qemu/qga/guest-agent-core.h
Michael Roth 3cf0bed836 qemu-ga: add guest-sync-delimited
guest-sync leaves it as an exercise to the user as to how to reliably
obtain the response to guest-sync if the client had previously read in a
partial response (due qemu-ga previously being restarted mid-"sentence"
due to reboot, forced restart, etc).

qemu-ga handles this situation on its end by having a client precede
their guest-sync request with a 0xFF byte (invalid UTF-8), which
qemu-ga/QEMU JSON parsers will treat as a flush event. Thus we can
reliably flush the qemu-ga parser state in preparation for receiving
the guest-sync request.

guest-sync-delimited provides the same functionality for a client: when
a guest-sync-delimited is issued, qemu-ga will precede it's response
with a 0xFF byte that the client can use as an indicator to flush its
buffer/parser state in preparation for reliably receiving the
guest-sync-delimited response.

It is also useful as an optimization for clients, since, after issuing a
guest-sync-delimited, clients can safely discard all stale data read
from the channel until the 0xFF is found.

More information available on the wiki:

http://wiki.qemu.org/Features/QAPI/GuestAgent#QEMU_Guest_Agent_Protocol

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
2012-03-12 15:09:23 -05:00

35 lines
1.1 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-core.h"
#include "qemu-common.h"
#define QGA_VERSION "1.0"
#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);