Commit 02130314 authored by Peter Xu's avatar Peter Xu Committed by Eric Blake
Browse files

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: default avatarPeter Xu <peterx@redhat.com>
Message-Id: <20180309090006.10018-11-peterx@redhat.com>
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
[eblake: touch up commit message]
Signed-off-by: default avatarEric Blake <eblake@redhat.com>
parent a5ed3525

monitor.c

+72 −5
Original line number Diff line number Diff line
@@ -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 @@ typedef struct { 
     * mode.

     */

    QmpCommandList *commands;

    bool qmp_caps[QMP_CAPABILITY__MAX];

} MonitorQMP;



/*
@@ -1042,8 +1044,42 @@ static void monitor_init_qmp_commands(void) 
                         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 @@ void qmp_qmp_capabilities(Error **errp) 
        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 @@ void monitor_resume(Monitor *mon) 
        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 @@ static void monitor_qmp_event(void *opaque, int event) 
    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++;

qapi/misc.json

+29 −3
Original line number Diff line number Diff line
@@ -10,21 +10,47 @@ 
#

# Enable QMP capabilities.

#

# Arguments: None.

# Arguments:

#

# @enable:   An optional list of QMPCapability values to enable.  The

#            client must not enable any capability that is not

#            mentioned in the QMP greeting message.  If the field is not

#            provided, it means no QMP capabilities will be enabled.

#            (since 2.12)

#

# Example:

#

# -> { "execute": "qmp_capabilities" }

# -> { "execute": "qmp_capabilities",

#      "arguments": { "enable": [ "oob" ] } }

# <- { "return": {} }

#

# Notes: This command is valid exactly when first connecting: it must be

# issued before any other command will be accepted, and will fail once the

# monitor is accepting other commands. (see qemu docs/interop/qmp-spec.txt)

#

# The QMP client needs to explicitly enable QMP capabilities, otherwise

# all the QMP capabilities will be turned off by default.

#

# Since: 0.13

#

##

{ 'command': 'qmp_capabilities' }

{ 'command': 'qmp_capabilities',

  'data': { '*enable': [ 'QMPCapability' ] } }



##

# @QMPCapability:

#

# Enumeration of capabilities to be advertised during initial client

# connection, used for agreeing on particular QMP extension behaviors.

#

# @oob:   QMP ability to support Out-Of-Band requests.

#         (Please refer to qmp-spec.txt for more information on OOB)

#

# Since: 2.12

#

##

{ 'enum': 'QMPCapability',

  'data': [ 'oob' ] }



##

# @VersionTriple:

tests/qmp-test.c

+9 −1
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
#include "qapi/qobject-input-visitor.h"

#include "qapi/util.h"

#include "qapi/visitor.h"

#include "qapi/qmp/qstring.h"



const char common_args[] = "-nodefaults -machine none";
@@ -79,6 +80,8 @@ static void test_qmp_protocol(void) 
    QDict *resp, *q, *ret;

    QList *capabilities;

    QTestState *qts;

    const QListEntry *entry;

    QString *qstr;



    qts = qtest_init_without_qmp_handshake(common_args);
@@ -88,7 +91,12 @@ static void test_qmp_protocol(void) 
    g_assert(q);

    test_version(qdict_get(q, "version"));

    capabilities = qdict_get_qlist(q, "capabilities");

    g_assert(capabilities && qlist_empty(capabilities));

    g_assert(capabilities);

    entry = qlist_first(capabilities);

    g_assert(entry);

    qstr = qobject_to(QString, entry->value);

    g_assert(qstr);

    g_assert_cmpstr(qstring_get_str(qstr), ==, "oob");

    QDECREF(resp);



    /* Test valid command before handshake */