Adding upstream version 0.14.1.upstream/0.14.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 957 insertions, 0 deletions

diff --git a/tevent_epoll.c b/tevent_epoll.c
new file mode 100644
index 0000000..1f1f47b
--- /dev/null
+++ b/tevent_epoll.c
@@ -0,0 +1,957 @@
+/* 
+   Unix SMB/CIFS implementation.
+
+   main select loop and event handling - epoll implementation
+
+   Copyright (C) Andrew Tridgell	2003-2005
+   Copyright (C) Stefan Metzmacher	2005-2013
+   Copyright (C) Jeremy Allison		2013
+
+     ** 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_internal.h"
+#include "tevent_util.h"
+
+struct epoll_event_context {
+	/* a pointer back to the generic event_context */
+	struct tevent_context *ev;
+
+	/* when using epoll this is the handle from epoll_create */
+	int epoll_fd;
+
+	pid_t pid;
+
+	bool panic_force_replay;
+	bool *panic_state;
+	bool (*panic_fallback)(struct tevent_context *ev, bool replay);
+};
+
+#define EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT	(1<<0)
+#define EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR	(1<<1)
+#define EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR	(1<<2)
+#define EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX	(1<<3)
+
+#ifdef TEST_PANIC_FALLBACK
+
+static int epoll_create_panic_fallback(struct epoll_event_context *epoll_ev,
+				       int size)
+{
+	if (epoll_ev->panic_fallback == NULL) {
+		return epoll_create(size);
+	}
+
+	/* 50% of the time, fail... */
+	if ((random() % 2) == 0) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	return epoll_create(size);
+}
+
+static int epoll_ctl_panic_fallback(struct epoll_event_context *epoll_ev,
+				    int epfd, int op, int fd,
+				    struct epoll_event *event)
+{
+	if (epoll_ev->panic_fallback == NULL) {
+		return epoll_ctl(epfd, op, fd, event);
+	}
+
+	/* 50% of the time, fail... */
+	if ((random() % 2) == 0) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	return epoll_ctl(epfd, op, fd, event);
+}
+
+static int epoll_wait_panic_fallback(struct epoll_event_context *epoll_ev,
+				     int epfd,
+				     struct epoll_event *events,
+				     int maxevents,
+				     int timeout)
+{
+	if (epoll_ev->panic_fallback == NULL) {
+		return epoll_wait(epfd, events, maxevents, timeout);
+	}
+
+	/* 50% of the time, fail... */
+	if ((random() % 2) == 0) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	return epoll_wait(epfd, events, maxevents, timeout);
+}
+
+#define epoll_create(_size) \
+	epoll_create_panic_fallback(epoll_ev, _size)
+#define epoll_ctl(_epfd, _op, _fd, _event) \
+	epoll_ctl_panic_fallback(epoll_ev,_epfd, _op, _fd, _event)
+#define epoll_wait(_epfd, _events, _maxevents, _timeout) \
+	epoll_wait_panic_fallback(epoll_ev, _epfd, _events, _maxevents, _timeout)
+#endif
+
+/*
+  called to set the panic fallback function.
+*/
+_PRIVATE_ void tevent_epoll_set_panic_fallback(struct tevent_context *ev,
+				bool (*panic_fallback)(struct tevent_context *ev,
+						       bool replay))
+{
+	struct epoll_event_context *epoll_ev =
+		talloc_get_type_abort(ev->additional_data,
+		struct epoll_event_context);
+
+	epoll_ev->panic_fallback = panic_fallback;
+}
+
+/*
+  called when a epoll call fails
+*/
+static void epoll_panic(struct epoll_event_context *epoll_ev,
+			const char *reason, bool replay)
+{
+	struct tevent_context *ev = epoll_ev->ev;
+	bool (*panic_fallback)(struct tevent_context *ev, bool replay);
+
+	panic_fallback = epoll_ev->panic_fallback;
+
+	if (epoll_ev->panic_state != NULL) {
+		*epoll_ev->panic_state = true;
+	}
+
+	if (epoll_ev->panic_force_replay) {
+		replay = true;
+	}
+
+	TALLOC_FREE(ev->additional_data);
+
+	if (panic_fallback == NULL) {
+		tevent_debug(ev, TEVENT_DEBUG_FATAL,
+			"%s (%s) replay[%u] - calling abort()\n",
+			reason, strerror(errno), (unsigned)replay);
+		abort();
+	}
+
+	tevent_debug(ev, TEVENT_DEBUG_ERROR,
+		     "%s (%s) replay[%u] - calling panic_fallback\n",
+		     reason, strerror(errno), (unsigned)replay);
+
+	if (!panic_fallback(ev, replay)) {
+		/* Fallback failed. */
+		tevent_debug(ev, TEVENT_DEBUG_FATAL,
+			"%s (%s) replay[%u] - calling abort()\n",
+			reason, strerror(errno), (unsigned)replay);
+		abort();
+	}
+}
+
+/*
+  map from TEVENT_FD_* to EPOLLIN/EPOLLOUT
+*/
+static uint32_t epoll_map_flags(uint16_t flags)
+{
+	uint32_t ret = 0;
+	if (flags & TEVENT_FD_READ) ret |= (EPOLLIN | EPOLLERR | EPOLLHUP);
+	if (flags & TEVENT_FD_WRITE) ret |= (EPOLLOUT | EPOLLERR | EPOLLHUP);
+	return ret;
+}
+
+/*
+ free the epoll fd
+*/
+static int epoll_ctx_destructor(struct epoll_event_context *epoll_ev)
+{
+	close(epoll_ev->epoll_fd);
+	epoll_ev->epoll_fd = -1;
+	return 0;
+}
+
+/*
+ init the epoll fd
+*/
+static int epoll_init_ctx(struct epoll_event_context *epoll_ev)
+{
+	epoll_ev->epoll_fd = epoll_create(64);
+	if (epoll_ev->epoll_fd == -1) {
+		tevent_debug(epoll_ev->ev, TEVENT_DEBUG_FATAL,
+			     "Failed to create epoll handle.\n");
+		return -1;
+	}
+
+	if (!ev_set_close_on_exec(epoll_ev->epoll_fd)) {
+		tevent_debug(epoll_ev->ev, TEVENT_DEBUG_WARNING,
+			     "Failed to set close-on-exec, file descriptor may be leaked to children.\n");
+	}
+
+	epoll_ev->pid = tevent_cached_getpid();
+	talloc_set_destructor(epoll_ev, epoll_ctx_destructor);
+
+	return 0;
+}
+
+static void epoll_update_event(struct epoll_event_context *epoll_ev, struct tevent_fd *fde);
+
+/*
+  reopen the epoll handle when our pid changes
+  see http://junkcode.samba.org/ftp/unpacked/junkcode/epoll_fork.c for an
+  demonstration of why this is needed
+ */
+static void epoll_check_reopen(struct epoll_event_context *epoll_ev)
+{
+	struct tevent_fd *fde;
+	bool *caller_panic_state = epoll_ev->panic_state;
+	bool panic_triggered = false;
+	pid_t pid = tevent_cached_getpid();
+
+	if (epoll_ev->pid == pid) {
+		return;
+	}
+
+	close(epoll_ev->epoll_fd);
+	epoll_ev->epoll_fd = epoll_create(64);
+	if (epoll_ev->epoll_fd == -1) {
+		epoll_panic(epoll_ev, "epoll_create() failed", false);
+		return;
+	}
+
+	if (!ev_set_close_on_exec(epoll_ev->epoll_fd)) {
+		tevent_debug(epoll_ev->ev, TEVENT_DEBUG_WARNING,
+			     "Failed to set close-on-exec, file descriptor may be leaked to children.\n");
+	}
+
+	epoll_ev->pid = pid;
+	epoll_ev->panic_state = &panic_triggered;
+	for (fde=epoll_ev->ev->fd_events;fde;fde=fde->next) {
+		fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
+		epoll_update_event(epoll_ev, fde);
+
+		if (panic_triggered) {
+			if (caller_panic_state != NULL) {
+				*caller_panic_state = true;
+			}
+			return;
+		}
+	}
+	epoll_ev->panic_state = NULL;
+}
+
+/*
+ epoll cannot add the same file descriptor twice, once
+ with read, once with write which is allowed by the
+ tevent backend. Multiplex the existing fde, flag it
+ as such so we can search for the correct fde on
+ event triggering.
+*/
+
+static int epoll_add_multiplex_fd(struct epoll_event_context *epoll_ev,
+				  struct tevent_fd *add_fde)
+{
+	struct epoll_event event;
+	struct tevent_fd *mpx_fde;
+	int ret;
+
+	/* Find the existing fde that caused the EEXIST error. */
+	for (mpx_fde = epoll_ev->ev->fd_events; mpx_fde; mpx_fde = mpx_fde->next) {
+		if (mpx_fde->fd != add_fde->fd) {
+			continue;
+		}
+
+		if (mpx_fde == add_fde) {
+			continue;
+		}
+
+		break;
+	}
+	if (mpx_fde == NULL) {
+		tevent_debug(epoll_ev->ev, TEVENT_DEBUG_FATAL,
+			     "can't find multiplex fde for fd[%d]",
+			     add_fde->fd);
+		return -1;
+	}
+
+	if (mpx_fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX) {
+		/* Logic error. Can't have more than 2 multiplexed fde's. */
+		tevent_debug(epoll_ev->ev, TEVENT_DEBUG_FATAL,
+			     "multiplex fde for fd[%d] is already multiplexed\n",
+			     mpx_fde->fd);
+		return -1;
+	}
+
+	/*
+	 * The multiplex fde must have the same fd, and also
+	 * already have an epoll event attached.
+	 */
+	if (!(mpx_fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT)) {
+		/* Logic error. Can't have more than 2 multiplexed fde's. */
+		tevent_debug(epoll_ev->ev, TEVENT_DEBUG_FATAL,
+			     "multiplex fde for fd[%d] has no event\n",
+			     mpx_fde->fd);
+		return -1;
+	}
+
+	/* Modify the mpx_fde to add in the new flags. */
+	ZERO_STRUCT(event);
+	event.events = epoll_map_flags(mpx_fde->flags);
+	event.events |= epoll_map_flags(add_fde->flags);
+	event.data.ptr = mpx_fde;
+	ret = epoll_ctl(epoll_ev->epoll_fd, EPOLL_CTL_MOD, mpx_fde->fd, &event);
+	if (ret != 0 && errno == EBADF) {
+		tevent_debug(epoll_ev->ev, TEVENT_DEBUG_ERROR,
+			     "EPOLL_CTL_MOD EBADF for "
+			     "add_fde[%p] mpx_fde[%p] fd[%d] - disabling\n",
+			     add_fde, mpx_fde, add_fde->fd);
+		DLIST_REMOVE(epoll_ev->ev->fd_events, mpx_fde);
+		mpx_fde->wrapper = NULL;
+		mpx_fde->event_ctx = NULL;
+		DLIST_REMOVE(epoll_ev->ev->fd_events, add_fde);
+		add_fde->wrapper = NULL;
+		add_fde->event_ctx = NULL;
+		return 0;
+	} else if (ret != 0) {
+		return ret;
+	}
+
+	/*
+	 * Make each fde->additional_data pointers point at each other
+	 * so we can look them up from each other. They are now paired.
+	 */
+	mpx_fde->additional_data = (struct tevent_fd *)add_fde;
+	add_fde->additional_data = (struct tevent_fd *)mpx_fde;
+
+	/* Now flag both fde's as being multiplexed. */
+	mpx_fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX;
+	add_fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX;
+
+	/* we need to keep the GOT_ERROR flag */
+	if (mpx_fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR) {
+		add_fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR;
+	}
+
+	return 0;
+}
+
+/*
+ add the epoll event to the given fd_event
+*/
+static void epoll_add_event(struct epoll_event_context *epoll_ev, struct tevent_fd *fde)
+{
+	struct epoll_event event;
+	int ret;
+	struct tevent_fd *mpx_fde = NULL;
+
+	fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
+	fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+
+	if (fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX) {
+		/*
+		 * This is a multiplexed fde, we need to include both
+		 * flags in the modified event.
+		 */
+		mpx_fde = talloc_get_type_abort(fde->additional_data,
+						struct tevent_fd);
+
+		mpx_fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
+		mpx_fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+	}
+
+	ZERO_STRUCT(event);
+	event.events = epoll_map_flags(fde->flags);
+	if (mpx_fde != NULL) {
+		event.events |= epoll_map_flags(mpx_fde->flags);
+	}
+	event.data.ptr = fde;
+	ret = epoll_ctl(epoll_ev->epoll_fd, EPOLL_CTL_ADD, fde->fd, &event);
+	if (ret != 0 && errno == EBADF) {
+		tevent_debug(epoll_ev->ev, TEVENT_DEBUG_ERROR,
+			     "EPOLL_CTL_ADD EBADF for "
+			     "fde[%p] mpx_fde[%p] fd[%d] - disabling\n",
+			     fde, mpx_fde, fde->fd);
+		DLIST_REMOVE(epoll_ev->ev->fd_events, fde);
+		fde->wrapper = NULL;
+		fde->event_ctx = NULL;
+		if (mpx_fde != NULL) {
+			DLIST_REMOVE(epoll_ev->ev->fd_events, mpx_fde);
+			mpx_fde->wrapper = NULL;
+			mpx_fde->event_ctx = NULL;
+		}
+		return;
+	} else if (ret != 0 && errno == EEXIST && mpx_fde == NULL) {
+		ret = epoll_add_multiplex_fd(epoll_ev, fde);
+		if (ret != 0) {
+			epoll_panic(epoll_ev, "epoll_add_multiplex_fd failed",
+				    false);
+			return;
+		}
+	} else if (ret != 0) {
+		epoll_panic(epoll_ev, "EPOLL_CTL_ADD failed", false);
+		return;
+	}
+
+	fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
+	/* only if we want to read we want to tell the event handler about errors */
+	if (fde->flags & TEVENT_FD_READ) {
+		fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+	}
+
+	if (mpx_fde == NULL) {
+		return;
+	}
+
+	mpx_fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
+	/* only if we want to read we want to tell the event handler about errors */
+	if (mpx_fde->flags & TEVENT_FD_READ) {
+		mpx_fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+	}
+}
+
+/*
+ delete the epoll event for given fd_event
+*/
+static void epoll_del_event(struct epoll_event_context *epoll_ev, struct tevent_fd *fde)
+{
+	struct epoll_event event;
+	int ret;
+	struct tevent_fd *mpx_fde = NULL;
+
+	fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
+	fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+
+	if (fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX) {
+		/*
+		 * This is a multiplexed fde, we need to modify both events.
+		 */
+		mpx_fde = talloc_get_type_abort(fde->additional_data,
+						struct tevent_fd);
+
+		mpx_fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
+		mpx_fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+	}
+
+	ZERO_STRUCT(event);
+	ret = epoll_ctl(epoll_ev->epoll_fd, EPOLL_CTL_DEL, fde->fd, &event);
+	if (ret != 0 && errno == ENOENT) {
+		/*
+		 * This can happen after a epoll_check_reopen
+		 * within epoll_event_fd_destructor.
+		 */
+		tevent_debug(epoll_ev->ev, TEVENT_DEBUG_TRACE,
+			     "EPOLL_CTL_DEL ignoring ENOENT for fd[%d]\n",
+			     fde->fd);
+		return;
+	} else if (ret != 0 && errno == EBADF) {
+		tevent_debug(epoll_ev->ev, TEVENT_DEBUG_WARNING,
+			     "EPOLL_CTL_DEL EBADF for "
+			     "fde[%p] mpx_fde[%p] fd[%d] - disabling\n",
+			     fde, mpx_fde, fde->fd);
+		DLIST_REMOVE(epoll_ev->ev->fd_events, fde);
+		fde->wrapper = NULL;
+		fde->event_ctx = NULL;
+		if (mpx_fde != NULL) {
+			DLIST_REMOVE(epoll_ev->ev->fd_events, mpx_fde);
+			mpx_fde->wrapper = NULL;
+			mpx_fde->event_ctx = NULL;
+		}
+		return;
+	} else if (ret != 0) {
+		epoll_panic(epoll_ev, "EPOLL_CTL_DEL failed", false);
+		return;
+	}
+}
+
+/*
+ change the epoll event to the given fd_event
+*/
+static void epoll_mod_event(struct epoll_event_context *epoll_ev, struct tevent_fd *fde)
+{
+	struct tevent_fd *mpx_fde = NULL;
+	struct epoll_event event;
+	int ret;
+
+	fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
+	fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+
+	if (fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX) {
+		/*
+		 * This is a multiplexed fde, we need to include both
+		 * flags in the modified event.
+		 */
+		mpx_fde = talloc_get_type_abort(fde->additional_data,
+						struct tevent_fd);
+
+		mpx_fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
+		mpx_fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+	}
+
+	ZERO_STRUCT(event);
+	event.events = epoll_map_flags(fde->flags);
+	if (mpx_fde != NULL) {
+		event.events |= epoll_map_flags(mpx_fde->flags);
+	}
+	event.data.ptr = fde;
+	ret = epoll_ctl(epoll_ev->epoll_fd, EPOLL_CTL_MOD, fde->fd, &event);
+	if (ret != 0 && errno == EBADF) {
+		tevent_debug(epoll_ev->ev, TEVENT_DEBUG_ERROR,
+			     "EPOLL_CTL_MOD EBADF for "
+			     "fde[%p] mpx_fde[%p] fd[%d] - disabling\n",
+			     fde, mpx_fde, fde->fd);
+		DLIST_REMOVE(epoll_ev->ev->fd_events, fde);
+		fde->wrapper = NULL;
+		fde->event_ctx = NULL;
+		if (mpx_fde != NULL) {
+			DLIST_REMOVE(epoll_ev->ev->fd_events, mpx_fde);
+			mpx_fde->wrapper = NULL;
+			mpx_fde->event_ctx = NULL;
+		}
+		return;
+	} else if (ret != 0) {
+		epoll_panic(epoll_ev, "EPOLL_CTL_MOD failed", false);
+		return;
+	}
+
+	fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
+	/* only if we want to read we want to tell the event handler about errors */
+	if (fde->flags & TEVENT_FD_READ) {
+		fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+	}
+
+	if (mpx_fde == NULL) {
+		return;
+	}
+
+	mpx_fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
+	/* only if we want to read we want to tell the event handler about errors */
+	if (mpx_fde->flags & TEVENT_FD_READ) {
+		mpx_fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+	}
+}
+
+static void epoll_update_event(struct epoll_event_context *epoll_ev, struct tevent_fd *fde)
+{
+	bool got_error = (fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR);
+	bool want_read = (fde->flags & TEVENT_FD_READ);
+	bool want_write= (fde->flags & TEVENT_FD_WRITE);
+	struct tevent_fd *mpx_fde = NULL;
+
+	if (fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX) {
+		/*
+		 * work out what the multiplexed fde wants.
+		 */
+		mpx_fde = talloc_get_type_abort(fde->additional_data,
+						struct tevent_fd);
+
+		if (mpx_fde->flags & TEVENT_FD_READ) {
+			want_read = true;
+		}
+
+		if (mpx_fde->flags & TEVENT_FD_WRITE) {
+			want_write = true;
+		}
+	}
+
+	/* there's already an event */
+	if (fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT) {
+		if (want_read || (want_write && !got_error)) {
+			epoll_mod_event(epoll_ev, fde);
+			return;
+		}
+		/* 
+		 * if we want to match the select behavior, we need to remove the epoll_event
+		 * when the caller isn't interested in events.
+		 *
+		 * this is because epoll reports EPOLLERR and EPOLLHUP, even without asking for them
+		 */
+		epoll_del_event(epoll_ev, fde);
+		return;
+	}
+
+	/* there's no epoll_event attached to the fde */
+	if (want_read || (want_write && !got_error)) {
+		epoll_add_event(epoll_ev, fde);
+		return;
+	}
+}
+
+/*
+  Cope with epoll returning EPOLLHUP|EPOLLERR on an event.
+  Return true if there's nothing else to do, false if
+  this event needs further handling.
+*/
+static bool epoll_handle_hup_or_err(struct epoll_event_context *epoll_ev,
+				struct tevent_fd *fde)
+{
+	if (fde == NULL) {
+		/* Nothing to do if no event. */
+		return true;
+	}
+
+	fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR;
+	/*
+	 * if we only wait for TEVENT_FD_WRITE, we should not tell the
+	 * event handler about it, and remove the epoll_event,
+	 * as we only report errors when waiting for read events,
+	 * to match the select() behavior
+	 */
+	if (!(fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR)) {
+		/*
+		 * Do the same as the poll backend and
+		 * remove the writeable flag.
+		 */
+		fde->flags &= ~TEVENT_FD_WRITE;
+		return true;
+	}
+	/* This has TEVENT_FD_READ set, we're not finished. */
+	return false;
+}
+
+/*
+  event loop handling using epoll
+*/
+static int epoll_event_loop(struct epoll_event_context *epoll_ev, struct timeval *tvalp)
+{
+	int ret, i;
+#define MAXEVENTS 1
+	struct epoll_event events[MAXEVENTS];
+	int timeout = -1;
+	int wait_errno;
+
+	if (tvalp) {
+		/* it's better to trigger timed events a bit later than too early */
+		timeout = ((tvalp->tv_usec+999) / 1000) + (tvalp->tv_sec*1000);
+	}
+
+	if (epoll_ev->ev->signal_events &&
+	    tevent_common_check_signal(epoll_ev->ev)) {
+		return 0;
+	}
+
+	tevent_trace_point_callback(epoll_ev->ev, TEVENT_TRACE_BEFORE_WAIT);
+	ret = epoll_wait(epoll_ev->epoll_fd, events, MAXEVENTS, timeout);
+	wait_errno = errno;
+	tevent_trace_point_callback(epoll_ev->ev, TEVENT_TRACE_AFTER_WAIT);
+
+	if (ret == -1 && wait_errno == EINTR && epoll_ev->ev->signal_events) {
+		if (tevent_common_check_signal(epoll_ev->ev)) {
+			return 0;
+		}
+	}
+
+	if (ret == -1 && wait_errno != EINTR) {
+		epoll_panic(epoll_ev, "epoll_wait() failed", true);
+		return -1;
+	}
+
+	if (ret == 0 && tvalp) {
+		/* we don't care about a possible delay here */
+		tevent_common_loop_timer_delay(epoll_ev->ev);
+		return 0;
+	}
+
+	for (i=0;i<ret;i++) {
+		struct tevent_fd *fde = talloc_get_type(events[i].data.ptr,
+						       struct tevent_fd);
+		uint16_t flags = 0;
+		struct tevent_fd *mpx_fde = NULL;
+
+		if (fde == NULL) {
+			epoll_panic(epoll_ev, "epoll_wait() gave bad data", true);
+			return -1;
+		}
+		if (fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX) {
+			/*
+			 * Save off the multiplexed event in case we need
+			 * to use it to call the handler function.
+			 */
+			mpx_fde = talloc_get_type_abort(fde->additional_data,
+							struct tevent_fd);
+		}
+		if (events[i].events & (EPOLLHUP|EPOLLERR)) {
+			bool handled_fde = epoll_handle_hup_or_err(epoll_ev, fde);
+			bool handled_mpx = epoll_handle_hup_or_err(epoll_ev, mpx_fde);
+
+			if (handled_fde && handled_mpx) {
+				epoll_update_event(epoll_ev, fde);
+				continue;
+			}
+
+			if (!handled_mpx) {
+				/*
+				 * If the mpx event was the one that needs
+				 * further handling, it's the TEVENT_FD_READ
+				 * event so switch over and call that handler.
+				 */
+				fde = mpx_fde;
+				mpx_fde = NULL;
+			}
+			flags |= TEVENT_FD_READ;
+		}
+		if (events[i].events & EPOLLIN) flags |= TEVENT_FD_READ;
+		if (events[i].events & EPOLLOUT) flags |= TEVENT_FD_WRITE;
+
+		if (flags & TEVENT_FD_WRITE) {
+			if (fde->flags & TEVENT_FD_WRITE) {
+				mpx_fde = NULL;
+			}
+			if (mpx_fde && mpx_fde->flags & TEVENT_FD_WRITE) {
+				fde = mpx_fde;
+				mpx_fde = NULL;
+			}
+		}
+
+		if (mpx_fde) {
+			/* Ensure we got the right fde. */
+			if ((flags & fde->flags) == 0) {
+				fde = mpx_fde;
+				mpx_fde = NULL;
+			}
+		}
+
+		/*
+		 * make sure we only pass the flags
+		 * the handler is expecting.
+		 */
+		flags &= fde->flags;
+		if (flags) {
+			return tevent_common_invoke_fd_handler(fde, flags, NULL);
+		}
+	}
+
+	return 0;
+}
+
+/*
+  create a epoll_event_context structure.
+*/
+static int epoll_event_context_init(struct tevent_context *ev)
+{
+	int ret;
+	struct epoll_event_context *epoll_ev;
+
+	/*
+	 * We might be called during tevent_re_initialise()
+	 * which means we need to free our old additional_data.
+	 */
+	TALLOC_FREE(ev->additional_data);
+
+	epoll_ev = talloc_zero(ev, struct epoll_event_context);
+	if (!epoll_ev) return -1;
+	epoll_ev->ev = ev;
+	epoll_ev->epoll_fd = -1;
+
+	ret = epoll_init_ctx(epoll_ev);
+	if (ret != 0) {
+		talloc_free(epoll_ev);
+		return ret;
+	}
+
+	ev->additional_data = epoll_ev;
+	return 0;
+}
+
+/*
+  destroy an fd_event
+*/
+static int epoll_event_fd_destructor(struct tevent_fd *fde)
+{
+	struct tevent_context *ev = fde->event_ctx;
+	struct epoll_event_context *epoll_ev = NULL;
+	bool panic_triggered = false;
+	struct tevent_fd *mpx_fde = NULL;
+	int flags = fde->flags;
+
+	if (ev == NULL) {
+		return tevent_common_fd_destructor(fde);
+	}
+
+	epoll_ev = talloc_get_type_abort(ev->additional_data,
+					 struct epoll_event_context);
+
+	/*
+	 * we must remove the event from the list
+	 * otherwise a panic fallback handler may
+	 * reuse invalid memory
+	 */
+	DLIST_REMOVE(ev->fd_events, fde);
+
+	if (fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX) {
+		mpx_fde = talloc_get_type_abort(fde->additional_data,
+						struct tevent_fd);
+
+		fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX;
+		mpx_fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX;
+
+		fde->additional_data = NULL;
+		mpx_fde->additional_data = NULL;
+
+		fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
+	}
+
+	epoll_ev->panic_state = &panic_triggered;
+	epoll_check_reopen(epoll_ev);
+	if (panic_triggered) {
+		return tevent_common_fd_destructor(fde);
+	}
+
+	if (mpx_fde != NULL) {
+		epoll_update_event(epoll_ev, mpx_fde);
+		if (panic_triggered) {
+			return tevent_common_fd_destructor(fde);
+		}
+	}
+
+	fde->flags = 0;
+	epoll_update_event(epoll_ev, fde);
+	fde->flags = flags;
+	if (panic_triggered) {
+		return tevent_common_fd_destructor(fde);
+	}
+	epoll_ev->panic_state = NULL;
+
+	return tevent_common_fd_destructor(fde);
+}
+
+/*
+  add a fd based event
+  return NULL on failure (memory allocation error)
+*/
+static struct tevent_fd *epoll_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 epoll_event_context *epoll_ev =
+		talloc_get_type_abort(ev->additional_data,
+		struct epoll_event_context);
+	struct tevent_fd *fde;
+	bool panic_triggered = false;
+
+	fde = tevent_common_add_fd(ev, mem_ctx, fd, flags,
+				   handler, private_data,
+				   handler_name, location);
+	if (!fde) return NULL;
+
+	talloc_set_destructor(fde, epoll_event_fd_destructor);
+
+	epoll_ev->panic_state = &panic_triggered;
+	epoll_check_reopen(epoll_ev);
+	if (panic_triggered) {
+		return fde;
+	}
+	epoll_ev->panic_state = NULL;
+
+	epoll_update_event(epoll_ev, fde);
+
+	return fde;
+}
+
+/*
+  set the fd event flags
+*/
+static void epoll_event_set_fd_flags(struct tevent_fd *fde, uint16_t flags)
+{
+	struct tevent_context *ev;
+	struct epoll_event_context *epoll_ev;
+	bool panic_triggered = false;
+
+	if (fde->flags == flags) return;
+
+	ev = fde->event_ctx;
+	epoll_ev = talloc_get_type_abort(ev->additional_data,
+					 struct epoll_event_context);
+
+	fde->flags = flags;
+
+	epoll_ev->panic_state = &panic_triggered;
+	epoll_check_reopen(epoll_ev);
+	if (panic_triggered) {
+		return;
+	}
+	epoll_ev->panic_state = NULL;
+
+	epoll_update_event(epoll_ev, fde);
+}
+
+/*
+  do a single event loop using the events defined in ev
+*/
+static int epoll_event_loop_once(struct tevent_context *ev, const char *location)
+{
+	struct epoll_event_context *epoll_ev =
+		talloc_get_type_abort(ev->additional_data,
+		struct epoll_event_context);
+	struct timeval tval;
+	bool panic_triggered = false;
+
+	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;
+	}
+
+	epoll_ev->panic_state = &panic_triggered;
+	epoll_ev->panic_force_replay = true;
+	epoll_check_reopen(epoll_ev);
+	if (panic_triggered) {
+		errno = EINVAL;
+		return -1;
+	}
+	epoll_ev->panic_force_replay = false;
+	epoll_ev->panic_state = NULL;
+
+	return epoll_event_loop(epoll_ev, &tval);
+}
+
+static const struct tevent_ops epoll_event_ops = {
+	.context_init		= epoll_event_context_init,
+	.add_fd			= epoll_event_add_fd,
+	.set_fd_close_fn	= tevent_common_fd_set_close_fn,
+	.get_fd_flags		= tevent_common_fd_get_flags,
+	.set_fd_flags		= epoll_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		= epoll_event_loop_once,
+	.loop_wait		= tevent_common_loop_wait,
+};
+
+_PRIVATE_ bool tevent_epoll_init(void)
+{
+	return tevent_register_backend("epoll", &epoll_event_ops);
+}