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88446e07b2
The driver URI scheme:
"$drivername:///embed?root=/some/path"
enables a new way to use the drivers by embedding them directly in the
calling process. To use this the process must have a thread running the
libvirt event loop. This URI will then cause libvirt to dynamically load
the driver module and call its global initialization function. This
syntax is applicable to any driver, but only those will have been
modified to support a custom root directory and embed URI path will
successfully open.
The application can now make normal libvirt API calls which are all
serviced in-process with no RPC layer involved.
It is required to specify an explicit root directory, and locks will be
acquired on this directory to avoid conflicting with another app that
might accidentally pick the same directory.
Use of '/' is not explicitly forbidden, but note that the file layout
used underneath the embedded driver root does not match the file
layout used by system/session mode drivers. So this cannot be used as
a backdoor to interact with, or fake, the system/session mode drivers.
Libvirt will create arbitrary files underneath this root directory. The
root directory can be kept untouched across connection open attempts if
the application needs persistence. The application is responsible for
purging everything underneath this root directory when finally no longer
required.
Even when a virt driver is used in embedded mode, it is still possible
for it to in turn use functionality that calls out to other secondary
drivers in libvirtd. For example an embedded instance of QEMU can open
the network, secret or storage drivers in the system libvirtd.
That said, the application would typically want to at least open an
embedded secret driver ("secret:///embed?root=/some/path"). Note that
multiple different embedded drivers can use the same root prefix and
co-operate just as they would inside a normal libvirtd daemon.
A key thing to note is that for this to work, the application that links
to libvirt *MUST* be built with -Wl,--export-dynamic to ensure that
symbols from libvirt.so are exported & thus available to the dynamically
loaded driver module. If libvirt.so itself was dynamically loaded then
RTLD_GLOBAL must be passed to dlopen().
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
59 lines
1.6 KiB
C
59 lines
1.6 KiB
C
/*
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* driver-state.h: entry points for state drivers
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*
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* Copyright (C) 2006-2014 Red Hat, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library. If not, see
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* <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#ifndef __VIR_DRIVER_H_INCLUDES___
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# error "Don't include this file directly, only use driver.h"
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#endif
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typedef enum {
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VIR_DRV_STATE_INIT_ERROR = -1,
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VIR_DRV_STATE_INIT_SKIPPED,
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VIR_DRV_STATE_INIT_COMPLETE,
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} virDrvStateInitResult;
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typedef virDrvStateInitResult
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(*virDrvStateInitialize)(bool privileged,
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const char *root,
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virStateInhibitCallback callback,
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void *opaque);
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typedef int
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(*virDrvStateCleanup)(void);
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typedef int
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(*virDrvStateReload)(void);
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typedef int
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(*virDrvStateStop)(void);
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typedef struct _virStateDriver virStateDriver;
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typedef virStateDriver *virStateDriverPtr;
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struct _virStateDriver {
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const char *name;
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bool initialized;
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virDrvStateInitialize stateInitialize;
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virDrvStateCleanup stateCleanup;
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virDrvStateReload stateReload;
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virDrvStateStop stateStop;
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};
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