTR_START_OFFSET, 8, 3,
+                             bytes, 5, 16, int_to_bytes(operstate))
+        elif ifname:
+            data = bytearray(40)
+            bytes = ifname.encode("utf-8")
+            struct.pack_into("HH4s", data, RTATTR_START_OFFSET, 8, 3, bytes)
+        elif operstate:
+            data = bytearray(40)
+            struct.pack_into("HHc", data, RTATTR_START_OFFSET, 5, 16,
+                             int_to_bytes(operstate))
+        struct.pack_into("=LHHLL", data, 0, len(data), msg_type, 0, 0, 0)
+        return data
+
+    def test_nic_attached_oper_down(self, m_read_netlink_socket, m_socket):
+        '''Test for a new nic attached'''
+        ifname = "eth0"
+        data_op_down = self._media_switch_data(ifname, RTM_NEWLINK, OPER_DOWN)
+        m_read_netlink_socket.side_effect = [data_op_down]
+        ifread = wait_for_nic_attach_event(m_socket, [])
+        self.assertEqual(m_read_netlink_socket.call_count, 1)
+        self.assertEqual(ifname, ifread)
+
+    def test_nic_attached_oper_up(self, m_read_netlink_socket, m_socket):
+        '''Test for a new nic attached'''
+        ifname = "eth0"
+        data_op_up = self._media_switch_data(ifname, RTM_NEWLINK, OPER_UP)
+        m_read_netlink_socket.side_effect = [data_op_up]
+        ifread = wait_for_nic_attach_event(m_socket, [])
+        self.assertEqual(m_read_netlink_socket.call_count, 1)
+        self.assertEqual(ifname, ifread)
+
+    def test_nic_attach_ignore_existing(self, m_read_netlink_socket, m_socket):
+        '''Test that we read only the interfaces we are interested in.'''
+        data_eth0 = self._media_switch_data("eth0", RTM_NEWLINK, OPER_DOWN)
+        data_eth1 = self._media_switch_data("eth1", RTM_NEWLINK, OPER_DOWN)
+        m_read_netlink_socket.side_effect = [data_eth0, data_eth1]
+        ifread = wait_for_nic_attach_event(m_socket, ["eth0"])
+        self.assertEqual(m_read_netlink_socket.call_count, 2)
+        self.assertEqual("eth1", ifread)
+
+    def test_nic_attach_read_first(self, m_read_netlink_socket, m_socket):
+        '''Test that we read only the interfaces we are interested in.'''
+        data_eth0 = self._media_switch_data("eth0", RTM_NEWLINK, OPER_DOWN)
+        data_eth1 = self._media_switch_data("eth1", RTM_NEWLINK, OPER_DOWN)
+        m_read_netlink_socket.side_effect = [data_eth0, data_eth1]
+        ifread = wait_for_nic_attach_event(m_socket, ["eth1"])
+        self.assertEqual(m_read_netlink_socket.call_count, 1)
+        self.assertEqual("eth0", ifread)
+
+    def test_nic_detached(self, m_read_netlink_socket, m_socket):
+        '''Test for an existing nic detached'''
+        ifname = "eth0"
+        data_op_down = self._media_switch_data(ifname, RTM_DELLINK, OPER_DOWN)
+        m_read_netlink_socket.side_effect = [data_op_down]
+        ifread = wait_for_nic_detach_event(m_socket)
+        self.assertEqual(m_read_netlink_socket.call_count, 1)
+        self.assertEqual(ifname, ifread)
+
+
+@mock.patch('cloudinit.sources.helpers.netlink.socket.socket')
+@mock.patch('cloudinit.sources.helpers.netlink.read_netlink_socket')
 class TestWaitForMediaDisconnectConnect(CiTestCase):
     with_logs = True