WHATSNEW: Add an entry for the LDB whole DB locking issue

[Samba.git] / lib / tevent / tevent_port.c

/*
   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) {
                int ret;
                if (val->associated_event) {
                        continue;
                }
                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) {
                if (ev->signal_events) {
                        tevent_common_check_signal(ev);
                }
                /*
                 * If no signal handlers we got an unsolicited
                 * signal wakeup. This can happen with epoll
                 * too. Just return and ignore.
                 */
                return 0;
        }

        if (ret == -1 && port_errno == ETIME) {
                /*
                 * If errno is set to ETIME it is possible that we still got an event.
                 * In that case we need to go through the processing loop so that we
                 * reassociate the received event with the port or the association will
                 * be lost so check the value of nget is 0 before returning.
                 */
                if (nget == 0) {
                        /* we don't care about a possible delay here */
                        tevent_common_loop_timer_delay(ev);
                        return 0;
                }
                /*
                 * Set the return value to 0 since we do not actually have an error and we
                 * do have events that need to be processed.  This keeps us from getting
                 * caught in the generic error test.
                 */
                ret = 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->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;
        }

        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;
}