qemu-e2k/qga/guest-agent-core.h
Michael Roth 39097daf15 qemu-ga: use key-value store to avoid recycling fd handles after restart
Hosts hold on to handles provided by guest-file-open for periods that can
span beyond the life of the qemu-ga process that issued them. Since these
are issued starting from 0 on every restart, we run the risk of issuing
duplicate handles after restarts/reboots.

As a result, users with a stale copy of these handles may end up
reading/writing corrupted data due to their existing handles effectively
being re-assigned to an unexpected file or offset.

We unfortunately do not issue handles as strings, but as integers, so a
solution such as using UUIDs can't be implemented without introducing a
new interface.

As a workaround, we fix this by implementing a persistent key-value store
that will be used to track the value of the last handle that was issued
across restarts/reboots to avoid issuing duplicates.

The store is automatically written to the same directory we currently
set via --statedir to track fsfreeze state, and so should be applicable
for stable releases where this flag is supported.

A follow-up can use this same store for handling fsfreeze state, but
that change is cosmetic and left out for now.

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Cc: qemu-stable@nongnu.org

* fixed guest_file_handle_add() return value from uint64_t to int64_t
2013-03-11 18:53:47 -05:00

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1.3 KiB
C

/*
* QEMU Guest Agent core declarations
*
* Copyright IBM Corp. 2011
*
* Authors:
* Adam Litke <aglitke@linux.vnet.ibm.com>
* Michael Roth <mdroth@linux.vnet.ibm.com>
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#include "qapi/qmp/dispatch.h"
#include "qemu-common.h"
#define QGA_READ_COUNT_DEFAULT 4096
typedef struct GAState GAState;
typedef struct GACommandState GACommandState;
extern GAState *ga_state;
void ga_command_state_init(GAState *s, GACommandState *cs);
void ga_command_state_add(GACommandState *cs,
void (*init)(void),
void (*cleanup)(void));
void ga_command_state_init_all(GACommandState *cs);
void ga_command_state_cleanup_all(GACommandState *cs);
GACommandState *ga_command_state_new(void);
bool ga_logging_enabled(GAState *s);
void ga_disable_logging(GAState *s);
void ga_enable_logging(GAState *s);
void slog(const gchar *fmt, ...);
void ga_set_response_delimited(GAState *s);
bool ga_is_frozen(GAState *s);
void ga_set_frozen(GAState *s);
void ga_unset_frozen(GAState *s);
const char *ga_fsfreeze_hook(GAState *s);
int64_t ga_get_fd_handle(GAState *s, Error **errp);
#ifndef _WIN32
void reopen_fd_to_null(int fd);
#endif