Commit 635db18f authored by Markus Armbruster's avatar Markus Armbruster
Browse files

qmp: Clean up how we enforce capability negotiation 



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 2d5a8346.

Signed-off-by: default avatarMarkus 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: default avatarEric Blake <eblake@redhat.com>
parent 9b0c9a63

monitor.c

+42 −34
Original line number Diff line number Diff line
@@ -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);