libdevmapper-event.c

Linux Device Mapper Source Code

/*
 * Copyright (C) 2005-2007 Red Hat, Inc. All rights reserved.
 *
 * This file is part of the device-mapper userspace tools.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU Lesser General Public License v.2.1.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include "lib.h"
#include "libdevmapper-event.h"
//#include "libmultilog.h"
#include "dmeventd.h"

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/file.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <sys/wait.h>
#include <arpa/inet.h>		/* for htonl, ntohl */

static int _sequence_nr = 0;

struct dm_event_handler {
	char *dso;

	char *dev_name;

	char *uuid;
	int major;
	int minor;
	uint32_t timeout;

	enum dm_event_mask mask;
};

static void _dm_event_handler_clear_dev_info(struct dm_event_handler *dmevh)
{
	if (dmevh->dev_name)
		dm_free(dmevh->dev_name);
	if (dmevh->uuid)
		dm_free(dmevh->uuid);
	dmevh->dev_name = dmevh->uuid = NULL;
	dmevh->major = dmevh->minor = 0;
}

struct dm_event_handler *dm_event_handler_create(void)
{
	struct dm_event_handler *dmevh = NULL;

	if (!(dmevh = dm_malloc(sizeof(*dmevh))))
		return NULL;

	dmevh->dso = dmevh->dev_name = dmevh->uuid = NULL;
	dmevh->major = dmevh->minor = 0;
	dmevh->mask = 0;
	dmevh->timeout = 0;

	return dmevh;
}

void dm_event_handler_destroy(struct dm_event_handler *dmevh)
{
	_dm_event_handler_clear_dev_info(dmevh);
	if (dmevh->dso)
		dm_free(dmevh->dso);
	dm_free(dmevh);
}

int dm_event_handler_set_dso(struct dm_event_handler *dmevh, const char *path)
{
	if (!path) /* noop */
		return 0;
	if (dmevh->dso)
		dm_free(dmevh->dso);

	dmevh->dso = dm_strdup(path);
	if (!dmevh->dso)
		return -ENOMEM;

	return 0;
}

int dm_event_handler_set_dev_name(struct dm_event_handler *dmevh, const char *dev_name)
{
	if (!dev_name)
		return 0;

	_dm_event_handler_clear_dev_info(dmevh);

	dmevh->dev_name = dm_strdup(dev_name);
	if (!dmevh->dev_name)
		return -ENOMEM;
	return 0;
}

int dm_event_handler_set_uuid(struct dm_event_handler *dmevh, const char *uuid)
{
	if (!uuid)
		return 0;

	_dm_event_handler_clear_dev_info(dmevh);

	dmevh->uuid = dm_strdup(uuid);
	if (!dmevh->dev_name)
		return -ENOMEM;
	return 0;
}

void dm_event_handler_set_major(struct dm_event_handler *dmevh, int major)
{
	int minor = dmevh->minor;

	_dm_event_handler_clear_dev_info(dmevh);

	dmevh->major = major;
	dmevh->minor = minor;
}

void dm_event_handler_set_minor(struct dm_event_handler *dmevh, int minor)
{
	int major = dmevh->major;

	_dm_event_handler_clear_dev_info(dmevh);

	dmevh->major = major;
	dmevh->minor = minor;
}

void dm_event_handler_set_event_mask(struct dm_event_handler *dmevh,
				     enum dm_event_mask evmask)
{
	dmevh->mask = evmask;
}

void dm_event_handler_set_timeout(struct dm_event_handler *dmevh, int timeout)
{
	dmevh->timeout = timeout;
}

const char *dm_event_handler_get_dso(const struct dm_event_handler *dmevh)
{
	return dmevh->dso;
}

const char *dm_event_handler_get_dev_name(const struct dm_event_handler *dmevh)
{
	return dmevh->dev_name;
}

const char *dm_event_handler_get_uuid(const struct dm_event_handler *dmevh)
{
	return dmevh->uuid;
}

int dm_event_handler_get_major(const struct dm_event_handler *dmevh)
{
	return dmevh->major;
}

int dm_event_handler_get_minor(const struct dm_event_handler *dmevh)
{
	return dmevh->minor;
}

int dm_event_handler_get_timeout(const struct dm_event_handler *dmevh)
{
	return dmevh->timeout;
}

enum dm_event_mask dm_event_handler_get_event_mask(const struct dm_event_handler *dmevh)
{
	return dmevh->mask;
}

static int _check_message_id(struct dm_event_daemon_message *msg)
{
	int pid, seq_nr;

	if ((sscanf(msg->data, "%d:%d", &pid, &seq_nr) != 2) ||
	    (pid != getpid()) || (seq_nr != _sequence_nr)) {
		log_error("Ignoring out-of-sequence reply from dmeventd. "
			  "Expected %d:%d but received %s", getpid(),
			  _sequence_nr, msg->data);
		return 0;
	}

	return 1;
}

/*
 * daemon_read
 * @fifos
 * @msg
 *
 * Read message from daemon.
 *
 * Returns: 0 on failure, 1 on success
 */
static int _daemon_read(struct dm_event_fifos *fifos,
			struct dm_event_daemon_message *msg)
{
	unsigned bytes = 0;
	int ret, i;
	fd_set fds;
	struct timeval tval = { 0, 0 };
	size_t size = 2 * sizeof(uint32_t);	/* status + size */
	char *buf = alloca(size);
	int header = 1;

	while (bytes < size) {
		for (i = 0, ret = 0; (i < 20) && (ret < 1); i++) {
			/* Watch daemon read FIFO for input. */
			FD_ZERO(&fds);
			FD_SET(fifos->server, &fds);
			tval.tv_sec = 1;
			ret = select(fifos->server + 1, &fds, NULL, NULL,
				     &tval);
			if (ret < 0 && errno != EINTR) {
				log_error("Unable to read from event server");
				return 0;
			}
		}
		if (ret < 1) {
			log_error("Unable to read from event server.");
			return 0;
		}

		ret = read(fifos->server, buf + bytes, size);
		if (ret < 0) {
			if ((errno == EINTR) || (errno == EAGAIN))
				continue;
			else {
				log_error("Unable to read from event server.");
				return 0;
			}
		}

		bytes += ret;
		if (bytes == 2 * sizeof(uint32_t) && header) {
			msg->cmd = ntohl(*((uint32_t *)buf));
			msg->size = ntohl(*((uint32_t *)buf + 1));
			buf = msg->data = dm_malloc(msg->size);
			size = msg->size;
			bytes = 0;
			header = 0;
		}
	}

	if (bytes != size) {
		if (msg->data)
			dm_free(msg->data);
		msg->data = NULL;
	}

	return bytes == size;
}

/* Write message to daemon. */
static int _daemon_write(struct dm_event_fifos *fifos,
			 struct dm_event_daemon_message *msg)
{
	unsigned bytes = 0;
	int ret = 0;
	fd_set fds;

	size_t size = 2 * sizeof(uint32_t) + msg->size;
	char *buf = alloca(size);
	char drainbuf[128];
	struct timeval tval = { 0, 0 };

	*((uint32_t *)buf) = htonl(msg->cmd);
	*((uint32_t *)buf + 1) = htonl(msg->size);
	memcpy(buf + 2 * sizeof(uint32_t), msg->data, msg->size);

	/* drain the answer fifo */
	while (1) {
		FD_ZERO(&fds);
		FD_SET(fifos->server, &fds);
		tval.tv_usec = 100;
		ret = select(fifos->server + 1, &fds, NULL, NULL, &tval);
		if ((ret < 0) && (errno != EINTR)) {
			log_error("Unable to talk to event daemon");
			return 0;
		}
		if (ret == 0)
			break;
		read(fifos->server, drainbuf, 127);
	}

	while (bytes < size) {
		do {
			/* Watch daemon write FIFO to be ready for output. */
			FD_ZERO(&fds);
			FD_SET(fifos->client, &fds);
			ret = select(fifos->client + 1, NULL, &fds, NULL, NULL);
			if ((ret < 0) && (errno != EINTR)) {
				log_error("Unable to talk to event daemon");
				return 0;
			}
		} while (ret < 1);

		ret = write(fifos->client, ((char *) buf) + bytes,
			    size - bytes);
		if (ret < 0) {
			if ((errno == EINTR) || (errno == EAGAIN))
				continue;
			else {
				log_error("Unable to talk to event daemon");
				return 0;
			}
		}

		bytes += ret;
	}

	return bytes == size;
}

static int _daemon_talk(struct dm_event_fifos *fifos,
			struct dm_event_daemon_message *msg, int cmd,
			const char *dso_name, const char *dev_name,
			enum dm_event_mask evmask, uint32_t timeout)
{
	const char *dso = dso_name ? dso_name : "";
	const char *dev = dev_name ? dev_name : "";
	const char *fmt = "%d:%d %s %s %u %" PRIu32;
	int msg_size;
	memset(msg, 0, sizeof(*msg));

	/*
	 * Set command and pack the arguments
	 * into ASCII message string.
	 */
	msg->cmd = cmd;
	if (cmd == DM_EVENT_CMD_HELLO)
		fmt = "%d:%d HELLO";
	if ((msg_size = dm_asprintf(&(msg->data), fmt, getpid(), _sequence_nr,
				    dso, dev, evmask, timeout)) < 0) {
		log_error("_daemon_talk: message allocation failed");
		return -ENOMEM;
	}
	msg->size = msg_size;

	/*
	 * Write command and message to and
	 * read status return code from daemon.
	 */
	if (!_daemon_write(fifos, msg)) {
		stack;
		dm_free(msg->data);
		msg->data = 0;
		return -EIO;
	}

	do {

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

		if (!_daemon_read(fifos, msg)) {
			stack;
			return -EIO;
		}
	} while (!_check_message_id(msg));

	_sequence_nr++;

	return (int32_t) msg->cmd;
}

/*
 * start_daemon
 *
 * This function forks off a process (dmeventd) that will handle
 * the events.  I am currently test opening one of the fifos to
 * ensure that the daemon is running and listening...  I thought
 * this would be less expensive than fork/exec'ing every time.
 * Perhaps there is an even quicker/better way (no, checking the
 * lock file is _not_ a better way).
 *
 * Returns: 1 on success, 0 otherwise
 */
static int _start_daemon(struct dm_event_fifos *fifos)
{
	int pid, ret = 0;
	int status;
	struct stat statbuf;

	if (stat(fifos->client_path, &statbuf))
		goto start_server;