Page MenuHomeClusterLabs Projects
Files F1702049

dbus.c
No OneTemporary
Actions

dbus.c
View Options

/*
* Copyright 2014-2022 the Pacemaker project contributors
*
* The version control history for this file may have further details.
*
* This source code is licensed under the GNU Lesser General Public License
* version 2.1 or later (LGPLv2.1+) WITHOUT ANY WARRANTY.
*/
#include <crm_internal.h>
#include <crm/crm.h>
#include <dbus/dbus.h>
#include <pcmk-dbus.h>
/*
* DBus message dispatch
*/
// List of DBus connections (DBusConnection*) with messages available
static GList *conn_dispatches = NULL;
/*!
* \internal
* \brief Save an indication that DBus messages need dispatching
*
* \param[in] connection DBus connection with messages to dispatch
* \param[in] new_status Dispatch status as reported by DBus library
* \param[in] data Ignored
*
* \note This is suitable to be used as a DBus status dispatch function.
* As mentioned in the DBus documentation, dbus_connection_dispatch() must
* not be called from within this function, and any re-entrancy is a bad
* idea. Instead, this should just flag the main loop that messages need
* to be dispatched.
*/
static void
update_dispatch_status(DBusConnection *connection,
DBusDispatchStatus new_status, void *data)
{
if (new_status == DBUS_DISPATCH_DATA_REMAINS) {
crm_trace("DBus connection has messages available for dispatch");
conn_dispatches = g_list_prepend(conn_dispatches, connection);
} else {
crm_trace("DBus connection has no messages available for dispatch "
"(status %d)", new_status);
}
}
/*!
* \internal
* \brief Dispatch available messages on all DBus connections
*/
static void
dispatch_messages(void)
{
for (GList *gIter = conn_dispatches; gIter != NULL; gIter = gIter->next) {
DBusConnection *connection = gIter->data;
while (dbus_connection_get_dispatch_status(connection)
== DBUS_DISPATCH_DATA_REMAINS) {
crm_trace("Dispatching available messages on DBus connection");
dbus_connection_dispatch(connection);
}
}
g_list_free(conn_dispatches);
conn_dispatches = NULL;
}
/*
* DBus file descriptor watches
*
* The DBus library allows the caller to register functions for the library to
* use for file descriptor notifications via a main loop.
*/
/* Copied from dbus-watch.c */
static const char*
dbus_watch_flags_to_string(int flags)
{
const char *watch_type;
if ((flags & DBUS_WATCH_READABLE) && (flags & DBUS_WATCH_WRITABLE)) {
watch_type = "read/write";
} else if (flags & DBUS_WATCH_READABLE) {
watch_type = "read";
} else if (flags & DBUS_WATCH_WRITABLE) {
watch_type = "write";
} else {
watch_type = "neither read nor write";
}
return watch_type;
}
/*!
* \internal
* \brief Dispatch data available on a DBus file descriptor watch
*
* \param[in,out] userdata Pointer to the DBus watch
*
* \return Always 0
* \note This is suitable for use as a dispatch function in
* struct mainloop_fd_callbacks (which means that a negative return value
* would indicate the file descriptor is no longer required).
*/
static int
dispatch_fd_data(gpointer userdata)
{
bool oom = FALSE;
DBusWatch *watch = userdata;
int flags = dbus_watch_get_flags(watch);
bool enabled = dbus_watch_get_enabled (watch);
crm_trace("Dispatching DBus watch for file descriptor %d "
"with flags %#x (%s)",
dbus_watch_get_unix_fd(watch), flags,
dbus_watch_flags_to_string(flags));
if (enabled && (flags & (DBUS_WATCH_READABLE|DBUS_WATCH_WRITABLE))) {
oom = !dbus_watch_handle(watch, flags);
} else if (enabled) {
oom = !dbus_watch_handle(watch, DBUS_WATCH_ERROR);
}
if (flags != dbus_watch_get_flags(watch)) {
flags = dbus_watch_get_flags(watch);
crm_trace("Dispatched DBus file descriptor watch: now %#x (%s)",
flags, dbus_watch_flags_to_string(flags));
}
if (oom) {
crm_crit("Could not dispatch DBus file descriptor data: Out of memory");
} else {
dispatch_messages();
}
return 0;
}
static void
watch_fd_closed(gpointer userdata)
{
crm_trace("DBus watch for file descriptor %d is now closed",
dbus_watch_get_unix_fd((DBusWatch *) userdata));
}
static struct mainloop_fd_callbacks pcmk_dbus_cb = {
.dispatch = dispatch_fd_data,
.destroy = watch_fd_closed,
};
static dbus_bool_t
add_dbus_watch(DBusWatch *watch, void *data)
{
int fd = dbus_watch_get_unix_fd(watch);
mainloop_io_t *client = mainloop_add_fd("dbus", G_PRIORITY_DEFAULT, fd,
watch, &pcmk_dbus_cb);
crm_trace("Added DBus watch for file descriptor %d", fd);
dbus_watch_set_data(watch, client, NULL);
return TRUE;
}
static void
toggle_dbus_watch(DBusWatch *watch, void *data)
{
// @TODO Should this do something more?
crm_debug("DBus watch for file descriptor %d is now %s",
dbus_watch_get_unix_fd(watch),
(dbus_watch_get_enabled(watch)? "enabled" : "disabled"));
}
static void
remove_dbus_watch(DBusWatch *watch, void *data)
{
crm_trace("Removed DBus watch for file descriptor %d",
dbus_watch_get_unix_fd(watch));
mainloop_del_fd((mainloop_io_t *) dbus_watch_get_data(watch));
}
static void
register_watch_functions(DBusConnection *connection)
{
dbus_connection_set_watch_functions(connection, add_dbus_watch,
remove_dbus_watch,
toggle_dbus_watch, NULL, NULL);
}
/*
* DBus main loop timeouts
*
* The DBus library allows the caller to register functions for the library to
* use for managing timers via a main loop.
*/
static gboolean
timer_popped(gpointer data)
{
crm_debug("%dms DBus timer expired",
dbus_timeout_get_interval((DBusTimeout *) data));
dbus_timeout_handle(data);
return FALSE;
}
static dbus_bool_t
add_dbus_timer(DBusTimeout *timeout, void *data)
{
int interval_ms = dbus_timeout_get_interval(timeout);
guint id = g_timeout_add(interval_ms, timer_popped, timeout);
if (id) {
dbus_timeout_set_data(timeout, GUINT_TO_POINTER(id), NULL);
}
crm_trace("Added %dms DBus timer", interval_ms);
return TRUE;
}
static void
remove_dbus_timer(DBusTimeout *timeout, void *data)
{
void *vid = dbus_timeout_get_data(timeout);
guint id = GPOINTER_TO_UINT(vid);
crm_trace("Removing %dms DBus timer", dbus_timeout_get_interval(timeout));
if (id) {
g_source_remove(id);
dbus_timeout_set_data(timeout, 0, NULL);
}
}
static void
toggle_dbus_timer(DBusTimeout *timeout, void *data)
{
bool enabled = dbus_timeout_get_enabled(timeout);
crm_trace("Toggling %dms DBus timer %s",
dbus_timeout_get_interval(timeout), (enabled? "off": "on"));
if (enabled) {
add_dbus_timer(timeout, data);
} else {
remove_dbus_timer(timeout, data);
}
}
static void
register_timer_functions(DBusConnection *connection)
{
dbus_connection_set_timeout_functions(connection, add_dbus_timer,
remove_dbus_timer,
toggle_dbus_timer, NULL, NULL);
}
/*
* General DBus utilities
*/
DBusConnection *
pcmk_dbus_connect(void)
{
DBusError err;
DBusConnection *connection;
dbus_error_init(&err);
connection = dbus_bus_get(DBUS_BUS_SYSTEM, &err);
if (dbus_error_is_set(&err)) {
crm_err("Could not connect to DBus: %s", err.message);
dbus_error_free(&err);
return NULL;
}
if (connection == NULL) {
return NULL;
}
/* Tell libdbus not to exit the process when a disconnect happens. This
* defaults to FALSE but is toggled on by the dbus_bus_get() call above.
*/
dbus_connection_set_exit_on_disconnect(connection, FALSE);
// Set custom handlers for various situations
register_timer_functions(connection);
register_watch_functions(connection);
dbus_connection_set_dispatch_status_function(connection,
update_dispatch_status,
NULL, NULL);
// Call the dispatch function to check for any messages waiting already
update_dispatch_status(connection,
dbus_connection_get_dispatch_status(connection),
NULL);
return connection;
}
void
pcmk_dbus_disconnect(DBusConnection *connection)
{
/* Per the DBus documentation, connections created with
* dbus_connection_open() are owned by libdbus and should never be closed.
*
* @TODO Should we call dbus_connection_unref() here?
*/
return;
}
// Custom DBus error names to use
#define ERR_NO_REQUEST "org.clusterlabs.pacemaker.NoRequest"
#define ERR_NO_REPLY "org.clusterlabs.pacemaker.NoReply"
#define ERR_INVALID_REPLY "org.clusterlabs.pacemaker.InvalidReply"
#define ERR_INVALID_REPLY_METHOD "org.clusterlabs.pacemaker.InvalidReply.Method"
#define ERR_INVALID_REPLY_SIGNAL "org.clusterlabs.pacemaker.InvalidReply.Signal"
#define ERR_INVALID_REPLY_TYPE "org.clusterlabs.pacemaker.InvalidReply.Type"
#define ERR_SEND_FAILED "org.clusterlabs.pacemaker.SendFailed"
/*!
* \internal
* \brief Check whether a DBus reply indicates an error occurred
*
* \param[in] pending If non-NULL, indicates that a DBus request was sent
* \param[in] reply Reply received from DBus
* \param[out] ret If non-NULL, will be set to DBus error, if any
*
* \return TRUE if an error was found, FALSE otherwise
*
* \note Following the DBus API convention, a TRUE return is exactly equivalent
* to ret being set. If ret is provided and this function returns TRUE,
* the caller is responsible for calling dbus_error_free() on ret when
* done using it.
*/
bool
pcmk_dbus_find_error(const DBusPendingCall *pending, DBusMessage *reply,
DBusError *ret)
{
DBusError error;
dbus_error_init(&error);
if (pending == NULL) {
dbus_set_error_const(&error, ERR_NO_REQUEST, "No request sent");
} else if (reply == NULL) {
dbus_set_error_const(&error, ERR_NO_REPLY, "No reply");
} else {
DBusMessageIter args;
int dtype = dbus_message_get_type(reply);
switch (dtype) {
case DBUS_MESSAGE_TYPE_METHOD_RETURN:
{
char *sig = NULL;
dbus_message_iter_init(reply, &args);
crm_trace("Received DBus reply with argument type '%s'",
(sig = dbus_message_iter_get_signature(&args)));
if (sig != NULL) {
dbus_free(sig);
}
}
break;
case DBUS_MESSAGE_TYPE_INVALID:
dbus_set_error_const(&error, ERR_INVALID_REPLY,
"Invalid reply");
break;
case DBUS_MESSAGE_TYPE_METHOD_CALL:
dbus_set_error_const(&error, ERR_INVALID_REPLY_METHOD,
"Invalid reply (method call)");
break;
case DBUS_MESSAGE_TYPE_SIGNAL:
dbus_set_error_const(&error, ERR_INVALID_REPLY_SIGNAL,
"Invalid reply (signal)");
break;
case DBUS_MESSAGE_TYPE_ERROR:
dbus_set_error_from_message(&error, reply);
break;
default:
dbus_set_error(&error, ERR_INVALID_REPLY_TYPE,
"Unknown reply type %d", dtype);
}
}
if (dbus_error_is_set(&error)) {
crm_trace("DBus reply indicated error '%s' (%s)",
error.name, error.message);
if (ret) {
dbus_error_init(ret);
dbus_move_error(&error, ret);
} else {
dbus_error_free(&error);
}
return TRUE;
}
return FALSE;
}
/*!
* \internal
* \brief Send a DBus request and wait for the reply
*
* \param[in,out] msg DBus request to send
* \param[in,out] connection DBus connection to use
* \param[out] error If non-NULL, will be set to error, if any
* \param[in] timeout Timeout to use for request
*
* \return DBus reply
*
* \note If error is non-NULL, it is initialized, so the caller may always use
* dbus_error_is_set() to determine whether an error occurred; the caller
* is responsible for calling dbus_error_free() in this case.
*/
DBusMessage *
pcmk_dbus_send_recv(DBusMessage *msg, DBusConnection *connection,
DBusError *error, int timeout)
{
const char *method = NULL;
DBusMessage *reply = NULL;
DBusPendingCall* pending = NULL;
CRM_ASSERT(dbus_message_get_type (msg) == DBUS_MESSAGE_TYPE_METHOD_CALL);
method = dbus_message_get_member (msg);
/* Ensure caller can reliably check whether error is set */
if (error) {
dbus_error_init(error);
}
if (timeout <= 0) {
/* DBUS_TIMEOUT_USE_DEFAULT (-1) tells DBus to use a sane default */
timeout = DBUS_TIMEOUT_USE_DEFAULT;
}
// send message and get a handle for a reply
if (!dbus_connection_send_with_reply(connection, msg, &pending, timeout)) {
if (error) {
dbus_set_error(error, ERR_SEND_FAILED,
"Could not queue DBus '%s' request", method);
}
return NULL;
}
dbus_connection_flush(connection);
if (pending) {
/* block until we receive a reply */
dbus_pending_call_block(pending);
/* get the reply message */
reply = dbus_pending_call_steal_reply(pending);
}
(void) pcmk_dbus_find_error(pending, reply, error);
if (pending) {
/* free the pending message handle */
dbus_pending_call_unref(pending);
}
return reply;
}
/*!
* \internal
* \brief Send a DBus message with a callback for the reply
*
* \param[in,out] msg DBus message to send
* \param[in,out] connection DBus connection to send on
* \param[in] done Function to call when pending call completes
* \param[in] user_data Data to pass to done callback
*
* \return Handle for reply on success, NULL on error
* \note The caller can assume that the done callback is called always and
* only when the return value is non-NULL. (This allows the caller to
* know where it should free dynamically allocated user_data.)
*/
DBusPendingCall *
pcmk_dbus_send(DBusMessage *msg, DBusConnection *connection,
void (*done)(DBusPendingCall *pending, void *user_data),
void *user_data, int timeout)
{
const char *method = NULL;
DBusPendingCall* pending = NULL;
CRM_ASSERT(done);
CRM_ASSERT(dbus_message_get_type(msg) == DBUS_MESSAGE_TYPE_METHOD_CALL);
method = dbus_message_get_member(msg);
if (timeout <= 0) {
/* DBUS_TIMEOUT_USE_DEFAULT (-1) tells DBus to use a sane default */
timeout = DBUS_TIMEOUT_USE_DEFAULT;
}
// send message and get a handle for a reply
if (!dbus_connection_send_with_reply(connection, msg, &pending, timeout)) {
crm_err("Could not send DBus %s message: failed", method);
return NULL;
} else if (pending == NULL) {
crm_err("Could not send DBus %s message: connection may be closed",
method);
return NULL;
}
if (dbus_pending_call_get_completed(pending)) {
crm_info("DBus %s message completed too soon", method);
/* Calling done() directly in this case instead of setting notify below
* breaks things
*/
}
if (!dbus_pending_call_set_notify(pending, done, user_data, NULL)) {
return NULL;
}
return pending;
}
bool
pcmk_dbus_type_check(DBusMessage *msg, DBusMessageIter *field, int expected,
const char *function, int line)
{
int dtype = 0;
DBusMessageIter lfield;
if (field == NULL) {
if (dbus_message_iter_init(msg, &lfield)) {
field = &lfield;
}
}
if (field == NULL) {
do_crm_log_alias(LOG_INFO, __FILE__, function, line,
"DBus reply has empty parameter list (expected '%c')",
expected);
return FALSE;
}
dtype = dbus_message_iter_get_arg_type(field);
if (dtype != expected) {
DBusMessageIter args;
char *sig;
dbus_message_iter_init(msg, &args);
sig = dbus_message_iter_get_signature(&args);
do_crm_log_alias(LOG_INFO, __FILE__, function, line,
"DBus reply has unexpected type "
"(expected '%c' not '%c' in '%s')",
expected, dtype, sig);
dbus_free(sig);
return FALSE;
}
return TRUE;
}
/*
* Property queries
*/
/* DBus APIs often provide queryable properties that use this standard
* interface. See:
* https://dbus.freedesktop.org/doc/dbus-specification.html#standard-interfaces-properties
*/
#define BUS_PROPERTY_IFACE "org.freedesktop.DBus.Properties"
// Callback prototype for when a DBus property query result is received
typedef void (*property_callback_func)(const char *name, // Property name
const char *value, // Property value
void *userdata); // Caller-provided data
// Data needed by DBus property queries
struct property_query {
char *name; // Property name being queried
char *target; // Name of DBus bus that query should be sent to
char *object; // DBus object path for object with the property
void *userdata; // Caller-provided data to supply to callback
property_callback_func callback; // Function to call when result is received
};
static void
free_property_query(struct property_query *data)
{
free(data->target);
free(data->object);
free(data->name);
free(data);
}
static char *
handle_query_result(DBusMessage *reply, struct property_query *data)
{
DBusError error;
char *output = NULL;
DBusMessageIter args;
DBusMessageIter variant_iter;
DBusBasicValue value;
dbus_error_init(&error);
// First, check if the reply contains an error
if (pcmk_dbus_find_error((void*)&error, reply, &error)) {
crm_err("DBus query for %s property '%s' failed: %s",
data->object, data->name, error.message);
dbus_error_free(&error);
goto cleanup;
}
// The lone output argument should be a DBus variant type
dbus_message_iter_init(reply, &args);
if (!pcmk_dbus_type_check(reply, &args, DBUS_TYPE_VARIANT,
__func__, __LINE__)) {
crm_err("DBus query for %s property '%s' failed: Unexpected reply type",
data->object, data->name);
goto cleanup;
}
// The variant should be a string
dbus_message_iter_recurse(&args, &variant_iter);
if (!pcmk_dbus_type_check(reply, &variant_iter, DBUS_TYPE_STRING,
__func__, __LINE__)) {
crm_err("DBus query for %s property '%s' failed: "
"Unexpected variant type", data->object, data->name);
goto cleanup;
}
dbus_message_iter_get_basic(&variant_iter, &value);
// There should be no more arguments (in variant or reply)
dbus_message_iter_next(&variant_iter);
if (dbus_message_iter_get_arg_type(&variant_iter) != DBUS_TYPE_INVALID) {
crm_err("DBus query for %s property '%s' failed: "
"Too many arguments in reply",
data->object, data->name);
goto cleanup;
}
dbus_message_iter_next(&args);
if (dbus_message_iter_get_arg_type(&args) != DBUS_TYPE_INVALID) {
crm_err("DBus query for %s property '%s' failed: "
"Too many arguments in reply", data->object, data->name);
goto cleanup;
}
crm_trace("DBus query result for %s: %s='%s'",
data->object, data->name, (value.str? value.str : ""));
if (data->callback) { // Query was asynchronous
data->callback(data->name, (value.str? value.str : ""), data->userdata);
} else { // Query was synchronous
output = strdup(value.str? value.str : "");
}
cleanup:
free_property_query(data);
return output;
}
static void
async_query_result_cb(DBusPendingCall *pending, void *user_data)
{
DBusMessage *reply = NULL;
char *value = NULL;
if (pending) {
reply = dbus_pending_call_steal_reply(pending);
}
value = handle_query_result(reply, user_data);
free(value);
if (reply) {
dbus_message_unref(reply);
}
}
/*!
* \internal
* \brief Query a property on a DBus object
*
* \param[in,out] connection An active connection to DBus
* \param[in] target DBus name that the query should be sent to
* \param[in] obj DBus object path for object with the property
* \param[in] iface DBus interface for property to query
* \param[in] name Name of property to query
* \param[in] callback If not NULL, perform query asynchronously and call
* this function when query completes
* \param[in,out] userdata Caller-provided data to provide to \p callback
* \param[out] pending If \p callback is not NULL, this will be set to
* handle for the reply (or NULL on error)
* \param[in] timeout Abort query if it takes longer than this (ms)
*
* \return NULL if \p callback is non-NULL (i.e. asynchronous), otherwise a
* newly allocated string with property value
* \note It is the caller's responsibility to free the result with free().
*/
char *
pcmk_dbus_get_property(DBusConnection *connection, const char *target,
const char *obj, const gchar * iface, const char *name,
property_callback_func callback, void *userdata,
DBusPendingCall **pending, int timeout)
{
DBusMessage *msg;
char *output = NULL;
struct property_query *query_data = NULL;
CRM_CHECK((connection != NULL) && (target != NULL) && (obj != NULL)
&& (iface != NULL) && (name != NULL), return NULL);
crm_trace("Querying DBus %s for %s property '%s'",
target, obj, name);
// Create a new message to use to invoke method
msg = dbus_message_new_method_call(target, obj, BUS_PROPERTY_IFACE, "Get");
if (msg == NULL) {
crm_err("DBus query for %s property '%s' failed: "
"Unable to create message", obj, name);
return NULL;
}
// Add the interface name and property name as message arguments
if (!dbus_message_append_args(msg,
DBUS_TYPE_STRING, &iface,
DBUS_TYPE_STRING, &name,
DBUS_TYPE_INVALID)) {
crm_err("DBus query for %s property '%s' failed: "
"Could not append arguments", obj, name);
dbus_message_unref(msg);
return NULL;
}
query_data = malloc(sizeof(struct property_query));
if (query_data == NULL) {
crm_crit("DBus query for %s property '%s' failed: Out of memory",
obj, name);
dbus_message_unref(msg);
return NULL;
}
query_data->target = strdup(target);
query_data->object = strdup(obj);
query_data->callback = callback;
query_data->userdata = userdata;
query_data->name = strdup(name);
CRM_CHECK((query_data->target != NULL)
&& (query_data->object != NULL)
&& (query_data->name != NULL),
free_property_query(query_data);
dbus_message_unref(msg);
return NULL);
if (query_data->callback) { // Asynchronous
DBusPendingCall *local_pending;
local_pending = pcmk_dbus_send(msg, connection, async_query_result_cb,
query_data, timeout);
if (local_pending == NULL) {
// async_query_result_cb() was not called in this case
free_property_query(query_data);
query_data = NULL;
}
if (pending) {
*pending = local_pending;
}
} else { // Synchronous
DBusMessage *reply = pcmk_dbus_send_recv(msg, connection, NULL,
timeout);
output = handle_query_result(reply, query_data);
if (reply) {
dbus_message_unref(reply);
}
}
dbus_message_unref(msg);
return output;
}

File Metadata

Mime Type
text/x-c
Expires
Tue, Oct 29, 8:41 PM (1 d, 16 h)
Storage Engine
blob
Storage Format
Raw Data
Storage Handle
916072
Default Alt Text
dbus.c (24 KB)

Event Timeline