qmp: introduce QMPCapability
There were no QMP capabilities defined. Define the first capability,
"oob", to allow out-of-band messages.
After this patch, we will allow QMP clients to enable QMP capabilities
when sending the first "qmp_capabilities" command. Originally we are
starting QMP session with no arguments like:
{ "execute": "qmp_capabilities" }
Now we can enable some QMP capabilities using (take OOB as example,
which is the only capability that we support):
{ "execute": "qmp_capabilities",
"arguments": { "enable": [ "oob" ] } }
When the "arguments" key is not provided, no capability is enabled.
For capability "oob", the monitor needs to be run on a dedicated IO
thread, otherwise the command will fail. For example, trying to enable
OOB on a MUXed typed QMP monitor will fail.
One thing to mention is that QMP capabilities are per-monitor, and also
when the connection is closed due to some reason, the capabilities will
be reset.
Also, touch up qmp-test.c to test the new bits.
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20180309090006.10018-11-peterx@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: touch up commit message]
Signed-off-by: Eric Blake <eblake@redhat.com>
diff --git a/monitor.c b/monitor.c
index 44b2fa2..d31ec70 100644
--- a/monitor.c
+++ b/monitor.c
@@ -59,6 +59,7 @@
#include "qapi/qmp/qjson.h"
#include "qapi/qmp/json-streamer.h"
#include "qapi/qmp/json-parser.h"
+#include "qapi/qmp/qlist.h"
#include "qom/object_interfaces.h"
#include "trace-root.h"
#include "trace/control.h"
@@ -170,6 +171,7 @@
* mode.
*/
QmpCommandList *commands;
+ bool qmp_caps[QMP_CAPABILITY__MAX];
} MonitorQMP;
/*
@@ -1042,8 +1044,42 @@
qmp_marshal_qmp_capabilities, QCO_NO_OPTIONS);
}
-void qmp_qmp_capabilities(Error **errp)
+static void qmp_caps_check(Monitor *mon, QMPCapabilityList *list,
+ Error **errp)
{
+ for (; list; list = list->next) {
+ assert(list->value < QMP_CAPABILITY__MAX);
+ switch (list->value) {
+ case QMP_CAPABILITY_OOB:
+ if (!mon->use_io_thr) {
+ /*
+ * Out-Of-Band only works with monitors that are
+ * running on dedicated IOThread.
+ */
+ error_setg(errp, "This monitor does not support "
+ "Out-Of-Band (OOB)");
+ return;
+ }
+ break;
+ default:
+ break;
+ }
+ }
+}
+
+/* This function should only be called after capabilities are checked. */
+static void qmp_caps_apply(Monitor *mon, QMPCapabilityList *list)
+{
+ for (; list; list = list->next) {
+ mon->qmp.qmp_caps[list->value] = true;
+ }
+}
+
+void qmp_qmp_capabilities(bool has_enable, QMPCapabilityList *enable,
+ Error **errp)
+{
+ Error *local_err = NULL;
+
if (cur_mon->qmp.commands == &qmp_commands) {
error_set(errp, ERROR_CLASS_COMMAND_NOT_FOUND,
"Capabilities negotiation is already complete, command "
@@ -1051,6 +1087,21 @@
return;
}
+ /* Enable QMP capabilities provided by the client if applicable. */
+ if (has_enable) {
+ qmp_caps_check(cur_mon, enable, &local_err);
+ if (local_err) {
+ /*
+ * Failed check on any of the capabilities will fail the
+ * entire command (and thus not apply any of the other
+ * capabilities that were also requested).
+ */
+ error_propagate(errp, local_err);
+ return;
+ }
+ qmp_caps_apply(cur_mon, enable);
+ }
+
cur_mon->qmp.commands = &qmp_commands;
}
@@ -3896,14 +3947,29 @@
readline_show_prompt(mon->rs);
}
-static QObject *get_qmp_greeting(void)
+static QObject *get_qmp_greeting(Monitor *mon)
{
+ QList *cap_list = qlist_new();
QObject *ver = NULL;
+ QMPCapability cap;
qmp_marshal_query_version(NULL, &ver, NULL);
- return qobject_from_jsonf("{'QMP': {'version': %p, 'capabilities': []}}",
- ver);
+ for (cap = 0; cap < QMP_CAPABILITY__MAX; cap++) {
+ if (!mon->use_io_thr && cap == QMP_CAPABILITY_OOB) {
+ /* Monitors that are not using IOThread won't support OOB */
+ continue;
+ }
+ qlist_append(cap_list, qstring_from_str(QMPCapability_str(cap)));
+ }
+
+ return qobject_from_jsonf("{'QMP': {'version': %p, 'capabilities': %p}}",
+ ver, cap_list);
+}
+
+static void monitor_qmp_caps_reset(Monitor *mon)
+{
+ memset(mon->qmp.qmp_caps, 0, sizeof(mon->qmp.qmp_caps));
}
static void monitor_qmp_event(void *opaque, int event)
@@ -3914,7 +3980,8 @@
switch (event) {
case CHR_EVENT_OPENED:
mon->qmp.commands = &qmp_cap_negotiation_commands;
- data = get_qmp_greeting();
+ monitor_qmp_caps_reset(mon);
+ data = get_qmp_greeting(mon);
monitor_json_emitter(mon, data);
qobject_decref(data);
mon_refcount++;
