networking: refactor wait_for_physdevs from cloudinit.net (#466)

* Refactor `cloudinit.net.wait_for_physdevs` to `cloudinit.distros.networking.Networking.wait_for_physdevs`
* Split the Linux-specific `udevadm_settle` call out to a separate abstract `Networking.settle` method; implement it on `LinuxNetworking` and add a `NotImplementedError` implementation to `BSDNetworking`
* Modify `wait_for_physdevs`s one callsite to use the new location

LP: #1884626

1 files changed, 151 insertions, 1 deletions

diff --git a/cloudinit/distros/tests/test_networking.py b/cloudinit/distros/tests/test_networking.py
index 2acb12f4..b9a63842 100644
--- a/cloudinit/distros/tests/test_networking.py
+++ b/cloudinit/distros/tests/test_networking.py
@@ -2,7 +2,39 @@ from unittest import mock
 
 import pytest
 
-from cloudinit.distros.networking import BSDNetworking, LinuxNetworking
+from cloudinit import net
+from cloudinit.distros.networking import (
+    BSDNetworking,
+    LinuxNetworking,
+    Networking,
+)
+
+# See https://docs.pytest.org/en/stable/example
+# /parametrize.html#parametrizing-conditional-raising
+from contextlib import ExitStack as does_not_raise
+
+
+@pytest.yield_fixture
+def generic_networking_cls():
+    """Returns a direct Networking subclass which errors on /sys usage.
+
+    This enables the direct testing of functionality only present on the
+    ``Networking`` super-class, and provides a check on accidentally using /sys
+    in that context.
+    """
+
+    class TestNetworking(Networking):
+        def is_physical(self, *args, **kwargs):
+            raise NotImplementedError
+
+        def settle(self, *args, **kwargs):
+            raise NotImplementedError
+
+    error = AssertionError("Unexpectedly used /sys in generic networking code")
+    with mock.patch(
+        "cloudinit.net.get_sys_class_path", side_effect=error,
+    ):
+        yield TestNetworking
 
 
 @pytest.yield_fixture
@@ -40,3 +72,121 @@ class TestLinuxNetworkingIsPhysical:
         device_dir.join("device").write("")
 
         assert LinuxNetworking().is_physical(devname)
+
+
+class TestBSDNetworkingSettle:
+    def test_settle_doesnt_error(self):
+        # This also implicitly tests that it doesn't use subp.subp
+        BSDNetworking().settle()
+
+
+@pytest.mark.usefixtures("sys_class_net")
+@mock.patch("cloudinit.distros.networking.util.udevadm_settle", autospec=True)
+class TestLinuxNetworkingSettle:
+    def test_no_arguments(self, m_udevadm_settle):
+        LinuxNetworking().settle()
+
+        assert [mock.call(exists=None)] == m_udevadm_settle.call_args_list
+
+    def test_exists_argument(self, m_udevadm_settle):
+        LinuxNetworking().settle(exists="ens3")
+
+        expected_path = net.sys_dev_path("ens3")
+        assert [
+            mock.call(exists=expected_path)
+        ] == m_udevadm_settle.call_args_list
+
+
+class TestNetworkingWaitForPhysDevs:
+    @pytest.fixture
+    def wait_for_physdevs_netcfg(self):
+        """This config is shared across all the tests in this class."""
+
+        def ethernet(mac, name, driver=None, device_id=None):
+            v2_cfg = {"set-name": name, "match": {"macaddress": mac}}
+            if driver:
+                v2_cfg["match"].update({"driver": driver})
+            if device_id:
+                v2_cfg["match"].update({"device_id": device_id})
+
+            return v2_cfg
+
+        physdevs = [
+            ["aa:bb:cc:dd:ee:ff", "eth0", "virtio", "0x1000"],
+            ["00:11:22:33:44:55", "ens3", "e1000", "0x1643"],
+        ]
+        netcfg = {
+            "version": 2,
+            "ethernets": {args[1]: ethernet(*args) for args in physdevs},
+        }
+        return netcfg
+
+    def test_skips_settle_if_all_present(
+        self, generic_networking_cls, wait_for_physdevs_netcfg,
+    ):
+        networking = generic_networking_cls()
+        with mock.patch.object(
+            networking, "get_interfaces_by_mac"
+        ) as m_get_interfaces_by_mac:
+            m_get_interfaces_by_mac.side_effect = iter(
+                [{"aa:bb:cc:dd:ee:ff": "eth0", "00:11:22:33:44:55": "ens3"}]
+            )
+            with mock.patch.object(
+                networking, "settle", autospec=True
+            ) as m_settle:
+                networking.wait_for_physdevs(wait_for_physdevs_netcfg)
+            assert 0 == m_settle.call_count
+
+    def test_calls_udev_settle_on_missing(
+        self, generic_networking_cls, wait_for_physdevs_netcfg,
+    ):
+        networking = generic_networking_cls()
+        with mock.patch.object(
+            networking, "get_interfaces_by_mac"
+        ) as m_get_interfaces_by_mac:
+            m_get_interfaces_by_mac.side_effect = iter(
+                [
+                    {
+                        "aa:bb:cc:dd:ee:ff": "eth0"
+                    },  # first call ens3 is missing
+                    {
+                        "aa:bb:cc:dd:ee:ff": "eth0",
+                        "00:11:22:33:44:55": "ens3",
+                    },  # second call has both
+                ]
+            )
+            with mock.patch.object(
+                networking, "settle", autospec=True
+            ) as m_settle:
+                networking.wait_for_physdevs(wait_for_physdevs_netcfg)
+            m_settle.assert_called_with(exists="ens3")
+
+    @pytest.mark.parametrize(
+        "strict,expectation",
+        [(True, pytest.raises(RuntimeError)), (False, does_not_raise())],
+    )
+    def test_retrying_and_strict_behaviour(
+        self,
+        strict,
+        expectation,
+        generic_networking_cls,
+        wait_for_physdevs_netcfg,
+    ):
+        networking = generic_networking_cls()
+        with mock.patch.object(
+            networking, "get_interfaces_by_mac"
+        ) as m_get_interfaces_by_mac:
+            m_get_interfaces_by_mac.return_value = {}
+
+            with mock.patch.object(
+                networking, "settle", autospec=True
+            ) as m_settle:
+                with expectation:
+                    networking.wait_for_physdevs(
+                        wait_for_physdevs_netcfg, strict=strict
+                    )
+
+        assert (
+            5 * len(wait_for_physdevs_netcfg["ethernets"])
+            == m_settle.call_count
+        )