Kevin Veen-Birkenbach
499e61346d
/sys/class/net/<if> is always a symlink into /sys/devices; in nested containers (sysbox runtime) that target is not visible, so the link is dead. iface_exists() used Path.exists(), which follows the link and therefore tested the visibility of the target instead of the existence of the interface. detect_egress_iface() discarded every interface it had correctly read from the routing table, so automtu aborted with "Could not detect egress interface" and rc=2 even though `ip -4 route show default` and `ip link show dev eth0` both worked. The documented escape hatch --egress-if was equally dead, because core.py validates it through the same call. Chosen fix: os.path.lexists() rather than probing netlink for existence. It asks the right question -- "is there an entry named <if>" -- and costs no subprocess on a healthy host. Netlink (`ip link show`) is only the fallback for when /sys/class/net itself is unavailable, so sysfs stays the preferred path everywhere. read_iface_mtu() gains the same cascade: sysfs first, MTU parsed from `ip link show dev <if>` when the sysfs path is unreadable, RuntimeError naming both sources when neither answers - no silent default. core.py turns that into an error line plus rc=3 instead of a traceback. list_ifaces() had the same defect (is_dir() on a dead symlink) and would have left Docker bridge detection blind in the same environments. Regression tests build a /sys replacement whose class/net/eth0 points at a missing target and mock the ip command: they fail if lexists becomes exists again, if the MTU fallback is removed, or if the symlink filter is dropped. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
251 lines
8.4 KiB
Python
251 lines
8.4 KiB
Python
import io
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import pathlib
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import tempfile
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import unittest
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from contextlib import redirect_stdout
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from types import SimpleNamespace
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from unittest.mock import patch
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from automtu import net
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from automtu.core import run_automtu
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def _args(**over) -> SimpleNamespace:
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base = {
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"dry_run": True,
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"egress_if": None,
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"prefer_wg_egress": False,
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"force_egress_mtu": None,
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"pmtu_target": None,
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"auto_pmtu_from_wg": False,
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"pmtu_min_payload": 1200,
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"pmtu_max_payload": 1472,
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"pmtu_timeout": 1.0,
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"pmtu_policy": "min",
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"apply_egress_mtu": False,
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"apply_wg_mtu": False,
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"apply_docker_mtu": False,
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"apply_all": False,
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"docker_if": None,
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"docker_no_user_bridges": False,
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"wg_if": "wg0",
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"wg_overhead": 80,
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"wg_min": 1280,
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"set_wg_mtu": None,
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"persist": None,
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"uninstall": False,
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"print_mtu": None,
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"print_json": False,
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}
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base.update(over)
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return SimpleNamespace(**base)
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class TestCore(unittest.TestCase):
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def test_run_automtu_happy_path_all_mocked(self) -> None:
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args = SimpleNamespace(
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dry_run=True,
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egress_if=None,
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prefer_wg_egress=False,
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force_egress_mtu=None,
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pmtu_target=["1.1.1.1,8.8.8.8"],
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auto_pmtu_from_wg=False,
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pmtu_min_payload=1200,
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pmtu_max_payload=1472,
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pmtu_timeout=1.0,
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pmtu_policy="min",
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apply_egress_mtu=True,
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apply_wg_mtu=True,
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apply_docker_mtu=False,
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apply_all=False,
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docker_if=None,
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docker_no_user_bridges=False,
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wg_if="wg0",
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wg_overhead=80,
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wg_min=1280,
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set_wg_mtu=None,
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persist=None,
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uninstall=False,
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print_mtu=None,
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print_json=False,
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)
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# PMTU probes: 1452 and 1500 -> min policy => 1452, effective=min(base(1500),1452)=1452
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# wg_mtu = 1452-80 = 1372
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with (
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patch("automtu.core.require_root", return_value=None),
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patch("automtu.core.detect_egress_iface", return_value="eth0"),
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patch("automtu.core.iface_exists", return_value=True),
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patch("automtu.core.read_iface_mtu", return_value=1500),
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patch("automtu.core.probe_pmtu", side_effect=[1452, 1500]),
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patch("automtu.core.set_iface_mtu") as mock_set,
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patch("automtu.core.wg_is_active", return_value=False),
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patch("automtu.core.wg_peer_endpoints", return_value=[]),
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patch("automtu.core.default_route_uses_iface", return_value=False),
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patch("automtu.core.detect_docker_ifaces", return_value=[]),
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):
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buf = io.StringIO()
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with redirect_stdout(buf):
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rc = run_automtu(args)
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self.assertEqual(rc, 0)
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s = buf.getvalue()
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self.assertIn("Detected egress interface: eth0", s)
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self.assertIn("Egress base MTU: 1500", s)
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self.assertIn("Selected Path MTU (policy=min): 1452", s)
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self.assertIn("Computed wg0 MTU: 1372", s)
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mock_set.assert_any_call("eth0", 1452, True)
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mock_set.assert_any_call("wg0", 1372, True)
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def test_run_automtu_apply_all_includes_docker_bridge(self) -> None:
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args = SimpleNamespace(
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dry_run=True,
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egress_if="eth0",
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prefer_wg_egress=False,
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force_egress_mtu=None,
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pmtu_target=None,
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auto_pmtu_from_wg=False,
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pmtu_min_payload=1200,
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pmtu_max_payload=1472,
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pmtu_timeout=1.0,
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pmtu_policy="min",
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apply_egress_mtu=False,
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apply_wg_mtu=False,
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apply_docker_mtu=False,
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apply_all=True, # expands in core()
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docker_if=None,
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docker_no_user_bridges=False,
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wg_if="wg0",
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wg_overhead=80,
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wg_min=1280,
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set_wg_mtu=None,
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persist=None,
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uninstall=False,
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print_mtu=None,
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print_json=False,
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)
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with (
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patch("automtu.core.require_root", return_value=None),
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patch(
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"automtu.core.iface_exists",
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side_effect=lambda name: name in {"eth0", "wg0", "docker0", "br-abc"},
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),
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patch("automtu.core.read_iface_mtu", return_value=1500),
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patch("automtu.core.set_iface_mtu") as mock_set,
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patch("automtu.core.wg_is_active", return_value=True),
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patch(
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"automtu.core.detect_docker_ifaces", return_value=["docker0", "br-abc"]
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),
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):
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buf = io.StringIO()
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with redirect_stdout(buf):
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rc = run_automtu(args)
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self.assertEqual(rc, 0)
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# egress applied
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mock_set.assert_any_call("eth0", 1500, True)
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# wg applied (1500-80=1420)
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mock_set.assert_any_call("wg0", 1420, True)
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# docker applied
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mock_set.assert_any_call("docker0", 1500, True)
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mock_set.assert_any_call("br-abc", 1500, True)
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def test_run_automtu_does_not_apply_wg_without_flag(self) -> None:
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args = SimpleNamespace(
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dry_run=True,
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egress_if="eth0",
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prefer_wg_egress=False,
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force_egress_mtu=None,
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pmtu_target=None,
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auto_pmtu_from_wg=False,
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pmtu_min_payload=1200,
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pmtu_max_payload=1472,
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pmtu_timeout=1.0,
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pmtu_policy="min",
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apply_egress_mtu=False,
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apply_wg_mtu=False,
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apply_docker_mtu=False,
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apply_all=False,
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docker_if=None,
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docker_no_user_bridges=False,
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wg_if="wg0",
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wg_overhead=80,
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wg_min=1280,
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set_wg_mtu=None,
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persist=None,
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uninstall=False,
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print_mtu=None,
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print_json=False,
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)
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with (
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patch("automtu.core.require_root", return_value=None),
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patch("automtu.core.iface_exists", return_value=True),
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patch("automtu.core.read_iface_mtu", return_value=1500),
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patch("automtu.core.set_iface_mtu") as mock_set,
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patch("automtu.core.detect_docker_ifaces", return_value=[]),
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):
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buf = io.StringIO()
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with redirect_stdout(buf):
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rc = run_automtu(args)
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self.assertEqual(rc, 0)
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mock_set.assert_not_called()
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class TestCoreInSysboxContainer(unittest.TestCase):
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"""Container with dead /sys/class/net symlinks: routing and ip link work."""
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def setUp(self) -> None:
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tmp = tempfile.TemporaryDirectory()
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self.addCleanup(tmp.cleanup)
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root = pathlib.Path(tmp.name)
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self.netdir = root / "class" / "net"
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self.netdir.mkdir(parents=True)
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for name in ("eth0", "lo"):
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(self.netdir / name).symlink_to(root / "devices" / "virtual" / "net" / name)
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@staticmethod
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def _fake_run(cmd: list[str]) -> str:
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if cmd[:5] == ["ip", "-4", "route", "show", "default"]:
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return "default via 172.28.0.1 dev eth0"
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if cmd[:3] == ["ip", "link", "show"] and cmd[-1] == "eth0":
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return (
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"2: eth0@if5: <BROADCAST,MULTICAST,UP> mtu 1450 qdisc noqueue state UP"
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)
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return ""
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def test_print_mtu_effective_yields_number_and_rc0(self) -> None:
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with (
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patch.object(net, "SYSFS_NET", self.netdir),
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patch.object(net, "_run", side_effect=self._fake_run),
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patch("automtu.core.probe_pmtu", return_value=1400),
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):
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buf = io.StringIO()
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with redirect_stdout(buf):
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rc = run_automtu(_args(pmtu_target=["1.1.1.1"], print_mtu="effective"))
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self.assertEqual(rc, 0)
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self.assertEqual(int(buf.getvalue().strip()), 1400)
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def test_explicit_egress_if_is_accepted(self) -> None:
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with (
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patch.object(net, "SYSFS_NET", self.netdir),
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patch.object(net, "_run", side_effect=self._fake_run),
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):
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buf = io.StringIO()
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with redirect_stdout(buf):
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rc = run_automtu(_args(egress_if="eth0", print_mtu="egress"))
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self.assertEqual(rc, 0)
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self.assertEqual(int(buf.getvalue().strip()), 1450)
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if __name__ == "__main__":
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unittest.main(verbosity=2)
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