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authorMichael Roth <mdroth@linux.vnet.ibm.com>2012-02-07 13:56:48 -0600
committerMichael Roth <mdroth@linux.vnet.ibm.com>2012-03-12 15:09:23 -0500
commit3cf0bed8369267184e5dc5b58882811519d67437 (patch)
treea9c32d61d08ec7ab795b1b2cc4d74252087e1130 /qga
parent3424fc9f16a1e7d1c48eb6d605eb0ca63e199ec2 (diff)
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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>
Diffstat (limited to 'qga')
-rw-r--r--qga/commands-posix.c3
-rw-r--r--qga/commands.c6
-rw-r--r--qga/guest-agent-core.h2
3 files changed, 8 insertions, 3 deletions
diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index 5b77fa9..7b2be2f 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -35,8 +35,6 @@
#include "qemu-queue.h"
#include "host-utils.h"
-static GAState *ga_state;
-
static void reopen_fd_to_null(int fd)
{
int nullfd;
@@ -909,7 +907,6 @@ error:
/* register init/cleanup routines for stateful command groups */
void ga_command_state_init(GAState *s, GACommandState *cs)
{
- ga_state = s;
#if defined(CONFIG_FSFREEZE)
ga_command_state_add(cs, guest_fsfreeze_init, guest_fsfreeze_cleanup);
#endif
diff --git a/qga/commands.c b/qga/commands.c
index b27407d..5bcceaa 100644
--- a/qga/commands.c
+++ b/qga/commands.c
@@ -29,6 +29,12 @@ void slog(const gchar *fmt, ...)
va_end(ap);
}
+int64_t qmp_guest_sync_delimited(int64_t id, Error **errp)
+{
+ ga_set_response_delimited(ga_state);
+ return id;
+}
+
int64_t qmp_guest_sync(int64_t id, Error **errp)
{
return id;
diff --git a/qga/guest-agent-core.h b/qga/guest-agent-core.h
index b5dfa5b..304525d 100644
--- a/qga/guest-agent-core.h
+++ b/qga/guest-agent-core.h
@@ -18,6 +18,7 @@
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,
@@ -30,3 +31,4 @@ 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);