path: root/lib/tevent/tevent_poll.c

/*
   Unix SMB/CIFS implementation.
   main select loop and event handling
   Copyright (C) Andrew Tridgell	2003-2005
   Copyright (C) Stefan Metzmacher	2005-2009

     ** NOTE! The following LGPL license applies to the tevent
     ** library. This does NOT imply that all of Samba is released
     ** under the LGPL

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 3 of the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/

#include "replace.h"
#include "system/filesys.h"
#include "system/select.h"
#include "tevent.h"
#include "tevent_util.h"
#include "tevent_internal.h"

struct poll_event_context {
	/* a pointer back to the generic event_context */
	struct tevent_context *ev;

	/*
	 * A DLIST for fresh fde's added by poll_event_add_fd but not
	 * picked up yet by poll_event_loop_once
	 */
	struct tevent_fd *fresh;
	/*
	 * A DLIST for disabled fde's.
	 */
	struct tevent_fd *disabled;
	/*
	 * one or more events were deleted or disabled
	 */
	bool deleted;

	/*
	 * These two arrays are maintained together.
	 */
	struct pollfd *fds;
	struct tevent_fd **fdes;
	unsigned num_fds;

	/*
	 * Signal fd to wake the poll() thread
	 */
	int signal_fd;
};

static int poll_event_context_destructor(struct poll_event_context *poll_ev)
{
	struct tevent_fd *fd, *fn;

	for (fd = poll_ev->fresh; fd; fd = fn) {
		fn = fd->next;
		fd->event_ctx = NULL;
		DLIST_REMOVE(poll_ev->fresh, fd);
	}

	for (fd = poll_ev->disabled; fd; fd = fn) {
		fn = fd->next;
		fd->event_ctx = NULL;
		DLIST_REMOVE(poll_ev->disabled, fd);
	}

	if (poll_ev->signal_fd == -1) {
		/*
		 * Non-threaded, no signal pipe
		 */
		return 0;
	}

	close(poll_ev->signal_fd);
	poll_ev->signal_fd = -1;

	if (poll_ev->num_fds == 0) {
		return 0;
	}
	if (poll_ev->fds[0].fd != -1) {
		close(poll_ev->fds[0].fd);
		poll_ev->fds[0].fd = -1;
	}
	return 0;
}

/*
  create a poll_event_context structure.
*/
static int poll_event_context_init(struct tevent_context *ev)
{
	struct poll_event_context *poll_ev;

	/*
	 * we might be called during tevent_re_initialise()
	 * which means we need to free our old additional_data
	 * in order to detach old fd events from the
	 * poll_ev->fresh list
	 */
	TALLOC_FREE(ev->additional_data);

	poll_ev = talloc_zero(ev, struct poll_event_context);
	if (poll_ev == NULL) {
		return -1;
	}
	poll_ev->ev = ev;
	poll_ev->signal_fd = -1;
	ev->additional_data = poll_ev;
	talloc_set_destructor(poll_ev, poll_event_context_destructor);
	return 0;
}

static bool set_nonblock(int fd)
{
	int val;

	val = fcntl(fd, F_GETFL, 0);
	if (val == -1) {
		return false;
	}
	val |= O_NONBLOCK;

	return (fcntl(fd, F_SETFL, val) != -1);
}

static int poll_event_context_init_mt(struct tevent_context *ev)
{
	struct poll_event_context *poll_ev;
	struct pollfd *pfd;
	int fds[2];
	int ret;

	ret = poll_event_context_init(ev);
	if (ret == -1) {
		return ret;
	}

	poll_ev = talloc_get_type_abort(
		ev->additional_data, struct poll_event_context);

	poll_ev->fds = talloc_zero(poll_ev, struct pollfd);
	if (poll_ev->fds == NULL) {
		return -1;
	}

	ret = pipe(fds);
	if (ret == -1) {
		return -1;
	}

	if (!set_nonblock(fds[0]) || !set_nonblock(fds[1])) {
		close(fds[0]);
		close(fds[1]);
		return -1;
	}

	poll_ev->signal_fd = fds[1];

	pfd = &poll_ev->fds[0];
	pfd->fd = fds[0];
	pfd->events = (POLLIN|POLLHUP);

	poll_ev->num_fds = 1;

	talloc_set_destructor(poll_ev, poll_event_context_destructor);

	return 0;
}

static void poll_event_wake_pollthread(struct poll_event_context *poll_ev)
{
	char c;
	ssize_t ret;

	if (poll_ev->signal_fd == -1) {
		return;
	}
	c = 0;
	do {
		ret = write(poll_ev->signal_fd, &c, sizeof(c));
	} while ((ret == -1) && (errno == EINTR));
}

static void poll_event_drain_signal_fd(struct poll_event_context *poll_ev)
{
	char buf[16];
	ssize_t ret;
	int fd;

	if (poll_ev->signal_fd == -1) {
		return;
	}

	if (poll_ev->num_fds < 1) {
		return;
	}
	fd = poll_ev->fds[0].fd;

	do {
		ret = read(fd, buf, sizeof(buf));
	} while (ret == sizeof(buf));
}

/*
  destroy an fd_event
*/
static int poll_event_fd_destructor(struct tevent_fd *fde)
{
	struct tevent_context *ev = fde->event_ctx;
	struct poll_event_context *poll_ev;
	uint64_t del_idx = fde->additional_flags;

	if (ev == NULL) {
		goto done;
	}

	poll_ev = talloc_get_type_abort(
		ev->additional_data, struct poll_event_context);

	if (del_idx == UINT64_MAX) {
		struct tevent_fd **listp =
			(struct tevent_fd **)fde->additional_data;

		DLIST_REMOVE((*listp), fde);
		goto done;
	}

	poll_ev->fdes[del_idx] = NULL;
	poll_ev->deleted = true;
	poll_event_wake_pollthread(poll_ev);
done:
	return tevent_common_fd_destructor(fde);
}

static void poll_event_schedule_immediate(struct tevent_immediate *im,
					  struct tevent_context *ev,
					  tevent_immediate_handler_t handler,
					  void *private_data,
					  const char *handler_name,
					  const char *location)
{
	struct poll_event_context *poll_ev = talloc_get_type_abort(
		ev->additional_data, struct poll_event_context);

	tevent_common_schedule_immediate(im, ev, handler, private_data,
					 handler_name, location);
	poll_event_wake_pollthread(poll_ev);
}

/*
  Private function called by "standard" backend fallback.
  Note this only allows fallback to "poll" backend, not "poll-mt".
*/
_PRIVATE_ void tevent_poll_event_add_fd_internal(struct tevent_context *ev,
						 struct tevent_fd *fde)
{
	struct poll_event_context *poll_ev = talloc_get_type_abort(
		ev->additional_data, struct poll_event_context);
	struct tevent_fd **listp;

	if (fde->flags != 0) {
		listp = &poll_ev->fresh;
	} else {
		listp = &poll_ev->disabled;
	}

	fde->additional_flags	= UINT64_MAX;
	fde->additional_data	= listp;

	DLIST_ADD((*listp), fde);
	talloc_set_destructor(fde, poll_event_fd_destructor);
}

/*
  add a fd based event
  return NULL on failure (memory allocation error)
*/
static struct tevent_fd *poll_event_add_fd(struct tevent_context *ev,
					   TALLOC_CTX *mem_ctx,
					   int fd, uint16_t flags,
					   tevent_fd_handler_t handler,
					   void *private_data,
					   const char *handler_name,
					   const char *location)
{
	struct poll_event_context *poll_ev = talloc_get_type_abort(
		ev->additional_data, struct poll_event_context);
	struct tevent_fd *fde;

	if (fd < 0) {
		return NULL;
	}

	fde = talloc(mem_ctx ? mem_ctx : ev, struct tevent_fd);
	if (fde == NULL) {
		return NULL;
	}
	fde->event_ctx		= ev;
	fde->fd			= fd;
	fde->flags		= flags;
	fde->handler		= handler;
	fde->close_fn		= NULL;
	fde->private_data	= private_data;
	fde->handler_name	= handler_name;
	fde->location		= location;
	fde->additional_flags	= UINT64_MAX;
	fde->additional_data	= NULL;

	tevent_poll_event_add_fd_internal(ev, fde);
	poll_event_wake_pollthread(poll_ev);

	/*
	 * poll_event_loop_poll will take care of the rest in
	 * poll_event_setup_fresh
	 */
	return fde;
}

/*
  set the fd event flags
*/
static void poll_event_set_fd_flags(struct tevent_fd *fde, uint16_t flags)
{
	struct tevent_context *ev = fde->event_ctx;
	struct poll_event_context *poll_ev;
	uint64_t idx = fde->additional_flags;
	uint16_t pollflags;

	if (ev == NULL) {
		return;
	}
	poll_ev = talloc_get_type_abort(
		ev->additional_data, struct poll_event_context);

	fde->flags = flags;

	if (idx == UINT64_MAX) {
		struct tevent_fd **listp =
			(struct tevent_fd **)fde->additional_data;

		/*
		 * We move it between the fresh and disabled lists.
		 */
		DLIST_REMOVE((*listp), fde);
		tevent_poll_event_add_fd_internal(ev, fde);
		poll_event_wake_pollthread(poll_ev);
		return;
	}

	if (fde->flags == 0) {
		/*
		 * We need to remove it from the array
		 * and move it to the disabled list.
		 */
		poll_ev->fdes[idx] = NULL;
		poll_ev->deleted = true;
		DLIST_REMOVE(ev->fd_events, fde);
		tevent_poll_event_add_fd_internal(ev, fde);
		poll_event_wake_pollthread(poll_ev);
		return;
	}

	pollflags = 0;

	if (flags & TEVENT_FD_READ) {
		pollflags |= (POLLIN|POLLHUP);
	}
	if (flags & TEVENT_FD_WRITE) {
		pollflags |= (POLLOUT);
	}
	poll_ev->fds[idx].events = pollflags;

	poll_event_wake_pollthread(poll_ev);
}

static bool poll_event_setup_fresh(struct tevent_context *ev,
				   struct poll_event_context *poll_ev)
{
	struct tevent_fd *fde, *next;
	unsigned num_fresh, num_fds;

	if (poll_ev->deleted) {
		unsigned first_fd = (poll_ev->signal_fd != -1) ? 1 : 0;
		unsigned i;

		for (i=first_fd; i < poll_ev->num_fds;) {
			fde = poll_ev->fdes[i];
			if (fde != NULL) {
				i++;
				continue;
			}

			/*
			 * This fde was talloc_free()'ed. Delete it
			 * from the arrays
			 */
			poll_ev->num_fds -= 1;
			if (poll_ev->num_fds == i) {
				break;
			}
			poll_ev->fds[i] = poll_ev->fds[poll_ev->num_fds];
			poll_ev->fdes[i] = poll_ev->fdes[poll_ev->num_fds];
			if (poll_ev->fdes[i] != NULL) {
				poll_ev->fdes[i]->additional_flags = i;
			}
		}
		poll_ev->deleted = false;
	}

	if (poll_ev->fresh == NULL) {
		return true;
	}

	num_fresh = 0;
	for (fde = poll_ev->fresh; fde; fde = fde->next) {
		num_fresh += 1;
	}
	num_fds = poll_ev->num_fds + num_fresh;

	/*
	 * We check the length of fdes here. It is the last one
	 * enlarged, so if the realloc for poll_fd->fdes fails,
	 * poll_fd->fds will have at least the size of poll_fd->fdes
	 */

	if (num_fds >= talloc_array_length(poll_ev->fdes)) {
		struct pollfd *tmp_fds;
		struct tevent_fd **tmp_fdes;
		unsigned array_length;

		array_length = (num_fds + 15) & ~15; /* round up to 16 */

		tmp_fds = talloc_realloc(
			poll_ev, poll_ev->fds, struct pollfd, array_length);
		if (tmp_fds == NULL) {
			return false;
		}
		poll_ev->fds = tmp_fds;

		tmp_fdes = talloc_realloc(
			poll_ev, poll_ev->fdes, struct tevent_fd *,
			array_length);
		if (tmp_fdes == NULL) {
			return false;
		}
		poll_ev->fdes = tmp_fdes;
	}

	for (fde = poll_ev->fresh; fde; fde = next) {
		struct pollfd *pfd;

		pfd = &poll_ev->fds[poll_ev->num_fds];

		pfd->fd = fde->fd;
		pfd->events = 0;
		pfd->revents = 0;

		if (fde->flags & TEVENT_FD_READ) {
			pfd->events |= (POLLIN|POLLHUP);
		}
		if (fde->flags & TEVENT_FD_WRITE) {
			pfd->events |= (POLLOUT);
		}

		fde->additional_flags = poll_ev->num_fds;
		poll_ev->fdes[poll_ev->num_fds] = fde;

		next = fde->next;
		DLIST_REMOVE(poll_ev->fresh, fde);
		DLIST_ADD(ev->fd_events, fde);

		poll_ev->num_fds += 1;
	}
	return true;
}

/*
  event loop handling using poll()
*/
static int poll_event_loop_poll(struct tevent_context *ev,
				struct timeval *tvalp)
{
	struct poll_event_context *poll_ev = talloc_get_type_abort(
		ev->additional_data, struct poll_event_context);
	int pollrtn;
	int timeout = -1;
	int poll_errno;
	struct tevent_fd *fde = NULL;
	struct tevent_fd *next = NULL;
	unsigned i;

	if (ev->signal_events && tevent_common_check_signal(ev)) {
		return 0;
	}

	if (tvalp != NULL) {
		timeout = tvalp->tv_sec * 1000;
		timeout += (tvalp->tv_usec + 999) / 1000;
	}

	poll_event_drain_signal_fd(poll_ev);

	if (!poll_event_setup_fresh(ev, poll_ev)) {
		return -1;
	}

	tevent_trace_point_callback(poll_ev->ev, TEVENT_TRACE_BEFORE_WAIT);
	pollrtn = poll(poll_ev->fds, poll_ev->num_fds, timeout);
	poll_errno = errno;
	tevent_trace_point_callback(poll_ev->ev, TEVENT_TRACE_AFTER_WAIT);

	if (pollrtn == -1 && poll_errno == EINTR && ev->signal_events) {
		tevent_common_check_signal(ev);
		return 0;
	}

	if (pollrtn == 0 && tvalp) {
		/* we don't care about a possible delay here */
		tevent_common_loop_timer_delay(ev);
		return 0;
	}

	if (pollrtn <= 0) {
		/*
		 * No fd's ready
		 */
		return 0;
	}

	/* at least one file descriptor is ready - check
	   which ones and call the handler, being careful to allow
	   the handler to remove itself when called */

	for (fde = ev->fd_events; fde; fde = next) {
		uint64_t idx = fde->additional_flags;
		struct pollfd *pfd;
		uint16_t flags = 0;

		next = fde->next;

		if (idx == UINT64_MAX) {
			continue;
		}

		pfd = &poll_ev->fds[idx];

		if (pfd->revents & POLLNVAL) {
			/*
			 * the socket is dead! this should never
			 * happen as the socket should have first been
			 * made readable and that should have removed
			 * the event, so this must be a bug.
			 *
			 * We ignore it here to match the epoll
			 * behavior.
			 */
			tevent_debug(ev, TEVENT_DEBUG_ERROR,
				     "POLLNVAL on fde[%p] fd[%d] - disabling\n",
				     fde, pfd->fd);
			poll_ev->fdes[idx] = NULL;
			poll_ev->deleted = true;
			DLIST_REMOVE(ev->fd_events, fde);
			fde->event_ctx = NULL;
			continue;
		}

		if (pfd->revents & (POLLHUP|POLLERR)) {
			/* If we only wait for TEVENT_FD_WRITE, we
			   should not tell the event handler about it,
			   and remove the writable flag, as we only
			   report errors when waiting for read events
			   to match the select behavior. */
			if (!(fde->flags & TEVENT_FD_READ)) {
				TEVENT_FD_NOT_WRITEABLE(fde);
				continue;
			}
			flags |= TEVENT_FD_READ;
		}
		if (pfd->revents & POLLIN) {
			flags |= TEVENT_FD_READ;
		}
		if (pfd->revents & POLLOUT) {
			flags |= TEVENT_FD_WRITE;
		}
		/*
		 * Note that fde->flags could be changed when using
		 * the poll_mt backend together with threads,
		 * that why we need to check pfd->revents and fde->flags
		 */
		flags &= fde->flags;
		if (flags != 0) {
			DLIST_DEMOTE(ev->fd_events, fde);
			fde->handler(ev, fde, flags, fde->private_data);
			return 0;
		}
	}

	for (i = 0; i < poll_ev->num_fds; i++) {
		if (poll_ev->fds[i].revents & POLLNVAL) {
			/*
			 * the socket is dead! this should never
			 * happen as the socket should have first been
			 * made readable and that should have removed
			 * the event, so this must be a bug or
			 * a race in the poll_mt usage.
			 */
			fde = poll_ev->fdes[i];
			tevent_debug(ev, TEVENT_DEBUG_WARNING,
				     "POLLNVAL on dangling fd[%d] fde[%p] - disabling\n",
				     poll_ev->fds[i].fd, fde);
			poll_ev->fdes[i] = NULL;
			poll_ev->deleted = true;
			if (fde != NULL) {
				DLIST_REMOVE(ev->fd_events, fde);
				fde->event_ctx = NULL;
			}
		}
	}

	return 0;
}

/*
  do a single event loop using the events defined in ev
*/
static int poll_event_loop_once(struct tevent_context *ev,
				const char *location)
{
	struct timeval tval;

	if (ev->signal_events &&
	    tevent_common_check_signal(ev)) {
		return 0;
	}

	if (ev->threaded_contexts != NULL) {
		tevent_common_threaded_activate_immediate(ev);
	}

	if (ev->immediate_events &&
	    tevent_common_loop_immediate(ev)) {
		return 0;
	}

	tval = tevent_common_loop_timer_delay(ev);
	if (tevent_timeval_is_zero(&tval)) {
		return 0;
	}

	return poll_event_loop_poll(ev, &tval);
}

static int poll_event_loop_wait(struct tevent_context *ev,
				const char *location)
{
	struct poll_event_context *poll_ev = talloc_get_type_abort(
		ev->additional_data, struct poll_event_context);

	/*
	 * loop as long as we have events pending
	 */
	while (tevent_common_have_events(ev) ||
	       poll_ev->fresh ||
	       poll_ev->disabled) {
		int ret;
		ret = _tevent_loop_once(ev, location);
		if (ret != 0) {
			tevent_debug(ev, TEVENT_DEBUG_FATAL,
				     "_tevent_loop_once() failed: %d - %s\n",
				     ret, strerror(errno));
			return ret;
		}
	}

	tevent_debug(ev, TEVENT_DEBUG_WARNING,
		     "poll_event_loop_wait() out of events\n");
	return 0;
}

static const struct tevent_ops poll_event_ops = {
	.context_init		= poll_event_context_init,
	.add_fd			= poll_event_add_fd,
	.set_fd_close_fn	= tevent_common_fd_set_close_fn,
	.get_fd_flags		= tevent_common_fd_get_flags,
	.set_fd_flags		= poll_event_set_fd_flags,
	.add_timer		= tevent_common_add_timer_v2,
	.schedule_immediate	= tevent_common_schedule_immediate,
	.add_signal		= tevent_common_add_signal,
	.loop_once		= poll_event_loop_once,
	.loop_wait		= poll_event_loop_wait,
};

_PRIVATE_ bool tevent_poll_init(void)
{
	return tevent_register_backend("poll", &poll_event_ops);
}

static const struct tevent_ops poll_event_mt_ops = {
	.context_init		= poll_event_context_init_mt,
	.add_fd			= poll_event_add_fd,
	.set_fd_close_fn	= tevent_common_fd_set_close_fn,
	.get_fd_flags		= tevent_common_fd_get_flags,
	.set_fd_flags		= poll_event_set_fd_flags,
	.add_timer		= tevent_common_add_timer_v2,
	.schedule_immediate	= poll_event_schedule_immediate,
	.add_signal		= tevent_common_add_signal,
	.loop_once		= poll_event_loop_once,
	.loop_wait		= poll_event_loop_wait,
};

_PRIVATE_ bool tevent_poll_mt_init(void)
{
	return tevent_register_backend("poll_mt", &poll_event_mt_ops);
}