Add Solaris ports as a tevent backend.

Signed-off-by: Jeremy Allison <jra@samba.org>
Reviewed-by: David Disseldorp <ddiss@samba.org>

Autobuild-User(master): David Disseldorp <ddiss@samba.org>
Autobuild-Date(master): Sun Feb 15 23:25:07 CET 2015 on sn-devel-104

1 files changed, 779 insertions, 0 deletions

diff --git a/lib/tevent/tevent_port.c b/lib/tevent/tevent_port.c
new file mode 100644
index 00000000000..93e94b2158f
--- /dev/null
+++ b/lib/tevent/tevent_port.c
@@ -0,0 +1,779 @@
+/*
+   Unix SMB/CIFS implementation.
+
+   Main select loop and event handling - Solaris port implementation.
+   Losely based on the Linux epoll backend.
+
+   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 port_associate_vals {
+	struct port_associate_vals *prev, *next;
+	struct port_event_context *port_ev;
+	int events;
+	struct tevent_fd *fde;
+	bool associated_event;
+};
+
+struct port_event_context {
+	/* a pointer back to the generic event_context */
+	struct tevent_context *ev;
+
+	/* This is the handle from port_create */
+	int port_fd;
+
+	pid_t pid;
+
+	/* List of associations. */
+	struct port_associate_vals *po_vals;
+};
+
+#define PORT_ADDITIONAL_FD_FLAG_HAS_ASSOCIATION	(1<<0)
+#define PORT_ADDITIONAL_FD_FLAG_REPORT_ERROR	(1<<1)
+#define PORT_ADDITIONAL_FD_FLAG_GOT_ERROR	(1<<2)
+#define PORT_ADDITIONAL_FD_FLAG_HAS_MPX		(1<<3)
+
+/*
+  Map from TEVENT_FD_* to POLLIN/POLLOUT
+*/
+static int port_map_flags(uint16_t flags)
+{
+	int ret = 0;
+	if (flags & TEVENT_FD_READ) ret |= (POLLIN | POLLERR | POLLHUP);
+	if (flags & TEVENT_FD_WRITE) ret |= (POLLOUT | POLLERR | POLLHUP);
+	return ret;
+}
+
+/*
+ Free the port fd
+*/
+static int port_ctx_destructor(struct port_event_context *port_ev)
+{
+	close(port_ev->port_fd);
+	port_ev->port_fd = -1;
+	return 0;
+}
+
+/*
+ Init the port fd
+*/
+static int port_init_ctx(struct port_event_context *port_ev)
+{
+	port_ev->port_fd = port_create();
+	if (port_ev->port_fd == -1) {
+		tevent_debug(port_ev->ev, TEVENT_DEBUG_FATAL,
+			     "Failed to create port handle.\n");
+		return -1;
+	}
+
+	if (!ev_set_close_on_exec(port_ev->port_fd)) {
+		tevent_debug(port_ev->ev, TEVENT_DEBUG_WARNING,
+			     "Failed to set close-on-exec, file descriptor may be leaked to children.\n");
+	}
+
+	port_ev->pid = getpid();
+	talloc_set_destructor(port_ev, port_ctx_destructor);
+
+	return 0;
+}
+
+/*
+ Functions to manage the lower level cache of associated events on the port_fd.
+*/
+
+static int port_associate_vals_destructor(struct port_associate_vals *val)
+{
+	DLIST_REMOVE(val->port_ev->po_vals, val);
+	memset(val, '\0', sizeof(struct port_associate_vals));
+	return 0;
+}
+
+/*
+ * TODO: As the port_association is per-fde, it should be possible to store it
+ * directly in fde->additional_data, alongside any multiplexed-fde. That way the
+ * lookup on store and delete would be avoided, and associate_all_events() could
+ * walk the ev->fd_events list.
+ */
+static bool store_port_association(struct port_event_context *port_ev,
+				struct tevent_fd *fde,
+				int events)
+{
+	struct port_associate_vals *val;
+
+	for (val = port_ev->po_vals; val; val = val->next) {
+		if (val->fde->fd == fde->fd) {
+			/* Association already attached to fd. */
+			if (val->events != events) {
+				val->events = events;
+				val->associated_event = false;
+			}
+			return true;
+		}
+	}
+
+	val = talloc_zero(port_ev, struct port_associate_vals);
+	if (val == NULL) {
+		return false;
+	}
+
+	val->port_ev = port_ev;
+	val->fde = fde;
+	val->events = events;
+	val->associated_event = false;
+
+	DLIST_ADD(port_ev->po_vals, val);
+	talloc_set_destructor(val, port_associate_vals_destructor);
+
+	return true;
+}
+
+static void delete_port_association(struct port_event_context *port_ev,
+				struct tevent_fd *fde)
+{
+	struct port_associate_vals *val;
+
+	for (val = port_ev->po_vals; val; val = val->next) {
+		if (val->fde == fde) {
+			if (val->associated_event) {
+				(void)port_dissociate(port_ev->port_fd,
+							PORT_SOURCE_FD,
+							fde->fd);
+			}
+			talloc_free(val);
+			return;
+		}
+	}
+}
+
+static int associate_all_events(struct port_event_context *port_ev)
+{
+	struct port_associate_vals *val;
+
+	for (val = port_ev->po_vals; val; val = val->next) {
+		if (val->associated_event) {
+			continue;
+		}
+		int ret = port_associate(port_ev->port_fd,
+					PORT_SOURCE_FD,
+					(uintptr_t)val->fde->fd,
+					val->events,
+					(void *)val);
+		if (ret != 0) {
+			return -1;
+		}
+		val->associated_event = true;
+	}
+	return 0;
+}
+
+static int port_update_event(struct port_event_context *port_ev, struct tevent_fd *fde);
+
+/*
+  Reopen the port handle when our pid changes.
+ */
+static int port_check_reopen(struct port_event_context *port_ev)
+{
+	struct tevent_fd *fde;
+
+	if (port_ev->pid == getpid()) {
+		return 0;
+	}
+
+	close(port_ev->port_fd);
+	port_ev->port_fd = port_create();
+	if (port_ev->port_fd == -1) {
+		tevent_debug(port_ev->ev, TEVENT_DEBUG_FATAL,
+				"port_create() failed");
+		return -1;
+	}
+
+	if (!ev_set_close_on_exec(port_ev->port_fd)) {
+		tevent_debug(port_ev->ev, TEVENT_DEBUG_WARNING,
+			     "Failed to set close-on-exec, file descriptor may be leaked to children.\n");
+	}
+
+	port_ev->pid = getpid();
+	for (fde=port_ev->ev->fd_events;fde;fde=fde->next) {
+		fde->additional_flags &= PORT_ADDITIONAL_FD_FLAG_HAS_ASSOCIATION;
+		if (port_update_event(port_ev, fde) != 0) {
+			return -1;
+		}
+	}
+	return 0;
+}
+
+/*
+ * Solaris ports 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 void port_setup_multiplex_fd(struct port_event_context *port_ev,
+				struct tevent_fd *add_fde,
+				struct tevent_fd *mpx_fde)
+{
+	/*
+	 * 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 = add_fde;
+	add_fde->additional_data = mpx_fde;
+
+	/* Now flag both fde's as being multiplexed. */
+	mpx_fde->additional_flags |= PORT_ADDITIONAL_FD_FLAG_HAS_MPX;
+	add_fde->additional_flags |= PORT_ADDITIONAL_FD_FLAG_HAS_MPX;
+
+	/* We need to keep the GOT_ERROR flag. */
+	if (mpx_fde->additional_flags & PORT_ADDITIONAL_FD_FLAG_GOT_ERROR) {
+		add_fde->additional_flags |= PORT_ADDITIONAL_FD_FLAG_GOT_ERROR;
+	}
+}
+
+/*
+ Add the port event to the given fd_event,
+ Or modify an existing event.
+*/
+
+static int port_add_event(struct port_event_context *port_ev, struct tevent_fd *fde)
+{
+	int flags = port_map_flags(fde->flags);
+	struct tevent_fd *mpx_fde = NULL;
+
+	fde->additional_flags &= ~PORT_ADDITIONAL_FD_FLAG_HAS_ASSOCIATION;
+	fde->additional_flags &= ~PORT_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+
+	if (fde->additional_flags & PORT_ADDITIONAL_FD_FLAG_HAS_MPX) {
+		/*
+		 * This is already 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 &= ~PORT_ADDITIONAL_FD_FLAG_HAS_ASSOCIATION;
+		mpx_fde->additional_flags &= ~PORT_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+
+		flags |= port_map_flags(mpx_fde->flags);
+	} else {
+		/*
+		 * Not (yet) a multiplexed event. See if there
+		 * is already an event with the same fd.
+		 */
+		for (mpx_fde = port_ev->ev->fd_events; mpx_fde; mpx_fde = mpx_fde->next) {
+			if (mpx_fde->fd != fde->fd) {
+				continue;
+			}
+			if (mpx_fde == fde) {
+				continue;
+			}
+			/* Same fd. */
+			break;
+		}
+		if (mpx_fde) {
+			if (mpx_fde->additional_flags & PORT_ADDITIONAL_FD_FLAG_HAS_MPX) {
+				/* Logic error. Can't have more then 2 multiplexed fde's. */
+				tevent_debug(port_ev->ev, TEVENT_DEBUG_FATAL,
+					"multiplex fde for fd[%d] is already multiplexed\n",
+					mpx_fde->fd);
+				return -1;
+			}
+			flags |= port_map_flags(mpx_fde->flags);
+		}
+	}
+
+	if (!store_port_association(port_ev,
+				fde,
+				flags)) {
+		tevent_debug(port_ev->ev, TEVENT_DEBUG_FATAL,
+			"store_port_association failed for fd[%d]\n",
+			fde->fd);
+		return -1;
+	}
+
+	/* Note we have an association now. */
+	fde->additional_flags |= PORT_ADDITIONAL_FD_FLAG_HAS_ASSOCIATION;
+	/* Only if we want to read do we tell the event handler about errors. */
+	if (fde->flags & TEVENT_FD_READ) {
+		fde->additional_flags |= PORT_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+	}
+	if (mpx_fde == NULL) {
+		return 0;
+	}
+	/* Set up the multiplex pointer. Does no harm if already multiplexed. */
+	port_setup_multiplex_fd(port_ev,
+				fde,
+				mpx_fde);
+
+	mpx_fde->additional_flags |= PORT_ADDITIONAL_FD_FLAG_HAS_ASSOCIATION;
+	/* Only if we want to read do we tell the event handler about errors. */
+	if (mpx_fde->flags & TEVENT_FD_READ) {
+		mpx_fde->additional_flags |= PORT_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+	}
+
+	return 0;
+}
+
+/*
+ Delete the port association for the given fd_event.
+*/
+
+static void port_del_event(struct port_event_context *port_ev, struct tevent_fd *fde)
+{
+	struct tevent_fd *mpx_fde = NULL;
+
+	fde->additional_flags &= ~PORT_ADDITIONAL_FD_FLAG_HAS_ASSOCIATION;
+	fde->additional_flags &= ~PORT_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+
+	if (fde->additional_flags & PORT_ADDITIONAL_FD_FLAG_HAS_MPX) {
+		/*
+		 * This is a multiplexed fde, we need to remove
+		 * both associations.
+		 */
+		mpx_fde = talloc_get_type_abort(fde->additional_data,
+						struct tevent_fd);
+
+		mpx_fde->additional_flags &= ~PORT_ADDITIONAL_FD_FLAG_HAS_ASSOCIATION;
+		mpx_fde->additional_flags &= ~PORT_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+		mpx_fde->additional_data = NULL;
+
+		fde->additional_data = NULL;
+	}
+	delete_port_association(port_ev, fde);
+}
+
+/*
+ Add or remove the port event from the given fd_event
+*/
+static int port_update_event(struct port_event_context *port_ev, struct tevent_fd *fde)
+{
+	bool got_error = (fde->additional_flags & PORT_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 & PORT_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;
+		}
+	}
+
+	if (fde->additional_flags & PORT_ADDITIONAL_FD_FLAG_HAS_ASSOCIATION) {
+		/* There's already an association. */
+		if (want_read || (want_write && !got_error)) {
+			return port_add_event(port_ev, fde);
+		}
+		/*
+		 * If we want to match the select behavior, we need to remove the port event
+		 * when the caller isn't interested in events.
+		 */
+		port_del_event(port_ev, fde);
+		return 0;
+	}
+
+	/* There's no port event attached to the fde. */
+	if (want_read || (want_write && !got_error)) {
+		return port_add_event(port_ev, fde);
+	}
+	return 0;
+}
+
+/*
+ Cope with port_get returning EPOLLHP|EPOLLERR on an association.
+ Return true if there's nothing else to do, false if this event
+ needs further handling.
+*/
+
+static bool port_handle_hup_or_err(struct port_event_context *port_ev,
+				struct tevent_fd *fde)
+{
+	if (fde == NULL) {
+		return true;
+	}
+
+	fde->additional_flags |= PORT_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 port association,
+	 * as we only report error when waiting for read events,
+	 * to match the select() behavior.
+	 */
+	if (!(fde->additional_flags & PORT_ADDITIONAL_FD_FLAG_REPORT_ERROR)) {
+		/*
+		 * Do the same as the poll backend and
+		 * remove the writable flag.
+		 */
+		fde->flags &= ~TEVENT_FD_WRITE;
+		return true;
+	}
+	/* This has TEVENT_FD_READ set, we're not finished. */
+	return false;
+}
+
+/*
+  Event loop handling using Solaris ports.
+*/
+static int port_event_loop(struct port_event_context *port_ev, struct timeval *tvalp)
+{
+	int ret;
+#define MAXEVENTS 1
+	port_event_t events[MAXEVENTS];
+	uint_t nget = 1;
+	uint_t max_events = MAXEVENTS;
+	uint_t i;
+	int port_errno;
+	struct timespec ts;
+	struct tevent_context *ev = port_ev->ev;
+
+	if (tvalp) {
+		ts.tv_sec = tvalp->tv_sec;
+		ts.tv_nsec = tvalp->tv_usec * 1000;
+	}
+
+	if (port_ev->ev->signal_events &&
+	    tevent_common_check_signal(ev)) {
+		return 0;
+	}
+
+	/*
+	 * Solaris triggers sending the event to the port
+	 * at the time the port association is done. Postpone
+	 * associating fd's until just before we get the events,
+	 * otherwise we can deadlock.
+	 */
+
+	if (associate_all_events(port_ev) != 0) {
+		return -1;
+	}
+
+	tevent_trace_point_callback(ev, TEVENT_TRACE_BEFORE_WAIT);
+	ret = port_getn(port_ev->port_fd, events, max_events, &nget, &ts);
+	port_errno = errno;
+	tevent_trace_point_callback(ev, TEVENT_TRACE_AFTER_WAIT);
+
+	if (ret == -1 && port_errno == EINTR && ev->signal_events) {
+		if (tevent_common_check_signal(ev)) {
+			return 0;
+		}
+	}
+
+	if (ret == -1 && port_errno == ETIME && tvalp) {
+		/* we don't care about a possible delay here */
+		tevent_common_loop_timer_delay(ev);
+		return 0;
+	}
+
+	if (ret == -1) {
+		tevent_debug(ev, TEVENT_DEBUG_ERROR,
+				"port_get failed (%s)\n",
+				strerror(errno));
+		return -1;
+	}
+
+	for (i = 0; i < nget; i++) {
+		struct tevent_fd *mpx_fde = NULL;
+		struct tevent_fd *fde = NULL;
+		uint16_t flags = 0;
+		struct port_associate_vals *val = talloc_get_type(events[i].portev_user,
+							struct port_associate_vals);
+		if (val == NULL) {
+			tevent_debug(ev, TEVENT_DEBUG_ERROR,
+				"port_getn() gave bad data");
+			return -1;
+		}
+
+		/* Mark this event as needing to be re-associated. */
+		val->associated_event = false;
+
+		fde = val->fde;
+
+		if (fde->additional_flags & PORT_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].portev_events & (POLLHUP|POLLERR)) {
+			bool handled_fde = port_handle_hup_or_err(port_ev, fde);
+			bool handled_mpx = port_handle_hup_or_err(port_ev, mpx_fde);
+
+			if (handled_fde && handled_mpx) {
+				return port_update_event(port_ev, fde);
+			}
+
+			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].portev_events & POLLIN) {
+			flags |= TEVENT_FD_READ;
+		}
+		if (events[i].portev_events & POLLOUT) {
+			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) {
+			fde->handler(ev, fde, flags, fde->private_data);
+			break;
+		}
+	}
+
+	return 0;
+}
+
+
+/*
+  create a port_event_context structure.
+*/
+static int port_event_context_init(struct tevent_context *ev)
+{
+	int ret;
+	struct port_event_context *port_ev;
+
+	/*
+	 * We might be called during tevent_re_initialise()
+	 * which means we need to free our old additional_data.
+	 */
+	TALLOC_FREE(ev->additional_data);
+
+	port_ev = talloc_zero(ev, struct port_event_context);
+	if (!port_ev) {
+		return -1;
+	}
+	port_ev->ev = ev;
+	port_ev->port_fd = -1;
+	port_ev->pid = (pid_t)-1;
+
+	ret = port_init_ctx(port_ev);
+	if (ret != 0) {
+		talloc_free(port_ev);
+		return ret;
+	}
+
+	ev->additional_data = port_ev;
+	return 0;
+}
+
+/*
+  destroy an fd_event
+*/
+static int port_event_fd_destructor(struct tevent_fd *fde)
+{
+	struct tevent_context *ev = fde->event_ctx;
+	struct port_event_context *port_ev = NULL;
+	struct tevent_fd *mpx_fde = NULL;
+	int flags = (int)fde->flags;
+
+	if (ev == NULL) {
+		return tevent_common_fd_destructor(fde);
+	}
+
+	port_ev = talloc_get_type_abort(ev->additional_data,
+					 struct port_event_context);
+
+	DLIST_REMOVE(ev->fd_events, fde);
+
+	if (fde->additional_flags & PORT_ADDITIONAL_FD_FLAG_HAS_MPX) {
+		mpx_fde = talloc_get_type_abort(fde->additional_data,
+						struct tevent_fd);
+
+		fde->additional_flags &= ~PORT_ADDITIONAL_FD_FLAG_HAS_MPX;
+		mpx_fde->additional_flags &= ~PORT_ADDITIONAL_FD_FLAG_HAS_MPX;
+
+		fde->additional_data = NULL;
+		mpx_fde->additional_data = NULL;
+
+		fde->additional_flags &= PORT_ADDITIONAL_FD_FLAG_HAS_ASSOCIATION;
+	}
+
+	(void)port_check_reopen(port_ev);
+
+	if (mpx_fde != NULL) {
+		(void)port_update_event(port_ev, mpx_fde);
+	}
+
+	fde->flags = 0;
+	(void)port_update_event(port_ev, fde);
+	fde->flags = flags;
+
+	return tevent_common_fd_destructor(fde);
+}
+
+/*
+  add a fd based event
+  return NULL on failure (memory allocation error)
+*/
+static struct tevent_fd *port_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 port_event_context *port_ev =
+				talloc_get_type_abort(ev->additional_data,
+				struct port_event_context);
+	struct tevent_fd *fde;
+
+	fde = tevent_common_add_fd(ev, mem_ctx, fd, flags,
+				   handler, private_data,
+				   handler_name, location);
+	if (!fde) {
+		return NULL;
+	}
+
+	talloc_set_destructor(fde, port_event_fd_destructor);
+
+	if (port_check_reopen(port_ev) != 0) {
+		TALLOC_FREE(fde);
+		return NULL;
+	}
+
+	if (port_update_event(port_ev, fde) != 0) {
+		TALLOC_FREE(fde);
+		return NULL;
+	}
+
+	return fde;
+}
+
+/*
+  set the fd event flags
+*/
+static void port_event_set_fd_flags(struct tevent_fd *fde, uint16_t flags)
+{
+	struct tevent_context *ev;
+	struct port_event_context *port_ev;
+
+	if (fde->flags == flags) {
+		return;
+	}
+
+	ev = fde->event_ctx;
+	port_ev = talloc_get_type_abort(ev->additional_data,
+				struct port_event_context);
+
+	fde->flags = flags;
+
+	(void)port_check_reopen(port_ev);
+	(void)port_update_event(port_ev, fde);
+}
+
+/*
+  do a single event loop using the events defined in ev
+*/
+static int port_event_loop_once(struct tevent_context *ev, const char *location)
+{
+	struct port_event_context *port_ev = talloc_get_type(ev->additional_data,
+							   struct port_event_context);
+	struct timeval tval;
+
+	if (ev->signal_events &&
+	    tevent_common_check_signal(ev)) {
+		return 0;
+	}
+
+	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;
+	}
+
+	if (port_check_reopen(port_ev) != 0) {
+		errno = EINVAL;
+		return -1;
+	}
+	return port_event_loop(port_ev, &tval);
+}
+
+static const struct tevent_ops port_event_ops = {
+	.context_init		= port_event_context_init,
+	.add_fd			= port_event_add_fd,
+	.set_fd_close_fn	= tevent_common_fd_set_close_fn,
+	.get_fd_flags		= tevent_common_fd_get_flags,
+	.set_fd_flags		= port_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		= port_event_loop_once,
+	.loop_wait		= tevent_common_loop_wait,
+};
+
+_PRIVATE_ bool tevent_port_init(void)
+{
+	if (!tevent_register_backend("port", &port_event_ops)) {
+		return false;
+	}
+	tevent_set_default_backend("port");
+	return true;
+}