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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 /qemu-ga.c
parent3424fc9f16a1e7d1c48eb6d605eb0ca63e199ec2 (diff)
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 'qemu-ga.c')
-rw-r--r--qemu-ga.c27
1 files changed, 22 insertions, 5 deletions
diff --git a/qemu-ga.c b/qemu-ga.c
index 1c90e6ef0d..d6f786e50d 100644
--- a/qemu-ga.c
+++ b/qemu-ga.c
@@ -41,6 +41,7 @@
#define QGA_VIRTIO_PATH_DEFAULT "\\\\.\\Global\\org.qemu.guest_agent.0"
#endif
#define QGA_PIDFILE_DEFAULT "/var/run/qemu-ga.pid"
+#define QGA_SENTINEL_BYTE 0xFF
struct GAState {
JSONMessageParser parser;
@@ -54,9 +55,10 @@ struct GAState {
#ifdef _WIN32
GAService service;
#endif
+ bool delimit_response;
};
-static struct GAState *ga_state;
+struct GAState *ga_state;
#ifdef _WIN32
DWORD WINAPI service_ctrl_handler(DWORD ctrl, DWORD type, LPVOID data,
@@ -198,6 +200,11 @@ static void ga_log(const gchar *domain, GLogLevelFlags level,
}
}
+void ga_set_response_delimited(GAState *s)
+{
+ s->delimit_response = true;
+}
+
#ifndef _WIN32
static void become_daemon(const char *pidfile)
{
@@ -254,7 +261,7 @@ fail:
static int send_response(GAState *s, QObject *payload)
{
const char *buf;
- QString *payload_qstr;
+ QString *payload_qstr, *response_qstr;
GIOStatus status;
g_assert(payload && s->channel);
@@ -264,10 +271,20 @@ static int send_response(GAState *s, QObject *payload)
return -EINVAL;
}
- qstring_append_chr(payload_qstr, '\n');
- buf = qstring_get_str(payload_qstr);
+ if (s->delimit_response) {
+ s->delimit_response = false;
+ response_qstr = qstring_new();
+ qstring_append_chr(response_qstr, QGA_SENTINEL_BYTE);
+ qstring_append(response_qstr, qstring_get_str(payload_qstr));
+ QDECREF(payload_qstr);
+ } else {
+ response_qstr = payload_qstr;
+ }
+
+ qstring_append_chr(response_qstr, '\n');
+ buf = qstring_get_str(response_qstr);
status = ga_channel_write_all(s->channel, buf, strlen(buf));
- QDECREF(payload_qstr);
+ QDECREF(response_qstr);
if (status != G_IO_STATUS_NORMAL) {
return -EIO;
}