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app: re-register event handler after libvirt daemon restart

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When libvirt daemon is restarted, qubesd attempt to re-connect to the
new instance transparently (through virConnect object wrapper). But the
code lacked re-registering event handlers.
Fix this by adding reconnect callback argument to virConnectWrappper, to
be called after new connection is established. This callback will
additionally get old connection as an argument, if any cleanup is
needed. The old connection is closed just after callback returns.

Use this to re-register event handler, but also unregister old handler
first. While full unregister wont work on since old libvirt daemon
instance is dead already, it will still cleanup client structures.

Since the old libvirt connection is closed now, adjust also domain
reconnection logic, to handle stale connection object. In that case
isAlive() call throws an exception.

Fixes QubesOS/qubes-issues#5303
This commit is contained in:
Marek Marczykowski-Górecki 2019-09-22 04:41:43 +02:00
parent 273238bd2a
commit 8e36a2ac61
No known key found for this signature in database
GPG Key ID: 063938BA42CFA724
1 changed files with 34 additions and 8 deletions
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42
qubes/app.py
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@ -76,7 +76,14 @@ class VirDomainWrapper:
self._vm = vm
def _reconnect_if_dead(self):
is_dead = not self._vm.connect().isAlive()
try:
is_dead = not self._vm.connect().isAlive()
except libvirt.libvirtError as ex:
if ex.get_error_code() == libvirt.VIR_ERR_INVALID_CONN:
# connection to libvirt was re-established in the meantime
is_dead = True
else:
raise
if is_dead:
# pylint: disable=protected-access
self._connection._reconnect_if_dead()
@ -102,14 +109,19 @@ class VirDomainWrapper:
class VirConnectWrapper:
# pylint: disable=too-few-public-methods
def __init__(self, uri):
def __init__(self, uri, reconnect_cb=None):
self._conn = libvirt.open(uri)
self._reconnect_cb = reconnect_cb
def _reconnect_if_dead(self):
is_dead = not self._conn.isAlive()
if is_dead:
self._conn = libvirt.open(self._conn.getURI())
# TODO: re-register event handlers
uri = self._conn.getURI()
old_conn = self._conn
self._conn = libvirt.open(uri)
if callable(self._reconnect_cb):
self._reconnect_cb(old_conn)
old_conn.close()
return is_dead
def _wrap_domain(self, ret):
@ -139,16 +151,20 @@ class VirConnectWrapper:
class VMMConnection:
'''Connection to Virtual Machine Manager (libvirt)'''
def __init__(self, offline_mode=None):
def __init__(self, offline_mode=None, libvirt_reconnect_cb=None):
'''
:param offline_mode: enable/disable offline mode; default is to
enable when running in chroot as root, otherwise disable
:param libvirt_reconnect_cb: callable to be called when connection to
libvirt is re-established; the callback is called with old connection
as argument
'''
if offline_mode is None:
offline_mode = bool(os.getuid() == 0 and
os.stat('/') != os.stat('/proc/1/root/.'))
self._offline_mode = offline_mode
self._libvirt_reconnect_cb = libvirt_reconnect_cb
self._libvirt_conn = None
self._xs = None
@ -179,7 +195,8 @@ class VMMConnection:
if 'xen.lowlevel.xc' in sys.modules:
self._xc = xen.lowlevel.xc.xc()
self._libvirt_conn = VirConnectWrapper(
qubes.config.defaults['libvirt_uri'])
qubes.config.defaults['libvirt_uri'],
reconnect_cb=self._libvirt_reconnect_cb)
libvirt.registerErrorHandler(self._libvirt_error_handler, None)
@property
@ -806,7 +823,8 @@ class Qubes(qubes.PropertyHolder):
self.pools = {}
#: Connection to VMM
self.vmm = VMMConnection(offline_mode=offline_mode)
self.vmm = VMMConnection(offline_mode=offline_mode,
libvirt_reconnect_cb=self.register_event_handlers)
#: Information about host system
self.host = QubesHost(self)
@ -1322,11 +1340,19 @@ class Qubes(qubes.PropertyHolder):
raise qubes.exc.QubesException('No driver %s for pool %s' %
(driver, name))
def register_event_handlers(self):
def register_event_handlers(self, old_connection=None):
'''Register libvirt event handlers, which will translate libvirt
events into qubes.events. This function should be called only in
'qubesd' process and only when mainloop has been already set.
'''
if old_connection:
try:
old_connection.domainEventDeregisterAny(
self._domain_event_callback_id)
except libvirt.libvirtError:
# the connection is probably in a bad state; but call the above
# anyway to cleanup the client structures
pass
self._domain_event_callback_id = (
self.vmm.libvirt_conn.domainEventRegisterAny(
None, # any domain