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qmp: Clean up how we enforce capability negotiation

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To enforce capability negotiation before normal operation,
handle_qmp_command() inspects every command before it's handed off to
qmp_dispatch().  This is a bit of a layering violation, and results in
duplicated code.

Before capability negotiation (!cur_mon->in_command_mode), we fail
commands other than "qmp_capabilities".  This is what enforces
capability negotiation.

Afterwards, we fail command "qmp_capabilities".

Clean this up as follows.

The obvious place to fail a command is the command itself, so move the
"afterwards" check to qmp_qmp_capabilities().

We do the "before" check in every other command, but that would be
bothersome.  Instead, start with an alternate list of commands that
contains only "qmp_capabilities".  Switch to the full list in
qmp_qmp_capabilities().

Additionally, replace the generic human-readable error message for
CommandNotFound by one that reminds the user to run qmp_capabilities.
Without that, we'd regress commit 2d5a834.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1488544368-30622-8-git-send-email-armbru@redhat.com>
[Mirco-optimization squashed in, commit message typo fixed]
Reviewed-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Markus Armbruster 2017-03-03 13:32:27 +01:00
parent 9b0c9a6349
commit 635db18f68
1 changed files with 42 additions and 34 deletions
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76
monitor.c
View file

@ -165,7 +165,7 @@ typedef struct {
* When command qmp_capabilities succeeds, we go into command
* mode.
*/
bool in_command_mode; /* are we in command mode? */
QmpCommandList *commands;
} MonitorQMP;
/*
@ -221,7 +221,7 @@ static int mon_refcount;
static mon_cmd_t mon_cmds[];
static mon_cmd_t info_cmds[];
QmpCommandList qmp_commands;
QmpCommandList qmp_commands, qmp_cap_negotiation_commands;
Monitor *cur_mon;
@ -416,7 +416,8 @@ static void monitor_qapi_event_emit(QAPIEvent event, QDict *qdict)
trace_monitor_protocol_event_emit(event, qdict);
QLIST_FOREACH(mon, &mon_list, entry) {
if (monitor_is_qmp(mon) && mon->qmp.in_command_mode) {
if (monitor_is_qmp(mon)
&& mon->qmp.commands != &qmp_cap_negotiation_commands) {
monitor_json_emitter(mon, QOBJECT(qdict));
}
}
@ -565,11 +566,6 @@ static void monitor_qapi_event_init(void)
qmp_event_set_func_emit(monitor_qapi_event_queue);
}
void qmp_qmp_capabilities(Error **errp)
{
cur_mon->qmp.in_command_mode = true;
}
static void handle_hmp_command(Monitor *mon, const char *cmdline);
static void monitor_data_init(Monitor *mon)
@ -921,7 +917,7 @@ CommandInfoList *qmp_query_commands(Error **errp)
{
CommandInfoList *list = NULL;
qmp_for_each_command(&qmp_commands, query_commands_cb, &list);
qmp_for_each_command(cur_mon->qmp.commands, query_commands_cb, &list);
return list;
}
@ -1001,6 +997,13 @@ static void qmp_unregister_commands_hack(void)
void monitor_init_qmp_commands(void)
{
/*
* Two command lists:
* - qmp_commands contains all QMP commands
* - qmp_cap_negotiation_commands contains just
* "qmp_capabilities", to enforce capability negotiation
*/
qmp_init_marshal(&qmp_commands);
qmp_register_command(&qmp_commands, "query-qmp-schema",
@ -1012,6 +1015,22 @@ void monitor_init_qmp_commands(void)
QCO_NO_OPTIONS);
qmp_unregister_commands_hack();
QTAILQ_INIT(&qmp_cap_negotiation_commands);
qmp_register_command(&qmp_cap_negotiation_commands, "qmp_capabilities",
qmp_marshal_qmp_capabilities, QCO_NO_OPTIONS);
}
void qmp_qmp_capabilities(Error **errp)
{
if (cur_mon->qmp.commands == &qmp_commands) {
error_set(errp, ERROR_CLASS_COMMAND_NOT_FOUND,
"Capabilities negotiation is already complete, command "
"ignored");
return;
}
cur_mon->qmp.commands = &qmp_commands;
}
/* set the current CPU defined by the user */
@ -3681,26 +3700,6 @@ static int monitor_can_read(void *opaque)
return (mon->suspend_cnt == 0) ? 1 : 0;
}
static bool invalid_qmp_mode(const Monitor *mon, const char *cmd,
Error **errp)
{
bool is_cap = g_str_equal(cmd, "qmp_capabilities");
if (is_cap && mon->qmp.in_command_mode) {
error_set(errp, ERROR_CLASS_COMMAND_NOT_FOUND,
"Capabilities negotiation is already complete, command "
"'%s' ignored", cmd);
return true;
}
if (!is_cap && !mon->qmp.in_command_mode) {
error_set(errp, ERROR_CLASS_COMMAND_NOT_FOUND,
"Expecting capabilities negotiation with "
"'qmp_capabilities' before command '%s'", cmd);
return true;
}
return false;
}
/*
* Input object checking rules
*
@ -3786,11 +3785,20 @@ static void handle_qmp_command(JSONMessageParser *parser, GQueue *tokens)
cmd_name = qdict_get_str(qdict, "execute");
trace_handle_qmp_command(mon, cmd_name);
if (invalid_qmp_mode(mon, cmd_name, &err)) {
goto err_out;
}
rsp = qmp_dispatch(cur_mon->qmp.commands, req);
rsp = qmp_dispatch(&qmp_commands, req);
if (mon->qmp.commands == &qmp_cap_negotiation_commands) {
qdict = qdict_get_qdict(qobject_to_qdict(rsp), "error");
if (qdict
&& !g_strcmp0(qdict_get_try_str(qdict, "class"),
QapiErrorClass_lookup[ERROR_CLASS_COMMAND_NOT_FOUND])) {
/* Provide a more useful error message */
qdict_del(qdict, "desc");
qdict_put(qdict, "desc",
qstring_from_str("Expecting capabilities negotiation"
" with 'qmp_capabilities'"));
}
}
err_out:
if (err) {
@ -3888,7 +3896,7 @@ static void monitor_qmp_event(void *opaque, int event)
switch (event) {
case CHR_EVENT_OPENED:
mon->qmp.in_command_mode = false;
mon->qmp.commands = &qmp_cap_negotiation_commands;
data = get_qmp_greeting();
monitor_json_emitter(mon, data);
qobject_decref(data);