libdevmapper-event.c

Linux Device Mapper Source Code

	if (!S_ISFIFO(statbuf.st_mode)) {
		log_error("%s is not a fifo.", fifos->client_path);
		return 0;
	}

	/* Anyone listening?  If not, errno will be ENXIO */
	fifos->client = open(fifos->client_path, O_WRONLY | O_NONBLOCK);
	if (fifos->client >= 0) {
		/* server is running and listening */

		close(fifos->client);
		return 1;
	} else if (errno != ENXIO) {
		/* problem */

		log_error("%s: Can't open client fifo %s: %s",
			  __func__, fifos->client_path, strerror(errno));
		stack;
		return 0;
	}

      start_server:
	/* server is not running */
	pid = fork();

	if (pid < 0)
		log_error("Unable to fork.");

	else if (!pid) {
		execvp(DMEVENTD_PATH, NULL);
		exit(EXIT_FAILURE);
	} else {
		if (waitpid(pid, &status, 0) < 0)
			log_error("Unable to start dmeventd: %s",
				  strerror(errno));
		else if (WEXITSTATUS(status))
			log_error("Unable to start dmeventd.");
		else
			ret = 1;
	}

	return ret;
}

/* Initialize client. */
static int _init_client(struct dm_event_fifos *fifos)
{
	/* FIXME? Is fifo the most suitable method? Why not share
	   comms/daemon code with something else e.g. multipath? */

	/* init fifos */
	memset(fifos, 0, sizeof(*fifos));
	fifos->client_path = DM_EVENT_FIFO_CLIENT;
	fifos->server_path = DM_EVENT_FIFO_SERVER;

	if (!_start_daemon(fifos)) {
		stack;
		return 0;
	}

	/* Open the fifo used to read from the daemon. */
	if ((fifos->server = open(fifos->server_path, O_RDWR)) < 0) {
		log_error("%s: open server fifo %s",
			  __func__, fifos->server_path);
		stack;
		return 0;
	}

	/* Lock out anyone else trying to do communication with the daemon. */
	if (flock(fifos->server, LOCK_EX) < 0) {
		log_error("%s: flock %s", __func__, fifos->server_path);
		close(fifos->server);
		return 0;
	}

/*	if ((fifos->client = open(fifos->client_path, O_WRONLY | O_NONBLOCK)) < 0) {*/
	if ((fifos->client = open(fifos->client_path, O_RDWR | O_NONBLOCK)) < 0) {
		log_error("%s: Can't open client fifo %s: %s",
			  __func__, fifos->client_path, strerror(errno));
		close(fifos->server);
		stack;
		return 0;
	}

	return 1;
}

static void _dtr_client(struct dm_event_fifos *fifos)
{
	if (flock(fifos->server, LOCK_UN))
		log_error("flock unlock %s", fifos->server_path);

	close(fifos->client);
	close(fifos->server);
}

/* Get uuid of a device */
static struct dm_task *_get_device_info(const struct dm_event_handler *dmevh)
{
	struct dm_task *dmt;
	struct dm_info info;

	if (!(dmt = dm_task_create(DM_DEVICE_INFO))) {
		log_error("_get_device_info: dm_task creation for info failed");
		return NULL;
	}

	if (dmevh->uuid)
		dm_task_set_uuid(dmt, dmevh->uuid);
	else if (dmevh->dev_name)
		dm_task_set_name(dmt, dmevh->dev_name);
	else if (dmevh->major && dmevh->minor) {
		dm_task_set_major(dmt, dmevh->major);
		dm_task_set_minor(dmt, dmevh->minor);
        }

	/* FIXME Add name or uuid or devno to messages */
	if (!dm_task_run(dmt)) {
		log_error("_get_device_info: dm_task_run() failed");
		goto failed;
	}

	if (!dm_task_get_info(dmt, &info)) {
		log_error("_get_device_info: failed to get info for device");
		goto failed;
	}

	if (!info.exists) {
		log_error("_get_device_info: device not found");
		goto failed;
	}

	return dmt;

failed:
	dm_task_destroy(dmt);
	return NULL;
}

/* Handle the event (de)registration call and return negative error codes. */
static int _do_event(int cmd, struct dm_event_daemon_message *msg,
		     const char *dso_name, const char *dev_name,
		     enum dm_event_mask evmask, uint32_t timeout)
{
	int ret;
	struct dm_event_fifos fifos;

	if (!_init_client(&fifos)) {
		stack;
		return -ESRCH;
	}

	ret = _daemon_talk(&fifos, msg, DM_EVENT_CMD_HELLO, 0, 0, 0, 0);

	if (msg->data)
		dm_free(msg->data);
	msg->data = 0;

	if (!ret)
		ret = _daemon_talk(&fifos, msg, cmd, dso_name, dev_name, evmask, timeout);

	/* what is the opposite of init? */
	_dtr_client(&fifos);

	return ret;
}

/* External library interface. */
int dm_event_register_handler(const struct dm_event_handler *dmevh)
{
	int ret = 1, err;
	const char *uuid;
	struct dm_task *dmt;
	struct dm_event_daemon_message msg = { 0, 0, NULL };

	if (!(dmt = _get_device_info(dmevh))) {
		stack;
		return 0;
	}

	uuid = dm_task_get_uuid(dmt);

	if ((err = _do_event(DM_EVENT_CMD_REGISTER_FOR_EVENT, &msg,
			     dmevh->dso, uuid, dmevh->mask, dmevh->timeout)) < 0) {
		log_error("%s: event registration failed: %s",
			  dm_task_get_name(dmt),
			  msg.data ? msg.data : strerror(-err));
		ret = 0;
	}

	if (msg.data)
		dm_free(msg.data);

	dm_task_destroy(dmt);

	return ret;
}

int dm_event_unregister_handler(const struct dm_event_handler *dmevh)
{
	int ret = 1, err;
	const char *uuid;
	struct dm_task *dmt;
	struct dm_event_daemon_message msg = { 0, 0, NULL };

	if (!(dmt = _get_device_info(dmevh))) {
		stack;
		return 0;
	}

	uuid = dm_task_get_uuid(dmt);

	if ((err = _do_event(DM_EVENT_CMD_UNREGISTER_FOR_EVENT, &msg,
			    dmevh->dso, uuid, dmevh->mask, dmevh->timeout)) < 0) {
		log_error("%s: event deregistration failed: %s",
			  dm_task_get_name(dmt),
			  msg.data ? msg.data : strerror(-err));
		ret = 0;
	}

	if (msg.data)
		dm_free(msg.data);

	dm_task_destroy(dmt);

	return ret;
}

/* Fetch a string off src and duplicate it into *dest. */
/* FIXME: move to separate module to share with the daemon. */
static char *_fetch_string(char **src, const int delimiter)
{
	char *p, *ret;

	if ((p = strchr(*src, delimiter)))
		*p = 0;

	if ((ret = dm_strdup(*src)))
		*src += strlen(ret) + 1;

	if (p)
		*p = delimiter;

	return ret;
}

/* Parse a device message from the daemon. */
static int _parse_message(struct dm_event_daemon_message *msg, char **dso_name,
			 char **uuid, enum dm_event_mask *evmask)
{
	char *id = NULL;
	char *p = msg->data;

	if ((id = _fetch_string(&p, ' ')) &&
	    (*dso_name = _fetch_string(&p, ' ')) &&
	    (*uuid = _fetch_string(&p, ' '))) {
		*evmask = atoi(p);

		dm_free(id);
		return 0;
	}

	if (id)
		dm_free(id);
	return -ENOMEM;
}

/*
 * Returns 0 if handler found; error (-ENOMEM, -ENOENT) otherwise.
 */
int dm_event_get_registered_device(struct dm_event_handler *dmevh, int next)
{
	int ret = 0;
	const char *uuid = NULL;
	char *reply_dso = NULL, *reply_uuid = NULL;
	enum dm_event_mask reply_mask = 0;
	struct dm_task *dmt = NULL;
	struct dm_event_daemon_message msg = { 0, 0, NULL };

	if (!(dmt = _get_device_info(dmevh))) {
		stack;
		return 0;
	}

	uuid = dm_task_get_uuid(dmt);

	if (!(ret = _do_event(next ? DM_EVENT_CMD_GET_NEXT_REGISTERED_DEVICE :
			     DM_EVENT_CMD_GET_REGISTERED_DEVICE,
			      &msg, dmevh->dso, uuid, dmevh->mask, 0))) {
		/* FIXME this will probably horribly break if we get
		   ill-formatted reply */
		ret = _parse_message(&msg, &reply_dso, &reply_uuid, &reply_mask);
	} else {
		ret = -ENOENT;
		goto fail;
	}

	dm_task_destroy(dmt);
	dmt = NULL;

	if (msg.data) {
		dm_free(msg.data);
		msg.data = NULL;
	}

	_dm_event_handler_clear_dev_info(dmevh);
	dmevh->uuid = dm_strdup(reply_uuid);
	if (!dmevh->uuid) {
		ret = -ENOMEM;
		goto fail;
	}

	if (!(dmt = _get_device_info(dmevh))) {
		ret = -ENXIO; /* dmeventd probably gave us bogus uuid back */
		goto fail;
	}

	dm_event_handler_set_dso(dmevh, reply_dso);
	dm_event_handler_set_event_mask(dmevh, reply_mask);

	if (reply_dso)
		dm_free(reply_dso);
	if (reply_uuid)
		dm_free(reply_uuid);

	dmevh->dev_name = dm_strdup(dm_task_get_name(dmt));
	if (!dmevh->dev_name) {
		ret = -ENOMEM;
		goto fail;
	}

	struct dm_info info;
	if (!dm_task_get_info(dmt, &info)) {
		ret = -1;
		goto fail;
	}

	dmevh->major = info.major;
	dmevh->minor = info.minor;

	dm_task_destroy(dmt);

	return ret;

 fail:
	if (msg.data)
		dm_free(msg.data);
	if (reply_dso)
		dm_free(reply_dso);
	if (reply_uuid)
		dm_free(reply_uuid);
	_dm_event_handler_clear_dev_info(dmevh);
	if (dmt)
		dm_task_destroy(dmt);
	return ret;
}

#if 0				/* left out for now */

static char *_skip_string(char *src, const int delimiter)
{
	src = srtchr(src, delimiter);
	if (src && *(src + 1))
		return src + 1;
	return NULL;
}

int dm_event_set_timeout(const char *device_path, uint32_t timeout)
{
	struct dm_event_daemon_message msg = { 0, 0, NULL };

	if (!device_exists(device_path))
		return -ENODEV;

	return _do_event(DM_EVENT_CMD_SET_TIMEOUT, &msg,
			 NULL, device_path, 0, timeout);
}

int dm_event_get_timeout(const char *device_path, uint32_t *timeout)
{
	int ret;
	struct dm_event_daemon_message msg = { 0, 0, NULL };

	if (!device_exists(device_path))
		return -ENODEV;
	if (!(ret = _do_event(DM_EVENT_CMD_GET_TIMEOUT, &msg, NULL, device_path,
			     0, 0))) {
		char *p = _skip_string(msg.data, ' ');
		if (!p) {
			log_error("malformed reply from dmeventd '%s'\n",
				  msg.data);
			return -EIO;
		}
		*timeout = atoi(p);
	}
	if (msg.data)
		dm_free(msg.data);
	return ret;
}
#endif