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fix: connection errors on VM actions name the host only to administrators

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When a VM action failed because its host could not be reached (the
connection could not be opened, or it dropped during the call), the
error page showed libvirt's connection error to any user: it names the
host and how it is reached, e.g. "ssh: connect to host 10.x port 22".
The lists and the VM page already keep that to administrators.

- Opening a connection now fails with ConnectionFailed (a subclass of
  OperationError). A dropped connection is recognized by its error
  domain and code (RPC/remote/SSH layer with a transport code, measured:
  a keepalive timeout is VIR_FROM_RPC/VIR_ERR_INTERNAL_ERROR); an
  operation the daemon does not support (VIR_ERR_NO_SUPPORT) is not
  treated as one.
- ExceptionMiddleware (pages and API) and the views that report the
  error themselves (snapshot, revert, disk deletion, clone) show it to
  superusers and view_instances users, and to everyone else "The host
  of this virtual machine cannot be reached right now." Errors of the
  operation itself ("domain is not running") are shown as before.

Checked on the test setup: powering on a VM of an unreachable compute
shows the owner the generic text and the administrator the error. The
tests fail on the previous code.
This commit is contained in:
catborise 2026-10-06 10:08:48 +03:00
parent 9c3a7cdbec
commit 802e90c79f
5 changed files with 133 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

9
instances/views.py
View file

@ -37,6 +37,7 @@ from libvirt import (VIR_DOMAIN_UNDEFINE_KEEP_NVRAM,
VIR_DOMAIN_RUNNING,
libvirtError)
from logs.views import addlogmsg
from webvirtcloud.middleware import error_text
from vrtManager import util
from vrtManager.create import wvmCreate
from vrtManager.instance import wvmInstances
@ -622,7 +623,7 @@ def destroy(request, pk):
try:
proxy.get_volume_by_path(path).delete(0)
except libvirtError as err:
messages.error(request, _("Disk %(path)s was not deleted: %(err)s") % {"path": path, "err": err})
messages.error(request, _("Disk %(path)s was not deleted: %(err)s") % {"path": path, "err": error_text(request, err)})
for path in shared:
messages.warning(request, _("Disk %(path)s is used by another VM and was kept") % {"path": path})
addlogmsg(
@ -1265,7 +1266,7 @@ def snapshot(request, pk):
instance.proxy.create_snapshot(name, desc)
except libvirtError as err:
# e.g. UEFI firmware whose NVRAM format does not allow internal snapshots
messages.error(request, _("Snapshot was not created: %(err)s") % {"err": err})
messages.error(request, _("Snapshot was not created: %(err)s") % {"err": error_text(request, err)})
else:
msg = _("Create snapshot: %(snap)s") % {"snap": name}
addlogmsg(request.user.username, instance.compute.name, instance.name, msg)
@ -1303,7 +1304,7 @@ def revert_snapshot(request, pk):
try:
instance.proxy.snapshot_revert(snap_name)
except libvirtError as err:
messages.error(request, _("Snapshot was not reverted: %(err)s") % {"err": err})
messages.error(request, _("Snapshot was not reverted: %(err)s") % {"err": error_text(request, err)})
return _back(request, pk, "managesnapshot")
msg = _("Successful revert snapshot: ")
msg += snap_name
@ -1882,7 +1883,7 @@ def clone(request, pk):
return redirect(reverse("instances:instance", args=[new_instance.id]))
except (libvirtError, ValueError, OSError) as e: # OSError includes a lock timeout
messages.error(request, e)
messages.error(request, error_text(request, e))
return get_safe_redirect(request, default=reverse("instances:instance", args=[pk]))

2
vrtManager/connection.py
View file

@ -342,7 +342,7 @@ class wvmConnectionManager(object):
return connection.connection
else:
# raise libvirt error
raise util.OperationError(connection.last_error)
raise util.ConnectionFailed(connection.last_error)
def host_is_up(self, conn_type, hostname, timeout=1):
"""True if the libvirt endpoint of hostname accepts a TCP (or Unix

5
vrtManager/util.py
View file

@ -22,6 +22,11 @@ class OperationError(libvirt.libvirtError):
self.err = None
class ConnectionFailed(OperationError):
"""The host could not be connected to; the message may name it and how it
is reached."""
def is_kvm_available(xml):
kvm_domains = get_xml_path(xml, "//domain/@type='kvm'")
return kvm_domains > 0

40
webvirtcloud/middleware.py
View file

@ -2,9 +2,45 @@ from django.contrib import messages
from django.http import JsonResponse
from django.shortcuts import render
from django.utils.translation import gettext_lazy as _
import libvirt
from libvirt import libvirtError
from vrtManager.util import ConnectionFailed
API_PREFIX = "/api/"
# errors of the connection to the host, not of the operation: both the
# domain and the code must match (a daemon that lacks a procedure answers
# VIR_FROM_RPC / VIR_ERR_NO_SUPPORT, which the user should see)
TRANSPORT_ERROR_DOMAINS = {libvirt.VIR_FROM_RPC, libvirt.VIR_FROM_REMOTE, libvirt.VIR_FROM_SSH, libvirt.VIR_FROM_LIBSSH}
TRANSPORT_ERROR_CODES = {
libvirt.VIR_ERR_INTERNAL_ERROR, # "connection closed due to keepalive timeout"
libvirt.VIR_ERR_SYSTEM_ERROR, # "Cannot recv data: ..."
libvirt.VIR_ERR_RPC,
libvirt.VIR_ERR_NO_CONNECT,
libvirt.VIR_ERR_AUTH_FAILED,
libvirt.VIR_ERR_AUTH_UNAVAILABLE,
libvirt.VIR_ERR_AUTH_CANCELLED,
libvirt.VIR_ERR_SSH,
libvirt.VIR_ERR_LIBSSH,
}
UNREACHABLE = _("The host of this virtual machine cannot be reached right now.")
def error_text(request, exception):
"""
The libvirt error to show. A connection error names the host and how it
is reached, which only administrators (superusers and the global
view_instances permission, who see the hosts) get; other users learn
that the host cannot be reached.
"""
connection_error = isinstance(exception, ConnectionFailed) or (
isinstance(exception, libvirtError)
and exception.get_error_domain() in TRANSPORT_ERROR_DOMAINS
and exception.get_error_code() in TRANSPORT_ERROR_CODES
)
user = getattr(request, "user", None)
if connection_error and not (user and (user.is_superuser or user.has_perm("instances.view_instances"))):
return str(UNREACHABLE)
return str(exception)
class ExceptionMiddleware:
@ -18,14 +54,14 @@ class ExceptionMiddleware:
# API clients get JSON with a failure status, not the HTML error page.
if request.path_info.startswith(API_PREFIX):
if isinstance(exception, libvirtError):
return JsonResponse({"detail": str(exception)}, status=400)
return JsonResponse({"detail": error_text(request, exception)}, status=400)
if isinstance(exception, TimeoutError):
return JsonResponse({"detail": "Operation is busy. Please retry."}, status=409)
return None
if isinstance(exception, libvirtError):
messages.error(
request,
_("libvirt Error - %(exception)s") % {"exception": exception},
_("libvirt Error - %(exception)s") % {"exception": error_text(request, exception)},
)
return render(request, "500.html", {"libvirt_error": True}, status=500)
# TODO: check connecting to host via VPN

84
webvirtcloud/test_connection_errors.py Normal file
View file

@ -0,0 +1,84 @@
"""An error page for a host that cannot be reached shows the connection error
(host, address) only to administrators; errors of the VM operation itself
are shown to everyone, as they explain what to do."""
from unittest.mock import MagicMock
import libvirt
from django.contrib.auth import get_user_model
from django.contrib.auth.models import Permission
from django.contrib.messages import get_messages
from django.contrib.messages.storage.fallback import FallbackStorage
from django.contrib.sessions.middleware import SessionMiddleware
from django.test import RequestFactory, TestCase
from vrtManager.util import ConnectionFailed
from webvirtcloud.middleware import ExceptionMiddleware, error_text
HOST_DETAIL = "ssh: connect to host 10.0.0.9 port 22: No route to host"
def libvirt_error(domain, text, code=libvirt.VIR_ERR_SYSTEM_ERROR):
err = libvirt.libvirtError.__new__(libvirt.libvirtError)
Exception.__init__(err, text)
err.err = (code, domain, text, 2, None, None, None, 0, 0)
return err
class ConnectionErrorPageTests(TestCase):
def setUp(self):
User = get_user_model()
self.owner = User.objects.create_user("ce-owner", password="pw")
self.admin = User.objects.create_superuser("ce-admin", "ce@example.com", "pw")
self.viewer = User.objects.create_user("ce-viewer", password="pw")
self.viewer.user_permissions.add(Permission.objects.get(codename="view_instances"))
self.viewer = User.objects.get(pk=self.viewer.pk)
def handle(self, user, exception, path="/instances/1/poweron/"):
request = RequestFactory().post(path)
SessionMiddleware(lambda r: None).process_request(request)
request._messages = FallbackStorage(request)
request.user = user
response = ExceptionMiddleware(MagicMock()).process_exception(request, exception)
return response, [str(m) for m in get_messages(request)]
def test_owner_does_not_see_connection_details(self):
for error in (
ConnectionFailed(f"Connection Failed: Cannot recv data: {HOST_DETAIL}"),
libvirt_error(libvirt.VIR_FROM_RPC, f"Cannot recv data: {HOST_DETAIL}"),
):
with self.subTest(error=str(error)):
response, messages = self.handle(self.owner, error)
self.assertEqual(response.status_code, 500)
self.assertNotIn("10.0.0.9", " ".join(messages))
self.assertTrue(any("cannot be reached" in m for m in messages), messages)
def test_administrators_see_connection_details(self):
for user in (self.admin, self.viewer):
with self.subTest(user=user.username):
_, messages = self.handle(user, libvirt_error(libvirt.VIR_FROM_RPC, f"Cannot recv data: {HOST_DETAIL}"))
self.assertIn("10.0.0.9", " ".join(messages))
def test_operation_errors_are_shown_to_everyone(self):
for error, text in (
(libvirt_error(libvirt.VIR_FROM_QEMU, "Requested operation is not valid: domain is not running",
libvirt.VIR_ERR_OPERATION_INVALID), "domain is not running"),
# a reachable daemon without the procedure answers from the RPC layer
(libvirt_error(libvirt.VIR_FROM_RPC, "this function is not supported by the connection driver: virDomainFoo",
libvirt.VIR_ERR_NO_SUPPORT), "not supported"),
):
with self.subTest(text=text):
_, messages = self.handle(self.owner, error)
self.assertIn(text, " ".join(messages))
def test_api_answers_the_same_way(self):
response, _ = self.handle(self.owner, ConnectionFailed(f"Connection Failed: {HOST_DETAIL}"), path="/api/v1/instances/1/")
self.assertEqual(response.status_code, 400)
self.assertNotIn(b"10.0.0.9", response.content)
response, _ = self.handle(self.admin, ConnectionFailed(f"Connection Failed: {HOST_DETAIL}"), path="/api/v1/instances/1/")
self.assertIn(b"10.0.0.9", response.content)
def test_views_that_report_the_error_themselves(self):
request = RequestFactory().post("/")
request.user = self.owner
self.assertNotIn("10.0.0.9", error_text(request, libvirt_error(libvirt.VIR_FROM_RPC, HOST_DETAIL)))
self.assertEqual(error_text(request, ValueError("bad name")), "bad name") # clone also reports these